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Sample records for allyl sulfides studies

  1. Theoretical Comparative Study of the Structure, Dynamics and Electronic Properties of Five Ally Molecules: Allicin, Methyl Propyl Disulfide (MPD), Allyl Methyl Sulfide (AMS), S-allyl cysteine (SAC) and S-allyl mercaptocysteine (SAMC)

    NASA Astrophysics Data System (ADS)

    Deniz Calisir, Emine; Erkoc, Sakir; Yildirim, Handan; Kara, Abdelkader; Rahman, Talat S.; Selvi, Mahmut; Erkoc, Figen

    2006-03-01

    The structural, dynamics and electronic properties of five allyl molecules have been investigated theoretically by performing semi-empirical molecular orbital (AM1 and PM3), ab-initio (RHF) and density functional theory calculations. The geometry of the molecules have been optimized, the vibrational spectra and the electronic properties of the molecules have been calculated in their ground states in gas phase. For each molecule, we found that the optimized geometries resulting from calculations based on the three levels of accuracy, to be very similar. However, we found that an accurate description of the vibrational properties of these molecules necessitates calculations at the ab-initio level. The electronic structures of these molecules were performed at the DFT level, resulting in an accurate description of the HOMO-LUMO gap and the local charges.

  2. Molecular mechanisms of garlic-derived allyl sulfides in the inhibition of skin cancer progression

    PubMed Central

    Wang, Hsiao-Chi; Pao, Jung; Lin, Shuw-Yuan; Sheen, Lee-Yan

    2012-01-01

    Skin cancer is a serious concern whose incidence is increasing at an alarming rate. Allyl sulfides—i.e., sulfur metabolites in garlic oil—have been demonstrated to have anticancer activity against several cancer types, although the mechanisms underlying these effects remain enigmatic. Our previous study showed that diallyl trisulfide (DATS) is more potent than mono- and disulfides against skin cancer. DATS inhibits cell growth of human melanoma A375 cells and basal cell carcinoma (BCC) cells by increasing the levels of intracellular reactive oxygen species (ROS) and DNA damage and by inducing G2/M arrest, endoplasmic reticulum (ER) stress, and mitochondria-mediated apoptosis, including the caspase-dependent and -independent pathways. This short review focuses on the molecular mechanisms of garlic-derived allyl sulfides on skin cancer prevention. PMID:23050963

  3. Dechalcogenative Allylic Selenosulfide And Disulfide Rearrangements: Complementary Methods For The Formation Of Allylic Sulfides In The Absence Of Electrophiles. Scope, Limitations, And Application To The Functionalization Of Unprotected Peptides In Aqueous Media

    PubMed Central

    Crich, David; Krishnamurthy, Venkataramanan; Brebion, Franck; Karatholuvhu, Maheswaran; Subramanian, Venkataraman; Hutton, Thomas K.

    2008-01-01

    Primary allylic selenosulfates (seleno Bunte salts) and selenocyanates transfer the allylic selenide moiety to thiols giving primary allylic selenosulfides, which undergo rearrangement in the presence of PPh3 with the loss of selenium to give allylically rearranged allyl alkyl sulfides. This rearrangement may be conducted with prenyl-type selenosulfides to give isoprenyl alkyl sulfides. Alkyl secondary and tertiary allylic disulfides, formed by sulfide transfer from allylic heteroaryl disulfides to thiols, undergo desulfurative allylic rearrangement on treatment with PPh3 in methanolic acetonitrile at room temperature. With nerolidyl alkyl disulfides this rearrangement provides an electrophile-free method for the introduction of the farnesyl chain onto thiols. Both rearrangements are compatible with the full range of functionality found in the proteinogenic amino acids and it is demonstrated that the desulfurative rearrangement functions in aqueous media, enabling the derivatization of unprotected peptides. It is also demonstrated that the allylic disulfide rearrangement can be inducted in the absence of phosphine at room temperature by treatment with piperidine, or simply by refluxing in methanol. Under these latter conditions the reaction is also applicable to allyl aryl disulfides, providing allylically rearranged allyl aryl sulfides in good yields. PMID:17655306

  4. Palladium-catalyzed allylic alkylation of simple ketones with allylic alcohols and its mechanistic study.

    PubMed

    Huo, Xiaohong; Yang, Guoqiang; Liu, Delong; Liu, Yangang; Gridnev, Ilya D; Zhang, Wanbin

    2014-06-23

    Allylic alcohols were directly used in Pd-catalyzed allylic alkylations of simple ketones under mild reaction conditions. The reaction proceeded smoothly at 20 °C by the concerted action of a Pd catalyst, a pyrrolidine co-catalyst, and a hydrogen-bonding solvent, and does not require any additional reagents. A computational study suggested that methanol plays a crucial role in the formation of the π-allylpalladium complex by lowering the activation barrier. PMID:24848670

  5. Allyl astatide

    SciTech Connect

    Norseev, Yu.V.; Vasaros, L.; Syuch, Z.

    1988-11-01

    Allyl astatide was prepared by the interhalogen exchange method, by replacement of the bromine in allyl bromide with astatide ion. The most favorable conditions for the synthesis were found by variations of the method that uses hydrazine hydrate and sodium formaldehyde sulfoxylate as reductants. A by-product is formed by the reaction of allyl bromide with excited astatine-211 which forms by disintegration of radon-211. Allyl astatide was identified by radio gas-liquid chromatography. Its retention indexes on nonpolar and weakly polar liquid phases were found. The stability of this newly prepared astatine compound was studied. The extrapolated boiling point of allyl astatide is 129 +/- 2/sup 0/C.

  6. Synthesis of unsaturated sulfides via cross-coupling of Grignard reagents with allylic electrophiles with simultaneous incorporation of sulfur into the metal-carbon bond

    SciTech Connect

    Dzhemilev, U.M.; Gribanova, E.V.; Ibragimov, A.G.

    1987-08-20

    Previous reports have described the synthesis of carbonyl compounds based on the reaction of CO with simple Mg and Sn-organic reagents in the presence of Ni- and Pd-containing catalysts. In order to explore the potential of this approach for the synthesis of unsaturated sulfides, they have investigated the cross-coupling of alkenylmagnesium halides, obtained via the hydromagnesionation of isoprene, with allyl ethers and esters in the presence of elemental sulfur (S/sub 8/, cyclooctasulfane), catalyzed by transition metal complexes. Their experiments revealed that in order to carry out these types of reactions it was necessary to use two and three-component catalyst systems based on Pd compounds (Pd(acac)/sub 2/, PdCl/sub 2/) in conjunction with Ph/sub 3/P, as well as AlET/sub 3/ or i-Bu/sub 2/AlH.

  7. Spectroscopic characterization of alumina-supported bis(allyl)iridium complexes : site-isolation, reactivity, and decomposition studies.

    SciTech Connect

    Trovitch, R. J.; Guo, N.; Janicke, M. T.; Li, H.; Marshall, C. L.; Miller, J. T.; Sattelberger, A. P.; John, K. D.; Baker, R. T.; LANL; Univ. of Ottawa

    2010-01-01

    The covalent attachment of tris(allyl)iridium to partially dehydroxylated ?-alumina is found to proceed via surface hydroxyl group protonation of one allyl ligand to form an immobilized bis(allyl)iridium moiety, (?AlO)Ir(allyl)2, as characterized by CP-MAS 13C NMR, inductively coupled plasma-mass spectrometry, and Ir L3 edge X-ray absorption spectroscopy. Extended X-ray absorption fine-structure (EXAFS) measurements taken on unsupported Ir(allyl)3 and several associated tertiary phosphine addition complexes suggest that the ?3-allyl ligands generally account for an Ir-C coordination number of 2 rather than 3, with an average Ir-C distance of 2.16 A. Using this knowledge, combined EXAFS and X-ray absorption near-edge structure studies reveal that a small amount of Ir0 is also formed upon reaction of Ir(allyl)3 with the surface. It was found that the addition of either 2,6-dimethylphenyl isocyanide or carbon monoxide to the supported complex allows spectroscopic identification of the supported bis(allyl)iridium complexes, (?AlO)Ir(allyl)2(CNAr) [Ar = 2,6-(CH3)2C6H4] and (?AlO)Ir(allyl)2(CO)2, respectively. Although samples of the supported bis(allyl)iridium complex are active for the dehydrogenation of cyclohexane to benzene at temperatures between 180 and 220C, in situ temperature-programmed reaction XAFS and continuous-flow reactor studies suggest that Ir0 nanoparticles, rather than a well-defined Ir3+ complex, are responsible for the observed activity.

  8. Spectroscopic characterization of alumina-supported bis(allyl)iridium complexes: site-isolation, reactivity, and decomposition studies.

    PubMed

    Trovitch, Ryan J; Guo, Neng; Janicke, Michael T; Li, Hongbo; Marshall, Christopher L; Miller, Jeffrey T; Sattelberger, Alfred P; John, Kevin D; Baker, R Thomas

    2010-03-01

    The covalent attachment of tris(allyl)iridium to partially dehydroxylated gamma-alumina is found to proceed via surface hydroxyl group protonation of one allyl ligand to form an immobilized bis(allyl)iridium moiety, (=AlO)Ir(allyl)(2), as characterized by CP-MAS (13)C NMR, inductively coupled plasma-mass spectrometry, and Ir L(3) edge X-ray absorption spectroscopy. Extended X-ray absorption fine-structure (EXAFS) measurements taken on unsupported Ir(allyl)(3) and several associated tertiary phosphine addition complexes suggest that the eta(3)-allyl ligands generally account for an Ir-C coordination number of 2 rather than 3, with an average Ir-C distance of 2.16 A. Using this knowledge, combined EXAFS and X-ray absorption near-edge structure studies reveal that a small amount of Ir(0) is also formed upon reaction of Ir(allyl)(3) with the surface. It was found that the addition of either 2,6-dimethylphenyl isocyanide or carbon monoxide to the supported complex allows spectroscopic identification of the supported bis(allyl)iridium complexes, (=AlO)Ir(allyl)(2)(CNAr) [Ar = 2,6-(CH(3))(2)C(6)H(4)] and (=AlO)Ir(allyl)(2)(CO)(2), respectively. Although samples of the supported bis(allyl)iridium complex are active for the dehydrogenation of cyclohexane to benzene at temperatures between 180 and 220 degrees C, in situ temperature-programmed reaction XAFS and continuous-flow reactor studies suggest that Ir(0) nanoparticles, rather than a well-defined Ir(3+) complex, are responsible for the observed activity. PMID:20112918

  9. The allylic chalcogen effect in olefin metathesis

    PubMed Central

    Lin, Yuya A

    2010-01-01

    Summary Olefin metathesis has emerged as a powerful tool in organic synthesis. The activating effect of an allylic hydroxy group in metathesis has been known for more than 10 years, and many organic chemists have taken advantage of this positive influence for efficient synthesis of natural products. Recently, the discovery of the rate enhancement by allyl sulfides in aqueous cross-metathesis has allowed the first examples of such a reaction on proteins. This led to a new benchmark in substrate complexity for cross-metathesis and expanded the potential of olefin metathesis for other applications in chemical biology. The enhanced reactivity of allyl sulfide, along with earlier reports of a similar effect by allylic hydroxy groups, suggests that allyl chalcogens generally play an important role in modulating the rate of olefin metathesis. In this review, we discuss the effect of allylic chalcogens in olefin metathesis and highlight its most recent applications in synthetic chemistry and protein modifications. PMID:21283554

  10. Structural studies in limestone sulfidation

    SciTech Connect

    Fenouil, L.A.; Lynn, S.

    1993-05-01

    This study investigates the sulfidation of limestone at high temperatures (700--900{degree}C) as the first step in the design of a High-Temperature Coal-Gas Clean-Up system using millimeter-size limestone particles. Several workers have found that the rate of this reaction significantly decreases after an initial 10 to 15% conversion of CaCO{sub 3} to CaS. The present work attempts to explain this feature. It is first established that millimeter-size limestone particles do not sinter at temperatures up to the CaCO{sub 3} calcination point (899{degree}C at 1.03 bar CO{sub 2} partial pressure). It is then shown that CaS sinters rapidly at 750 to 900{degree}C if CO{sub 2} is present in the gas phase. Scanning Electron Microscope (SEM) photographs and Electron Dispersive Spectroscopy (EDS) data reveal that the CaS product layer sinters and forms a quasi-impermeable coating around the CaCO{sub 3} grains that greatly hinders more H{sub 2}S from reaching the still unreacted parts of the stone. Moreover, most of the pores initially present within the limestone structure begin to disappear or, at least, are significantly reduced in size. From then on, subsequent conversion is limited by diffusion of H{sub 2}S through the CaS layer, possibly by S{sup 2{minus}} ionic diffusion. The kinetics is then adequately described by a shrinking-core model, in which a sharp front of completely converted limestone is assumed to progress toward the center of the pellet. Finally, experimental evidence and computer simulations using simple sintering models suggest that the CaS sintering, responsible for the sharp decrease in the sulfidation rate, is surface-diffusion controlled.

  11. Iridium-catalyzed allylic substitutions with cyclometalated phosphoramidite complexes bearing a dibenzocyclooctatetraene ligand: preparation of (π-allyl)Ir complexes and computational and NMR spectroscopic studies.

    PubMed

    Raskatov, Jevgenij A; Jäkel, Mascha; Straub, Bernd F; Rominger, Frank; Helmchen, Günter

    2012-11-01

    (π-Allyl)Ir complexes derived from dibenzocyclooctatetraene and phosphoramidites by cyclometalation are effective catalysts for allylic substitution reactions of linear monosubstituted allylic carbonates. These catalysts provide exceptionally high degrees of regioselectivity and allow the reactions to be run under aerobic conditions. A series of (π-allyl)Ir complexes were prepared and characterized by X-ray crystal structure analyses. An allylic amination with aniline displayed different resting states depending on the presence of a strong base. DFT calculations were carried out on the mechanistic aspects of these reactions. The results suggest that for the (π-allyl)Ir complexes, the formation and reactions with nucleophiles proceed with comparable rates. PMID:23018807

  12. Experimental and Kinetic Modeling Study of 2-Methyl-2-Butene: Allylic Hydrocarbon Kinetics.

    PubMed

    Westbrook, Charles K; Pitz, William J; Mehl, Marco; Glaude, Pierre-Alexandre; Herbinet, Olivier; Bax, Sarah; Battin-Leclerc, Frederique; Mathieu, Olivier; Petersen, Eric L; Bugler, John; Curran, Henry J

    2015-07-16

    Two experimental studies have been carried out on the oxidation of 2-methyl-2-butene, one measuring ignition delay times behind reflected shock waves in a stainless steel shock tube, and the other measuring fuel, intermediate, and product species mole fractions in a jet-stirred reactor (JSR). The shock tube ignition experiments were carried out at three different pressures, approximately 1.7, 11.2, and 31 atm, and at each pressure, fuel-lean (ϕ = 0.5), stoichiometric (ϕ = 1.0), and fuel-rich (ϕ = 2.0) mixtures were examined, with each fuel/oxygen mixture diluted in 99% Ar, for initial postshock temperatures between 1330 and 1730 K. The JSR experiments were performed at nearly atmospheric pressure (800 Torr), with stoichiometric fuel/oxygen mixtures with 0.01 mole fraction of 2M2B fuel, a residence time in the reactor of 1.5 s, and mole fractions of 36 different chemical species were measured over a temperature range from 600 to 1150 K. These JSR experiments represent the first such study reporting detailed species measurements for an unsaturated, branched hydrocarbon fuel larger than iso-butene. A detailed chemical kinetic reaction mechanism was developed to study the important reaction pathways in these experiments, with particular attention on the role played by allylic C-H bonds and allylic pentenyl radicals. The results show that, at high temperatures, this olefinic fuel reacts rapidly, similar to related alkane fuels, but the pronounced thermal stability of the allylic pentenyl species inhibits low temperature reactivity, so 2M2B does not produce "cool flames" or negative temperature coefficient behavior. The connections between olefin hydrocarbon fuels, resulting allylic fuel radicals, the resulting lack of low-temperature reactivity, and the gasoline engine concept of octane sensitivity are discussed. PMID:25822578

  13. DFT studies on the palladium-catalyzed dearomatization reaction between naphthalene allyl chloride and allyltributylstannane.

    PubMed

    Cao, Wei; Tian, Dongxu; Han, Dongxue

    2015-10-01

    The Pd-catalyzed dearomatization of naphthalene allyl chloride with allyltributylstannane has been investigated using density functional theory (DFT) calculations at the B3LYP level. The calculations indicate that the (ŋ(1)-allyl)(ŋ(3)-allyl)Pd(PH3) complex is responsible for the formation of ortho-dearomatized product. Moreover it is easy to produce the ortho-dearomatized product when reductive elimination starts from (ŋ(3)-allylnaphthalene)(ŋ(1)-allyl)Pd complex 7, while it is easy to form the para-dearomatized product when reductive elimination starts from (ŋ(3)-allylnaphthalene)(ŋ(1)-allyl)Pd complex 9. The Stille coupling products can't be produced due to high reaction energy barrier. Graphical Abstract Two mechanisms of dearomatization are investigated by DFT, and (ŋ(1)-allyl)(ŋ(3)-allyl)Pd(PH3) complexes are the main intermediates for ortho-dearomatized product.

  14. Allyl chloride

    Integrated Risk Information System (IRIS)

    Allyl chloride ; CASRN 107 - 05 - 1 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Ef

  15. Allyl alcohol

    Integrated Risk Information System (IRIS)

    Allyl alcohol ; CASRN 107 - 18 - 6 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Eff

  16. A Spectroscopic and Theoretical Study of Weak Intramolecular OH\\cdots π Interactions in Allyl Carbinol and Methallyl Carbinol

    NASA Astrophysics Data System (ADS)

    Schroeder, Sidsel D.; Mackeprang, Kasper; Kjaergaard, Henrik G.

    2013-06-01

    The weak intramolecular OH\\cdots π interactions in allyl carbinol and methallyl carbinol have been studied using a combination of NIR spectroscopy and theory. The third OH-stretching overtone region of vapor phase allyl carbinol and methallyl carbinol have been recorded with intracavity laser photoacoustic spectroscopy to study the effect of an enhanced OH\\cdots π interaction in methallyl carbinol arising from the electron donating methyl group. Local mode calculations were employed to assign the observed bands. The OH-stretching transition frequency of methallyl carbinol was observed to be red shifted relative to the OH-stretching transition frequency of allyl carbinol. A red shift of the transition frequency is in this context normally interpreted as a signature of hydrogen bonding. Whether the OH\\cdots π interaction can be categorized as a hydrogen bond will be discussed in this talk.

  17. Interplay of metal-allyl and metal-metal bonding in dimolybdenum allyl complexes.

    SciTech Connect

    Trovitch, R. J.; John, K. D.; Martin, R. L.; Obrey, S. J.; Sattelberger, A. P.; Scott, B. L.; Baker, R. T.; LANL; Univ. of Ottawa

    2009-01-01

    Addition of PMe{sub 3} to Mo{sub 2}(allyl){sub 4} afforded Mo{sub 2}(allyl){sub 4}(PMe{sub 3}){sub 2}, in which two of the allyl groups adopt an unprecedented {mu}{sub 2}-{eta}{sup 1}, {eta}{sup 3} bonding mode; theoretical studies elucidate the roles of the {sigma}- and {pi}-donor ligands in the interplay of metal-allyl and metal-metal bonding.

  18. Interplay of metal-allyl and metal-metal bonding in dimolybdenum allyl complexes

    SciTech Connect

    John, Kevin D; Martin, Richard L; Obrey, Steven J; Scott, Brian L

    2008-01-01

    Addition of PMe{sub 3} to Mo{sub 2}(allyl){sub 4} afforded Mo{sub 2}(allyl){sub 4}(PMe{sub 3}){sub 2}, in which two of the allyl groups adopt an unprecedented {mu}{sub 2{sup -}}{eta}{sup 1}, {eta}{sup 3} bonding mode; theoretical studies elucidate the role sof the {sigma}- and {pi}-donor ligands in the interplay of metal-allyl and metal-metal bonding.

  19. Enantiomerization of Allylic Trifluoromethyl Sulfoxides Studied by HPLC Analysis and DFT Calculations.

    PubMed

    Bailly, Laetitia; Petit, Emilie; Maeno, Mayaka; Shibata, Norio; Trapp, Oliver; Cardinael, Pascal; Chataigner, Isabelle; Cahard, Dominique

    2016-02-01

    Enantiomerization of allylic trifluoromethyl sulfoxides occurs spontaneously at room temperature through the corresponding allylic trifluoromethanesulfenates via a [2,3]-sigmatropic rearrangement. Dynamic enantioselective high-performance liquid chromatography (HPLC) analysis revealed the stereodynamics of these sulfoxides ranging from chromatographic resolution to peak coalescence at temperatures between 5 and 53 °C. The rate constant of enantiomerization and activation parameters were determined and compared with Density Functional Theory (DFT) calculations.

  20. FTIR studies of iron-carbonyl intermediates in allylic alcohol photoisomerization.

    PubMed

    Chong, Thiam Seong; Tan, Sze Tat; Fan, Wai Yip

    2006-06-23

    The 532 or 355 nm laser-induced photoisomerization of allylic alcohols to aldehydes catalyzed by [Fe(3)(CO)(12)] or [Fe(CO)(4)PPh(3)] in hexane was investigated. The Fourier transform infrared (FTIR) absorption spectra of iron-carbonyl intermediate species such as [Fe(CO)(5)], [Fe(CO)(4)(R-C(3)H(4)OH)], and more importantly the pi-allyl iron-carbonyl hydride species [FeH(CO)(3)(R-C(3)H(3)OH)] (R=H, Me, Ph) were recorded during the catalytic process using [Fe(3)(CO)(12)] as the catalytic precursor. When [Fe(CO)(4)PPh(3)] was photolyzed with 355 nm, [FeH(CO)(3)(R-C(3)H(3)OH)] was also generated indicating the common occurrence of the species in these two systems. The pi-allyl hydride species is long believed to be a key intermediates and its detection here lends support to the pi-allyl mechanism of the photoisomerization of allyl alcohols.

  1. Radical Cation/Radical Reactions: A Fourier Transform Ion Cyclotron Resonance Study of Allyl Radical Reacting with Aromatic Radical Cations

    PubMed Central

    Russell, Amber L.; Rohrs, Henry W.; Read, David; Giblin, Daryl E.; Gaspar, Peter P.; Gross, Michael L.

    2010-01-01

    A method for the study of reactions of open-shell neutrals (radicals) and radical cations is described. Pyrolysis (25–1500 °C) of thermally labile compounds, such as, 1,5-hexadiene via a Chen nozzle yields a seeded beam of reactive species in helium. The pyrolysis products are then analyzed by electron ionization (EI) or reacted with stored ions. Electron ionization of the pyrolysis products of 1,5-hexadiene shows that both the allyl radical and allene are generated. Reactions of benzene radical cations and the pyrolysis products of 1,5-hexadiene result in carbon-carbon bond formation. Those reactions of allyl radical with the benzene radical cation yield the C7H7+ ion of m/z 91, permitting an unusual entry into arenium ions. The reaction of allene with benzene radical cation in contrast yields C9H10+. and C9H9+. PMID:20401179

  2. VUV Photoionization Study of the Allyl Radical from Premixed Gasoline/Oxygen Flame

    NASA Astrophysics Data System (ADS)

    Yang, Rui; Yang, Bin; Huang, Chao-qun; Wei, Li-xia; Wang, Jing; Shan, Xiao-bin; Sheng, Liu-si; Zhang, Yun-wu; Qi, Fei; Yao, Chun-de; Li, Qi; Ji, Qing

    2006-02-01

    The allyl radical has been observed in a low-pressure premixed gasoline/oxygen/argon flame by using tunable vacuum ultraviolet photoionization mass spectrometry. The ionization potential of the allyl radical is derived to be (8.13 ± 0.02) eV from photoionization efficiency curve. In addition, a high level ab initio Gaussian-3 (G3) method was used to calculate the energies of the radical and its cation. The calculated adiabatic ionization potential is 8.18 eV, which is in excellent agreement with the experimental value. The result is helpful for identifying the allyl radical formed from other flames and for understanding the mechanism of soot formation.

  3. Synthetic Studies on Tricyclic Diterpenoids: Direct Allylic Amination Reaction of Isopimaric Acid Derivatives.

    PubMed

    Timoshenko, Mariya A; Kharitonov, Yurii V; Shakirov, Makhmut M; Bagryanskaya, Irina Yu; Shults, Elvira E

    2016-02-01

    A selective synthesis of 7- or 14-nitrogen containing tricyclic diterpenoids was completed according to a strategy in which the key step was the catalyzed direct allylic amination of methyl 14α-hydroxy-15,16-dihydroisopimarate with a wide variety of nitrogenated nucleophiles. It was revealed that the selectivity of the reaction depends on the nature of nucleophile. The catalyzed reaction of the mentioned diterpenoid allylic alcohol with 3-nitroaniline, 3-(trifluoromethyl)aniline, and 4-(trifluoromethyl)aniline yield the subsequent 7α-, 7β- and 14αnitrogen-containing diterpenoids. The reaction with 2-nitroaniline, 4-nitro-2-chloroaniline, 4-methoxy-2-nitroaniline, phenylsulfamide, or tert-butyl carbamate proceeds with the formation of 7α-nitrogen-substituted diterpenoids as the main products. PMID:27308214

  4. Mechanistic Study on Oxorhenium-Catalyzed Deoxydehydration and Allylic Alcohol Isomerization.

    PubMed

    Wu, Di; Zhang, Yugen; Su, Haibin

    2016-05-20

    The reaction mechanism of 1,2×n-deoxydehydration (DODH; n=1, 2, 3 …) reactions with 1-butanol as a reductant in the presence of methyltrioxorhenium(VII) catalyst has been investigated by DFT. The reduced rhenium compound, methyloxodihydroxyrhenium(V), serves as the catalytically relevant species in both allylic alcohol isomerization and subsequent DODH processes. Compared with three-step pathway A, involving [1,3]-transposition of allylic alcohols, direct two-step pathway B is an alternative option with lower activation barriers. The rate-limiting step of the DODH reaction is the first hydrogen transfer in methyltrioxorhenium(VII) reduction. Moreover, the increase in the distance between two hydroxyl groups in direct 1,2×n-DODH reactions for C4 and C6 diols results in a higher barrier height. PMID:26991093

  5. Regiodivergent Addition of Phenols to Allylic Oxides

    PubMed Central

    Vaccarello, David N.; Moschitto, Matthew J.; Lewis, Chad A.

    2015-01-01

    The regiodivergent addition of substituted phenols to allylic-oxides has been demonstrated using C2-symmetric palladium complexes. Complex phenol donors tyrosine, estradiol, and griseofulvin follow the predictive model. The Tsuji-Trost reaction is a powerful method to append both O- and C-donors to η3-allyl systems.1 The η3-allyl progenitor structures include allylic esters, carbonates, halides, and oxides. Internal allylic oxides2 remain one of the few systems that retain a marker of stereochemical induction with the newly liberated carbinol. The origin of the products can be traced to the diastereomeric η3-allyl intermediate and stereoisomer of oxide employed. We have recently identified3 a system capable of the conversion of racemic allylic oxides to distinct enantioenriched regioisomers using achiral phenol donors (Scheme 1). The allylic oxide regio-resolution (AORR) allowed the preparation of enantioenriched carbasugar natural products. We have now expanded this study to include a diverse array of achiral and chiral phenol donors. PMID:25933102

  6. Computational study of dissociative electron attachment to π-allyl ruthenium (II) tricarbonyl bromide

    NASA Astrophysics Data System (ADS)

    Thorman, Rachel M.; Bjornsson, Ragnar; Ingólfsson, Oddur

    2016-08-01

    Motivated by the current interest in low energy electron induced fragmentation of organometallic complexes in focused electron beam induced deposition (FEBID) we have evaluated different theoretical protocols for the calculation of thermochemical threshold energies for DEA to the organometallic complex π-allyl ruthenium (II) tricarbonyl bromide. Several different computational methods including density functional theory (DFT), hybrid-DFT and coupled cluster were evaluated for their ability to predict these threshold energies and compared with the respective experimental values. Density functional theory and hybrid DFT methods were surprisingly found to have poor reliability in the modelling of several DEA reactions; however, the coupled cluster method LPNO-pCCSD/2a was found to produce much more accurate results. Using the local correlation pair natural orbital (LPNO) methodology, high level coupled cluster calculations for open-shell systems of this size are now affordable, paving the way for reliable theoretical DEA predictions of such compounds.

  7. Theoretical study on the gas phase reaction of allyl chloride with hydroxyl radical.

    PubMed

    Zhang, Yunju; Chao, Kai; Sun, Jingyu; Zhang, Wanqiao; Shi, Haijie; Yao, Cen; Su, Zhongmin; Pan, Xiumei; Zhang, Jingping; Wang, Rongshun

    2014-02-28

    The reaction of allyl chloride with the hydroxyl radical has been investigated on a sound theoretical basis. This is the first time to gain a conclusive insight into the reaction mechanism and kinetics for important pathways in detail. The reaction mechanism confirms that OH addition to the C=C double bond forms the chemically activated adducts, IM1 (CH2CHOHCH2Cl) and IM2 (CH2OHCHCH2Cl) via low barriers, and direct H-abstraction paths may also occur. Variational transition state model and multichannel RRKM theory are employed to calculate the temperature-, pressure-dependent rate constants. The calculated rate constants are in good agreement with the experimental data. At 100 Torr with He as bath gas, IM6 formed by collisional stabilization is the major products in the temperature range 200-600 K; the production of CH2CHCHCl via hydrogen abstractions becomes dominant at high temperatures (600-3000 K). PMID:24588171

  8. Computational study of dissociative electron attachment to π-allyl ruthenium (II) tricarbonyl bromide

    NASA Astrophysics Data System (ADS)

    Thorman, Rachel M.; Bjornsson, Ragnar; Ingólfsson, Oddur

    2016-08-01

    Motivated by the current interest in low energy electron induced fragmentation of organometallic complexes in focused electron beam induced deposition (FEBID) we have evaluated different theoretical protocols for the calculation of thermochemical threshold energies for DEA to the organometallic complex π-allyl ruthenium (II) tricarbonyl bromide. Several different computational methods including density functional theory (DFT), hybrid-DFT and coupled cluster were evaluated for their ability to predict these threshold energies and compared with the respective experimental values. Density functional theory and hybrid DFT methods were surprisingly found to have poor reliability in the modelling of several DEA reactions; however, the coupled cluster method LPNO-pCCSD/2a was found to produce much more accurate results. Using the local correlation pair natural orbital (LPNO) methodology, high level coupled cluster calculations for open-shell systems of this size are now affordable, paving the way for reliable theoretical DEA predictions of such compounds. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.

  9. Theoretical study on the gas phase reaction of allyl alcohol with hydroxyl radical.

    PubMed

    Zhang, Yunju; Chao, Kai; Sun, Jingyu; Su, Zhongmin; Pan, Xiumei; Zhang, Jingping; Wang, Rongshun

    2013-08-01

    The complex potential energy surface of allyl alcohol (CH2CHCH2OH) with hydroxyl radical (OH) has been investigated at the G3(MP2)//MP2/6-311++G(d,p) level. On the surface, two kinds of pathways are revealed, namely, direct hydrogen abstraction and addition/elimination. Rice-Ramsperger-Kassel-Marcus theory and transition state theory are carried out to calculate the total and individual rate constants over a wide temperature and pressure region with tunneling correction. It is predicted that CH2CHOHCH2OH (IM1) formed by collisional stabilization is dominate in the temperature range (200-440 K) at atmospheric pressure with N2 (200-315 K at 10 Torr Ar and 100 Torr He). The production of CH2CHCHOH + H2O via direct hydrogen abstraction becomes dominate at higher temperature. The kinetic isotope effect (KIE) has also been calculated for the title reaction. Moreover, the calculated rate constants and KIE are in good agreement with the experimental data.

  10. Kinetic studies of sulfide mineral oxidation and xanthate adsorption

    NASA Astrophysics Data System (ADS)

    Mendiratta, Neeraj K.

    2000-10-01

    Sulfide minerals are a major source of metals; however, certain sulfide minerals, such as pyrite and pyrrhotite, are less desirable. Froth flotation is a commonly used separation technique, which requires the use of several reagents to float and depress different sulfide minerals. Xanthate, a thiol collector, has gained immense usage in sulfide minerals flotation. However, some sulfides are naturally hydrophobic and may float without a collector. Iron sulfides, such as pyrite and pyrrhotite, are few of the most abundant minerals, yet economically insignificant. Their existence with other sulfide minerals leads to an inefficient separation process as well as environmental problems, such as acid mine drainage during mining and processing and SO 2 emissions during smelting process. A part of the present study is focused on understanding their behavior, which leads to undesired flotation and difficulties in separation. The major reasons for the undesired flotation are attributed to the collectorless hydrophobicity and the activation with heavy metal ions. To better understand the collectorless hydrophobicity of pyrite, Electrochemical Impedance Spectroscopy (EIS) of freshly fractured pyrite electrodes was used to study the oxidation and reduction of the mineral. The EIS results showed that the rate of reaction increases with oxidation and reduction. At moderate oxidizing potentials, the rate of reaction is too slow to replenish hydrophilic iron species leaving hydrophobic sulfur species on the surface. However, at higher potentials, iron species are replaced fast enough to depress its flotation. Effects of pH and polishing were also explored using EIS. Besides collectorless hydrophobicity, the activation of pyrrhotite with nickel ions and interaction with xanthate ions makes the separation more difficult. DETA and SO2 are commonly used as pyrrhotite depressants; however, the mechanism is not very well understood. Contact angle measurements, cyclic voltammetry and Tafel

  11. Resonance Raman spectrum of the allyl-d5 radical and the force field analysis of the allyl radical

    NASA Astrophysics Data System (ADS)

    Liu, Xianming; Getty, James D.; Kelly, Peter B.

    1993-08-01

    Resonance Raman spectra of the allyl-d5 radical have been obtained with excitation between 247 and 223 nm. Analysis of the spectra yields the first observation of fundamental frequencies, nu4, nu5, and nu7 and overtone frequencies 2nu9, 2nu10, and 2nu12. The new vibrational data are combined with previously observed frequencies of allyl-h5 and allyl-d5 radical to produce the force field analysis for the allyl radical. This study suggests reassignment of several previously observed infrared (IR) bands. Experimental frequencies and assignments for allyl-h5 and allyl-d5 are compared with results from ab initio calculations. Force constants obtained in the present work are compared with the force constants of other sp2 hybridization molecules such as benzene, allene, and ethylene.

  12. Copper-catalyzed borylative allyl-allyl coupling reaction.

    PubMed

    Semba, Kazuhiko; Bessho, Naoto; Fujihara, Tetsuaki; Terao, Jun; Tsuji, Yasushi

    2014-08-18

    Borylative allyl-allyl coupling using allenes, bis(pinacolato)diboron, and allyl phosphates has been developed in the presence of a copper catalyst bearing an N-heterocyclic carbene ligand. The reaction affords boryl-substituted 1,5-diene derivatives in good to high yields with high regioselectivity and Z selectivity. PMID:24986738

  13. Morphology and thermal studies of zinc sulfide and cadmium sulfide nanoparticles in polyvinyl alcohol matrix

    NASA Astrophysics Data System (ADS)

    Osuntokun, Jejenija; Ajibade, Peter A.

    2016-09-01

    Zn(II) and Cd(II) metal complexes of 1-cyano-1-carboethoxyethylene-2,2-dithiolato-κS,S'-bis(N,N-dimethylthiourea-κS) have been synthesized and characterized with analytical and spectroscopic techniques. The complexes were thermolysed in hexadecylamine at 200 °C to prepare ZnS and CdS nanoparticles. The nanoparticles were characterized with scanning electron microscope (SEM), transmission electron microscope (TEM), and powder X-ray diffraction (p-XRD). TEM images showed spherically shaped nanoparticles, whose sizes are in the range 4.33-7.21 nm for ZnS and 4.95-7.7 nm CdS respectively and XRD confirmed cubic crystalline phases for the nanoparticles. The optical band gap energy evaluated from the absorption spectra are 2.88 eV (430 nm) and 2.81 eV (440 nm) for the ZnS and CdS nanoparticles respectively. The as-prepared metal sulfide nanoparticles were further incorporated into polyvinyl alcohol (PVA) to give ZnS/PVA and CdS/PVA composites. The polymer nanocomposites were studied to investigate their morphology and thermal properties relative to the pure PVA. XRD diffractions indicated that the crystalline phases of the nanoparticles and the sizes in PVA matrices remained unaltered. Infra-red spectra studies revealed interactions between the PVA and the metal sulfide nanoparticles and TGA studies show that the ZnS/PVA and CdS/PVA nanocomposites exhibit better thermal stability than the pure PVA.

  14. NTP Technical Report on the comparative toxicity studies of allyl acetate (CAS No. 591-87-7), allyl alcohol (CAS No. 107-18-6) and acrolein (CAS No. 107-02-8) administered by gavage to F344/N rats and B6C3F1 mice.

    PubMed

    Irwin, Rick D

    2006-07-01

    Allyl acetate, allyl alcohol, and acrolein are used in the manufacture of detergents, plastics, pharmaceuticals, and chemicals and as agricultural agents and food additives. Male and female F344/N rats and B6C3F(1) mice received allyl acetate, allyl alcohol, or acrolein by gavage for 14 weeks. Genetic toxicology studies were conducted in Salmonella typhimurium, Drosophila melanogaster, cultured Chinese hamster ovary cells, rat bone marrow erythrocytes, and mouse peripheral blood erythrocytes. Groups of 10 male and 10 female rats were administered 0, 6, 12, 25, 50, or 100 mg allyl acetate/kg body weight, 0, 1.5, 3, 6, 12, or 25 mg/kg allyl alcohol, or 0, 0.75, 1.25, 2.5, 5, or 10 mg/kg acrolein in 0.5% methylcellulose by gavage, 5 days per week for 14 weeks. Groups of 10 male and 10 female mice were administered 0, 8, 16, 32, 62.5, or 125 mg/kg allyl acetate, 0, 3, 6, 12, 25, or 50 mg/kg allyl alcohol, or 0, 1.25, 2.5, 5, 10, or 20 mg/kg acrolein in 0.5% methylcellulose by gavage, 5 days per week for 14 weeks. In the allyl acetate rat study, all males and females in the 100 mg/kg groups died or were killed moribund by day 8; there were no other deaths. In the allyl alcohol study, all rats survived to the end of the study except one 6 mg/kg female. In the acrolein rat study, eight males and eight females in the 10 mg/kg groups died by week 9 of the study. Two males in the 2.5 and 5 mg/kg groups and one or two females in the 1.25, 2.5, and 5 mg/kg groups also died early; two of these deaths were gavage accidents. In the allyl acetate mouse study, all males and females in the 125 mg/kg group died during the first week of the study. All other early deaths, except five 62.5 mg/kg males and one 32 mg/kg female, were gavage accidents. In the allyl alcohol mouse study, one 50 mg/kg female died due to a gavage accident; all other animals survived to the end of the study. In the acrolein mouse study, all males and females administered 20 mg/kg died during the first week of

  15. Near-silence of isothiocyanate carbon in (13)C NMR spectra: a case study of allyl isothiocyanate.

    PubMed

    Glaser, Rainer; Hillebrand, Roman; Wycoff, Wei; Camasta, Cory; Gates, Kent S

    2015-05-01

    (1)H and (13)C NMR spectra of allyl isothiocyanate (AITC) were measured, and the exchange dynamics were studied to explain the near-silence of the ITC carbon in (13)C NMR spectra. The dihedral angles α = ∠(C1-C2-C3-N4) and β = ∠(C2-C3-N4-C5) describe the conformational dynamics (conformation change), and the bond angles γ = ∠(C3-N4-C5) and ε = ∠(N4-C5-S6) dominate the molecular dynamics (conformer flexibility). The conformation space of AITC contains three minima, Cs-M1 and enantiomers M2 and M2'; the exchange between conformers is very fast, and conformational effects on (13)C chemical shifts are small (νM1 - νM2 < 3 ppm). Isotropic chemical shifts, ICS(γ), were determined for sp, sp(x), and sp(2) N-hybridization, and the γ dependencies of δ(N4) and δ(C5) are very large (10-33 ppm). Atom-centered density matrix propagation trajectories show that every conformer can access a large region of the potential energy surface AITC(γ,ε,...) with 120° < γ < 180° and 155° < ε < 180°. Because the extreme broadening of the (13)C NMR signal of the ITC carbon is caused by the structural flexibility of every conformer of AITC, the analysis provides a general explanation for the near-silence of the ITC carbon in (13)C NMR spectra of organic isothiocyanates.

  16. Carcinogenesis Studies of Allyl Isovalerate (CAS No. 2835-39-4) in F344/N Rats and B6C3F1 Mice (Gavage Studies).

    PubMed

    1983-05-01

    Allyl isovalerate, a synthetic fragrance and flavoring ingredient in use since the 1950's, may be found in various products at the following concentrations: soap, 30 ppm; detergent, 3 ppm; creams, 15 ppm; perfume, 50 ppm; nonalcoholic beverages, 9 ppm; ice cream, 18 ppm; candy, 22 ppm; baked goods, 15-48 ppm; and gelatins and puddings, 1 ppm. A colorless liquid with an apple-like odor and taste, allyl isovalerate is approved by the U.S. Food and Drug Administration for use in foods. Specific production figures are not available, but U.S. production in 1980 exceeded 1,000 pounds. Carcinogenesis studies of allyl isovalerate (96% pure) were conducted by administering the test chemical in corn oil gavage to groups of 50 male and 50 female F344/N rats and to groups of 50 male and 50 female B6C3F1 mice at doses of 31 or 62 mg/kg. The doses selected were based on the chemically-induced toxic effects and depressed weight gains obtained from the 13-week studies. Doses were administered five times per week for 103 weeks. Groups of 50 rats and 50 mice of each sex received corn oil by gavage on the same dosing schedule and served as vehicle controls. Survival and mean body weight gain of rats of each sex and male mice were not adversely affected by the administration of allyl isovalerate. The significantly lower survival (P=0.001) and the lower mean body weight of low-dose female as compared with controls are likely consequences of the high incidence of a genital tract infection in the low-dose females. This infection was probably responsible for the deaths of 11/19 control, 22/33 low-dose, and 13/25 high-dose female mice that died before the end of the study. Squamous cell papillomas and epithelial hyperplasia of the nonglandular stomach were observed in dosed male mice in the 2-year studies (squamous cell papillomas: 0/50, 1/50, 2%, 3/48, 6%; epithelial hyperplasia: 1/50, 2%, 1/50, 2%, 7/48, 15%). The papillomas occurred with a significant positive trend (P<0.05). The

  17. Adsorption of acrolein, propanal, and allyl alcohol on Pd(111): a combined infrared reflection–absorption spectroscopy and temperature programmed desorption study

    PubMed Central

    Dostert, Karl-Heinz; O'Brien, Casey P.; Mirabella, Francesca; Ivars-Barceló, Francisco

    2016-01-01

    Atomistic-level understanding of the interaction of α,β-unsaturated aldehydes and their derivatives with late transition metals is of fundamental importance for the rational design of new catalytic materials with the desired selectivity towards C 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 C vs. CO bond partial hydrogenation. In this study, we investigate the interaction of acrolein, and its partial hydrogenation products propanal and allyl alcohol, with Pd(111) as a prototypical system. A combination of infrared reflection–absorption spectroscopy (IRAS) and temperature programmed desorption (TPD) experiments was applied under well-defined ultrahigh vacuum (UHV) conditions to obtain detailed information on the adsorption geometries of acrolein, propanal, and allyl alcohol as a function of coverage. We compare the IR spectra obtained for

  18. Asymmetric Synthesis of β-Substituted α-Methylenebutyro- lactones via TRIP-Catalyzed Allylation: Mechanistic Studies and Application to the Synthesis of (S)-(−)-Hydroxymatairesinol

    PubMed Central

    Fuchs, Michael; Schober, Markus; Orthaber, Andreas; Faber, Kurt

    2013-01-01

    Asymmetric allylation of (hetero)aromatic aldehydes by a zinc(II)-allylbutyrolactone species catalyzed by a chiral BINOL-type phosphoric acid gave β-substituted α-methylenebutyrolactones in 68 to >99% ee and 52–91% isolated yield. DFT studies on the intermediate Zn2+-complex – crucial for chiral induction – suggest a six-membered ring intermediate, which allows the phosphoric acid moiety to activate the aldehyde. The methodology was applied to the synthesis of the antitumour natural product (S)-(−)-hydroxymatairesinol. PMID:24415960

  19. Transition state region in the A-Band photodissociation of allyl iodide--A femtosecond extreme ultraviolet transient absorption study.

    PubMed

    Bhattacherjee, Aditi; Attar, Andrew R; Leone, Stephen R

    2016-03-28

    Femtosecond extreme ultraviolet (XUV) transient absorption spectroscopy based on a high-harmonic generation source is used to study the 266 nm induced A-band photodissociation dynamics of allyl iodide (CH2 =CHCH2I). The photolysis of the C-I bond at this wavelength produces iodine atoms both in the ground ((2)P3/2, I) and spin-orbit excited ((2)P1/2, I*) states, with the latter as the predominant channel. Using XUV absorption at the iodine N4/5 edge (45-60 eV), the experiments constitute a direct probe of not only the long-lived atomic iodine reaction products but also the fleeting transition state region of the repulsive nIσ(∗) C-I excited states. Specifically, three distinct features are identified in the XUV transient absorption spectrum at 45.3 eV, 47.4 eV, and 48.4 eV (denoted transients A, B, and C, respectively), which arise from the repulsive valence-excited nσ(∗) states and project onto the high-lying core-excited states of the dissociating molecule via excitation of 4d(I) core electrons. Transients A and B originate from 4d(I) → n(I) core-to-valence transitions, whereas transient C is best assigned to a 4d(I) →σ(∗)(C-I) transition. The measured differential absorbance of these new features along with the I/I* branching ratios known from the literature is used to suggest a more definitive assignment, albeit provisional, of the transients to specific dissociative states within the A-band manifold. The transients are found to peak around 55 fs-65 fs and decay completely by 145 fs-185 fs, demonstrating the ability of XUV spectroscopy to map the evolution of reactants into products in real time. The similarity in the energies of transients A and B with analogous features observed in methyl iodide [Attar et al. J. Phys. Chem. Lett. 6, 5072, (2015)] together with the new observation of transient C in the present work provides a more complete picture of the valence electronic structure in the transition state region. The results provide a benchmark

  20. Transition state region in the A-Band photodissociation of allyl iodide—A femtosecond extreme ultraviolet transient absorption study

    NASA Astrophysics Data System (ADS)

    Bhattacherjee, Aditi; Attar, Andrew R.; Leone, Stephen R.

    2016-03-01

    Femtosecond extreme ultraviolet (XUV) transient absorption spectroscopy based on a high-harmonic generation source is used to study the 266 nm induced A-band photodissociation dynamics of allyl iodide (CH2 =CHCH2I). The photolysis of the C—I bond at this wavelength produces iodine atoms both in the ground (2P3/2, I) and spin-orbit excited (2P1/2, I*) states, with the latter as the predominant channel. Using XUV absorption at the iodine N4/5 edge (45-60 eV), the experiments constitute a direct probe of not only the long-lived atomic iodine reaction products but also the fleeting transition state region of the repulsive nIσ∗C—I excited states. Specifically, three distinct features are identified in the XUV transient absorption spectrum at 45.3 eV, 47.4 eV, and 48.4 eV (denoted transients A, B, and C, respectively), which arise from the repulsive valence-excited nσ∗ states and project onto the high-lying core-excited states of the dissociating molecule via excitation of 4d(I) core electrons. Transients A and B originate from 4d(I) → n(I) core-to-valence transitions, whereas transient C is best assigned to a 4d(I) →σ∗(C—I) transition. The measured differential absorbance of these new features along with the I/I* branching ratios known from the literature is used to suggest a more definitive assignment, albeit provisional, of the transients to specific dissociative states within the A-band manifold. The transients are found to peak around 55 fs-65 fs and decay completely by 145 fs-185 fs, demonstrating the ability of XUV spectroscopy to map the evolution of reactants into products in real time. The similarity in the energies of transients A and B with analogous features observed in methyl iodide [Attar et al. J. Phys. Chem. Lett. 6, 5072, (2015)] together with the new observation of transient C in the present work provides a more complete picture of the valence electronic structure in the transition state region. The results provide a benchmark for

  1. XAFS characterization of industrial catalysts: in situ study of phase transformation of nickel sulfide

    NASA Astrophysics Data System (ADS)

    Wang, J.; Jia, Z.; Wang, Q.; Zhao, S.; Xu, Z.; Yang, W.; Frenkel, A. I.

    2016-05-01

    The online sulfiding process for nickel-contained catalyst often ends up with a nickel sulfide mixture in refinery plant. To elucidate the local environment of nickel and its corresponding sulfur species, a model catalyst (nickel sulfide) and model thermal process were employed to explore the possibilities for characterization of real catalysts in industrial conditions. The present investigation shows effectiveness of in situ XANES and EXAFS measurements for studying the phase stability and phase composition in these systems, which could be used to simulate real sulfiding process in industrial reactions, such as hydrodesulfurizations of oil.

  2. Theoretical Studies on Heavy Metal Sulfides in Solution

    SciTech Connect

    Tossell, John A.

    2007-10-31

    concepts have been worked out and we are therefore proposing to move to a new area, that of humic acids (while continuing our studies complexes formed by As oxides and sulfides, now applied to functional groups present in humic acids).

  3. Biosynthesis of mercapturic acids from allyl alcohol, allyl esters and acrolein

    PubMed Central

    Kaye, Clive M.

    1973-01-01

    1. 3-Hydroxypropylmercapturic acid, i.e. N-acetyl-S-(3-hydroxypropyl)-l-cysteine, was isolated, as its dicyclohexylammonium salt, from the urine of rats after the subcutaneous injection of each of the following compounds: allyl alcohol, allyl formate, allyl propionate, allyl nitrate, acrolein and S-(3-hydroxypropyl)-l-cysteine. 2. Allylmercapturic acid, i.e. N-acetyl-S-allyl-l-cysteine, was isolated from the urine of rats after the subcutaneous injection of each of the following compounds: triallyl phosphate, sodium allyl sulphate and allyl nitrate. The sulphoxide of allylmercapturic acid was detected in the urine excreted by these rats. 3. 3-Hydroxypropylmercapturic acid was identified by g.l.c. as a metabolite of allyl acetate, allyl stearate, allyl benzoate, diallyl phthalate, allyl nitrite, triallyl phosphate and sodium allyl sulphate. 4. S-(3-Hydroxypropyl)-l-cysteine was detected in the bile of a rat dosed with allyl acetate. PMID:4762754

  4. Formation, stability, and reactivity studies of neutral iron sulfide clusters

    NASA Astrophysics Data System (ADS)

    Yin, Shi; Wang, Zhechen; Bernstein, Elliot

    2014-03-01

    Different methods are used to generate neutral iron sulfide clusters to study their formation, stability, and reactivity, employing a time of flight mass spectrometer (TOFMS) with VUV (118 nm) radiation single photon ionization (SPI). Neutral FemSn (m = 1-4, n = 1-6), and hydrogen containing FemSnHx (x >0, n > m) clusters are generated by the reaction of seeded H2S in a helium carrier gas with laser ablated iron metal within a supersonic nozzle. The observed strong signal of association products Fe2S2(SH)0,1 M (M = CO, C2H4, C3H6) suggest that the Fe2S2(SH)0,1 clusters have the high activity for interactions with these small molecules. In order to avoid the effect for reactivity from hydrogen containing clusters, pure FemSnclusters are generated through laser ablation of a mixed iron/sulfur target in the presence of a pure helium carrier gas. (FeS)m (m = 1-4) is observed to be the most stable series. Reaction of CO and H2 on neutral (FeS)1,2clusters is farther investigated both experimentally and theoretically. A size dependent reactivity of iron sulfide clusters toward CO is characterized. The reaction FeS + CO --> Fe + OCS is found for the FeS cluster. Products Fe2S 213COH2 and Fe2S 213COH4 are identified for reactions of 13CO and H2 on Fe2S2 clusters: this suggests that the Fe2S2 cluster has a high catalytic activity for hydrogenation reactions of CO to form formaldehyde and methanol. DFT calculations are performed to explore the potential energy surfaces for the two reactions: Fe2S2 + CO + 2H2 --> Fe2S2 + CH3OH; and Fe2S2 + CO + H2 --> Fe2S2 + CH2O.

  5. Studies of the cryptic allylic pyrophosphate isomerase activity of trichodiene synthase using the anomalous substrate 6,7-dihydrofarnesyl pyrophosphate.

    PubMed

    Cane, D E; Pawlak, J L; Horak, R M

    1990-06-12

    Two enantiomeric analogues of farnesyl pyrophosphate (1) were tested as inhibitors and anomalous substrates of trichodiene synthase, which catalyzes the cyclization of trans,trans-farnesyl pyrophosphate (1) to the sesquiterpene hydrocarbon trichodiene (2). The reaction has been shown to involve preliminary isomerization of 1 to the tertiary allylic isomer nerolidyl pyrophosphate (3) which is cyclized without detectable release of the intermediate from the active site of the cyclase. Both (7S)-trans-6,7-dihydrofarnesyl pyrophosphate (7a) and (7R)-trans-6,7-dihydrofarnesyl pyrophosphate (7b), prepared from (3R)- and (3S)- citronellol (9a and 9b), respectively, proved to be modest competitive inhibitors of trichodiene synthase. The values of Ki(7a), 395 nM, and Ki(7b), 220 nM, were 10-15 times the observed Km for 1 and half the Ki of inorganic pyrophosphate alone. Incubation of either 7a or 7b with trichodiene synthase resulted in formation of a mixture of products which by radio/gas-liquid chromatographic and GC/selected ion mass spectrometric analysis was shown to be composed of 80-85% isomeric trienes 19-21 and 15-20% allylic alcohols 12 and 18. Examination of the water-soluble products resulting from incubation of 7a also revealed the generation of 24% of the isomeric cis-6,7-dihydrofarnesyl pyrophosphate (26). The combined rate of formation of anomalous alcoholic and olefinic products was 10% the Vmax determined for the conversion of 1 to 2. The results can be explained by initial enzyme-catalyzed isomerization of dihydrofarnesyl pyrophosphate (7) to the corresponding tertiary allylic isomer dihydronerolidyl pyrophosphate (8). Since the latter intermediate is unable to cyclize due to the absence of the 6,7-double bond, ionization of 8 and quenching of the resulting ion pair by deprotonation, capture of water, or collapse to the isomeric primary pyrophosphate esters will generate the observed spectrum of anomalous products. PMID:2386780

  6. Enantiomeric separation of glycidyl tosylate by CE: application to the study of catalytic asymmetric epoxidation of allyl alcohol.

    PubMed

    Morante-Zarcero, Sonia; Crego, Antonio L; del Hierro, Isabel; Sierra, Isabel; Marina, Maria Luisa

    2008-11-01

    A CE method using CDs as chiral selectors was developed and validated to achieve the separation of glycidyl tosylate enantiomers originated by in situ derivatization of glycidol enantiomers obtained in asymmetric epoxidation of allyl alcohol with chiral titanium-tartrate complexes as catalysts. The effects of the nature, pH and concentration of the buffer, the nature and concentration of chiral selector, the addition of SDS, methanol, ethanol or 2-propanol, the capillary temperature, the effective capillary length and the applied voltage on the chiral resolution of glycidyl tosylate enantiomers were investigated. The best separation conditions were achieved using a Tris-borate buffer mixture (50 and 25 mM, respectively) at pH=9.3 with a dual CD system consisting of 2.5% succinyl-beta-CD and 1.0% beta-CD w/v at 15 degrees C. A baseline separation (resolution approximately 2.0) of the glycidyl tosylate enantiomers was obtained in a relatively short time (less than 12 min). Satisfactory results were obtained in terms of linearity (r>0.99) and intermediate precision (RSD below 8.5%). The LOD and LOQ were 3.0 and 10.0 mg/L, respectively, and the recoveries ranged from 99.8 to 108.8%. Finally, the method was applied to the determination of the enantiomeric excess and the yield obtained in the asymmetric epoxidation of allyl alcohol employing chiral titanium-tartrate complexes as catalysts after an in situ derivatization of glycidol enantiomers to glycidyl tosylate.

  7. Tsuji-Trost N-allylation with allylic acetates using cellulose-Pd catalyst

    EPA Science Inventory

    Allylic amines are synthesized using heterogeneous cellulose-Pd catalyst via N-allylation of amines; aliphatic and benzyl amines undergo facile reaction with substituted and unsubstituted allyl acetates in high yields.

  8. Aryne 1,2,3-Trifunctionalization with Aryl Allyl Sulfoxides.

    PubMed

    Li, Yuanyuan; Qiu, Dachuan; Gu, Rongrong; Wang, Junli; Shi, Jiarong; Li, Yang

    2016-08-31

    An aryne 1,2,3-trisubstitution with aryl allyl sulfoxides is accomplished, featuring an incorporation of C-S, C-O, and C-C bonds on the consecutive positions of a benzene ring. The reaction condition is mild with broad substrate scope. Preliminary mechanistic study suggests a cascade formal [2 + 2] reaction of aryne with S═O bond, an allyl S → O migration, and a Claisen rearrangement. PMID:27527334

  9. Velocity Map Imaging Study of Ion-Radical Chemistry: Charge Transfer and Carbon-Carbon Bond Formation in the Reactions of Allyl Radicals with C(.).

    PubMed

    Pei, Linsen; Farrar, James M

    2016-08-11

    We present an experimental and computational study of the dynamics of collisions of ground state carbon cations with allyl radicals, C3H5, at a collision energy of 2.2 eV. Charge transfer to produce the allyl cation, C3H5(+), is exoergic by 3.08 eV and proceeds via energy resonance such that the electron transfer occurs without a significant change in nuclear velocities. The products have sufficient energy to undergo the dissociation process C3H5(+) → C3H4(+) + H. Approximately 80% of the reaction products are ascribed to charge transfer, with ∼40% of those products decaying via loss of a hydrogen atom. We also observe products arising from the formation of new carbon-carbon bonds. The experimental velocity space flux distributions for the four-carbon products are symmetric about the centroid of the reactants, providing direct evidence that the products are mediated by formation of a C4H5(+) complex living at least a few rotational periods. The primary four-carbon reaction products are formed by elimination of molecular hydrogen from the C4H5(+) complex. More than 75% of the nascent C4H3(+) products decay by C-H bond cleavage to yield a C4H2(+) species. Quantum chemical calculations at the MP2/6-311+g(d,p) level of theory support the formation of a nonplanar cyclic C4H5(+) adduct that is produced when the p-orbital containing the unpaired electron on C(+) overlaps with the unpaired spin density on the terminal carbon atoms in allyl. Product formation then occurs by 1,2-elimination of molecular hydrogen from the cyclic intermediate to form a planar cyclic C4H3(+) product. The large rearrangement in geometry as the C4H3(+) products are formed is consistent with high vibrational excitation in that product and supports the observation that the majority of those products decay to form the C4H2(+) species. PMID:27434380

  10. Synthesis and study of Sr-substituted misfit layer sulfides

    SciTech Connect

    Grippa, A.Yu. . E-mail: grippa@icr.chem.msu.ru; Lidin, S.; D'yachenko, O.G.; Rupasov, D.P.; Antipov, E.V.

    2005-01-04

    Two series of [(Ln{sub 1/3}Sr{sub 2/3}S){sub 1.5}]{sub 1.15}NbS{sub 2} (1.5Q/1H) and (Ln{sub 1-x}Sr{sub x}S){sub 1+y}NbS{sub 2} (1Q/1H) misfit layer sulfides have been synthesised and studied by X-ray powder and single crystal diffraction, EDX-analysis and magnetic measurements. For the early lanthanides (Ln = La, Ce) only the (Ln{sub 1-x}Sr{sub x}S){sub 1+y}NbS{sub 2} (x < 0.40-0.45, y = 0.15-0.17) compounds were formed whereas for late lanthanides (Ln = Pr, Nd, Sm, Gd-Er, Yb, Lu), and yttrium, both types of phases can be obtained. The crystal structure of (Pr{sub 0.55}Sr{sub 0.45}S){sub 1.15}NbS{sub 2} has been refined on the basis of X-ray single crystal data using the superspace approach. It consists of double layers [Pr{sub 0.55}Sr{sub 0.45}S] of NaCl-type (Q-part: a = 5.799(3) A, b = 5.810(2) A, c = 23.331(9) A, z = 4) and NbS{sub 2}-sandwiches (H-part: a = 3.332(3) A), z = 8, yielding a q-vector q = ({alpha} 0 0), {alpha} = 0.74) alternating along the c-direction. The superspace group pair is Fm2m ({alpha} 0 0):Fm2m ({alpha} 0 0) (No. 42.7). The refinement converged to R{sub w(obs)} = 0.069. According to the structure refinement and EDX-analysis data in the [Pr{sub 0.55}Sr{sub 0.45}S]-slab almost half of the Pr-atoms are randomly replaced by Sr. The minimal formal value of charge transfer from the Q- to the H-part of the structure necessary to stabilise the misfit Nb-based layer sulfides has been estimated as about 0.6 e per Nb atom.

  11. The effects of vehicles on the human dermal irritation potentials of allyl esters.

    PubMed

    Politano, Valerie T; Isola, Daniel A; Lalko, Jon; Api, Anne Marie

    2006-01-01

    Allyl esters, frequently used in the fragrance industry, often contain a certain percentage of free allyl alcohol. Allyl alcohol is known to have a potential for delayed skin irritation. Also present in the finished product are different solvent systems, or vehicles, which are used to deliver the fragrances based upon their intended application. This study was conducted to determine whether different vehicles affect the skin irritation potential of five different allyl esters. The allyl esters tested were allyl amyl glycolate, allyl caproate, allyl (cyclohexyloxy)acetate, allyl cyclohexylpropionate, and allyl phenoxyacetate in the vehicles diethyl phthalate, 3:1 diethyl phthalate:ethanol, and 1:3 diethyl phthalate:ethanol at concentrations of 0.1%, 0.5%, 1.0%, and 2.0% (w/w). A modified cumulative irritation test was conducted in 129 human subjects. Test materials (0.3 ml) were applied under occlusion to skin sites on the back for 1 day (24 h) using Hill Top chambers. Irritation was assessed at 1, 2, 4, and 5 days following application of test materials. Cumulative irritation scores varied considerably among test materials. There were no delayed irritation observations. The highest irritation scores were observed at the 2.0% concentration for all test materials. The irritation scores for allyl amyl glycolate, allyl (cyclohexyloxy)acetate, and allyl phenoxyacetate were highest in 1:3 diethyl phthalate:ethanol, thus the resulting calculated no-observed-effect levels, 0.12%, 0.03%, and 0%, respectively, were much lower for this vehicle compared to the diethyl phthalate vehicle, 0.33%, 0.26%, 0.25%, respectively. These data showed a trend for lower concentration thresholds to induce irritation when higher levels of ethanol were used in the vehicle.

  12. Studies of molybdena-alumina catalysts XVI. Effect of high-temperature sulfiding

    SciTech Connect

    Miciukiewicz, J. ); Massoth, F.E. )

    1989-10-01

    Candia et. al. recently reported an increase in hydrodesulfurization (HDS) activity of CoMo/Al{sub 2}O{sub 3} catalysts sulfided at 600 C. They attributed the increase in activity to a more active CoMoS phase (Type II) compared to the regular Type I CoMoS phase found in catalysts sulfided at 400 C. Breysse et. al. found a similar effect with NiW/Al{sub 2}O{sub 3} catalysts. Prada Silvy et. al., however, reported no change in HDS activity in sulfiding CoMo/Al{sub 2}O{sub 3} catalysts up to 700 C. In these studies, sintering of the support occurred due to the higher sulfiding temperatures employed compared with the original calcining temperature of the catalyst ({approximately}500 C). The authors decided to determine the effect of sulfiding temperature on the HDS and hydrogenation (HYD) activity of Mo and CoMo catalysts on an alumina support stabilized by calcining at a higher temperature than that used in the sulfiding treatments in order to avoid the complications due to support sintering during sulfiding. The catalysts were sulfided at 400, 550, or 700 C. Sulfided catalysts were characterized by CO{sub 2} and NO chemisorption using a pulse technique. At least duplicate measurements were made on each sample. Catalytic activities for HDS of thiophene and HYD of hexene were carried out at 350 C and under atmospheric pressure in a fixed-bed reactor. Pseudo first-order rate constants were calculated from conversions.

  13. Technological aspects of the microbial treatment of sulfide-rich wastewaters: a case study.

    PubMed

    Sublette, K L; Kolhatkar, R; Raterman, K

    1998-01-01

    Thiobacillus denitrificans has been shown to be an effective biocatalyst for the treatment of a variety of sulfide-laden waste streams including sour water, sour gases, and refinery spent-sulfidic caustics. The term 'sour' originated in the petroleum industry to describe a waste contaminated with hydrogen sulfide or salts of sulfide and bisulfide. The microbial treatment of sour waste streams resulting from the production or refining of natural gas and crude oil have been investigated in this laboratory for many years. The application of this technology to the treatment of sour wastes on a commercially useful scale has presented several technical barriers including substrate inhibition (sulfide), product inhibition (sulfate), the need for septic operation, biomass recycle and recovery, mixed waste issues, and the need for large-scale cultivation of the organism for process startup. The removal of these barriers through process improvements are discussed in terms of a case study of the full-scale treatment of sulfide-rich wastewater. The ability of T. denitrificans to deodorize and detoxify an oil-field produced water containing sulfides was evaluated under full-scale field conditions at Amoco Production Co. Salt Creek Field in Midwest, WY. More than 800 m3/d of produced water containing 100 mg/L sulfide and total dissolved solids of 4800 mg/L were successfully biotreated in an earthen pit (3000 m3) over a six-month period. Complete removal of sulfides and elimination of associated odors were observed. The system could be upset by severe hydraulic disturbances; however, the system recovered rapidly when normal influent flow rates were restored.

  14. Product distribution study of the Cl-atom initiated oxidation of ethyl methyl sulfide and diethyl sulfide

    NASA Astrophysics Data System (ADS)

    Oksdath-Mansilla, Gabriela; Peñéñory, Alicia B.; Barnes, Ian; Wiesen, Peter; Teruel, Mariano A.

    2014-03-01

    The products formed in the gas-phase reactions of Cl atoms with (CH3CH2)2S and CH3CH2SCH3 have been investigated in a large volume reactor in NOx-free air at atmospheric pressure and (298 ± 2) K using long path “in situ” FTIR spectroscopy for the analysis. HCl, SO2 and CH3CHO were identified as the major products for both reactions. For the Cl + CH3CH2SCH3 reaction HCHO was also identified as a major product. The yields of the products obtained for the reaction of Cl with (CH3CH2)2S were (59 ± 2) %, (52 ± 5) % and (103 ± 4) % for HCl, SO2 and CH3CHO, respectively. For the reaction of Cl with CH3CH2SCH3 yields of (43 ± 5) %, (55 ± 3) %, (58 ± 3) % and (53 ± 5) % were obtained for HCl, SO2, CH3CHO and HCHO, respectively. This is the first products and mechanistic study for the gas-phase Cl-initiated oxidation of non-CH3SCH3 alkyl sulfides. Comparison with previous results for the reaction of Cl with dimethyl sulfide is made and simple atmospheric degradation mechanisms are postulated to explain the formation of the observed products.

  15. Voltammetric study of the anodic oxidation of sulfide ions in molten fluorides

    SciTech Connect

    Minh, N.Q.; Yao, N.P.

    1983-05-01

    Information regarding the electrochemical behavior of sulfide ions in molten salts is important for questions of battery technology in the case of high-temperature secondary batteries, and for metallurgical molten-salt processes. The present investigation is concerned with the electrochemical behavior of sulfide in molten LiF-NaF. The investigation has the objective to evaluate the feasibility of the LiF-NaF melt as solvent for the electrolysis of Al2S3. The results are presented of a voltammetric study of the electrochemical oxidation of sulfide in LiF-NaF eutectic at 1023 K. It is found that the anodic oxidation of sulfide ions in LiF-NaF eutectic is reversible and diffusion controlled. The obtained experimental data correspond to the reaction mechanism 2S(2-) yields reversibly S2(2-) + 2e(-).

  16. Nickel-Catalyzed Allylic Alkylation with Diarylmethane Pronucleophiles: Reaction Development and Mechanistic Insights.

    PubMed

    Sha, Sheng-Chun; Jiang, Hui; Mao, Jianyou; Bellomo, Ana; Jeong, Soo A; Walsh, Patrick J

    2016-01-18

    Palladium-catalyzed allylic substitution reactions are among the most efficient methods to construct C-C bonds between sp(3)-hybridized carbon atoms. In contrast, much less work has been done with nickel catalysts, perhaps because of the different mechanisms of the allylic substitution reactions. Palladium catalysts generally undergo substitution by a "soft"-nucleophile pathway, wherein the nucleophile attacks the allyl group externally. Nickel catalysts are usually paired with "hard" nucleophiles, which attack the metal before C-C bond formation. Introduced herein is a rare nickel-based catalyst which promotes substitution with diarylmethane pronucleophiles by the soft-nucleophile pathway. Preliminary studies on the asymmetric allylic alkylation are promising.

  17. Why does the Conductivity of a Nickel Catalyst Increase during Sulfidation? An Exemplary Study Using an In Operando Sensor Device

    PubMed Central

    Fremerey, Peter; Jess, Andreas; Moos, Ralf

    2015-01-01

    In order to study the sulfidation of a catalyst fixed bed, an in operando single pellet sensor was designed. A catalyst pellet from the fixed bed was electrically contacted and its electrical response was correlated with the catalyst behavior. For the sulfidation tests, a nickel catalyst was used and was sulfidized with H2S. This catalyst had a very low conductivity in the reduced state. During sulfidation, the conductivity of the catalyst increased by decades. A reaction from nickel to nickel sulfide occurred. This conductivity increase by decades during sulfidation had not been expected since both nickel and nickel sulfides behave metallic. Only by assuming a percolation phenomenon that originates from a volume increase of the nickel contacts when reacting to nickel sulfides, this effect can be explained. This assumption was supported by sulfidation tests with differently nickel loaded catalysts and it was quantitatively estimated by a general effective media theory. The single pellet sensor device for in operando investigation of sulfidation can be considered as a valuable tool to get further insights into catalysts under reaction conditions. PMID:26512669

  18. Why does the Conductivity of a Nickel Catalyst Increase during Sulfidation? An Exemplary Study Using an In Operando Sensor Device.

    PubMed

    Fremerey, Peter; Jess, Andreas; Moos, Ralf

    2015-10-23

    In order to study the sulfidation of a catalyst fixed bed, an in operando single pellet sensor was designed. A catalyst pellet from the fixed bed was electrically contacted and its electrical response was correlated with the catalyst behavior. For the sulfidation tests, a nickel catalyst was used and was sulfidized with H₂S. This catalyst had a very low conductivity in the reduced state. During sulfidation, the conductivity of the catalyst increased by decades. A reaction from nickel to nickel sulfide occurred. This conductivity increase by decades during sulfidation had not been expected since both nickel and nickel sulfides behave metallic. Only by assuming a percolation phenomenon that originates from a volume increase of the nickel contacts when reacting to nickel sulfides, this effect can be explained. This assumption was supported by sulfidation tests with differently nickel loaded catalysts and it was quantitatively estimated by a general effective media theory. The single pellet sensor device for in operando investigation of sulfidation can be considered as a valuable tool to get further insights into catalysts under reaction conditions.

  19. The Reaction of Carbon Dioxide with Palladium Allyl Bonds

    PubMed Central

    Wu, Jianguo; Green, Jennifer C.; Hruszkewycz, Damian P.; Incarvito, Christopher D.; Schmeier, Timothy J.

    2010-01-01

    A family of palladium allyl complexes of the type bis(2-methylallyl)Pd(L) (L = PMe3 (1), PEt3 (2), PPh3 (3) or NHC (4); NHC = 1,3-Bis(2,6-diisopropylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene) have been prepared through the reaction of bis(2-methylallyl)Pd with the appropriate free ligand. Compounds 1–4 contain one η1 and one η3-2-methylallyl ligand and 3 was characterized by X-ray crystallography. These complexes react rapidly with CO2 at low temperature to form well defined unidentate palladium carboxylates of the type (η3-2-methylallyl)Pd(OC(O)C4H7)(L) (L = PMe3 (6), PEt3 (7), PPh3 (8) or NHC (9). The structure of 9 was elucidated using X-ray crystallography. The mechanism of the reaction of 1–4 with CO2 was probed using a combination of experimental and theoretical (density functional theory) studies. The coordination mode of the allyl ligand is crucial and whereas nucleophilic η1-allyls react rapidly with CO2, η3-allyls do not react. We propose that the reaction of η1-palladium allyls with CO2 does not proceed via direct insertion of CO2 into the Pd-C bond but through nucleophilic attack of the terminal olefin on electrophilic CO2, followed by an associative substitution at palladium. PMID:21218132

  20. Characteristics of the interaction of azulene with water and hydrogen sulfide: A computational study.

    PubMed

    Cabaleiro-Lago, Enrique M; Rodríguez-Otero, Jesús; Peña-Gallego, Angeles

    2008-08-28

    A computational study was carried out for studying the characteristics of the interaction between azulene and water or hydrogen sulfide. In azulene...water complex the water molecule is located with both hydrogen atoms pointing toward the aromatic cloud but displaced to the five-membered ring. Hydrogen sulfide adopts a similar arrangement but located roughly over the central C-C bond of azulene. Calculations show that hydrogen sulfide interacts with azulene more strongly (-4.19 kcal/mol) than water (-3.76 kcal/mol), although this is only revealed at the highest levels of calculation. The nature of the interaction is electrostatic and dispersive in the same percentage for water cluster, whereas for hydrogen sulfide dispersion is the dominant contribution. Clusters containing two water molecules are controlled by the possibility of establishing an O-H...O hydrogen bond. As a consequence, the most stable structure corresponds to the interaction between a water dimer and azulene, with an interaction energy amounting to -11.77 kcal/mol. Hydrogen sulfide interaction is stronger with azulene than with itself, so structures with S-H...S contact and others, where H(2)S only interacts with azulene, present similar interaction energies (-8.02 kcal/mol for the most stable one).

  1. Spectroscopic study of Se(IV) removal from water by reductive precipitation using sulfide.

    PubMed

    Jung, Bahngmi; Safan, Aya; Batchelor, Bill; Abdel-Wahab, Ahmed

    2016-11-01

    This study investigates the removal of selenium (IV) from water by reductive precipitation using sodium sulfide at neutral pH. Also, it examines the application of UV light as an activating method to enhance reductive precipitation. Furthermore, this work evaluates the effects of sulfide dose and solution pH on behavior of Se(IV) reduction. Selenium was effectively removed in sulfide solution at both neutral and acidic pH. UV irradiation did not enhance removal efficiency of Se(IV) at conditions tested, but it affected solids morphology and composition. SEM/EDS and XPS results showed that selenite was reduced to elemental Se or Se-S precipitates (e.g. SenS8-n) in sulfide solution. High resolution S 2p XPS spectra suggested the presence of sulfur-containing anions (e.g. S2O3(2-), HSO3(-), etc.) or elemental S (S(0)), monosulfide (S(2-)), and polysulfides (Sn(2-)), which could be produced from sulfide photolysis or reaction with Se. In addition, large aggregates of irregular shape, which suggest Se-S precipitates or elemental sulfur, were found more prominently at pH 4 than at pH 7, and they were more noticeable in the presence of UV with longer reaction times. In addition, XRD patterns showed that gray elemental Se solids were dominant in experiments without UV, whereas Se-S precipitates (Se3S5) with an orange color were found in those with UV. PMID:27552695

  2. Computational study of the interaction of indole-like molecules with water and hydrogen sulfide.

    PubMed

    Cabaleiro-Lago, Enrique M; Rodríguez-Otero, Jesús; Peña-Gallego, Ángeles

    2011-10-01

    The characteristics of the interaction between water and hydrogen sulfide with indole and a series of analogs obtained by substituting the NH group of indole by different heteroatoms have been studied by means of ab initio calculations. In all cases, minima were found corresponding to structures where water and hydrogen sulfide interact by means of X-H···π contacts. The interaction energies for all these π complexes are quite similar, spanning from -13.5 to -18.8 kJ/mol, and exhibiting the stability sequence NH > CH(2) ≈ PH > Se ≈ S > O, for both water and hydrogen sulfide. Though interaction energies are similar, hydrogen sulfide complexes are slightly favored over their water counterparts when interacting with the π cloud. σ-Type complexes were also considered for the systems studied, but only in the case of water complexes this kind of complexes is relevant. Only for complexes formed by water and indole, a significantly more stable σ-type complex was found with an interaction energy amounting to -23.6 kJ/mol. Oxygen and phosphorous derivatives also form σ-type complexes of similar stability as that observed for π ones. Despite the similar interaction energies exhibited by complexes with water and hydrogen sulfide, the nature of the interaction is very different. For π complexes with water the main contributions to the interaction energy are electrostatic and dispersive contributing with similar amounts, though slightly more from electrostatics. On the contrary, in hydrogen sulfide complexes dispersion is by far the main stabilizing contribution. For the σ-type complexes, the interaction is clearly dominated by the electrostatic contribution, especially in the indole-water complex.

  3. Allyl isothiocyanate from mustard seed is effective in reducing the levels of volatile sulfur compounds responsible for intrinsic oral malodor.

    PubMed

    Tian, Minmin; Hanley, A Bryan; Dodds, Michael W J

    2013-06-01

    Oral malodor is a major social and psychological issue that affects general populations. Volatile sulfur compounds (VSCs), particularly hydrogen sulfide (H₂S) and methyl mercaptan (CH₃SH), are responsible for most oral malodor. The objectives for this study were to determine whether allyl isothiocyanate (AITC) at an organoleptically acceptable level can eliminate VSCs containing a free thiol moiety and further to elucidate the mechanism of action and reaction kinetics. The study revealed that gas chromatograph with a sulfur detector demonstrated a good linearity, high accuracy and sensitivity on analysis of VSCs. Zinc salts eliminate the headspace level of H₂S but not CH₃SH. AITC eliminates both H₂S and CH₃SH via a nucleophilic addition reaction. In addition, a chemical structure-activity relationship study revealed that the presence of unsaturated group on the side chain of the isothiocyanate accelerates the elimination of VSCs. PMID:23470258

  4. Double-blind efficacy study of selenium sulfide in tinea versicolor.

    PubMed

    Sánchez, J L; Torres, V M

    1984-08-01

    Selenium sulfide (2.5%) lotion applied daily for 10 minutes for 7 consecutive days was found to be an effective therapeutic agent, significantly superior to the vehicle, in a double-blind study in the treatment of tinea versicolor. Mild transitory contact dermatitis of the primary irritant type occurred in all the treatment groups and was apparently due to the detergent base.

  5. Complex Allylation by the Direct Cross-Coupling of Imines with Unactivated Allylic Alcohols**

    PubMed Central

    Takahashi, Masayuki; McLaughlin, Martin; Micalizio, Glenn C.

    2010-01-01

    We report a reaction for the convergent coupling of allylic alcohols with imines that delivers stereodefined homoallylic amines. The process proceeds with net allylic transposition, without the intermediacy of allylic organometallic reagents, and forges two stereodefined centers and a geometrically defined di- or trisubstituted alkene with very high levels of selectivity. PMID:19360820

  6. A computational study of adhesion between rubber and metal sulfides at rubber-brass interface

    NASA Astrophysics Data System (ADS)

    Ling, Chian Ye; Hirvi, Janne T.; Suvanto, Mika; Bazhenov, Andrey S.; Ajoviita, Tommi; Markkula, Katriina; Pakkanen, Tapani A.

    2015-05-01

    Computational study at level of density functional theory has been carried out in order to investigate the adhesion between rubber and brass plated steel cord, which has high importance in tire manufacturing. Adsorption of natural rubber based adsorbate models has been studied on zinc sulfide, ZnS(1 1 0), and copper sulfide, Cu2S(1 1 1) and CuS(0 0 1), surfaces as the corresponding phases are formed in adhesive interlayer during rubber vulcanization. Saturated hydrocarbons exhibited weak interactions, whereas unsaturated hydrocarbons and sulfur-containing adsorbates interacted with the metal atoms of sulfide surfaces more strongly. Sulfur-containing adsorbates interacted with ZnS(1 1 0) surface stronger than unsaturated hydrocarbons, whereras both Cu2S(1 1 1) and CuS(0 0 1) surfaces showed opposite adsorption preference as unsaturated hydrocarbons adsorbed stronger than sulfur-containing adsorbates. The different interaction strength order can play role in rubber-brass adhesion with different relative sulfide concentrations. Moreover, Cu2S(1 1 1) surface exhibits higher adsorption energies than CuS(0 0 1) surface, possibly indicating dominant role of Cu2S in the adhesion between rubber and brass.

  7. O-Allylation of phenols with allylic acetates in aqueous media using a magnetically separable catalytic system

    EPA Science Inventory

    Allylic ethers were synthesized in water using magnetically recoverable heterogeneous Pd catalyst via O-allylation of phenols with allylic acetates under ambient conditions. Aqueous reaction medium, easy recovery of the catalyst using an external magnet, efficient recycling, and ...

  8. Chronoamperometric study of mild steel pitting in sodium sulfide aqueous solution

    SciTech Connect

    Otero, T.F.; Achucarro, C. . Dept. de Ciencia y Tecnologia de Polimeros)

    1994-08-01

    Mild steel samples were studied by chronoamperometry in sodium sulfide (Na[sub 2]S) aqueous solution. Pit nucleation and growth also were monitored by optical microscopy. The influence of variables such as temperature, polarization potential, surface roughness, the presence of electrochemically generated oxide layers, and the simultaneous presence of potassium hydroxide (KOH) was studied. The influence of each parameter on pit shape and growth was reviewed. Different reactions and competitive processes were proposed based on the experimental results.

  9. Interdisciplinary neurotoxicity inhalation studies: Carbon disulfide and carbonyl sulfide research in F344 rats

    SciTech Connect

    Sills, Robert C. . E-mail: sills@niehs.nih.gov; Harry, G. Jean; Valentine, William M.; Morgan, Daniel L.

    2005-09-01

    Inhalation studies were conducted on the hazardous air pollutants, carbon disulfide, which targets the central nervous system (spinal cord) and peripheral nervous system (distal portions of long myelinated axons), and carbonyl sulfide, which targets the central nervous system (brain). The objectives were to investigate the neurotoxicity of these compounds by a comprehensive evaluation of function, structure, and mechanisms of disease. Through interdisciplinary research, the major finding in the carbon disulfide inhalation studies was that carbon disulfide produced intra- and intermolecular protein cross-linking in vivo. The observation of dose-dependent covalent cross-linking in neurofilament proteins prior to the onset of lesions is consistent with this process contributing to the development of the neurofilamentous axonal swellings characteristic of carbon disulfide neurotoxicity. Of significance is that valine-lysine thiourea cross-linking on rat globin and lysine-lysine thiourea cross-linking on erythrocyte spectrin reflect cross-linking events occurring within the axon and could potentially serve as biomarkers of carbon disulfide exposure and effect. In the carbonyl sulfide studies, using magnetic resonance microscopy (MRM), we determined that carbonyl sulfide targets the auditory pathway in the brain. MRM allowed the examination of 200 brain slices and made it possible to identify the most vulnerable sites of neurotoxicity, which would have been missed in our traditional neuropathology evaluations. Electrophysiological studies were focused on the auditory system and demonstrated decreases in auditory brain stem evoked responses. Similarly, mechanistic studies focused on evaluating cytochrome oxidase activity in the posterior colliculus and parietal cortex. A decrease in cytochrome oxidase activity was considered to be a contributing factor to the pathogenesis of carbonyl sulfide neurotoxicity.

  10. A study of the trace sulfide mineral assemblages in the Stillwater Complex, Montana, USA

    NASA Astrophysics Data System (ADS)

    Aird, Hannah M.; Ferguson, Katherine M.; Lehrer, Malia L.; Boudreau, Alan E.

    2016-07-01

    The sulfide assemblages of the Stillwater Complex away from the well-studied ore zones are composed mainly of variable proportions of pyrrhotite, chalcopyrite, pentlandite, and ±pyrite. Excluding vein assemblages and those affected by greenschist and lower temperature alteration, the majority can be classified into two broad assemblages, defined here as pristine (multiphase, often globular in shape) or volatile-bearing (multiphase, high-temperature, volatile-rich minerals such as biotite, hornblende, or an unmixed calcite-dolomite assemblage). The volatile-bearing assemblages are mainly found within and below the J-M reef, where native copper and sphalerite are also locally present. Pristine sulfides are found throughout the stratigraphy. Both groups can be affected by apparent S loss in the form of pyrite being converted to magnetite and chalcopyrite to a Cu-Fe-oxide (delafossite), with little to no silicate alteration. An upward trend from pentlandite-rich to pyrrhotite-rich to pyrite-rich assemblages is observed in the footwall rocks in upper GN-I, and the same trend repeats from just below the reef and continues into the overlying N-II and GN-II. Modeling suggests that the sulfide Ni in the Peridotite Zone is largely controlled by silicate Ni. When taken together, observations are most readily explained by the remobilization of selected elements by a high-temperature fluid with the apparent loss of S > Cu > Ni. This could concentrate ore metals by vapor refining, eventually producing a platinum group element-enriched sulfide ore zone, such as the J-M reef.

  11. Study of the interaction between water and hydrogen sulfide with polycyclic aromatic hydrocarbons.

    PubMed

    Cabaleiro-Lago, Enrique M; Carrazana-García, Jorge A; Rodríguez-Otero, Jesús

    2009-06-21

    A computational study has been carried out for determining the characteristics of the interaction between one water and hydrogen sulfide molecule with a series of polycyclic aromatic hydrocarbons of increasing size, namely, benzene, anthracene, triphenylene, coronene, circumcoronene, and dicircumcoronene. Potential energy curves were calculated for structures where H(2)X (X=O,S) molecule is located over the central six-membered ring with its hydrogen atoms pointing toward to (mode A) or away from (mode B) the hydrocarbon. The accuracy of different methods has been tested against the results of coupled cluster calculations extrapolated to basis set limit for the smaller hydrocarbons. The spin component scaled MP2 (SCS-MP2) method and a density functional theory method empirically corrected for dispersion (DFT-D) reproduce fairly well the results of high level calculations and therefore were employed for studying the larger systems, though DFT-D seems to underestimate the interaction in hydrogen sulfide clusters. Water complexes in mode A have interaction energies that hardly change with the size of the hydrocarbon due to compensation between the increase in the correlation contribution to the interaction energy and the increase in the repulsive character of the Hartree-Fock energy. For all the other clusters studied, there is a continuous increase in the intensity of the interaction as the size of the hydrocarbon increases, suggesting already converged values for circumcoronene. The interaction energy for water clusters extrapolated to an infinite number of carbon atoms amounts to -13.0 and -15.8 kJ/mol with SCS-MP2 and DFT-D, respectively. Hydrogen sulfide interacts more strongly than water with the hydrocarbons studied, leading to a limiting value of -21.7 kJ/mol with the SCS-MP2 method. Also, complexes in mode B are less stable than the corresponding A structures, with interaction energies amounting to -8.2 and -18.2 kJ/mol for water and hydrogen sulfide

  12. Cross coupling of dialkylmagnesium derivatives with allylic compounds catalyzed by copper salts

    SciTech Connect

    Ibragimov, A.G.; Dzhemilev, U.M.; Saraev, R.A.

    1985-07-20

    The reaction of allylic compounds with Grignard reagents catalyzed by salts of copper, nickel, iron and cobalt, titanium and palladium is a simple and efficient method for the preparation of unsaturated hydrocarbons. However, information concerning the use of dialkylmagnesium derivatives, which are more reactive than Grignard reagents, is extremely limited in these reactions. To continue a study of the cross-coupling of allylic compounds with dialkylmagnesium derivatives in an effort to expand the scope of this reaction and to elucidate the effect of the R/sub 2/Mg reagent structure on its reactivity, the authors investigated the reaction of dialkylmagnesium and diarlmagnesium reagents with allylic ethers and esters, thioethers, and amines, by the action of transition metal salts. This work demonstrates the feasibility of the preparation of unsaturated hydrocarbons of given structure by the cross-coupling of dialkylmagnesium derivatives with functional allylic compounds by the action of catalytic amounts of copper complexes.

  13. Iridium-Catalyzed Enantioselective Allylic Substitution of Enol Silanes from Vinylogous Esters and Amides.

    PubMed

    Chen, Ming; Hartwig, John F

    2015-11-01

    The enol silanes of vinylogous esters and amides are classic dienes for Diels-Alder reactions. Here, we report their reactivity as nucleophiles in Ir-catalyzed, enantioselective allylic substitution reactions. A variety of allylic carbonates react with these nucleophiles to give allylated products in good yields with high enantioselectivities and excellent branched-to-linear ratios. These reactions occur with KF or alkoxide as the additive, but mechanistic studies suggest that these additives do not activate the enol silanes. Instead, they serve as bases to promote the cyclometalation to generate the active Ir catalyst. The carbonate anion, which was generated from the oxidative addition of the allylic carbonate, likely activates the enol silanes to trigger their activity as nucleophiles for reactions with the allyliridium electrophile. The synthetic utility of this method was illustrated by the synthesis of the anti-muscarinic drug, fesoterodine. PMID:26441002

  14. Synthesis of acrylic and allylic bifunctional cross-linking monomers derived from PET waste

    NASA Astrophysics Data System (ADS)

    Cruz-Aguilar, A.; Herrera-González, A. M.; Vázquez-García, R. A.; Navarro-Rodríguez, D.; Coreño, J.

    2013-06-01

    An acrylic and two novel allylic monomers synthesized from bis (hydroxyethyl) terephthalate, BHET, are reported. This was obtained by glycolysis of post-consumer PET with boiling ethylene glycol. The bifunctional monomer bis(2-(acryloyloxy)ethyl) terephthalate was obtained from acryloyl chloride, while the allylic monomers 2-(((allyloxi)carbonyl)oxy) ethyl (2-hydroxyethyl) terephthalate and bis(2-(((allyloxi)carbonyl)oxy)ethyl) terephthalate, from allyl chloroformate. Cross-linking was studied in bulk polymerization using two different thermal initiators. Monomers were analyzed by means of 1H NMR and the cross-linked polymers by infrared spectroscopy. Gel content higher than 90% was obtained for the acrylic monomer. In the case of the mixture of the allylic monomers, the cross-linked polymer was 80 % using BPO initiator, being this mixture 24 times less reactive than the acrylic monomer.

  15. Electron Microscopy Study of Exotic Nanostructures of Cadmium Sulfide

    NASA Astrophysics Data System (ADS)

    Dong, Lifeng; Jiao, Jun

    2005-04-01

    In this article, two simple methods, evaporation-condensation and catalytic thermal evaporation, were used to investigate the synthesis of CdS nanostructures for nanoscale optoelectronic applications. To understand their growth mechanisms, various electron microscopy and microanalysis techniques were utilized in characterizing their morphologies, internal structures, growth directions and elemental compositions. The electron microscopy study reveals that when using the evaporation-condensation method, branched CdS nanorods and self-assembled arrays of CdS nanorods were synthesized at 800°C and 1000°C, respectively. Instead of morphological differences, both types of CdS nanorods grew along the [0001] direction. However, when using the catalytic thermal evaporation method (Au as the catalyst), patterned CdS nanowires and nanobelts were formed at the temperature region of 500 600°C and 600 750°C, respectively. Their growth direction was along the direction [1010] instead of [0001]. Based on the microscopy and microanalysis results, we propose some growth mechanisms in relation to the growth processes of those exotic CdS nanostructures.

  16. Molecular Beam Optical Study of Gold Sulfide and Gold Oxide

    NASA Astrophysics Data System (ADS)

    Zhang, Ruohan; Yu, Yuanqin; Steimle, Timothy

    2016-06-01

    Gold-sulfur and gold-oxygen bonds are key components to numerous established and emerging technologies that have applications as far ranging as medical imaging, catalysis, electronics, and material science. A major theoretical challenge for describing this bonding is correctly accounting for the large relativistic and electron correlation effects. Such effects are best studied in diatomic, AuX, molecules. Recently, the observed AuS electronic state energy ordering was measured and compared to a simple molecular orbital diagram prediction. Here we more thoroughly investigate the nature of the electronic states of both AuS and AuO from the analysis of high-resolution (FWHM\\cong35MHz) optical Zeeman spectroscopy of the (0,0){B}2Σ--{X}2Π3/2 bands. The determined fine and hyperfine parameters for the {B}2Σ- state of AuO differ from those extracted from the analysis of a hot, Doppler-limited, spectrum. It is demonstrated that the nature of the {B}2Σ- states of AuO and AuS are radically different. The magnetic tuning of AuO and AuS indicates that the {B}2Σ- states are heavily contaminated. Supported by the National Science Foundation under Grant No.1265885. D. L. Kokkin, R. Zhang, T. C. Steimle, I. A. Wyse, B. W. Pearlman and T. D. Varberg, J. Phys. Chem. A., 119(48), 4412, 2015. L. C. O'Brien, B. A. Borchert, A. Farquhar, S. Shaji, J. J. O'Brien and R. W. Field, J. Mol. Spectrosc., 252(2), 136, 2008

  17. Hemolytic anemia and induction of phase II detoxification enzymes by diprop-1-enyl sulfide in rats: dose-response study.

    PubMed

    Munday, Rex; Munday, Christine M; Munday, John S

    2005-12-14

    Epidemiological evidence indicates that a high dietary intake of plants of the Allium family, such as garlic and onions, is associated with a decreased risk of cancer in humans. It has been suggested that this chemopreventative effect involves the ability of the aliphatic sulfides derived from these vegetables to increase tissue activities of phase II detoxification enzymes. Several highly effective inducers from garlic have been identified, but most of the previously studied compounds from onion have proved to be only weakly active. In the present study, the inductive activity of another onion-derived sulfide, diprop-1-enyl sulfide, has been investigated. This substance was a potent inducer of phase II enzymes in rats, showing significant effects in the lungs and in the lower part of the gastrointestinal tract, suggesting that diprop-1-enyl sulfide could be a useful chemopreventative agent at these sites. At high dose levels, diprop-1-enyl sulfide caused hemolytic anemia, which may be due to in vivo conversion of the sulfide to active metabolites. PMID:16332117

  18. The effects of γ-irradiation on garlic oil content in garlic bulbs and on the radiolysis of allyl trisulfide

    NASA Astrophysics Data System (ADS)

    Genshuan, Wei; Guanghui, Wang; Ruipu, Yang; Jilan, Wu

    1996-02-01

    A study of the effects of γ-radiation on garlic oil content in garlic bulbs and on the radiolysis of allyl trisulfide and disulfide was carried out. The content of garlic oil in fresh garlic bulbs treated by gamma ray keeps nearly constant when stored for 10 months. The main components of garlic oil are allyl trisulfide (about 60%) and allyl disulfide (about 30%). The G values of radiolysis products of allyl disulfide and trisulfide in ethanol system were determined. The results show that allyl trisulfide is a very effective solvated electron scavenger and can oxidize CH 3CHOH radical into acetaldehyde, which means that the formation of 2,3-butanediol is extensively inhibited.

  19. Copper-Catalyzed Enantioselective Allyl-Allyl Coupling between Allylic Boronates and Phosphates with a Phenol/N-Heterocyclic Carbene Chiral Ligand.

    PubMed

    Yasuda, Yuto; Ohmiya, Hirohisa; Sawamura, Masaya

    2016-08-26

    Copper-catalyzed enantioselective allyl-allyl coupling between allylboronates and either Z-acyclic or cyclic allylic phosphates using a new chiral N-heterocyclic carbene ligand, bearing a phenolic hydroxy, is reported. This reaction occurs with exceptional SN 2'-type regioselectivities and high enantioselectivities to deliver chiral 1,5-diene derivatives with a tertiary stereogenic center at the allylic/homoallylic position. PMID:27467163

  20. Structure-Activity Relationship Study on Isothiocyanates: Comparison of TRPA1-Activating Ability between Allyl Isothiocyanate and Specific Flavor Components of Wasabi, Horseradish, and White Mustard.

    PubMed

    Terada, Yuko; Masuda, Hideki; Watanabe, Tatsuo

    2015-08-28

    Allyl isothiocyanate (ITC) (4) is the main pungent component in wasabi, and it generates an acrid sensation by activating TRPA1. The flavor and pungency of ITCs vary depending on the compound. However, the differences in activity to activate TRPA1 between ITCs are not known except for a few compounds. To investigate the effect of carbon chain length and substituents of ITCs, the TRPA1-activiting ability of 16 ITCs was measured. Since most of the ITCs showed nearly equal TRPA1-activiting potency, the ITC moiety is likely the predominant contributor to their TRPA1-activating abilities, and contributions of other functional groups to their activities to activate TRPA1 are comparatively small.

  1. N-Allylation of amines with allyl acetates using chitosan-immobilized palladium

    EPA Science Inventory

    A simple procedure for N-Allylation of allyl Acetates has been developed using a biodegradable and easily recyclable heterogeneous chitosan-supported palladium catalyst. The general methodology, applicable to wide range of substrates, has sustainable features that include a ligan...

  2. Novel palladium complex-catalyzed reaction of magnesium amides with allylic electrophiles

    SciTech Connect

    Dzhemilev, U.M.; Ibragimov, A.G.; Minsker, D.L.; Muslukhov, R.R.

    1987-08-20

    In order to develop an efficient method for the synthesis of higher order unsaturated tertiary amines, and also to explore a new method for the formation of C-N bonds, they have investigated the transition metal complex-catalyzed reaction of magnesium amides with electrophiles; the electrophiles selected for study included allyl ethers and esters, as well as sulfones, sulfides and quaternized allylamines. The effects of the nature and structure of the catalyst components, as well as of the reaction conditions, on product yield were examined in the case of the reaction of diethyl (bromomagnesium)amine with diallyl ether, and revealed that the highest yield of diethylallyl-amine (I) was achieved using Pd(acac)/sub 2/ (3-5 mole %) and Ph/sub 3/P (1:2) as catalyst in THF solution at 50/sup 0/C for 5 h. Other transition metal (Ni, Fe, Zr, Ti, Cu) compounds were also examined as catalysts, but the yield of (I) did not exceed 15% with these compounds. Bimetallic catalysts based on Zr (Cp/sub 2/ZrCl, Py/sub 2/ZrCl/sub 6/, (RO)/sub 4/Zr) and Ni (Ni(acac)/sub 2/ and NiCl/sub 2/) were successful in forming (I) from diethyl (bromomagnesium)amine and diallyl ether in 60% yield.

  3. Asymmetric synthesis of N-allylic indoles via regio- and enantioselective allylation of aryl hydrazines

    PubMed Central

    Xu, Kun; Gilles, Thomas; Breit, Bernhard

    2015-01-01

    The asymmetric synthesis of N-allylic indoles is important for natural product synthesis and pharmaceutical research. The regio- and enantioselective N-allylation of indoles is a true challenge due to the favourable C3-allylation. We develop here a new strategy to the asymmetric synthesis of N-allylic indoles via rhodium-catalysed N-selective coupling of aryl hydrazines with allenes followed by Fischer indolization. The exclusive N-selectivities and good to excellent enantioselectivities are achieved applying a rhodium(I)/DTBM-Segphos or rhodium(I)/DTBM-Binap catalyst. This method permits the practical synthesis of valuable chiral N-allylated indoles, and avoids the N- or C-selectivity issue. PMID:26137886

  4. Selenium Sulfide

    MedlinePlus

    Selenium sulfide comes in a lotion and is usually applied as a shampoo. As a shampoo, selenium sulfide usually is used twice a week for the first ... it is irritating. Rinse off all of the lotion.Do not use this medication on children younger ...

  5. Structural evolution and stabilities of neutral and anionic clusters of lead sulfide: joint anion photoelectron and computational studies.

    PubMed

    Koirala, Pratik; Kiran, Boggavarapu; Kandalam, Anil K; Fancher, Charles A; de Clercq, Helen L; Li, Xiang; Bowen, Kit H

    2011-10-01

    The geometric and electronic structures of both neutral and negatively charged lead sulfide clusters, (PbS)(n)/(PbS)(n)(-) (n = 2-10) were investigated in a combined anion photoelectron spectroscopy and computational study. Photoelectron spectra provided vertical detachment energies (VDEs) for the cluster anions and estimates of electron affinities (EA) for their neutral cluster counterparts, revealing a pattern of alternating EA and VDE values in which even n clusters exhibited lower EA and VDE values than odd n clusters up until n = 8. Computations found neutral lead sulfide clusters with even n to be thermodynamically more stable than their immediate (odd n) neighbors, with a consistent pattern also being found in their HOMO-LUMO gaps. Analysis of neutral cluster dissociation energies found the Pb(4)S(4) cube to be the preferred product of the queried fragmentation processes, consistent with our finding that the lead sulfide tetramer exhibits enhanced stability; it is a magic number species. Beyond n = 10, computational studies showed that neutral (PbS)(n) clusters in the size range, n = 11-15, prefer two-dimensional stacking of face-sharing lead sulfide cubical units, where lead and sulfur atoms possess a maximum of five-fold coordination. The preference for six-fold coordination, which is observed in the bulk, was not observed at these cluster sizes. Taken together, the results show a preference for the formation of slightly distorted, fused cuboids among small lead sulfide clusters.

  6. In-situ STM study of sulfide adsorption on Au(100) in alkaline solution

    NASA Astrophysics Data System (ADS)

    Schlaup, Christian; Wandelt, Klaus

    2015-01-01

    The adsorption of sulfide on a Au(100) electrode from a 0.01 M NaOH + 0.5 mM Na2S electrolyte was studied by in situ scanning tunneling microscopy (STM) and cyclic voltammetry (CV). Starting with a sulfur free electrode surface at low potentials the subsequent formation of a p(2 × 2)-S, a c(2 × 6)-S and a c(2 × 2)-S phase was observed during potential increase. Only the p(2 × 2)-S (ΘS = 0.25 ML) phase appears as a single species phase; the c(2 × 6)-S (ΘS = 0.33 ML) and the c(2 × 2)-S (ΘS = 0. 5 ML) phase are accompanied by the simultaneous appearance of additional "dimer" particles. Concomitant changes of the step morphology and the results of the electrochemical characterization strongly suggest that these additional particles contain both, sulfur and gold atoms. Upon further potential increase the formation of a phase consisting of ring-like units was found, which is well known for Au(111) surfaces in the presence of sulfur. This phase is, by analogy, interpreted as a gold sulfide compound formed under electrochemical conditions.

  7. Bacterial leaching of a sulfide ore by Thiobacillus ferrooxidans and Thiobacillus thiooxidans: I. Shake flask studies.

    PubMed

    Lizama, H M; Suzuki, I

    1988-06-20

    Bacterial leaching of a sulfide ore containing pyrite, chalcopyrite, and sphalerite was studied in shake flask experiments using Thiobacillus ferrooxidans and Thiobacillus thiooxidans strains isolated from mine sites. The Fe(2+)grown T. ferrooxidans isolates solubilized sphalerite preferentially over chalcopyrite leaching 7-10% Cu, 68-76% Zn, and 10-22% Fe from the ore in 18 days. The sulfur grown T. thiooxidans isolates leached Zn much more slowly and very little Fe, with a Cu-Zn extraction ratio twice the value obtained with T. ferrooxidans. The ore adapted T. ferrooxidans started solubilizing Cu and Zn without a lag period. The ore-adapted T. thiooxidans extracted Cu as well as T. ferrooxidans, but the extraction of Zn or Fe was still much slower in the low-phosphate medium, while in the high-phosphate medium it approached the value obtained with T. ferrooxidans. A high Cu-Zn extraction ratio of 0.34 was obtained with T. thiooxidans in the low phosphate medium. In the mixed-culture experiments with T. ferrooxidans and T. thiooxidans, the culture behaved as T. thiooxidans in the low-phosphate medium with a higher Cu-Zn extraction ratio and as T. ferrooxidans in the high-phosphate medium with a lower Cu-Zn extraction ratio. It is concluded that T. ferrooxidans and T. thiooxidans solubilize sulfide minerals by different mechanisms.

  8. Transition‐Metal‐Free Borylation of Allylic and Propargylic Alcohols

    PubMed Central

    Miralles, Núria; Alam, Rauful

    2016-01-01

    Abstract The base‐catalyzed allylic borylation of tertiary allylic alcohols allows the synthesis of 1,1‐disubstituted allyl boronates, in moderate to high yield. The unexpected tandem performance of the Lewis acid–base adduct, [Hbase]+[MeO‐B2pin2]− favored the formation of 1,2,3‐triborylated species from the tertiary allylic alcohols and 1‐propargylic cyclohexanol at 90 °C. PMID:26934578

  9. Solubility, stability, and electrochemical studies of sulfur-sulfide solutions in organic solvents

    NASA Technical Reports Server (NTRS)

    Fielder, W. L.; Singer, J.

    1978-01-01

    A preliminary study of the sulfur electrode in organic solvents suggests that the system warrants further investigation for use in a low temperature (100 deg to 120 C) Na-S secondary battery. A qualitative screening was undertaken at 120 C to determine the solubilities and stabilities of Na2S and Na2S2 in representatives of many classes of organic solvents. From the screening and quantitative studies, two classes of solvents were selected for work; amides and cyclic polyalcohols. Voltammetric and Na-S cell charge discharge studies of sulfide solutions in organic solvents (e.g., N, N-dimethylformamide) at 120 C suggested that the reversibilities of the reactions on Pt or high density graphite were moderately poor. However, the sulfur electrode was indeed reducible (and oxidizable) through the range of elemental sulfur to Na2S. Reactions and mechanisms are proposed for the oxidation reduction processes occurring at the sulfur electrode.

  10. A comparative study of antioxidants S-allyl cysteine sulfoxide and vitamin E on the damages induced by nicotine in rats.

    PubMed

    Helen, A; Krishnakumar, K; Vijayammal, P L; Augusti, K T

    2003-03-01

    The dietary consumption of antioxidant-rich fruits and vegetables is inversely correlated with the incidence of various diseases like cardiovascular diseases and lung cancer. We have tried to find out how far the S-allyl cysteine sulfoxide (SACS) isolated from garlic (Allium Sativum L.) can combat the nicotine-induced peroxidative damage in rats. The effects have been compared with the standard antioxidant vitamin E. Administration of SACS or vitamin E (100 mg/kg) to nicotine (0.6 mg/kg) treated rats for 21 days showed decreased concentrations of thiobarbituric acid reactive substances, hydroperoxides, and conjugated dienes in liver, lungs, and heart as compared with the values found in rats treated with nicotine alone. The activities of catalase and superoxide dismutase increased. The levels of the antioxidants like vitamins A, C, and E in the liver and glutathione in all tissues increased significantly in SACS-treated or vitamin E fed rats. However, the antioxidant status was higher when vitamin E was administered as compared with SACS administered to nicotine-treated rats. PMID:12571405

  11. A novel method for improving cerussite sulfidization

    NASA Astrophysics Data System (ADS)

    Feng, Qi-cheng; Wen, Shu-ming; Zhao, Wen-juan; Cao, Qin-bo; Lü, Chao

    2016-06-01

    Evaluation of flotation behavior, solution measurements, and surface analyses were performed to investigate the effects of chloride ion addition on the sulfidization of cerussite in this study. Micro-flotation tests indicate that the addition of chloride ions prior to sulfidization can significantly increase the flotation recovery of cerussite, which is attributed to the formation of more lead sulfide species on the mineral surface. Solution measurement results suggest that the addition of chloride ions prior to sulfidization induces the transformation of more sulfide ions from pulp solution onto the mineral surface by the formation of more lead sulfide species. X-ray diffraction and energy-dispersive spectroscopy indicate that more lead sulfide species form on the mineral surface when chloride ions are added prior to sulfidization. These results demonstrate that the addition of chloride ions prior to sulfidization can significantly improve the sulfidization of cerussite, thereby enhancing the flotation performance.

  12. Liquid immiscibility between arsenide and sulfide melts: evidence from a LA-ICP-MS study in magmatic deposits at Serranía de Ronda (Spain)

    NASA Astrophysics Data System (ADS)

    Piña, R.; Gervilla, F.; Barnes, S.-J.; Ortega, L.; Lunar, R.

    2015-03-01

    The chromite-Ni arsenide (Cr-Ni-As) and sulfide-graphite (S-G) deposits from the Serranía de Ronda (Málaga, South Spain) contain an arsenide assemblage (nickeline, maucherite and nickeliferous löllingite) that has been interpreted to represent an arsenide melt and a sulfide-graphite assemblage (pyrrhotite, pentlandite, chalcopyrite and graphite) that has been interpreted to represent a sulfide melt, both of which have been interpreted to have segregated as immiscible liquids from an arsenic-rich sulfide melt. We have determined the platinum-group element (PGE), Au, Ag, Se, Sb, Bi and Te contents of the arsenide and sulfide assemblages using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to establish their partitioning behaviour during the immiscibility of an arsenide melt from a sulfide melt. Previous experimental work has shown that PGE partition more strongly into arsenide melts than into sulfide melts and our results fit with this observation. Arsenide minerals are enriched in all PGE, but especially in elements with the strongest affinity for the arsenide melt, including Ir, Rh and Pt. In contrast and also in agreement with previous studies, Se and Ag partition preferentially into the sulfide assemblage. The PGE-depleted nature of sulfides in the S-G deposits along with the discordant morphologies of the bodies suggest that these sulfides are not mantle sulfides, but that they represent the crystallization product of a PGE-depleted sulfide melt due to the sequestering of PGE by an arsenide melt.

  13. Study of electrical and thermoelecrical properties of sulfides Tm x Mn1- x S

    NASA Astrophysics Data System (ADS)

    Aplesnin, S. S.; Romanova, O. B.; Galyas, A. I.; Sokolov, V. V.

    2016-01-01

    Variable-valence Tm x Mn1- x S (0 ⩽ x ⩽ 0.15) compounds have been synthesized and their structural, electrical, and thermoelectrical properties have been studied in the temperature range of 80-1100 K. The regions of existence of solid solutions of sulfides Tm x Mn1- x S with the NaCl-type fcc lattice have been determined. It has been found that, as thulium ions are substituted for manganese cations, the electrical resistivity increases, and the lattice parameter increases more sharply than that corresponding to the Vegard's law. The study of the temperature dependences of the thermopower coefficient has revealed that the current carrier sign is retained to 500 K for all the substitution concentrations, and the charge carrier type changes from the hole type to the electron type with variations in the temperature. The experimental data have been explained in terms of the exciton model.

  14. Acidification and sulfide formation control during reductive dechlorination of 1,2-dichloroethane in groundwater: Effectiveness and mechanistic study.

    PubMed

    Wang, S Y; Chen, S C; Lin, Y C; Kuo, Y C; Chen, J Y; Kao, C M

    2016-10-01

    To enhance the reductive dechlorination of 1,2-dichloroethane (DCA) in groundwater, substrate injection may be required. However, substrate biodegradation causes groundwater acidification and sulfide production, which inhibits the bacteria responsible for DCA dechlorination and results in an odor problem. In the microcosm study, the effectiveness of the addition of ferrous sulfate (FS), desulfurization slag (DS), and nanoscale zero-valent iron (nZVI) on acidification and sulfide control was studied during reductive dechlorination of DCA, and the emulsified substrate (ES) was used as the substrate. Up to 94% of the sulfide was removed with FS and DS addition (0.25 wt%) (initial DCA concentration = 13.5 mg/L). FS and DS amendments resulted in the formation of a metal sulfide, which reduced the hydrogen sulfide concentration as well as the subsequent odor problem. Approximately 96% of the DCA was degraded under reductive dechlorination with nZVI or DS addition using ES as the substrate. In microcosms with nZVI or DS addition, the sulfide concentration was reduced to less than 15 μg/L. Acidification can be controlled via hydroxide ions production after nZVI oxidation and reaction of free CaO (released from DS) with water, which enhanced DCA dechlorination. The quantitative polymerase chain reaction results confirmed that the microcosms with nZVI added had the highest Dehalococcoides population (up to 2.5 × 10(8) gene copies/g soil) due to effective acidification control. The α-elimination mechanism was the main abiotic process, and reductive dechlorination dominated by Dehalococcides was the biotic mechanism that resulted in DCA removal. More than 22 bacterial species were detected, and dechlorinating bacteria existed in soils under alkaline and acidic conditions. PMID:27376861

  15. Acidification and sulfide formation control during reductive dechlorination of 1,2-dichloroethane in groundwater: Effectiveness and mechanistic study.

    PubMed

    Wang, S Y; Chen, S C; Lin, Y C; Kuo, Y C; Chen, J Y; Kao, C M

    2016-10-01

    To enhance the reductive dechlorination of 1,2-dichloroethane (DCA) in groundwater, substrate injection may be required. However, substrate biodegradation causes groundwater acidification and sulfide production, which inhibits the bacteria responsible for DCA dechlorination and results in an odor problem. In the microcosm study, the effectiveness of the addition of ferrous sulfate (FS), desulfurization slag (DS), and nanoscale zero-valent iron (nZVI) on acidification and sulfide control was studied during reductive dechlorination of DCA, and the emulsified substrate (ES) was used as the substrate. Up to 94% of the sulfide was removed with FS and DS addition (0.25 wt%) (initial DCA concentration = 13.5 mg/L). FS and DS amendments resulted in the formation of a metal sulfide, which reduced the hydrogen sulfide concentration as well as the subsequent odor problem. Approximately 96% of the DCA was degraded under reductive dechlorination with nZVI or DS addition using ES as the substrate. In microcosms with nZVI or DS addition, the sulfide concentration was reduced to less than 15 μg/L. Acidification can be controlled via hydroxide ions production after nZVI oxidation and reaction of free CaO (released from DS) with water, which enhanced DCA dechlorination. The quantitative polymerase chain reaction results confirmed that the microcosms with nZVI added had the highest Dehalococcoides population (up to 2.5 × 10(8) gene copies/g soil) due to effective acidification control. The α-elimination mechanism was the main abiotic process, and reductive dechlorination dominated by Dehalococcides was the biotic mechanism that resulted in DCA removal. More than 22 bacterial species were detected, and dechlorinating bacteria existed in soils under alkaline and acidic conditions.

  16. Asymmetric synthesis of allylic sulfonic acids: enantio- and regioselective iridium-catalyzed allylations of Na2SO3.

    PubMed

    Liu, Wei; Zhao, Xiao-ming; Zhang, Hong-bo; Zhang, Liang; Zhao, Ming-zhu

    2014-12-15

    An enantioselective allylation reaction of allylic carbonates with sodium sulfite (Na2 SO3 ) catalyzed by Ir complex was accomplished, providing allylic sulfonic acids in good to excellent yields with a high level of enantio- and regioselectivities. (R)-2-Phenyl-2-sulfoacetic acid, a key intermediate for the synthesis of Cefsulodin and Sulbenicillin, was synthesized as well.

  17. Asymmetric synthesis of allylic sulfonic acids: enantio- and regioselective iridium-catalyzed allylations of Na2SO3.

    PubMed

    Liu, Wei; Zhao, Xiao-ming; Zhang, Hong-bo; Zhang, Liang; Zhao, Ming-zhu

    2014-12-15

    An enantioselective allylation reaction of allylic carbonates with sodium sulfite (Na2 SO3 ) catalyzed by Ir complex was accomplished, providing allylic sulfonic acids in good to excellent yields with a high level of enantio- and regioselectivities. (R)-2-Phenyl-2-sulfoacetic acid, a key intermediate for the synthesis of Cefsulodin and Sulbenicillin, was synthesized as well. PMID:25367779

  18. Preliminary study of the electrolysis of aluminum sulfide in molten salts

    SciTech Connect

    Minh, N.Q.; Loutfy, R.O.; Yao, N.P.

    1983-02-01

    A preliminary laboratory-scale study of the electrolysis of aluminum sulfide in molten salts investigated the (1) solubility of Al/sub 2/S/sub 3/ in molten salts, (2) electrochemical behavior of Al/sub 2/S/sub 3/, and (3) electrolysis of Al/sub 2/S/sub 3/ with the determination of current efficiency as a function of current density. The solubility measurements show that MgCl/sub 2/-NaCl-KCl eutectic electrolyte at 1023 K can dissolve up to 3.3 mol % sulfide. The molar ratio of sulfur to aluminum in the eutectic is about one, which suggests that some sulfur remains undissolved, probably in the form of MgS. The experimental data and thermodynamic calculations suggest that Al/sub 2/S/sub 3/ dissolves in the eutectic to form AlS/sup +/ species in solution. Addition of AlCl/sub 3/ to the eutectic enhances the solubility of Al/sub 2/S/sub 3/; the solubility increases with increasing AlCl/sub 3/ concentration. The electrode reaction mechanism for the electrolysis of Al/sub 2/S/sub 3/ was elucidated by using linear sweep voltammetry. The cathodic reduction of aluminum-ion-containing species to aluminum proceeds by a reversible, diffusion-controlled, three-electron reaction. The anodic reaction involves the two-electron discharge of sulfide-ion-containing species, followed by the fast dimerization of sulfur atoms to S/sub 2/. Electrolysis experiments show that Al/sub 2/S/sub 3/ dissolved in molten MgCl/sub 2/-NaCl-KCl eutectic or in eutectic containing AlCl/sub 3/ can be electrolyzed to produce aluminum and sulfur. In the eutectic at 1023 K, the electrolysis can be conducted up to about 300 mA/cm/sup 2/ for the saturation solubility of Al/sub 2/S/sub 3/. Although these preliminary results are promising, additional studies are needed to elucidate many critical operating parameters before the technical potential of the electrolysis can be accurately assessed. 20 figures, 18 tables.

  19. Experimental Studies on the Sulfide Capacities of CaO-SiO2-CrOx Slags

    NASA Astrophysics Data System (ADS)

    Wang, Lijun; Seetharaman, Seshadri

    2010-04-01

    To understand the desulfurization process during the refining of Cr-containing steel grades, this work was initiated to study the reactions between Cr-sulfur and chromium-containing slags. The sulfide capacities of CaO-SiO2-CrOx pseudo-ternary slags were measured using the traditional gas-slag equilibration technique between 1823 K and 1923 K. Sixteen different slag compositions were examined, and two different equilibrium oxygen partial pressures were used to understand the impact of the varying valence of Cr on the sulfide capacities. The results showed that log10 Cs varied linearly with the reciprocal T, and the slope was higher than the corresponding value reported for the binary CaO-SiO2 of corresponding composition. It was difficult to isolate the relative effects of the bi- and trivalent Cr in the slags because the Cr2+/Cr3+ ratio was influenced by the basicity of the slag. By using the equation developed by these authors earlier that related Cr2+/Cr3+ with basicity, oxygen partial pressure, and temperature, it was possible to obtain an approximate trend of the CrO effect on the sulfide capacities; viz. the sulfide shows a decreasing trend as Cr2+ replaces Ca2+ in the slag. With a continued increase of Cr2+ content, indications of the occurrence of a minimum point were observed; beyond which the sulfide capacities showed a slight increasing trend. The latter was attributed, based on slag-structure analysis by Gaskell et al., to the increasing extent of the polymerization reaction releasing oxygen ions for sulfide reactions.

  20. Cadmium Telluride, Cadmium Telluride/Cadmium Sulfide Core/Shell, and Cadmium Telluride/Cadmium Sulfide/Zinc Sulfide Core/Shell/Shell Quantum Dots Study

    NASA Astrophysics Data System (ADS)

    Yan, Yueran

    aqueous phase can quench CdTe/CdS QDs. Additionally, the stability of the different ligands capped CdTe/CdS QDs was tested by dialysis measurement, the hydrodynamic diameters of CdTe and CdTe/CdS core/shell QDs were measured by dynamic light scattering, and dissolving issue was found when CdTe and CdTe/CdS core/shell QDs were diluted in CHCl3. We have characterized the CdTe core and the CdTe/CdS core/shell QDs by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), small angle X-ray scattering (SAXS), and ICP-OES measurements. We have found that the CdTe core was of a zincblende structure, and the shell was a wurtzite structure. And the CdTe/CdS QDs were core/shell QDs instead of alloying QDs. We have also analyzed the photophysical properties of CdTe and CdTe/CdS core/shell QDs. Time-resolved photoluminescence (PL) measurements showed the emission decay lifetimes in the tens of nanoseconds. Additionally, ultrafast charge carrier relaxation dynamics of the CdTe core and CdTe/CdS core/shell QDs were studied by the femtosecond transient absorption (TA) spectroscopy. The transient absorption spectra of CdTe and CdTe/CdS core/shell QDs showed multiple bleaches, which have been assigned to the 1S3/2(h)-1S(e), 2S3/2(h)-1S(e), and 1P3/2(h)-1P(e) transitions. The spectral shifts of these bleaches after shell deposition have been analyzed in the context of a quasi-type-II carrier distribution in the core/shell samples, and interestingly the red shift was only contributed from the conduction band energy levels shifting to lower energy. In addition, the ultrafast evolution of these bleach features has been examined to extract electron cooling rates in these samples. A fast decay component in the 1S3/2(h)-1S(e) transition of the small CdTe QDs was discovered due to the hole being trapped by the defects on the surface of QD. Further, we have studied the PL quenching process of the air exposed CdTe QDs via the PL decay and transient absorption measurements. Oxygen

  1. Evaluation of thiosulfate as a substitute for hydrogen sulfide in sour corrosion fatigue studies

    NASA Astrophysics Data System (ADS)

    Kappes, Mariano Alberto

    This work evaluates the possibility of replacing hydrogen sulfide (H 2S) with thiosulfate anion (S2O32- ) in sour corrosion fatigue studies. H2S increases the corrosion fatigue crack growth rate (FCGR) and can be present in carbon steel risers and flowlines used in off-shore oil production. Corrosion tests with gaseous H2S require special facilities with safety features, because H2S is a toxic and flammable gas. The possibility of replacing H2S with S2O32-, a non-toxic anion, for studying stress corrosion cracking of stainless and carbon steels in H2S solutions was first proposed by Tsujikawa et al. ( Tsujikawa et al., Corrosion, 1993. 49(5): p. 409-419). In this dissertation, Tsujikawa work will be extended to sour corrosion fatigue of carbon steels. H2S testing is often conducted in deareated condition to avoid oxygen reaction with sulfide that yields sulfur and to mimic oil production conditions. Nitrogen deareation was also adopted in S2O3 2- testing, and gas exiting the cell was forced through a sodium hydroxide trap. Measurements of the sulfide content of this trap were used to estimate the partial pressure of H2S in nitrogen, and Henry's law was used to estimate the content of H2S in the solution in the cell. H2S was produced by a redox reaction of S2O 32-, which required electrons from carbon steel corrosion. This reaction is spontaneous at the open circuit potential of steel. Therefore, H2S concentration was expected to be maximum at the steel surface, and this concentration was estimated by a mass balance analysis. Carbon steel specimens exposed to S2O32- containing solutions developed a film on their surface, composed by iron sulfide and cementite. The film was not passivating and a good conductor of electrons. Hydrogen permeation experiments proved that this film controls the rate of hydrogen absorption of steels exposed to thiosulfate containing solutions. The absorption of hydrogen in S2O3 2- solutions was compared with the absorption of hydrogen in

  2. First principles study of transition metal (TM=Pb, Cu) oxides/sulfides

    NASA Astrophysics Data System (ADS)

    Caudle, Sean; Tao, Meng; Peng, Xihong

    2012-10-01

    Earth-abundant transition meal oxides/sulfides have inspired special research attention recently due to their potential applications in solar cells. A clear understanding of the fundamental properties of these materials, especially the electronic properties and their tunability via chemical doping, are critically important towards the applications. In this presentation, we report first principles density-functional theory (DFT) study on the electronic structures of Pb and Cu oxides/sulfides and their oxysulfides compositions. The band structure and bandgap can be systematically tuned by increasing S component in the metal oxides. For example, the DFT predicted bandgap for PbO is 1.72 eV. While the bandgaps for PbO0.937 S0.063, PbO0.875S0.125, and PbO0.75S0.25 are 1.64 eV, 1.43 eV, and 0.79 eV, respectively. For Cu2O, the standard DFT seriously underestimates the bandgap to be 0.49 eV, compared to the experimental value of 2.17 eV. Two methods, DFT+U and hybrid functional (HSE06), were implemented to overcome this problem. Our results showed that DFT+U method fails and the bandgap doesn't further open up by providing a U potential. The hybrid functional predicts the bandgap to be 2.00 eV, which is in a good agreement with the experimental value.

  3. A double-blind comparative study of sodium sulfacetamide lotion 10% versus selenium sulfide lotion 2.5% in the treatment of pityriasis (tinea) versicolor.

    PubMed

    Hull, Cheryl A; Johnson, Sandra Marchese

    2004-06-01

    Pityriasis (tinea) versicolor, which consists of hyperpigmented and hypopigmented scaly patches, is often difficult to treat. A double-blind comparative study between once-a-day sodium sulfacetamide lotion and selenium sulfide lotion was undertaken. Both treatments were safe and efficacious. Selenium sulfide was statistically more efficacious (76.2% vs 47.8%, P=.013).

  4. A study on the mechanism of stress corrosion cracking of duplex stainless steels in hot alkaline-sulfide solution

    NASA Astrophysics Data System (ADS)

    Chasse, Kevin Robert

    Duplex stainless steels (DSS) generally have superior strength and corrosion resistance as compared to most standard austenitic and ferritic stainless grades owing to a balanced microstructure of austenite and ferrite. As a result of having favorable properties, DSS have been selected for the construction of equipment in pulp and paper, chemical processing, nuclear, oil and gas as well as other industries. The use of DSS has been restricted in some cases because of stress corrosion cracking (SCC), which can initiate and grow in either the ferrite or austenite phase depending on the environment. Thorough understanding of SCC mechanisms of DSS in chloride- and hydrogen sulfide-containing solutions has been useful for material selection in many environments. However, understanding of SCC mechanisms of DSS in sulfide-containing caustic solutions is limited, which has restricted the capacity to optimize process and equipment design in pulp and paper environments. Process environments may contain different concentrations of hydroxide, sulfide, and chloride, altering corrosion and SCC susceptibility of each phase. Crack initiation and growth behavior will also change depending on the relative phase distribution and properties of austenite and ferrite. The role of microstructure and environment on the SCC of standard grade UNS S32205 and lean grade UNS S32101 in hot alkaline-sulfide solution were evaluated in this work using electrochemical, film characterization, mechanical testing, X-ray diffraction, and microscopy techniques. Microstructural aspects, which included residual stress state, phase distribution, phase ratio, and microhardness, were related to the propensity for SCC crack initiation in different simulated alkaline pulping liquors at 170 °C. Other grades of DSS and reference austenitic and superferritic grades of stainless steel were studied using exposure coupons for comparison to understand compositional effects and individual phase susceptibility

  5. Electrochemical behavior of silver sulfide

    SciTech Connect

    Drouven, B.U.E.

    1982-01-01

    The electrochemical behavior of silver sulfide in sulfuric acid as well as in nitric acid was studied using electrodes made from synthetic silver sulfide. The primary techniques used were potentiostatic, potentiodynamic, galvanostatic and corrosion cell experiments. The cathodic reaction of silver sulfide produces silver and hydrogen sulfide. This reaction mechanism is a sequential two step charge transfer involving a single electron in each step. Silver ions are produced from silver sulfide upon applying an anodic potential. The dissolution rate of silver sulfide can be so high that the formation of silver sulfate occurs which partially covers the silver sulfide surface and inhibits a further rate increase. The sulfur from the silver sulfide will be oxidized at low overpotentials to elemental sulfur; at high overpotentials, the oxidation to sulfate or bisulfate is observed. The results suggest that the catalysis of chalcopyrite by the addition of silver ions is caused by the formation and subsequent dissolution of silver sulfide leaving a porous layer behind. The understanding of the reaction mechanism of silver sulfide dissolution and its optimization will significantly improve the economic evaluation of industrial processes using the catalyzed leaching of chalcopyrite. The present knowledge of the catalysis indicates that other ions may be substituted for silver ions which would increase the feasibility of hydrometallurgical processes.

  6. Stereochemistry of ring-opening/cross metathesis reactions of exo- and endo-7-oxabicyclo[2.2.1]hept-5-ene-2-carbonitriles with allyl alcohol and allyl acetate

    PubMed Central

    Dąbrowski, Michał; Szczepaniak, Lech; Morzycki, Jacek W; Witkowski, Stanisław

    2015-01-01

    Summary The ROCM reactions of exo- and endo-2-cyano-7-oxanorbornenes with allyl alcohol or allyl acetate promoted by different ruthenium alkylidene catalysts were studied. The stereochemical outcome of the reactions was established. The issues concerning chemo- (ROCM vs ROMP), regio- (1-2- vs 1-3-product formation), and stereo- (E/Z isomerism) selectivity of reactions under various conditions are discussed. Surprisingly good yields of the ROCM products were obtained under neat conditions. PMID:26664608

  7. Sulfur isotope study of a modern intertidal environment, and the interpretation of ancient sulfides

    NASA Astrophysics Data System (ADS)

    Chambers, L. A.

    1982-05-01

    Extensive sulfur isotope distribution data for sulfides precipitated in an intertidal environment show no distinctive features when compared with isotope values for other marine, sedimentary sulfides. The fractionation ranges from α = 1.030 to α = 1.048. The pattern is characteristic for a system essentially open to sulfate, and isotope analyses of interstitial sulfates are corroborative. A population of sulfate-reducing bacteria of the order of 10 9 organisms per cc of interstitial water is indicated. Seasonal variation of the isotope distribution reflects a transient sulfide composition and a bacterial population in which the fractionation effect is indirectly controlled by temperature. The data presented for this modern shallow water environment are at variance with an earlier assessment of isotopic distributions in ancient sulfides which linked shallow water environments with limited fractionation (α ⩽ 1.025) in a closed system.

  8. Study of the mechanism of the hydrogen sulfide/dolomite reaction. Final report for the period July 1976-December 1979

    SciTech Connect

    Li, K.; Rogan, F.H.; Yen, J.H.; Huang, C.S.; Spencer, J.L.

    1980-06-01

    The kinetics and structural changes of the basic reactions - half-calcination, sulfidation and carbonation - involved in the cyclic use of dolomite for hot-gas desulfurization were investigated over wide ranges of experimental conditions including the origin of dolomite, pellet size and method of pretreatment. Kinetic data were collected for samples of spherical pellets in a high-temperature/high-pressure thermogravimetric analysis system specifically designed and constructed for this study. Solid-phase structures at various stages of each reaction were analyzed by optical and scanning electron microscopy, energy-dispersive x-ray analysis, nitrogen adsorption, and mercury porosimetry. Based on the kinetic and structural data for each reaction, models were developed and mathematically formulated. Agreement between model and experiment in all cases is generally good. Cyclic experiments of the sulfidation of half-calcined dolomite and the carbonation of sulfided dolomite were also performed. The adsorption capacity of dolomite for hydrogen sulfide was found to decrease at first and remain approximately constant upon continued cycling. However, a 75% utilization of calcium atoms in the dolomite was shown to be possible under certain selected conditions. 33 figures, 4 tables.

  9. Theoretical study of adducts of dimethyl sulfide with hydroperoxyl and hydroxyl radicals

    NASA Astrophysics Data System (ADS)

    Aloisio, Simone

    2006-08-01

    Structures and energies of complexes of dimethyl sulfide (DMS) with hydroxyl (OH) and hydroperoxyl (HO 2) radicals have been studied using ab initio and density functional theory. Two isomers of the complex between OH and DMS were found, one dipole-dipole complex and one 3e -/2c complex. The binding energies ( D0) of these two complexes have been found to be consistent with previous studies. This is the first reported study of the complex between DMS and HO 2. One structure was found for this complex, and the binding energy ( D0) has been determined to be 9.0 kcal mol -1 using the fully optimized MP2/6-311++G(3df,3pd) level of theory. Vibrational and rotational constants are also presented for all of complexes calculated. Thermodynamic parameters and equilibrium constants for the formation of these complexes from the monomers have been calculated. The results have been related to laboratory experiments studying these reactions, and some implications to oxidation of DMS in the atmosphere have been discussed.

  10. A comprehensive study on atomic layer deposition of molybdenum sulfide for electrochemical hydrogen evolution

    NASA Astrophysics Data System (ADS)

    Kwon, Do Hyun; Jin, Zhenyu; Shin, Seokhee; Lee, Wook-Seong; Min, Yo-Sep

    2016-03-01

    Atomic layer deposition (ALD) has emerged as an efficient method to design and prepare catalysts with atomic precision. Here, we report a comprehensive study on ALD of molybdenum sulfide (MoSx) for an electrocatalytic hydrogen evolution reaction. By using molybdenum hexacarbonyl and dimethyldisulfide as the precursors of Mo and S, respectively, the MoSx catalysts are grown at 100 °C on porous carbon fiber papers (CFPs). The ALD process results in the growth of particle-like MoSx on the CFP due to the lack of adsorption sites, and its crystallographic structure is a mixture of amorphous and nano-crystalline phases. In order to unveil the intrinsic activity of the ALD-MoSx, the exchange current densities, Tafel slopes, and turnover frequencies of the catalysts grown under various ALD conditions have been investigated by considering the fractional surface coverage of MoSx on the CFP and catalytically-active surface area. In addition, the ALD-MoSx/CFP catalysts exhibit excellent catalytic stability due to the strong adhesion of MoSx on the CFP and the mixed phase.Atomic layer deposition (ALD) has emerged as an efficient method to design and prepare catalysts with atomic precision. Here, we report a comprehensive study on ALD of molybdenum sulfide (MoSx) for an electrocatalytic hydrogen evolution reaction. By using molybdenum hexacarbonyl and dimethyldisulfide as the precursors of Mo and S, respectively, the MoSx catalysts are grown at 100 °C on porous carbon fiber papers (CFPs). The ALD process results in the growth of particle-like MoSx on the CFP due to the lack of adsorption sites, and its crystallographic structure is a mixture of amorphous and nano-crystalline phases. In order to unveil the intrinsic activity of the ALD-MoSx, the exchange current densities, Tafel slopes, and turnover frequencies of the catalysts grown under various ALD conditions have been investigated by considering the fractional surface coverage of MoSx on the CFP and catalytically

  11. Kinetic and mechanistic study of reaction between sulfide and sulfite in aqueous solution

    SciTech Connect

    Siu, T.; Jia, C.Q.

    1999-10-01

    The reaction between sulfide and sulfite in neutral to weak alkaline aqueous solutions was studied by following thiosulfate and sulfite concentrations using ion chromatography. The thiosulfate formation rate from the reaction 2HS{sup {minus}} + 4HSO{sub 3}{sup {minus}} {yields} 3S{sub 2}O{sub 3}{sup 2{minus}} + 3H{sub 2}O at pH 8 to 9 was found to be d[S{sub 2}O{sub 3}{sup 2{minus}}]/dt = k{sub A}[HS{sup {minus}}][HSO{sub 3}{sup {minus}}]{sup 2}, where k{sub A} = 1.1 x 10{sup 12} exp({minus}48000/RT) M{sup {minus}2} s{sup {minus}1}. A mechanism for this reaction has been proposed with disulfite (S{sub 2}O{sub 5}{sup 2{minus}}) and HSO{sub 2}{sup {minus}} intermediates. The measured rate of sulfite disappearance was higher than that calculated from the stoichiometry of the above reaction. This phenomenon is attributed to other reactions, that consume sulfite and form other sulfur compounds such as polythionates, polysulfides, and elemental sulfur. These reactions were treated as a single reaction, whose rate was found to be ({minus}d[HSO{sub 3}{sup {minus}}]/dt){sub B} = k{sub B}[H{sup +}]{sup {minus}0.6}[HS{sup {minus}}]{sup 0.7}[HSO{sub 3}{sup {minus}}]{sup 1.5}, where k{sub B} = 5 x 10{sup {minus}5} M{sup {minus}0.6} s{sup {minus}1} at 20 C. A kinetic model was established on the basis of the kinetic data obtained in this and a previous work. The experimental data at pH 7 agreed with the model prediction in a satisfactory manner. The biphasic behavior of thiosulfate is considered to be critical in developing a new sulfur-producing flue gas desulfurization (SP-FGD) process based on sulfur dioxide absorption using sodium sulfide solution.

  12. Carbonyl sulfide

    Integrated Risk Information System (IRIS)

    Carbonyl sulfide ; CASRN 463 - 58 - 1 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic

  13. Hydrogen sulfide

    Integrated Risk Information System (IRIS)

    Hydrogen sulfide ; 7783 - 06 - 4 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effec

  14. Selenium sulfide

    Integrated Risk Information System (IRIS)

    Selenium sulfide ; CASRN 7446 - 34 - 6 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic

  15. Palladium-catalyzed Allylic Substitution with (η6-arene–CH2Z)Cr(CO)3-based Nucleophiles

    PubMed Central

    Zhang, Jiadi; Stanciu, Corneliu; Wang, Beibei; Hussain, Mahmud M.; Da, Chao-Shan; Carroll, Patrick J.; Dreher, Spencer D.; Walsh, Patrick J.

    2011-01-01

    Although the palladium-catalyzed Tsuji-Trost allylic substitution reaction has been intensively studied, there is a lack of general methods to employ simple benzylic nucleophiles. Such a method would facilitate access to “α-2-propenyl benzyl” motifs, which are common structural motifs in bioactive compounds and natural products. We report herein the palladium-catalyzed allylation reaction of toluene-derived pronucleophiles activated by tricarbonylchromium. A variety of cyclic and acyclic allylic electrophiles can be employed with in situ generated (η6-C6H5–CHLiR)Cr(CO)3 nucleophiles. Catalyst identification was performed by high throughput experimentation (HTE) and led to the Xantphos/palladium hit, which proved to be a general catalyst for this class of reactions. In addition to η6-toluene complexes, benzyl amine and ether derivatives (η6-C6H5–CH2Z)Cr(CO)3 (Z=NR2, OR) are also viable pronucleophiles, allowing C–C bond-formation alpha to heteroatoms with excellent yields. Finally, a tandem allylic substitution/demetallation procedure is described that affords the corresponding metal-free allylic substitution products. This method will be a valuable complement to the existing arsenal of nucleophiles with applications in allylic substitution reactions. PMID:22047504

  16. Scandium(III)-catalyzed enantioselective allylation of isatins using allylsilanes.

    PubMed

    Hanhan, Nadine V; Tang, Yng C; Tran, Ngon T; Franz, Annaliese K

    2012-05-01

    The scandium(III)-catalyzed enantioselective Hosomi-Sakurai allylation of isatins with various substituted allylic silanes is described. A catalyst loading as low as 0.05 mol % is utilized at room temperature to afford the 3-allyl-3-hydroxy-2-oxindoles in excellent yields and enantioselectivity up to 99% ee, including a demonstration of a gram-scale reaction. The effects of additives and varying silyl groups were explored to demonstrate the scope and application.

  17. Dehydrative Direct C-H Allylation with Allylic Alcohols under [Cp*Co(III)] Catalysis.

    PubMed

    Suzuki, Yudai; Sun, Bo; Sakata, Ken; Yoshino, Tatsuhiko; Matsunaga, Shigeki; Kanai, Motomu

    2015-08-17

    The unique reactivity of [Cp*Co(III)] over [Cp*Rh(III)] was demonstrated. A cationic [Cp*Co(III)] catalyst promoted direct dehydrative C-H allylation with non-activated allyl alcohols, thus giving C2-allylated indoles, pyrrole, and phenyl-pyrazole in good yields, while analogous [Cp*Rh(III)] catalysts were not effective. The high γ-selectivity and C2-selectivity indicated that the reaction proceeded by directing-group-assisted C-H metalation. DFT calculations suggested that the γ-selective substitution reaction proceeded by C-H metalation and insertion of a C-C double bond, with subsequent β-hydroxide elimination. The [Cp*Co(III)] catalyst favored β-hydroxide elimination over β-hydride elimination.

  18. A comprehensive study on atomic layer deposition of molybdenum sulfide for electrochemical hydrogen evolution.

    PubMed

    Kwon, Do Hyun; Jin, Zhenyu; Shin, Seokhee; Lee, Wook-Seong; Min, Yo-Sep

    2016-04-01

    Atomic layer deposition (ALD) has emerged as an efficient method to design and prepare catalysts with atomic precision. Here, we report a comprehensive study on ALD of molybdenum sulfide (MoSx) for an electrocatalytic hydrogen evolution reaction. By using molybdenum hexacarbonyl and dimethyldisulfide as the precursors of Mo and S, respectively, the MoSx catalysts are grown at 100 °C on porous carbon fiber papers (CFPs). The ALD process results in the growth of particle-like MoSx on the CFP due to the lack of adsorption sites, and its crystallographic structure is a mixture of amorphous and nano-crystalline phases. In order to unveil the intrinsic activity of the ALD-MoSx, the exchange current densities, Tafel slopes, and turnover frequencies of the catalysts grown under various ALD conditions have been investigated by considering the fractional surface coverage of MoSx on the CFP and catalytically-active surface area. In addition, the ALD-MoSx/CFP catalysts exhibit excellent catalytic stability due to the strong adhesion of MoSx on the CFP and the mixed phase. PMID:26973254

  19. Sulfidization of Au(111) from thioacetic acid: an experimental and theoretical study.

    PubMed

    Fischer, Jeison A; Zoldan, Vinícius C; Benitez, Guillermo; Rubert, Aldo A; Ramirez, Eduardo A; Carro, Pilar; Salvarezza, Roberto C; Pasa, André A; Vela, Maria E

    2012-10-30

    We have studied the adsorption of thioacetic acid (TAAH) on Au(111) from solution deposition. The close proximity of the SH groups to CO groups makes this molecule very attractive for exploring the effect of the functional group on the stability of the S-C and S-Au bonds. Although thioacetic acid was supposed to decompose slowly in water by hydrolysis supplying hydrogen sulfide, this behavior is not expected in nonpolar solvents such as toluene or hexane. Therefore, we have used these solvents for TAAH self-assembly on the Au(111) surface. The characterization of the adsorbates has been done by electrochemical techniques, X-ray photoelectron spectroscopy (XPS), and scanning tunneling microscopy (STM). We have found that even in nonpolar solvents thioacetic acid decomposes to S. The results have been discussed on the basis that the adsorbed species suffer a cleavage on the Au surface, leaving the S attached to it. The dissociation is a spontaneous process that reaches the final state very fast once it is energetically favorable, as can be interpreted from DFT calculations. The thioacetic acid adsorption reveals the strong effect that produces a functional group and the key role of the S-H bond cleavage in the self-assembly process. PMID:23002810

  20. Genetic Targets of Hydrogen Sulfide in Ventilator-Induced Lung Injury – A Microarray Study

    PubMed Central

    Spassov, Sashko; Pfeifer, Dietmar; Strosing, Karl; Ryter, Stefan; Hummel, Matthias; Faller, Simone; Hoetzel, Alexander

    2014-01-01

    Recently, we have shown that inhalation of hydrogen sulfide (H2S) protects against ventilator-induced lung injury (VILI). In the present study, we aimed to determine the underlying molecular mechanisms of H2S-dependent lung protection by analyzing gene expression profiles in mice. C57BL/6 mice were subjected to spontaneous breathing or mechanical ventilation in the absence or presence of H2S (80 parts per million). Gene expression profiles were determined by microarray, sqRT-PCR and Western Blot analyses. The association of Atf3 in protection against VILI was confirmed with a Vivo-Morpholino knockout model. Mechanical ventilation caused a significant lung inflammation and damage that was prevented in the presence of H2S. Mechanical ventilation favoured the expression of genes involved in inflammation, leukocyte activation and chemotaxis. In contrast, ventilation with H2S activated genes involved in extracellular matrix remodelling, angiogenesis, inhibition of apoptosis, and inflammation. Amongst others, H2S administration induced Atf3, an anti-inflammatory and anti-apoptotic regulator. Morpholino mediated reduction of Atf3 resulted in elevated lung injury despite the presence of H2S. In conclusion, lung protection by H2S during mechanical ventilation is associated with down-regulation of genes related to oxidative stress and inflammation and up-regulation of anti-apoptotic and anti-inflammatory genes. Here we show that Atf3 is clearly involved in H2S mediated protection. PMID:25025333

  1. Cp*Co(III)-Catalyzed Dehydrative C-H Allylation of 6-Arylpurines and Aromatic Amides Using Allyl Alcohols in Fluorinated Alcohols.

    PubMed

    Bunno, Youka; Murakami, Nanami; Suzuki, Yudai; Kanai, Motomu; Yoshino, Tatsuhiko; Matsunaga, Shigeki

    2016-05-01

    Cp*Co(III)-catalyzed C-H allylation of various aromatic C-H bonds using allyl alcohols as allylating reagents is described. Improved reaction conditions using fluorinated alcohol solvents afforded efficient directed C-H allylation of 6-arylpurines, benzamides, and a synthetically useful Weinreb amide with good functional group compatibility.

  2. Sulfur isotope values in the sulfidic Frasassi cave system, central Italy: A case study of a chemolithotrophic S-based ecosystem

    NASA Astrophysics Data System (ADS)

    Zerkle, Aubrey L.; Jones, Daniel S.; Farquhar, James; Macalady, Jennifer L.

    2016-01-01

    Sulfide oxidation forms a critical step in the global sulfur cycle, although this process is notoriously difficult to constrain due to the multiple pathways and highly reactive intermediates involved. Multiple sulfur isotopes (δ34S and Δ33S) can provide a powerful tool for unravelling sulfur cycling processes in modern (and ancient) environments, although they have had limited application to systems with well-resolved oxidative S cycling. In this study, we report the major (δ34S) and minor (Δ33S) isotope values of sulfur compounds in streams and sediments from the sulfidic Frasassi cave system, Marche Region, Italy. These microaerophilic cave streams host prominent white biofilms dominated by chemolithotrophic organisms that oxidize sulfide to S0, allowing us to estimate S isotope fractionations associated with in situ sulfide oxidation and to evaluate any resulting isotope biosignatures. Our results demonstrate that chemolithotrophic sulfide oxidation produces 34S enrichments in the S0 products that are larger than those previously measured in laboratory experiments, with 34εS0-H2S of up to 8‰ calculated. These small reverse isotope effects are similar to those produced during phototrophic sulfide oxidation (⩽7‰), but distinct from the small normal isotope effects previously calculated for abiotic oxidation of sulfide with O2 (∼-5‰). An inverse correlation between the magnitude of 34εS0-H2S effects and sulfide availability, along with substantial differences in Δ33S, both support complex sulfide oxidation pathways and intracellular recycling of S intermediates by organisms inhabiting the biofilms. At the ecosystem level, we calculate fractionations of less than 40‰ between sulfide and sulfate in the water column and in the sediments. These fractionations are smaller than those typically calculated for systems dominated by sulfate reduction (>50‰), and contrast with the commonly held assumption that oxidative recycling of sulfide generally

  3. Copper-catalyzed enantioselective allylic substitution with alkylboranes.

    PubMed

    Shido, Yoshinori; Yoshida, Mika; Tanabe, Masahito; Ohmiya, Hirohisa; Sawamura, Masaya

    2012-11-14

    The first catalytic enantioselective allylic substitution reaction with alkylboron compounds has been achieved. The reaction between alkyl-9-BBN reagents and primary allylic chlorides proceeded with excellent γ-selectivities and high enantioselectivities under catalysis of a Cu(I)-DTBM-SEGPHOS system. The protocol produces terminal alkenes with an allylic stereogenic center branched with functionalized sp(3)-alkyl groups. The reaction with a γ-silicon-substituted allyl chloride affords an efficient strategy for the enantioselective synthesis of functionalized α-stereogenic chiral allylsilanes. PMID:23106350

  4. Palladium-catalyzed mono-N-allylation of unprotected anthranilic acids with allylic alcohols in aqueous media.

    PubMed

    Hikawa, Hidemasa; Yokoyama, Yuusaku

    2011-10-21

    Palladium-catalyzed N-allylation of anthranilic acids 1a-j with allyl alcohol 2a in the presence of Pd(OAc)(2), sodium diphenylphosphinobenzene-3-sulfonate (TPPMS) in THF-H(2)O at room temperature gave only mono-N-allylated anthranilic acids 3a-j in good yields (70-98%). The reactions of 4-bromoanthranilic acid 1i with 2-methyl-3-buten-2-ol 2b showed complete chemoselectivity in N-allylation (neutral conditions) and C-vinylation (basic conditions). In our catalytic system, the keys to success are use of an unprotected anthranilic acid as a starting material and the presence of water in the reaction medium. The carboxyl group of anthranilic acid and water may play important roles for the smooth generation of the π-allyl palladium species by activation of the hydroxyl group of the allylic alcohol. PMID:21919524

  5. Thioarsenates in sulfidic waters.

    PubMed

    Stauder, S; Raue, B; Sacher, F

    2005-08-15

    It has long been recognized that the formation of soluble arsenic sulfur complexes plays a key role for the mobility and toxicity of arsenic in sulfate-reducing environments. Knowledge of the exact arsenic species is essential to understand the behavior of arsenic in sulfidic aquifers and to develop remediation strategies. In the past, monomeric and trimeric thioarsenites were assumed to be the existing species in sulfidic systems. In this study, thioarsenates were identified by IC-ICP/MS in arsenite- and sulfide-containing solutions as well as in a reduced groundwater from a contaminated site. The unexpected finding of an oxidation of As(lll) to As(V) in thioarsenates in strongly reducing systems can be explained by the high affinity between As(Ill) and sulfur. In sulfide-containing solutions without oxidant, As(lll) therefore undergoes disproportionation to thioarsenates (As(V)) and elemental arsenic. It has previously been supposed that mobility as well as toxicity of arsenic increases if the redox state decreases. For sulfidic waters, the opposite is probably the case. Thus, the formation of thioarsenates could be used in connection with remediation strategies. Thioarsenates are highly sensitive to oxygen and pH. This is important for analytical procedures. A loss of soluble arsenic as well as a conversion to arsenite and arsenate may occur if water samples containing thioarsenates are analyzed with conventional methods.

  6. Silicon-directed rhenium-catalyzed allylic carbaminations and oxidative fragmentations of γ-silyl allylic alcohols.

    PubMed

    Chavhan, Sanjay W; Cook, Matthew J

    2014-04-22

    A highly regioselective allylic substitution of β-silyl allylic alcohols has been achieved that provides the branched isomer as a single product. This high level of regiocontrol is achieved through the use of a vinyl silane group that can perform a Hiyama coupling providing 1,3-disubstituted allylic amines. An unusual oxidative fragmentation product was also observed at elevated temperature that appears to proceed by a Fleming-Tamao-type oxidation-elimination pathway.

  7. Mineralogical studies of sulfide samples and volatile concentrations of basalt glasses from the southern Juan de Fuca Ridge

    NASA Technical Reports Server (NTRS)

    Brett, Robin; Evans, Howard T., Jr.; Wandless, M. V.; Gibson, E. K., Jr.; Hedenquist, Jeffrey W.

    1987-01-01

    Sulfide samples obtained from Alvin dives on the southern Juan de Fuca Ridge were examined, showing the presence of two previously undiscovered minerals, both formed at low temperatures. The first detection of lizardite, starkeyite, and anatase in such an environment is also reported. Sulfide geothermometry involving the Cu-Fe-S system shows a vent temperature of less than 328 C for one sample. Ice-melting temperatures on inclusions from this sample are about -2.8 C, and fluid inclusion studies on crystals near this sample show pressure-corrected homogenization temperatures of 268 and 285 C. Volatile concentrations from vesicle-free basalt glass from the vent field are found to be about 0.0013 wt pct CO2 and 0.16 wt pct H2O.

  8. Synthesis of Branched Alkylboronates by Copper-Catalyzed Allylic Substitution Reactions of Allylic Chlorides with 1,1-Diborylalkanes.

    PubMed

    Kim, Junghoon; Park, Sangwoo; Park, Jinyoung; Cho, Seung Hwan

    2016-01-22

    Reported herein is a copper-catalyzed S(N)2'-selective allylic substitution reaction using readily accessible allylic chlorides and 1,1-diborylalkanes, a reaction which proceeds with chemoselective C-B bond activation of the 1,1-diborylalkanes. In the presence of a catalytic amount of [Cu(IMes)Cl] [IMes=1,3-bis(2,4,6-trimethylphenyl)imidazole-2-ylidene] and LiOtBu as a base, a range of primary and secondary allylic chlorides undergo the S(N)2'-selective allylic substitution reaction to produce branched alkylboronates. The synthetic utilities of the obtained alkylboronates are also presented. PMID:26666468

  9. Raman and photoluminescence studies of poly (p-phenylene sulfide) films

    SciTech Connect

    Pan, Z.

    1992-01-01

    Scope and method of study. Micro-Raman and photoluminescence (PL) measurements have been performed on various poly (p-phenylene sulfide) (PPS) films to investigate the morphology and emission properties of this important polymer material. A cw argon laser at 514.5 nm was used in the Raman study while a pulsed Nd:YAG laser at 355 nm was used in the PL study. A phenylene-sulfur stretching vibration model was proposed to interpret the influence of polymer crystallinity on the Raman spectrum and to calculate the effective force constant. A lattice relaxation model was developed to explain the vibronic structure in the PL spectrum and the electron-phonon coupling in PPS. Findings and conclusions: It was found that: (i) the intensity, and the line profile of the main Raman band at 1076 cm[sup [minus]1] were related to the crystallinity of the PPS film; (ii) the effective stretching and bending force constants between the phenylene ring and the sulfur atom were determined; (iii) new Raman lines at 840 and 919 cm[sup [minus]1] were observed and assigned to the out of plane C-H bending modes; (iv) the vibronic structure with energy spacing equal to the phenylene-sulfur stretching mode was observed in low temperature PL spectrum of all PPS samples, which provided evidence that the electronic transition was coupled to the intrachain stretching in PPS; (V) the electron-phonon coupling strength and the temporary lattice distortion were determined for the unaged and aged films. The coupling strength was reduced in the aged sample possibly due to the increased [pi]-orbital overlap caused by the crosslinking which resulted from the thermal-aging process.

  10. Studying inhibition of calcium oxalate stone formation: an in vitro approach for screening hydrogen sulfide and its metabolites

    PubMed Central

    Vaitheeswari, S.; Sriram, R.; Brindha, P.; Kurian, Gino A.

    2015-01-01

    ABSTRACT Purpose: Calcium oxalate urolithiasis is one of the most common urinary tract diseases and is of high prevalence. The present study proposes to evaluate the antilithiatic property of hydrogen sulfide and its metabolites like thiosulfate & sulfate in an in vitro model. Materials and Methods: The antilithiatic activity of sodium hydrogen sulfide (NaSH), sodium thiosulfate (Na2S2O3) and sodium sulfate (Na2SO4) on the kinetics of calcium oxalate crystal formation was investigated both in physiological buffer and in urine from normal and recurrent stone forming volunteers. The stones were characterized by optical and spectroscopic techniques. Results: The stones were characterized to be monoclinic, prismatic and bipyramidal habit which is of calcium monohydrate and dihydrate nature. The FTIR displayed fingerprint corresponding to calcium oxalate in the control while in NaSH treated, S=O vibrations were visible in the spectrum. The order of percentage inhibition was NaSH>Na2S2O3>Na2SO4. Conclusion: Our study indicates that sodium hydrogen sulfide and its metabolite thiosulfate are inhibitors of calcium oxalate stone agglomeration which makes them unstable both in physiological buffer and in urine. This effect is attributed to pH changes and complexing of calcium by S2O3 2-and SO4 2- moiety produced by the test compounds. PMID:26200543

  11. Mineralogical and isotopic studies of base metal sulfides from the Jiawula Ag-Pb-Zn deposit, Inner Mongolia, NE China

    NASA Astrophysics Data System (ADS)

    Niu, Si-Da; Li, Sheng-Rong; Santosh, M.; Zhang, De-Hui; Li, Zeng-Da; Shan, Meng-Jie; Lan, Yi-Xiang; Gao, De-Rong; Zhao, Wen-Bin

    2016-01-01

    The Jiawula Ag-Pb-Zn deposit is located in the northern part of the Da Hinggan Mountains metallogenic belt in the eastern section of the Central Asian Orogenic Belt. Sphalerite, galena, pyrite, chalcopyrite, and arsenopyrite are the major sulfide minerals occurring in this deposit. Here we report results from electron probe micro-analysis (EPMA), thermoelectricity, and sulfur isotope studies of the constituent silver minerals and sulfide phases of the Jiawula deposit. Petrographic observations and EPMA study reveal abundant silver mineralization in the ore, especially within sphalerite and galena. Discrete grains of silver minerals (including argentite, pyrargyrite, and canfieldite) and isomorphism in silver-bearing sulfides are identified. Silver and tellurium contents in galena are relatively high and show interrelationship. Significant substitution of S by Te in the galena lattice facilitates silver entering the galena structure, which might have been promoted by relatively low lg fS2. The thermoelectric coefficient of pyrite shows a marked gradient from N-type to P-type from pre- to post-metallogenic stages. Pyrites in Jiawula are enriched in Co and As and in the absence of Ni, displaying features typical of epithermal deposits. The isotopic data present a close relationship between the sulfur source and magmatism.

  12. Kinetics of the reaction of diethylene glycol bis-chloroformate with allyl alcohol

    SciTech Connect

    Alekseev, N.N.; Shtoda, N.F.; Dzumedzei, N.V.

    1988-10-01

    The kinetics of diethylene glycol bis-chloroformate solvolysis by excess allyl alcohol in toluene and carbon tetrachloride has been studied. Under conditions of a pseudofirst order reaction with respect to diethylene glycol bis-chloroformate the activation parameters confirm an addition-detachment mechanism.

  13. Biomonitoring the intake of garlic via urinary excretion of allyl mercapturic acid.

    PubMed

    Verhagen, H; Hageman, G J; Rauma, A L; Versluis-de Haan, G; van Herwijnen, M H; de Groot, J; Törrönen, R; Mykkänen, H

    2001-08-01

    Allium vegetables (onions, leeks, chives) and in particular garlic have been claimed to have health-promoting potential. This study was conducted to get insight into the perspectives for monitoring the intake of garlic by a biomarker approach. Chemically, the biomarker results from exposure to gamma-glutamyl-S-allyl-l-cysteine, which is first hydrolysed by gamma-glutamine-transpeptidase resulting in the formation of S-allyl-l-cysteine. The latter compound is subsequently N-acetylated by N-acetyltransferase into S-allyl-mercapturic acid (ALMA) and excreted into urine. The mercapturic acid was measured in urine using gaschromatography with mass spectrometry. Thus the intake of garlic was determined to check the compliance of garlic intake in a placebo-controlled intervention study. Results indicate that S-allyl-mercapturic acid could be detected in 15 out of 16 urine samples of garlic supplement takers, indicating good compliance. In addition, the intake of garlic was also monitored in a cross-section study of vegans versus controls in Finland, in which no differences in garlic consumption nor in ALMA output were recorded between vegans and controls. These data indicate good possibilities for further studies in the field of biomarkers to investigate the putative chemopreventive effects of garlic and garlic-containing products. PMID:11520428

  14. Studies of the surface reactivity of metal oxyhydroxides and sulfides with relevance to environmental chemistry

    NASA Astrophysics Data System (ADS)

    Pierre-Louis, Andro-Marc

    With the benefits of an ever increasing advance of industrialization around the globe come formidable environmental problems. Three environmental problems that have relevance to the research described in this thesis are the 1) buildup of atmospheric CO2 gas through the burning of fossil fuels, 2) eutrophication of aquatic systems, and 3) the acidification of environments from acid mine drainage (AMD) resulting from coal-mining activities. In particular research is presented in this thesis that investigated the surface chemistry of CO2 and phosphate (PO43-) on a suite of environmentally relevant iron oxyhydroxide materials and the chemistry of phospholipid molecules on environmentally relevant iron sulfide surfaces to suppress AMD. To develop a microscopic understanding of the surface chemistry of the different systems, an array of experimental and computational techniques were used in the research. Techniques included X-ray photoelectron spectroscopy, atomic adsorption, X-ray diffraction, scanning transmission microscopy with electron dispersive X-ray spectroscopy (STEM/EDS), ion chromatography (IC), and attenuated total reflectance Fourier transform Infrared (ATR-FTIR). Results from the latter technique were interpreted with the aid of density function theory (DFT) calculations. Iron oxyhydroxides, which consisted of ferrihydrite (FeOOH), goethite (α-FeOOH), ferrimagnetic ferrihydrite (FerriFh), and aluminum-doped iron oxyhydroxide (content from 0-100 mol%) were synthesized and studied before and after exposure to gaseous CO2, CO32-, and PO43- species. FeOOH and mixed Al/Fe oxyhydroxide surfaces showed high affinities for the formation of carbonate and bicarbonate species upon exposure to gaseous CO2. Within the Al/Fe oxyhydroxide circumstance, a low Al level of incorporation in the iron oxyhydroxide structure caused a slight increase in surface area and increase in the amount of oxyanion (e.g., CO32- or PO43-) adsorption up to an Al level of 30 mol%. Significant

  15. Studies of the surface reactivity of metal oxyhydroxides and sulfides with relevance to environmental chemistry

    NASA Astrophysics Data System (ADS)

    Pierre-Louis, Andro-Marc

    With the benefits of an ever increasing advance of industrialization around the globe come formidable environmental problems. Three environmental problems that have relevance to the research described in this thesis are the 1) buildup of atmospheric CO2 gas through the burning of fossil fuels, 2) eutrophication of aquatic systems, and 3) the acidification of environments from acid mine drainage (AMD) resulting from coal-mining activities. In particular research is presented in this thesis that investigated the surface chemistry of CO2 and phosphate (PO43-) on a suite of environmentally relevant iron oxyhydroxide materials and the chemistry of phospholipid molecules on environmentally relevant iron sulfide surfaces to suppress AMD. To develop a microscopic understanding of the surface chemistry of the different systems, an array of experimental and computational techniques were used in the research. Techniques included X-ray photoelectron spectroscopy, atomic adsorption, X-ray diffraction, scanning transmission microscopy with electron dispersive X-ray spectroscopy (STEM/EDS), ion chromatography (IC), and attenuated total reflectance Fourier transform Infrared (ATR-FTIR). Results from the latter technique were interpreted with the aid of density function theory (DFT) calculations. Iron oxyhydroxides, which consisted of ferrihydrite (FeOOH), goethite (α-FeOOH), ferrimagnetic ferrihydrite (FerriFh), and aluminum-doped iron oxyhydroxide (content from 0-100 mol%) were synthesized and studied before and after exposure to gaseous CO2, CO32-, and PO43- species. FeOOH and mixed Al/Fe oxyhydroxide surfaces showed high affinities for the formation of carbonate and bicarbonate species upon exposure to gaseous CO2. Within the Al/Fe oxyhydroxide circumstance, a low Al level of incorporation in the iron oxyhydroxide structure caused a slight increase in surface area and increase in the amount of oxyanion (e.g., CO32- or PO43-) adsorption up to an Al level of 30 mol%. Significant

  16. Sulfidation of silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Levard, C.; Michel, F. M.; Brown, G. E.

    2010-12-01

    the kinetics of sulfidation and in solubility behavior. The results of this type of fundamental study are important for predicting the behavior and fate of Ag-NPs in natural ecosystems. For example, aggregation caused by sulfidation may limit transport in porous media such as soils. Modification of surface charge during the sulfidation process may have an important impact on electrostatic interactions between Ag-NPs and charged phases such as natural organic matter. Finally, it is well known that Ag+ has a greater toxicity than metallic Ag (3) and the observed decrease in solubility of Ag-NPs after sulfidation may strongly impact the toxicity of silver in the environment. (1) www.nanotechproject.org (2) F. Fievet, J.P. Lagier, B. Blin, B. Beaudoin and M. Figlarz, Solid State Ionics 32/33, 198 (1989) (3) G.A. Sotiriou and S.E. Pratsinis, Environmental Science & Technology 14, 5649 (2010).

  17. Density functional theory studies of the adsorption of hydrogen sulfide on aluminum doped silicane.

    PubMed

    Sánchez-Ochoa, Francisco; Guerrero-Sánchez, Jonathan; Canto, Gabriel I; Cocoletzi, Gregorio H; Takeuchi, Noboru

    2013-08-01

    First principles total energy calculations have been performed to study the hydrogen sulfide (H2S) adsorption on silicane, an unusual one monolayer of Si(111) surface hydrogenated on both sides. The H2S adsorption may take place in dissociative or non-dissociative forms. Silicane has been considered as: (A) non-doped with a hydrogen vacancy, and doped in two main configurations; (B) with an aluminum replacing a hydrogen atom and (C-n; n = 1, 2, 3) with an aluminum replacing a silicon atom at a lattice site. In addition, three supercells; 4x4, 3x3 and 2x2 have been explored for both non-doped and doped silicane. The non-dissociative adsorption takes place in geometries (A), (C-1), (C-2) and (C-3) while the dissociative in (B). Adsorption energies of the dissociative case are larger than those corresponding to the non-dissociated cases. In the dissociative adsorption, the molecule is fragmented in a HS structure and a H atom which are bonded to the aluminum to form a H-S-Al-H structure. The presence of the doping produces some electronic changes as the periodicity varies. Calculations of the total density of states (DOS) indicate that in most cases the energy gap decreases as the periodicity changes from 4x4 to 2x2. The features of the total DOS are explained in terms of the partial DOS. The reported charge density plots explain quite well the chemisorptions and physisorptions of the molecule on silicane in agreement with adsorption energies.

  18. Spectroscopic study on sorption of hydrogen sulfide by means of red soil.

    PubMed

    Ko, T H; Chu, H

    2005-07-01

    This paper reports the results of the characterization of red soils in relation to the sorption of H2S from coal gas at 500 degrees C by spectroscopic techniques in order to provide more information on red soils' structural change both before and after reaction. In addition, by-products analysis has also been studied using Fourier transform infrared (FTIR) spectroscopy. Before and after the experiments the red soils were characterized with X-ray powder diffraction (XRPD), energy dispersion spectrum (EDS), X-ray photoelectron spectroscopy (XPS) and FTIR spectroscopy. XRPD results indicate that iron oxide species disappear from the original to reacted red soil. EDS analysis shows that a significant amount of sulfur is present in the reacted red soil, which is in agreement with the results of the elemental analysis and the calculated value based on breakthrough curve. XPS regression fitting results further indicate that sulfur retention may be associated with the iron oxides. S 2p XPS fittings point out that the major sulfur species present in the reacted red soil are composed of S(-2), elemental sulfur, polysulfide, sulfite and sulfate. Additionally, the binding energy of iron shifts to a lower position for the reacted red soil, which indicates that iron oxides in the original red soil have been converted into iron sulfide. Appreciable amounts of the by-products CO2, SO2 and COS are detected by on-line FTIR spectroscopy during the initial and later stages of the sorption process. The formation of CO2 is related to the water-shift reaction, and SO2 is probably attributable to the reaction of organic matters and H2S. The concentration of COS is quantified by GC/FPD and found it to be about 350 ppm, which is close to the equilibrium concentration of the reaction of inlet CO and H2S at a temperature of 500 degrees C.

  19. Equilibriums between Cu, Fe, and Zn sulfides and oxides in chloride solution: A thermodynamic study

    NASA Astrophysics Data System (ADS)

    Strel'Tsova, N. I.

    2009-10-01

    The results of thermodynamic modeling of equilibriums between Cu, Fe, and Zn sulfides and oxides pertaining to the Cu-Fe-Zn-S-O2 system in water and aqueous chloride solution are presented. The system comprises solid phases of constant composition: pyrite, pyrrhotite, hematite, magnetite, wüstite, γ-iron, chalcocite, covellite, cuprite, native copper, chalcopyrite, and bornite, as well as more than 100 ions, complexes, and molecules in an aqueous solution. The GIBBS program with the UNITHERM thermodynamic dataset used in calculations allows numerical analysis of phase assemblages in a dry system and in equilibrium with an aqueous solution. How the temperature, pressure, and the composition of the solution in the system opened for oxygen and sulfur affects the composition of phase assemblages was considered in temperature and pressure ranges of 50-350 C and 100-1000 bar, respectively. Decrease in temperature leads to a shift in stability fields of the studied phases toward the region of elevated oxygen and sulfur partial pressures. Variation of temperature is an important factor affecting precipitation of ore minerals, primarily, Cu- and Zn-bearing. The calculation results are presented in tables and diagrams. Each point in the (log m_{S_{tot} } - log f_{O_2 } ) diagram is characterized by a single possible assemblage of phases equilibrated with a solution of the given composition within the considered temperature and pressure range. Since the composition of the mineral assemblage is controlled by physicochemical conditions at the moment of mineral formation, comparison of the calculation results with mineral assemblages at ore deposits makes it possible to estimate the parameters of ore deposition at the early stage of investigation, including oxygen and sulfur activity and, occasionally, the composition and salinity of the solution. These parameters control the formation of such assemblages.

  20. Mineral-chemical studies of metamorphosed hydrothermal alteration in the Kristineberg volcanogenic massive sulfide district, Sweden

    NASA Astrophysics Data System (ADS)

    Hannington, Mark D.; Kjarsgaard, Ingrid M.; Galley, Alan G.; Taylor, Bruce

    2003-06-01

    The massive sulfide deposits of the Kristineberg area, Sweden, occur within a 2- to 3-km-thick succession of felsic volcaniclastic rocks belonging to the Skellefte Group. The volcanic pile is intruded by a synvolcanic Jorn-type granitoid (Viterliden intrusive complex) and is overlain by a thick sequence of metasedimentary rocks (Vargfors Group). Mineralization occurs at two main stratigraphic levels, at the base of the felsic volcanic succession and at the contact with the metasedimentary rocks of the Vargfors Group. The Kristineberg Cu-Zn mine is the largest deposit (approximately 21 Mt) and occurs at the base of the volcanic pile, close to the contact with the Viterliden intrusive complex. Four smaller deposits (Ravliden, Ravlidmyran, Horntrask and Nyliden) occur along the upper ore horizon. These deposits are thought to be related to a late intrusive phase of the Viterliden complex which cuts the altered volcanic rocks at the Kristineberg deposit. Within an area of about 50 km2 surrounding the Kristineberg deposit, felsic volcanic rocks between the two ore horizons are affected by extensive albite-destructive alteration (sodium depletion) and development of chlorite and muscovite (strong co-enrichment in magnesium and potassium). The Kristineberg deposit is enveloped by a large and partly transposed quartz-chlorite alteration zone, approximately 2 km in diameter, and a distal but coherent pyrite-quartz-muscovite alteration zone extending as far as 4 km from the deposit. Chlorite(±talc) in the mine area is notably magnesium-rich and contains anomalous F, Ba, Zn and Mn. High fluorine is also present in coexisting muscovite and phlogopite. The magnesium-rich chlorite alteration contrasts sharply with the iron enrichment observed in many other felsic, volcanic-hosted Precambrian massive sulfide deposits. This may indicate fixation of iron by large amounts of pyrite in the section or entrainment of large amounts of seawater in the hydrothermal upflow zones. Kyanite

  1. Nanostructured metal sulfides for energy storage.

    PubMed

    Rui, Xianhong; Tan, Huiteng; Yan, Qingyu

    2014-09-01

    Advanced electrodes with a high energy density at high power are urgently needed for high-performance energy storage devices, including lithium-ion batteries (LIBs) and supercapacitors (SCs), to fulfil the requirements of future electrochemical power sources for applications such as in hybrid electric/plug-in-hybrid (HEV/PHEV) vehicles. Metal sulfides with unique physical and chemical properties, as well as high specific capacity/capacitance, which are typically multiple times higher than that of the carbon/graphite-based materials, are currently studied as promising electrode materials. However, the implementation of these sulfide electrodes in practical applications is hindered by their inferior rate performance and cycling stability. Nanostructures offering the advantages of high surface-to-volume ratios, favourable transport properties, and high freedom for the volume change upon ion insertion/extraction and other reactions, present an opportunity to build next-generation LIBs and SCs. Thus, the development of novel concepts in material research to achieve new nanostructures paves the way for improved electrochemical performance. Herein, we summarize recent advances in nanostructured metal sulfides, such as iron sulfides, copper sulfides, cobalt sulfides, nickel sulfides, manganese sulfides, molybdenum sulfides, tin sulfides, with zero-, one-, two-, and three-dimensional morphologies for LIB and SC applications. In addition, the recently emerged concept of incorporating conductive matrices, especially graphene, with metal sulfide nanomaterials will also be highlighted. Finally, some remarks are made on the challenges and perspectives for the future development of metal sulfide-based LIB and SC devices. PMID:25073046

  2. Nanostructured metal sulfides for energy storage.

    PubMed

    Rui, Xianhong; Tan, Huiteng; Yan, Qingyu

    2014-09-01

    Advanced electrodes with a high energy density at high power are urgently needed for high-performance energy storage devices, including lithium-ion batteries (LIBs) and supercapacitors (SCs), to fulfil the requirements of future electrochemical power sources for applications such as in hybrid electric/plug-in-hybrid (HEV/PHEV) vehicles. Metal sulfides with unique physical and chemical properties, as well as high specific capacity/capacitance, which are typically multiple times higher than that of the carbon/graphite-based materials, are currently studied as promising electrode materials. However, the implementation of these sulfide electrodes in practical applications is hindered by their inferior rate performance and cycling stability. Nanostructures offering the advantages of high surface-to-volume ratios, favourable transport properties, and high freedom for the volume change upon ion insertion/extraction and other reactions, present an opportunity to build next-generation LIBs and SCs. Thus, the development of novel concepts in material research to achieve new nanostructures paves the way for improved electrochemical performance. Herein, we summarize recent advances in nanostructured metal sulfides, such as iron sulfides, copper sulfides, cobalt sulfides, nickel sulfides, manganese sulfides, molybdenum sulfides, tin sulfides, with zero-, one-, two-, and three-dimensional morphologies for LIB and SC applications. In addition, the recently emerged concept of incorporating conductive matrices, especially graphene, with metal sulfide nanomaterials will also be highlighted. Finally, some remarks are made on the challenges and perspectives for the future development of metal sulfide-based LIB and SC devices.

  3. Nanostructured metal sulfides for energy storage

    NASA Astrophysics Data System (ADS)

    Rui, Xianhong; Tan, Huiteng; Yan, Qingyu

    2014-08-01

    Advanced electrodes with a high energy density at high power are urgently needed for high-performance energy storage devices, including lithium-ion batteries (LIBs) and supercapacitors (SCs), to fulfil the requirements of future electrochemical power sources for applications such as in hybrid electric/plug-in-hybrid (HEV/PHEV) vehicles. Metal sulfides with unique physical and chemical properties, as well as high specific capacity/capacitance, which are typically multiple times higher than that of the carbon/graphite-based materials, are currently studied as promising electrode materials. However, the implementation of these sulfide electrodes in practical applications is hindered by their inferior rate performance and cycling stability. Nanostructures offering the advantages of high surface-to-volume ratios, favourable transport properties, and high freedom for the volume change upon ion insertion/extraction and other reactions, present an opportunity to build next-generation LIBs and SCs. Thus, the development of novel concepts in material research to achieve new nanostructures paves the way for improved electrochemical performance. Herein, we summarize recent advances in nanostructured metal sulfides, such as iron sulfides, copper sulfides, cobalt sulfides, nickel sulfides, manganese sulfides, molybdenum sulfides, tin sulfides, with zero-, one-, two-, and three-dimensional morphologies for LIB and SC applications. In addition, the recently emerged concept of incorporating conductive matrices, especially graphene, with metal sulfide nanomaterials will also be highlighted. Finally, some remarks are made on the challenges and perspectives for the future development of metal sulfide-based LIB and SC devices.

  4. Kinetic resolution of allyl fluorides by enantioselective allylic trifluoromethylation based on silicon-assisted C-F bond cleavage.

    PubMed

    Nishimine, Takayuki; Fukushi, Kazunobu; Shibata, Naoyuki; Taira, Hiromi; Tokunaga, Etsuko; Yamano, Akihito; Shiro, Motoo; Shibata, Norio

    2014-01-01

    Two birds, one stone! The first kinetic resolution of allyl fluorides was achieved by the development of an organocatalyzed enantioselective allylic trifluoromethylation. Two kinds of chiral fluorinated compounds, which incorporate C*F and C*CF3 units, respectively, can thus be accessed by a single transformation.

  5. Photooxygenation of allylic alcohols: kinetic comparison of unfunctionalized alkenes with prenol-type allylic alcohols, ethers and acetates.

    PubMed

    Griesbeck, Axel G; Adam, Waldemar; Bartoschek, Anna; El-Idreesy, Tamer T

    2003-08-01

    The kinetics of the chemical and physical quenching of the first excited singlet state of oxygen [1O2 (1delta(g))] by unfunctionalized alkenes 1-4, allylic alcohols 5-7 and 9, allylic acetates 8 and 11, and the allylic ether 10 display small solvent-polarity effects on the reactivity. The regioselectivity of the singlet oxygen ene reaction is solvent independent for the unfunctionalized alkenes as well as the prenol-type substrates, the latter showing substantial solvent effects on the diastereoselectivity. Pronounced physical quenching is detected only for the allylic alcohols 5 and 6. These results are interpreted in terms of the interactions between singlet oxygen and the allylic hydroxy groups, conformationally promoted by allylic strain which lead either to chemical activation or to physical quenching. The results for substrate 9 in deuterated v.s non-deuterated methanol are in accord with hydrogen bonding between the allylic alcohol and 1O2, which directs the diastereoselectivity of the ene reaction with chiral allylic alcohols.

  6. Metabolism, excretion, and pharmacokinetics of S-allyl-L-cysteine in rats and dogs.

    PubMed

    Amano, Hirotaka; Kazamori, Daichi; Itoh, Kenji; Kodera, Yukihiro

    2015-05-01

    The metabolism, excretion, and pharmacokinetics of S-allyl-l-cysteine (SAC), an active key component of garlic supplements, were examined in rats and dogs. A single dose of SAC was administered orally or i.v. to rats (5 mg/kg) and dogs (2 mg/kg). SAC was well absorbed (bioavailability >90%) and its four metabolites-N-acetyl-S-allyl-l-cysteine (NAc-SAC), N-acetyl-S-allyl-l-cysteine sulfoxide (NAc-SACS), S-allyl-l-cysteine sulfoxide (SACS), and l-γ-glutamyl-S-allyl-l-cysteine-were identified in the plasma and/or urine. Renal clearance values (<0.01 l/h/kg) of SAC indicated its extensive renal reabsorption, which contributed to the long elimination half-life of SAC, especially in dogs (12 hours). The metabolism of SAC to NAc-SAC, principal metabolite of SAC, was studied in vitro and in vivo. Liver and kidney S9 fractions of rats and dogs catalyzed both N-acetylation of SAC and deacetylation of NAc-SAC. After i.v. administration of NAc-SAC, SAC appeared in the plasma and its concentration declined in parallel with that of NAc-SAC. These results suggest that the rate and extent of the formation of NAc-SAC are determined by the N-acetylation and deacetylation activities of liver and kidney. Also, NAc-SACS was detected in the plasma after i.v. administration of either NAc-SAC or SACS, suggesting that NAc-SACS could be formed via both N-acetylation of SACS and S-oxidation of NAc-SAC. In conclusion, this study demonstrated that the pharmacokinetics of SAC in rats and dogs is characterized by its high oral bioavailability, N-acetylation and S-oxidation metabolism, and extensive renal reabsorption, indicating the critical roles of liver and kidney in the elimination of SAC.

  7. Allyl 4-hydroxy­phenyl carbonate

    PubMed Central

    Flores Ahuactzin, Víctor Hugo; López, Delia; Bernès, Sylvain

    2009-01-01

    The title mol­ecule, C10H10O4, is a functionalized carbonate used in the synthetic route to organic glasses. The central CH fragment of the allyl group is disordered over two positions, with occupancies in a 0.758 (10):0.242 (10)ratio. This disorder reflects the torsional flexibility of the oxygen–allyl group, although both disordered parts present the expected anti­clinal conformation, with O—CH2—CH=CH2 torsion angles of −111 (2) and 119.1 (4)°. The crystal structure is based on chains parallel to [010], formed by O⋯H—O hydrogen bonds involving hydroxyl and carbonyl groups as donors and acceptors, respectively. The mol­ecular packing is further stabilized by two weak C—H⋯π contacts from the benzene ring of the asymmetric unit with two benzene rings of neighboring mol­ecules. PMID:21582877

  8. Mineralogical, petrological, and geochemical studies of the Limahe mafic-ultramatic intrusion and associated Ni-Cu sulfide ores, SW China

    NASA Astrophysics Data System (ADS)

    Tao, Yan; Li, Chusi; Song, Xie-Yan; Ripley, Edward M.

    2008-11-01

    The Limahe Ni-Cu sulfide deposit is hosted by a small mafic-ultramafic intrusion (800 × 200 × 300 m) that is temporally associated with the voluminous Permian flood basalts in SW China. The objective of this study is to better understand the origin of the deposit in the context of regional magmatism which is important for the ongoing mineral exploration in the region. The Limahe intrusion is a multiphase intrusion with an ultramafic unit at the base and a mafic unit at the top. The two rock units have intrusive contacts and exhibit similar mantle-normalized trace element patterns and Sr-Nd isotopic compositions but significantly different cumulus mineralogy and major element compositions. The similarities suggest that they are related to a common parental liquid, whereas the differences point to magma differentiation by olivine crystallization at depth. Sulfide mineralization is restricted to the ultramafic unit. The abundances of sulfides in the ultramafic unit generally increase towards the basal contacts with sedimentary footwall. The δ 34S values of sulfide minerals from the Limahe deposit are elevated, ranging from +2.4 to +5.4‰. These values suggest the involvement of external S with elevated δ 34S values. The mantle-normalized platinum-group element (PGE) patterns of bulk sulfide ores are similar to those of picrites associated with flood basalts in the region. The abundances of PGE in the sulfide ores, however, are significantly lower than that of sulfide liquid expected to segregate from undepleted picrite magma. Cr-spinel and olivine are present in the Limahe ultramafic rocks as well as in the picrites. Mantle-normalized trace element patterns of the Limahe intrusion generally resemble those of the picrites. However, negative Nb-Ta anomalies, common features of contamination with the lower or middle crust, are present in the intrusion but absent in the picrites. Sr-Nd isotopes suggest that the Limahe intrusion experienced higher degrees of

  9. Volcanogenic Massive Sulfide Deposit Density

    USGS Publications Warehouse

    Mosier, Dan L.; Singer, Donald A.; Berger, Vladimir I.

    2007-01-01

    A mineral-deposit density model for volcanogenic massive sulfide deposits was constructed from 38 well-explored control areas from around the world. Control areas contain at least one exposed volcanogenic massive sulfide deposit. The control areas used in this study contain 150 kuroko, 14 Urals, and 25 Cyprus massive sulfide subtypes of volcanogenic massive sulfide deposits. For each control area, extent of permissive rock, number of exposed volcanogenic massive sulfide deposits, map scale, deposit age, and deposit density were determined. The frequency distribution of deposit densities in these 38 control areas provides probabilistic estimates of the number of deposits for tracts that are permissive for volcanogenic massive sulfide deposits-90 percent of the control areas have densities of 100 or more deposits per 100,000 square kilometers, 50 percent of the control areas have densities of 700 or more deposits per 100,000 square kilometers, and 10 percent of the control areas have densities of 3,700 or more deposits per 100,000 square kilometers. Both map scale and the size of the control area are shown to be predictors of deposit density. Probabilistic estimates of the number of volcanogenic massive sulfide deposits can be made by conditioning the estimates on sizes of permissive area. The model constructed for this study provides a powerful tool for estimating the number of undiscovered volcanogenic massive sulfide deposits when conducting resource assessments. The value of these deposit densities is due to the consistency of these models with the grade and tonnage and the descriptive models. Mineral-deposit density models combined with grade and tonnage models allow reasonable estimates of the number, size, and grades of volcanogenic massive sulfide deposits to be made.

  10. Acceleration effect of an allylic hydroxy group on ring-closing enyne metathesis of terminal alkynes: scope, application, and mechanistic insights.

    PubMed

    Imahori, Tatsushi; Ojima, Hidetomo; Yoshimura, Yuichi; Takahata, Hiroki

    2008-01-01

    An interesting acceleration effect of an allylic hydroxy group on ring-closing enyne metathesis has been found. Ring-closing enyne metathesis of terminal alkynes possessing an allylic hydroxy group proceeded smoothly without the ethylene atmosphere generally necessary to promote the reaction. The synthesis of (+)-isofagomine with the aid of this efficient reaction has been demonstrated. Mechanistic studies of the acceleration effect were also carried out. Results of NMR studies suggested that the reaction proceeded via an "ene-then-yne" pathway. Kinetic studies indicated switching of the rate-determining step as a consequence of the presence of an allylic hydroxy group. These results suggest acceleration of the reentry step of Ru-carbene species by the allylic hydroxy group.

  11. Genome Wide Association Mapping in Arabidopsis thaliana Identifies Novel Genes Involved in Linking Allyl Glucosinolate to Altered Biomass and Defense

    PubMed Central

    Francisco, Marta; Joseph, Bindu; Caligagan, Hart; Li, Baohua; Corwin, Jason A.; Lin, Catherine; Kerwin, Rachel E.; Burow, Meike; Kliebenstein, Daniel J.

    2016-01-01

    A key limitation in modern biology is the ability to rapidly identify genes underlying newly identified complex phenotypes. Genome wide association studies (GWAS) have become an increasingly important approach for dissecting natural variation by associating phenotypes with genotypes at a genome wide level. Recent work is showing that the Arabidopsis thaliana defense metabolite, allyl glucosinolate (GSL), may provide direct feedback regulation, linking defense metabolism outputs to the growth, and defense responses of the plant. However, there is still a need to identify genes that underlie this process. To start developing a deeper understanding of the mechanism(s) that modulate the ability of exogenous allyl GSL to alter growth and defense, we measured changes in plant biomass and defense metabolites in a collection of natural 96 A. thaliana accessions fed with 50 μM of allyl GSL. Exogenous allyl GSL was introduced exclusively to the roots and the compound transported to the leaf leading to a wide range of heritable effects upon plant biomass and endogenous GSL accumulation. Using natural variation we conducted GWAS to identify a number of new genes which potentially control allyl responses in various plant processes. This is one of the first instances in which this approach has been successfully utilized to begin dissecting a novel phenotype to the underlying molecular/polygenic basis. PMID:27462337

  12. Genome Wide Association Mapping in Arabidopsis thaliana Identifies Novel Genes Involved in Linking Allyl Glucosinolate to Altered Biomass and Defense.

    PubMed

    Francisco, Marta; Joseph, Bindu; Caligagan, Hart; Li, Baohua; Corwin, Jason A; Lin, Catherine; Kerwin, Rachel E; Burow, Meike; Kliebenstein, Daniel J

    2016-01-01

    A key limitation in modern biology is the ability to rapidly identify genes underlying newly identified complex phenotypes. Genome wide association studies (GWAS) have become an increasingly important approach for dissecting natural variation by associating phenotypes with genotypes at a genome wide level. Recent work is showing that the Arabidopsis thaliana defense metabolite, allyl glucosinolate (GSL), may provide direct feedback regulation, linking defense metabolism outputs to the growth, and defense responses of the plant. However, there is still a need to identify genes that underlie this process. To start developing a deeper understanding of the mechanism(s) that modulate the ability of exogenous allyl GSL to alter growth and defense, we measured changes in plant biomass and defense metabolites in a collection of natural 96 A. thaliana accessions fed with 50 μM of allyl GSL. Exogenous allyl GSL was introduced exclusively to the roots and the compound transported to the leaf leading to a wide range of heritable effects upon plant biomass and endogenous GSL accumulation. Using natural variation we conducted GWAS to identify a number of new genes which potentially control allyl responses in various plant processes. This is one of the first instances in which this approach has been successfully utilized to begin dissecting a novel phenotype to the underlying molecular/polygenic basis.

  13. Genome Wide Association Mapping in Arabidopsis thaliana Identifies Novel Genes Involved in Linking Allyl Glucosinolate to Altered Biomass and Defense.

    PubMed

    Francisco, Marta; Joseph, Bindu; Caligagan, Hart; Li, Baohua; Corwin, Jason A; Lin, Catherine; Kerwin, Rachel E; Burow, Meike; Kliebenstein, Daniel J

    2016-01-01

    A key limitation in modern biology is the ability to rapidly identify genes underlying newly identified complex phenotypes. Genome wide association studies (GWAS) have become an increasingly important approach for dissecting natural variation by associating phenotypes with genotypes at a genome wide level. Recent work is showing that the Arabidopsis thaliana defense metabolite, allyl glucosinolate (GSL), may provide direct feedback regulation, linking defense metabolism outputs to the growth, and defense responses of the plant. However, there is still a need to identify genes that underlie this process. To start developing a deeper understanding of the mechanism(s) that modulate the ability of exogenous allyl GSL to alter growth and defense, we measured changes in plant biomass and defense metabolites in a collection of natural 96 A. thaliana accessions fed with 50 μM of allyl GSL. Exogenous allyl GSL was introduced exclusively to the roots and the compound transported to the leaf leading to a wide range of heritable effects upon plant biomass and endogenous GSL accumulation. Using natural variation we conducted GWAS to identify a number of new genes which potentially control allyl responses in various plant processes. This is one of the first instances in which this approach has been successfully utilized to begin dissecting a novel phenotype to the underlying molecular/polygenic basis. PMID:27462337

  14. Experimental study of the behavior of molybdenum in hot sulfide-carbonate solutions

    SciTech Connect

    Agapova, G.F.; Shmariovich, E.M.; Vorob'ev, I.M.; Khitarov, D.N.

    1987-04-01

    Previous experiments have characterized the behavior of uranium in sulfide-carbonate solutions at 200/sup 0/C, analogous to the solutions that produced many endogenous pitchblende deposits, as indicated by fluid inclusions in minerals and by mineralogical and geochemical data. Molybdenum often accompanies uranium in endogenous pitchblende and related deposits and may form economic accumulations as low-temperature molybdenite. There have been repeated discussions on the forms taken by molybdenum and the reasons for deposition in such ores. The experiments described here indicate the existence of various complexes of molybdenum under different conditions and explain some of the paragenesis of molybdenum minerals with uranium minerals. 12 references, 3 figures, 1 table.

  15. Mineralogical studies of sulfide samples and volatile concentrations of basalt glasses from the southern Juan de Fuca Ridge.

    PubMed

    Brett, R; Evans, H T; Gibson, E K; Hedenquist, J W; Wandless, M V; Sommer, M A

    1987-10-10

    Sulfide samples obtained from the U.S. Geological Survey's DSRV Alvin dives on the southern Juan de Fuca Ridge closely resemble those from the same area described by Koski et al. (1984). Major minerals include sphalerite, wurtzite, pyrite, marcasite, isocubanite, anhydrite, and chalcopyrite. Equilibrium, if attained at all, during deposition of most sulfides was a transient event over a few tens of micrometers at most and was perturbed by rapid temperature and compositional changes of the circulating fluid. Two new minerals were found: one, a hydrated Zn, Fe hydroxy-chlorosulfate, and the other, a (Mn, Mg, Fe) hydroxide or hydroxy-hydrate. Both were formed at relatively low temperatures. Lizardite, starkeyite, and anatase were found for the first time in such an environment. Sulfide geothermometry involving the system Cu-Fe-S indicates a vent temperature of <328 degrees C for one sample. Fluid inclusion studies on crystals from the same vicinity of the same sample give pressure-corrected homogenization temperatures of 268 degrees and 285 degrees C. Ice-melting temperatures on inclusions from the same sample are about -2.8 degrees C, indicating that the equivalent salinity of the trapped fluid is about 50% greater than that of seawater. Volatile concentrations from vesicle-free basalt glass from the vent field are about 0.013 wt% CO2 and 0.16 wt% H2O, CO2 contents in these samples yield an entrapment depth of 2200 m of seawater, which is the depth from which the samples were collected.

  16. Study on application of biological iron sulfide composites in treating vanadium-extraction wastewater containing chromium (VI) and chromium reclamation.

    PubMed

    Xie, Yi-Fei; Li, Xu-Dong; Li, Fu-De

    2013-04-01

    In this study, the Cr(VI)-resistant properties and regeneration characteristics of biological iron sulfide composites were investigated, which consist of sulfate reducing bacteria (SRB) and its in situ synthesized nanosized iron sulfides. Then the application of the composites in treating vanadium-extraction wastewater containing high concentration Cr(VI) and reclaiming Cr were performed. It was found that SRB in composites still survived after being used to treat vanadium-extraction wastewater, which could reduce reaction products Fe3+ and sulphur into Fe2+ and S2 by using them as the electron accepters and thus regenerating biological iron sulfide composites. The SRB also could be resistant to 600 mgl(-1) Cr(VI) and reduce it gradually. Based on the Cr(VI)-resistant properties and regeneration characteristics of the composites, a reduction-regeneration recirculation process for treating vanadium-extraction wastewater and reclamation of Cr was developed. The results indicated that the contaminants in effluent reached the Chinese discharge standard of pollutants for vanadium industry (GB 26452-2011), i.e. the concentration of total Cr(TCr) was less than 0.912 mgl(-1), Cr(VI) was less than 0.017 mgl(-1) and V was less than 0.260 mgl(-1). After 10 cycles of treatment, the Cr2O3 content in sludge reached 41.03%, and the ratio of Cr2O3/FeO was 7.35. The sludge reached the chemical and metallurgical (hydrometallurgy) grade of chromite ore and could be reclaimed. PMID:24620597

  17. Study on application of biological iron sulfide composites in treating vanadium-extraction wastewater containing chromium (VI) and chromium reclamation.

    PubMed

    Xie, Yi-Fei; Li, Xu-Dong; Li, Fu-De

    2013-04-01

    In this study, the Cr(VI)-resistant properties and regeneration characteristics of biological iron sulfide composites were investigated, which consist of sulfate reducing bacteria (SRB) and its in situ synthesized nanosized iron sulfides. Then the application of the composites in treating vanadium-extraction wastewater containing high concentration Cr(VI) and reclaiming Cr were performed. It was found that SRB in composites still survived after being used to treat vanadium-extraction wastewater, which could reduce reaction products Fe3+ and sulphur into Fe2+ and S2 by using them as the electron accepters and thus regenerating biological iron sulfide composites. The SRB also could be resistant to 600 mgl(-1) Cr(VI) and reduce it gradually. Based on the Cr(VI)-resistant properties and regeneration characteristics of the composites, a reduction-regeneration recirculation process for treating vanadium-extraction wastewater and reclamation of Cr was developed. The results indicated that the contaminants in effluent reached the Chinese discharge standard of pollutants for vanadium industry (GB 26452-2011), i.e. the concentration of total Cr(TCr) was less than 0.912 mgl(-1), Cr(VI) was less than 0.017 mgl(-1) and V was less than 0.260 mgl(-1). After 10 cycles of treatment, the Cr2O3 content in sludge reached 41.03%, and the ratio of Cr2O3/FeO was 7.35. The sludge reached the chemical and metallurgical (hydrometallurgy) grade of chromite ore and could be reclaimed.

  18. Copper(I)-Catalyzed Allylic Substitutions with a Hydride Nucleophile.

    PubMed

    Nguyen, T N Thanh; Thiel, Niklas O; Pape, Felix; Teichert, Johannes F

    2016-05-20

    An easily accessible copper(I)/N-heterocyclic carbene (NHC) complex enables a regioselective hydride transfer to allylic bromides, an allylic reduction. The resulting aryl- and alkyl-substituted branched α-olefins, which are valuable building blocks for synthesis, are obtained in good yields and regioselectivity. A commercially available silane, (TMSO)2Si(Me)H, is employed as hydride source. This protocol offers a unified alternative to the established metal-catalyzed allylic substitutions with carbon nucleophiles, as no adaption of the catalyst to the nature of the nucleophile is required. PMID:27151495

  19. Chemical tools for the study of hydrogen sulfide (H2S) and sulfane sulfur and their applications to biological studies.

    PubMed

    Takano, Yoko; Shimamoto, Kazuhito; Hanaoka, Kenjiro

    2016-01-01

    Hydrogen sulfide (H2S) functions in many physiological processes, including relaxation of vascular smooth muscles, mediation of neurotransmission, inhibition of insulin signaling, and regulation of inflammation. On the other hand, sulfane sulfur, which is a sulfur atom with six valence electrons but no charge, has the unique ability to bind reversibly to other sulfur atoms to form hydropersulfides (R-S-SH) and polysulfides (-S-Sn-S-). H2S and sulfane sulfur always coexist, and recent work suggests that sulfane sulfur species may be the actual signaling molecules in at least some biological phenomena. For example, one of the mechanisms of activity regulation of proteins by H2S is the S-sulfhydration of cysteine residues (protein Cys-SSH). In this review, we summarize recent progress on chemical tools for the study of H2S and sulfane sulfur, covering fluorescence probes utilizing various design strategies, H2S caged compounds, inhibitors of physiological H2S-producing enzymes (cystathionine γ-lyase, cystathionine β-synthase and 3-mercaptopyruvate sulfurtransferase), and labeling reagents. Fluorescence probes offer particular advantages as chemical tools to study physiological functions of biomolecules, including ease of use and real-time, nondestructive visualization of biological processes in live cells and tissues. PMID:26798192

  20. Chemical tools for the study of hydrogen sulfide (H2S) and sulfane sulfur and their applications to biological studies

    PubMed Central

    Takano, Yoko; Shimamoto, Kazuhito; Hanaoka, Kenjiro

    2016-01-01

    Hydrogen sulfide (H2S) functions in many physiological processes, including relaxation of vascular smooth muscles, mediation of neurotransmission, inhibition of insulin signaling, and regulation of inflammation. On the other hand, sulfane sulfur, which is a sulfur atom with six valence electrons but no charge, has the unique ability to bind reversibly to other sulfur atoms to form hydropersulfides (R-S-SH) and polysulfides (-S-Sn-S-). H2S and sulfane sulfur always coexist, and recent work suggests that sulfane sulfur species may be the actual signaling molecules in at least some biological phenomena. For example, one of the mechanisms of activity regulation of proteins by H2S is the S-sulfhydration of cysteine residues (protein Cys-SSH). In this review, we summarize recent progress on chemical tools for the study of H2S and sulfane sulfur, covering fluorescence probes utilizing various design strategies, H2S caged compounds, inhibitors of physiological H2S-producing enzymes (cystathionine γ-lyase, cystathionine β-synthase and 3-mercaptopyruvate sulfurtransferase), and labeling reagents. Fluorescence probes offer particular advantages as chemical tools to study physiological functions of biomolecules, including ease of use and real-time, nondestructive visualization of biological processes in live cells and tissues. PMID:26798192

  1. Palladium/N-heterocyclic carbene catalysed regio and diastereoselective reaction of ketones with allyl reagents via inner-sphere mechanism

    PubMed Central

    Bai, Da-Chang; Yu, Fei-Le; Wang, Wan-Ying; Chen, Di; Li, Hao; Liu, Qing-Rong; Ding, Chang-Hua; Chen, Bo; Hou, Xue-Long

    2016-01-01

    The palladium-catalysed allylic substitution reaction is one of the most important reactions in transition-metal catalysis and has been well-studied in the past decades. Most of the reactions proceed through an outer-sphere mechanism, affording linear products when monosubstituted allyl reagents are used. Here, we report an efficient Palladium-catalysed protocol for reactions of β-substituted ketones with monosubstituted allyl substrates, simply by using N-heterocyclic carbene as ligand, leading to branched products with up to three contiguous stereocentres in a (syn, anti)-mode with excellent regio and diastereoselectivities. The scope of the protocol in organic synthesis has been examined preliminarily. Mechanistic studies by both experiments and density functional theory (DFT) calculations reveal that the reaction proceeds via an inner-sphere mechanism—nucleophilic attack of enolate oxygen on Palladium followed by C–C bond-forming [3,3']-reductive elimination. PMID:27283477

  2. NMR studies of chiral P,S-chelate platinum, rhodium, and iridium complexes and the X-ray structure of a palladium(II) allyl derivative

    SciTech Connect

    Albinati, A.; Eckert, J.; Pregosin, P.; Ruegger, H.; Salzmann, R.; Stoessel, C.

    1997-02-18

    Several Rh(I), Ir(III), and Pt(II) complexes of the chiral P,S-bidentate ligand 2 have been prepared and characterized. Detailed two-dimensional NMR studies show that (i) the boat-type chelate ring and the stereogenic sulfur center can invert rapidly at ambient temperature and (ii) the sulfur donor may dissociate, essentially destroying the chiral pocket. The solid-state structure of [Pt({eta}{sup 3}-C{sub 3}H{sub 5})(2)]PF{sub 6} (3) has been determined and the sulfur substituent shown to have an axial orientation. The six-membered chelate ring takes up a boat-like conformation. As shown by an X-ray diffraction study for 3, and via incoherent inelastic neutron scattering (IINS) measurements for the Pd analog, 4, the OH group is remote from the metal atom. 42 refs., 11 figs., 6 tabs.

  3. Glutathione-garlic sulfur conjugates: slow hydrogen sulfide releasing agents for therapeutic applications.

    PubMed

    Bhuiyan, Ashif Iqbal; Papajani, Vilma Toska; Paci, Maurizio; Melino, Sonia

    2015-01-01

    Natural organosulfur compounds (OSCs) from Allium sativum L. display antioxidant and chemo-sensitization properties, including the in vitro inhibition of tumor cell proliferation through the induction of apoptosis. Garlic water- and oil-soluble allyl sulfur compounds show distinct properties and the capability to inhibit the proliferation of tumor cells. In the present study, we optimized a new protocol for the extraction of water-soluble compounds from garlic at low temperatures and the production of glutathionyl-OSC conjugates during the extraction. Spontaneously, Cys/GSH-mixed-disulfide conjugates are produced by in vivo metabolism of OSCs and represent active molecules able to affect cellular metabolism. Water-soluble extracts, with (GSGaWS) or without (GaWS) glutathione conjugates, were here produced and tested for their ability to release hydrogen sulfide (H2S), also in the presence of reductants and of thiosulfate:cyanide sulfurtransferase (TST) enzyme. Thus, the TST catalysis of the H2S-release from garlic OSCs and their conjugates has been investigated by molecular in vitro experiments. The antiproliferative properties of these extracts on the human T-cell lymphoma cell line, HuT 78, were observed and related to histone hyperacetylation and downregulation of GAPDH expression. Altogether, the results presented here pave the way for the production of a GSGaWS as new, slowly-releasing hydrogen sulfide extract for potential therapeutic applications. PMID:25608858

  4. Stabilization of lead sulfide nanoparticles by polyamines in aqueous solutions. A structural study of the dispersions.

    PubMed

    Koupanou, Elena; Ahualli, Silvia; Glatter, Otto; Delgado, Angel; Krumeich, Frank; Leontidis, Epameinondas

    2010-11-16

    Lead sulfide (PbS) nanoparticles have been synthesized in aqueous solutions by a reaction between inorganic lead salts and sodium sulfide and stabilized using the cationic polyelectrolytes branched poly(ethylenimine) (PEI), poly(allylamine hydrochloride) (PAH), and poly(diallyldimethylammonium chloride) (PDDA). The structures of the polyamine-stabilized nanoparticle dispersions were examined in detail using UV-vis spectroscopy, small-angle X-ray scattering (SAXS), static and dynamic electrophoretic mobility measurements, and transmission electron microscopy (TEM). Considerable differences were found between the stabilizing efficiencies of these polyelectrolytes, which cannot be attributed to their charge densities or their persistence lengths. Small monodisperse nanoparticles of PbS with a tight stabilizing shell were consistently found only when PEI was used as a stabilizer even at high pH values, although its charge density is then very low. The excellence of PEI as a stabilizer is mainly due to the extensive branching of the chains and the presence of uncharged secondary and tertiary amine groups, which apparently serve as good anchoring points at the nanoparticle surfaces. None of the polyelectrolytes examined here provide long-term protection of the nanoparticles toward oxidation by air, showing that a need for more complex multipurpose stabilizers exists for aqueous PbS dispersions.

  5. Sulfide chemiluminescence detection

    DOEpatents

    Spurlin, Stanford R.; Yeung, Edward S.

    1985-01-01

    A method of chemiluminescently determining a sulfide which is either hydrogen sulfide or methyl mercaptan by reacting the sulfide with chlorine dioxide at low pressure and under conditions which allow a longer reaction time in emission of a single photon for every two sulfide containing species, and thereafter, chemiluminescently detecting and determining the sulfide. The invention also relates not only to the detection method, but the novel chemical reaction and a specifically designed chemiluminescence detection cell for the reaction.

  6. Sulfide chemiluminescence detection

    DOEpatents

    Spurlin, S.R.; Yeung, E.S.

    1985-11-26

    A method is described for chemiluminescently determining a sulfide which is either hydrogen sulfide or methyl mercaptan by reacting the sulfide with chlorine dioxide at low pressure and under conditions which allow a longer reaction time in emission of a single photon for every two sulfide containing species, and thereafter, chemiluminescently detecting and determining the sulfide. The invention also relates not only to the detection method, but the novel chemical reaction and a specifically designed chemiluminescence detection cell for the reaction. 4 figs.

  7. Regio- and enantiospecific rhodium-catalyzed allylic etherification reactions using copper(I) alkoxides: influence of the copper halide salt on selectivity.

    PubMed

    Evans, P Andrew; Leahy, David K

    2002-07-10

    The transition metal-catalyzed allylic etherification represents a fundamentally important cross-coupling reaction for the construction of allylic ethers. We have developed a new regio- and enantiospecific rhodium-catalyzed allylic etherification of acyclic unsymmetrical allylic alcohol derivatives using copper(I) alkoxides derived from primary, secondary and tertiary alcohols. This study demonstrates that the choice of copper(I) halide salt is crucial for obtaining excellent regio- and enantiospecificity, providing another example of the effect of halide ions in asymmetric transition metal-catalyzed reactions. Finally, the ability to alter the reactivity of the alkali metal alkoxides in this manner may provide a useful method for related metal-catalyzed cross-coupling reactions involving heteroatoms.

  8. Enantioselective synthesis of α-tri- and α-tetrasubstituted allylsilanes by copper-catalyzed asymmetric allylic substitution of allyl phosphates with silylboronates.

    PubMed

    Takeda, Momotaro; Shintani, Ryo; Hayashi, Tamio

    2013-05-17

    A copper/N-heterocyclic carbene-catalyzed asymmetric allylic substitution of allyl phosphates with a silylboronate has been developed to give highly enantioenriched allylsilanes. High regioselectivity has been achieved by employing NaOH as the base, and this catalyst system is effective for both γ-mono- and disubstituted allyl phosphates. PMID:23647080

  9. Mössbauer study of electrochemically deposited amorphous iron-sulfide-oxide thin films

    NASA Astrophysics Data System (ADS)

    Ichimura, Masaya; Kajima, Takahiro; Kawai, Shoichi; Mibu, Ko

    2016-03-01

    Iron-sulfide-oxide thin films, which are promising candidates for solar cell materials, were deposited by electrochemical deposition. As-deposited and annealed films were characterized by Mössbauer spectroscopy, X-ray diffraction (XRD), and Raman scattering at room temperature. The as-deposited film is amorphous, and the oxygen content is about 1/4 of the sulfur content (S/Fe ≈ 1.5, O/Fe ≈ 0.4). The Mössbauer spectrum for the as-deposited film is a doublet with a broad line profile having hyperfine parameters similar to those of FeS2 pyrite or marcasite. This indicates that Fe atoms are in the Fe2+ low-spin state, as in FeS2.

  10. A SeCSe-Pd(II) pincer complex as a highly efficient catalyst for allylation of aldehydes with allyltributyltin.

    PubMed

    Yao, Qingwei; Sheets, Matthew

    2006-07-01

    An air- and moisture-stable SeCSe-Pd(II) pincer complex was synthesized and found to catalyze the nucleophilic allylation of aldehydes with allyltributyltin. The allylation of a variety of aromatic and aliphatic aldehydes to give the corresponding homoallyl alcohols was performed at room temperature to 60 degrees C in yields ranging from 50% (for typical aliphatic aldehydes) to up to 97% (for aromatic aldehydes) using 5 x 10(-3) to 1 mol % of the Pd catalyst. NMR spectroscopic study indicated that a sigma-allylpalladium intermediate was formed and possibly functions as the nucleophilic species that undergoes addition to the aldehydes. PMID:16808533

  11. A SeCSe-Pd(II) pincer complex as a highly efficient catalyst for allylation of aldehydes with allyltributyltin.

    PubMed

    Yao, Qingwei; Sheets, Matthew

    2006-07-01

    An air- and moisture-stable SeCSe-Pd(II) pincer complex was synthesized and found to catalyze the nucleophilic allylation of aldehydes with allyltributyltin. The allylation of a variety of aromatic and aliphatic aldehydes to give the corresponding homoallyl alcohols was performed at room temperature to 60 degrees C in yields ranging from 50% (for typical aliphatic aldehydes) to up to 97% (for aromatic aldehydes) using 5 x 10(-3) to 1 mol % of the Pd catalyst. NMR spectroscopic study indicated that a sigma-allylpalladium intermediate was formed and possibly functions as the nucleophilic species that undergoes addition to the aldehydes.

  12. Intramolecular Tsuji-Trost-type Allylation of Carboxylic Acids: Asymmetric Synthesis of Highly π-Allyl Donative Lactones.

    PubMed

    Suzuki, Yusuke; Seki, Tomoaki; Tanaka, Shinji; Kitamura, Masato

    2015-08-01

    Tsuji-Trost-type asymmetric allylation of carboxylic acids has been realized by using a cationic CpRu complex with an axially chiral picolinic acid-type ligand (Cl-Naph-PyCOOH: naph = naphthyl, py = pyridine). The carboxylic acid and allylic alcohol intramolecularly condense by the liberation of water without stoichiometric activation of either nucleophile or electrophile part, thereby attaining high atom- and step-economy, and low E factor. This success can be ascribed to the higher reactivity of allylic alcohols as compared with the allyl ester products in soft Ru/hard Brønstead acid combined catalysis, which can function under slightly acidic conditions unlike the traditional Pd-catalyzed system. Detailed analysis of the stereochemical outcome of the reaction using an enantiomerically enriched D-labeled substrate provides an intriguing view of enantioselection. PMID:26199057

  13. Chemical Bonding in Sulfide Minerals

    SciTech Connect

    Vaughan, David J.; Rosso, Kevin M.

    2006-08-01

    An understanding of chemical bonding and electronic structure in sulfide minerals is central to any attempt at understanding their crystal structures, stabilities and physical properties. It is also an essential precursor to understanding reactivity through modeling surface structure at the molecular scale. In recent decades, there have been remarkable advances in first principles (ab initio) methods for the quantitative calculation of electronic structure. These advances have been made possible by the very rapid development of high performance computers. Several review volumes that chart the applications of these developments in mineralogy and geochemistry are available (Tossell and Vaughan, 1992; Cygan and Kubicki, 2001). An important feature of the sulfide minerals is the diversity of their electronic structures, as evidenced by their electrical and magnetic properties (see Pearce et al. 2006, this volume). Thus, sulfide minerals range from insulators through semiconductors to metals, and exhibit every type of magnetic behavior. This has presented problems for those attempting to develop bonding models for sulfides, and also led to certain misconceptions regarding the kinds of models that may be appropriate. In this chapter, chemical bonding and electronic structure models for sulfides are reviewed with emphasis on more recent developments. Although the fully ab initio quantitative methods are now capable of a remarkable degree of sophistication in terms of agreement with experiment and potential to interpret and predict behavior with varying conditions, both qualitative and more simplistic quantitative approaches will also be briefly discussed. This is because we believe that the insights which they provide are still helpful to those studying sulfide minerals. In addition to the application of electronic structure models and calculations to solid sulfides, work on sulfide mineral surfaces (Rosso and Vaughan 2006a,b) and solution complexes and clusters (Rickard

  14. Hydrogen Sulfide Oxidation by Myoglobin.

    PubMed

    Bostelaar, Trever; Vitvitsky, Victor; Kumutima, Jacques; Lewis, Brianne E; Yadav, Pramod K; Brunold, Thomas C; Filipovic, Milos; Lehnert, Nicolai; Stemmler, Timothy L; Banerjee, Ruma

    2016-07-13

    Enzymes in the sulfur network generate the signaling molecule, hydrogen sulfide (H2S), from the amino acids cysteine and homocysteine. Since it is toxic at elevated concentrations, cells are equipped to clear H2S. A canonical sulfide oxidation pathway operates in mitochondria, converting H2S to thiosulfate and sulfate. We have recently discovered the ability of ferric hemoglobin to oxidize sulfide to thiosulfate and iron-bound hydropolysulfides. In this study, we report that myoglobin exhibits a similar capacity for sulfide oxidation. We have trapped and characterized iron-bound sulfur intermediates using cryo-mass spectrometry and X-ray absorption spectroscopy. Further support for the postulated intermediates in the chemically challenging conversion of H2S to thiosulfate and iron-bound catenated sulfur products is provided by EPR and resonance Raman spectroscopy in addition to density functional theory computational results. We speculate that the unusual sensitivity of skeletal muscle cytochrome c oxidase to sulfide poisoning in ethylmalonic encephalopathy, resulting from the deficiency in a mitochondrial sulfide oxidation enzyme, might be due to the concentration of H2S by myoglobin in this tissue. PMID:27310035

  15. A randomized, double-blind study comparing the efficacy of selenium sulfide shampoo 1% and ciclopirox shampoo 1% as adjunctive treatments for tinea capitis in children.

    PubMed

    Chen, Catherine; Koch, Laine H; Dice, James E; Dempsey, Kimberly K; Moskowitz, Alan B; Barnes-Eley, Myra L; Hubbard, Thomas W; Williams, Judith V

    2010-01-01

    Our objective was to compare the efficacy of selenium sulfide shampoo 1% and ciclopirox shampoo 1% as adjunctive treatments for tinea capitis in children. Forty children aged 1-11 years with clinically diagnosed tinea capitis were randomized to receive selenium sulfide shampoo 1% or ciclopirox shampoo 1% twice a week as adjuncts to an 8-week course of ultramicronized griseofulvin dosed at 10-12 mg/kg/day. At weeks 2, 4, and 8, subjects returned to the clinic for evaluation and scalp cultures. Subjects then returned for follow-up visits 4 weeks after completing treatment. Overall, by 8 weeks, 30 of 33 (90.9%) treated children demonstrated mycological cure. Selenium sulfide shampoo 1% and ciclopirox shampoo 1% were equally effective as adjunctive treatments for tinea capitis in children in our study.

  16. (E)-4-(3-(3,5-dimethoxyphenyl)allyl)-2-methoxyphenol inhibits growth of colon tumors in mice

    PubMed Central

    Son, Dong Ju; Choi, Min Gi; Choi, Jeong Soon; Nam, Kyung Tak; Kim, Hae Deun; Rodriguez, Kevin; Gann, Benjamin; Ham, Young Wan; Han, Sang Bae; Hong, Jin Tae

    2015-01-01

    In our previous study, we found that (E)-2,4-bis(p-hydroxyphenyl)-2-butenal showed anti-cancer effect, but it showed lack of stability and drug likeness. We have prepared several (E)-2,4-bis(p-hydroxyphenyl)-2-butenal analogues by Heck reaction. We selected two compounds which showed significant inhibitory effect of colon cancer cell growth. Thus, we evaluated the anti-cancer effects and possible mechanisms of one compound (E)-4-(3-(3,5-dimethoxyphenyl)allyl)-2-methoxyphenol in vitro and in vivo. In this study, we found that (E)-4-(3-(3,5-dimethoxyphenyl)allyl)-2-methoxyphenol induced apoptotic cell death in a dose dependent manner (0-15 μg/ml) through activation of Fas and death receptor (DR) 3 in HCT116 and SW480 colon cancer cell lines. Moreover, the combination treatment with (E)-4-(3-(3,5-dimethoxyphenyl)allyl)-2-methoxyphenol and nuclear factor κB (NF-κB) inhibitor, phenylarsine oxide (0.1 μM) or signal transducer and activator of transcription 3 (STAT3) inhibitor, Stattic (50 μM) increased the expression of Fas and DR3 more significantly. In addition, (E)-4-(3-(3,5-dimethoxyphenyl)allyl)-2-methoxyphenol suppressed the DNA binding activity of both STAT3 and NF-κB. Knock down of STAT3 or NF-κB p50 subunit by STAT3 small interfering RNA (siRNA) or p50 siRNA magnified (E)-4-(3-(3,5-dimethoxyphenyl)allyl)-2-methoxyphenol-induced inhibitory effect on colon cancer cell growth. Besides, the expression of Fas and DR3 was increased in STAT3 siRNA or p50 siRNA transfected cells. Moreover, docking model and pull-down assay showed that (E)-4-(3-(3,5-dimethoxyphenyl)allyl)-2-methoxyphenol directly bound to STAT3 and NF-κB p50 subunit. Furthermore, (E)-4-(3-(3,5-dimethoxyphenyl)allyl)-2-methoxyphenol inhibited colon tumor growth in a dose dependent manner (2.5 mg/kg-5 mg/kg) in mice. Therefore, these findings indicated that (E)-4-(3-(3,5-dimethoxyphenyl)allyl)-2-methoxyphenol may be a promising anti-cancer agent for colon cancer with more advanced research. PMID

  17. Laboratory studies of Aedes aegypti (L.) attraction to ketones, sulfides and primary chloroalkanes tested alone and in combination with l-lactic acid

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The attraction of female Aedes aegypti to single compounds and binary compositions comprised of L-lactic acid and an additional saturated compound from a set of ketones, sulfides, and chloroalkanes was studied using a triple-cage dual-port olfactometer. These chemical classes were studied because o...

  18. Epoxidation of allyl alcohol to glycidol over the microporous TS-1 catalyst.

    PubMed

    Wróblewska, Agnieszka; Fajdek, Anna

    2010-07-15

    The results of the epoxidation of allyl alcohol with 30% hydrogen peroxide over the TS-1 catalyst have been presented. The studies were carried out under the atmospheric pressure and at the presence of methanol as a solvent. The influence of the following technological parameters on the course of epoxidation was examined: the temperature of 20-60 degrees C, the molar ratio of AA/H(2)O(2) 1:1-5:1, the methanol concentration of 5-90 wt%, the catalyst content of 0.1-5.0 wt% and the reaction time 5-300 min. The main functions describing the process were the selectivity to glycidol in relation to allyl alcohol consumed, the conversion of substrates, and the selectivity of transformation to organic compounds in relation to hydrogen peroxide consumed. The parameters at which the functions describing the process reached the highest values were determined.

  19. Biotechnological reduction of sulfide in an industrial primary wastewater treatment system: A sustainable and successful case study

    SciTech Connect

    Rajamani, S.

    1996-12-31

    The leather industry is an important export-oriented industry in India, with more than 3,000 tanneries located in different clusters. Sodium sulfide, a toxic chemical, is used in large quantities to remove hair and excess flesh from hides and skins. Most of the sodium sulfide used in the process is discharged as waste in the effluent, which causes serious environmental problems. Reduction of sulfide in the effluent is generally achieved by means of chemicals in the pretreatment system, which involves aerobic mixing using large amounts of chemicals and high energy, and generating large volumes of sludge. A simple biotechnological system that uses the residual biosludge from the secondary settling tank was developed, and the commercial-scale application established that more than 90% of the sulfide could be reduced in the primary treatment system. In addition to the reduction of sulfide, foul smells, BOD and COD are reduced to a considerable level. 3 refs., 2 figs., 1 tab.

  20. Mössbauer study on microwave synthesized (Cu,Fe) sulfide composites and correlation with natural mineral—cubanite

    NASA Astrophysics Data System (ADS)

    Pareek, Sarita; Rais, Anwar; Tripathi, Amita; Chandra, Usha

    2008-09-01

    In nature, the mineral ‘Cubanite’ with composition CuFe2S3 occurs in orthorhombic structure in the matrix of chalcopyrite and pyrrhotite. Synthesis of this mineral in the laboratory conditions has not been reported yet. An attempt to synthesize the orthorhombic Cu-Fe-Sulfide (cubanite) by resistive as well as microwave heating technique is reported. MW-heated sample shows the presence of orthorhombic component along with isocubanite and pyrrhotite. The synthesized samples were studied in details through XRD and Mössbauer spectroscopy. The synthesis process, responsible for different proportions of the minerals, may indicate the conditions of their genesis in nature. Formation of isocubanite (cubic cubanite) seems unavoidable under the conditions of synthesis. The striking indistinguishable character of cubanite and chalcopyrite could be challenged through Mössbauer hyperfine parameter—the hyperfine field of chalcopyrite (~37 T) being quite different from that of cubanite (~33 T).

  1. Efficient epoxidation of a terminal alkene containing allylic hydrogen atoms: trans-methylstyrene on Cu{111}.

    PubMed

    Cropley, Rachael L; Williams, Federico J; Urquhart, Andrew J; Vaughan, Owain P H; Tikhov, Mintcho S; Lambert, Richard M

    2005-04-27

    The selective oxidation of trans-methylstyrene, a phenyl-substituted propene that contains labile allylic hydrogen atoms, has been studied on Cu{111}. Mass spectrometry and synchrotron fast XPS were used to detect, respectively, desorbing gaseous products and the evolution of surface species as a function of temperature and time. Efficient partial oxidation occurs yielding principally the epoxide, and the behavior of the system is sensitive to the order in which reactants are adsorbed. The latter is understandable in terms of differences in the spatial distribution of oxygen adatoms; isolated adatoms lead to epoxidation, while islands of "oxidic" oxygen do not. NEXAFS data taken over a range of coverages and in the presence and absence of coadsorbed oxygen indicate that the adsorbed alkene lies essentially flat with the allylic hydrogen atoms close to the surface. The photoemission results and comparison with the corresponding behavior of styrene on Cu{111} strongly suggest that allylic hydrogen abstraction is indeed a critical factor that limits epoxidation selectivity. An overall mechanism consistent with the structural and reactive properties is proposed.

  2. Pendant Allyl Crosslinking as a Tunable Shape Memory Actuator for Vascular Applications

    PubMed Central

    Zachman, Angela L.; Lee, Sue Hyun; Balikov, Daniel A.; Kim, Kwangho; Bellan, Leon M.; Sung, Hak-Joon

    2015-01-01

    Thermo-responsive shape memory polymers (SMPs) can be fit into small-bore incisions and recover their functional shape upon deployment in the body. This property is of significant interest for developing the next generation of minimally-invasive medical devices. To be used in such applications, SMPs should exhibit adequate mechanical strengths that minimize adverse compliance mismatch-induced host responses (e.g. thrombosis, hyperplasia), be biodegradable, and demonstrate switch-like shape recovery near body temperature with favorable biocompatibility. Combinatorial approaches are essential in optimizing SMP material properties for a particular application. In this study, a new class of thermo-responsive SMPs with pendant, photocrosslinkable allyl groups, x%poly( -caprolactone)-co-y%( -allyl carboxylate -caprolactone) (x%PCL-y%ACPCL), are created in a robust, facile manner with readily tunable material properties. Thermomechanical and shape memory properties can be drastically altered through subtle changes in allyl composition. Molecular weight and gel content can also be altered in this combinatorial format to fine-tune material properties. Materials exhibit high elastic, switch-like shape recovery near 37 °C. Endothelial compatibility is comparable to tissue culture polystyrene (TCPS) and 100%PCL in vitro and vascular compatibility is demonstrated in vivo in a murine model of hindlimb ischemia, indicating promising suitability for vascular applications. PMID:26072363

  3. Cadmium sulfide membranes

    DOEpatents

    Spanhel, Lubomir; Anderson, Marc A.

    1992-07-07

    A method is described for the creation of novel q-effect cadmium sulfide membranes. The membranes are made by first creating a dilute cadmium sulfide colloid in aqueous suspension and then removing the water and excess salts therefrom. The cadmium sulfide membrane thus produced is luminescent at room temperature and may have application in laser fabrication.

  4. Cadmium sulfide membranes

    DOEpatents

    Spanhel, Lubomir; Anderson, Marc A.

    1991-10-22

    A method is described for the creation of novel q-effect cadmium sulfide membranes. The membranes are made by first creating a dilute cadmium sulfide colloid in aqueous suspension and then removing the water and excess salts therefrom. The cadmium sulfide membrane thus produced is luminescent at room temperature and may have application in laser fabrication.

  5. SULFIDE MINERALS IN SEDIMENTS

    EPA Science Inventory

    The formation processes of metal sulfides in sediments, especially iron sulfides, have been the subjects of intense scientific research because of linkages to the global biogeochemical cycles of iron, sulfur, carbon, and oxygen. Transition metal sulfides (e.g., NiS, CuS, ZnS, Cd...

  6. Molecular cytotoxicity mechanisms of allyl alcohol (acrolein) in budding yeast.

    PubMed

    Golla, Upendarrao; Bandi, Goutham; Tomar, Raghuvir S

    2015-06-15

    Allyl alcohol (AA) is one of the environmental pollutants used as a herbicide and industrial chemical. AA undergoes enzymatic oxidation in vivo to form Acrolein (Acr), a highly reactive and ubiquitous environmental toxicant. The exposure to AA/Acr has detrimental effects on cells and is highly fatal. In corroboration to the current literature describing AA/Acr toxicity, this study aimed to investigate the molecular cytotoxicity mechanisms of AA/Acr using budding yeast as a eukaryotic model organism. Genome-wide transcriptome analysis of cells treated with a sublethal dose of AA (0.4 mM) showed differential regulation of approximately 30% of the yeast genome. Functional enrichment analysis of the AA transcriptome revealed that genes belong to diverse cellular processes including the cell cycle, DNA damage repair, metal homeostasis, stress response genes, ribosomal biogenesis, metabolism, meiosis, ubiquitination, cell morphogenesis, and transport. Moreover, we have identified novel molecular targets of AA/Acr through genetic screening, which belongs to oxidative stress, DNA damage repair, iron homeostasis, and cell wall integrity. This study also demonstrated the epigenetic basis of AA/Acr toxicity mediated through histone tails and chromatin modifiers. Interestingly, our study disclosed the use of pyrazole and ethanol as probable antidotes for AA intoxication. For the first time, this study also demonstrated the reproductive toxicity of AA/Acr using the yeast gametogenesis (spermatogenesis) model. Altogether, this study unravels the molecular mechanisms of AA/Acr cytotoxicity and facilitates the prediction of biomarkers for toxicity assessment and therapeutic approaches. PMID:25919230

  7. Scalable and sustainable electrochemical allylic C-H oxidation.

    PubMed

    Horn, Evan J; Rosen, Brandon R; Chen, Yong; Tang, Jiaze; Chen, Ke; Eastgate, Martin D; Baran, Phil S

    2016-05-01

    New methods and strategies for the direct functionalization of C-H bonds are beginning to reshape the field of retrosynthetic analysis, affecting the synthesis of natural products, medicines and materials. The oxidation of allylic systems has played a prominent role in this context as possibly the most widely applied C-H functionalization, owing to the utility of enones and allylic alcohols as versatile intermediates, and their prevalence in natural and unnatural materials. Allylic oxidations have featured in hundreds of syntheses, including some natural product syntheses regarded as "classics". Despite many attempts to improve the efficiency and practicality of this transformation, the majority of conditions still use highly toxic reagents (based around toxic elements such as chromium or selenium) or expensive catalysts (such as palladium or rhodium). These requirements are problematic in industrial settings; currently, no scalable and sustainable solution to allylic oxidation exists. This oxidation strategy is therefore rarely used for large-scale synthetic applications, limiting the adoption of this retrosynthetic strategy by industrial scientists. Here we describe an electrochemical C-H oxidation strategy that exhibits broad substrate scope, operational simplicity and high chemoselectivity. It uses inexpensive and readily available materials, and represents a scalable allylic C-H oxidation (demonstrated on 100 grams), enabling the adoption of this C-H oxidation strategy in large-scale industrial settings without substantial environmental impact.

  8. Scalable and sustainable electrochemical allylic C–H oxidation

    NASA Astrophysics Data System (ADS)

    Horn, Evan J.; Rosen, Brandon R.; Chen, Yong; Tang, Jiaze; Chen, Ke; Eastgate, Martin D.; Baran, Phil S.

    2016-05-01

    New methods and strategies for the direct functionalization of C–H bonds are beginning to reshape the field of retrosynthetic analysis, affecting the synthesis of natural products, medicines and materials. The oxidation of allylic systems has played a prominent role in this context as possibly the most widely applied C–H functionalization, owing to the utility of enones and allylic alcohols as versatile intermediates, and their prevalence in natural and unnatural materials. Allylic oxidations have featured in hundreds of syntheses, including some natural product syntheses regarded as “classics”. Despite many attempts to improve the efficiency and practicality of this transformation, the majority of conditions still use highly toxic reagents (based around toxic elements such as chromium or selenium) or expensive catalysts (such as palladium or rhodium). These requirements are problematic in industrial settings; currently, no scalable and sustainable solution to allylic oxidation exists. This oxidation strategy is therefore rarely used for large-scale synthetic applications, limiting the adoption of this retrosynthetic strategy by industrial scientists. Here we describe an electrochemical C–H oxidation strategy that exhibits broad substrate scope, operational simplicity and high chemoselectivity. It uses inexpensive and readily available materials, and represents a scalable allylic C–H oxidation (demonstrated on 100 grams), enabling the adoption of this C–H oxidation strategy in large-scale industrial settings without substantial environmental impact.

  9. Scalable and sustainable electrochemical allylic C-H oxidation.

    PubMed

    Horn, Evan J; Rosen, Brandon R; Chen, Yong; Tang, Jiaze; Chen, Ke; Eastgate, Martin D; Baran, Phil S

    2016-05-01

    New methods and strategies for the direct functionalization of C-H bonds are beginning to reshape the field of retrosynthetic analysis, affecting the synthesis of natural products, medicines and materials. The oxidation of allylic systems has played a prominent role in this context as possibly the most widely applied C-H functionalization, owing to the utility of enones and allylic alcohols as versatile intermediates, and their prevalence in natural and unnatural materials. Allylic oxidations have featured in hundreds of syntheses, including some natural product syntheses regarded as "classics". Despite many attempts to improve the efficiency and practicality of this transformation, the majority of conditions still use highly toxic reagents (based around toxic elements such as chromium or selenium) or expensive catalysts (such as palladium or rhodium). These requirements are problematic in industrial settings; currently, no scalable and sustainable solution to allylic oxidation exists. This oxidation strategy is therefore rarely used for large-scale synthetic applications, limiting the adoption of this retrosynthetic strategy by industrial scientists. Here we describe an electrochemical C-H oxidation strategy that exhibits broad substrate scope, operational simplicity and high chemoselectivity. It uses inexpensive and readily available materials, and represents a scalable allylic C-H oxidation (demonstrated on 100 grams), enabling the adoption of this C-H oxidation strategy in large-scale industrial settings without substantial environmental impact. PMID:27096371

  10. Reactions of allylic radicals that impact molecular weight growth kinetics.

    PubMed

    Wang, Kun; Villano, Stephanie M; Dean, Anthony M

    2015-03-01

    The reactions of allylic radicals have the potential to play a critical role in molecular weight growth (MWG) kinetics during hydrocarbon oxidation and/or pyrolysis. Due to their stability (when compared to alkyl radicals), they can accumulate to relatively high concentrations. Thus, even though the rate coefficients for their various reactions are small, the rates of these reactions may be significant. In this work, we use electronic structure calculations to examine the recombination, addition, and abstraction reactions of allylic radicals. For the recombination reaction of allyl radicals, we assign a high pressure rate rule that is based on experimental data. Once formed, the recombination product can potentially undergo an H-atom abstraction reaction followed by unimolecular cyclization and β-scission reactions. Depending upon the conditions (e.g., higher pressures) these pathways can lead to the formation of stable MWG species. The addition of allylic radicals to olefins can also lead to MWG species formation. Once again, cyclization of the adduct followed by β-scission is an important energy accessible route. Since the recombination and addition reactions produce chemically-activated adducts, we have explored the pressure- and temperature-dependence of the overall rate constants as well as that for the multiple product channels. We describe a strategy for estimating these pressure-dependencies for systems where detailed electronic structure information is not available. We also derive generic rate rules for hydrogen abstraction reactions from olefins and diolefins by methyl and allyl radicals.

  11. Catalytic asymmetric generation of (Z)-disubstituted allylic alcohols.

    PubMed

    Salvi, Luca; Jeon, Sang-Jin; Fisher, Ethan L; Carroll, Patrick J; Walsh, Patrick J

    2007-12-26

    A one-pot method for the direct preparation of enantioenriched (Z)-disubstituted allylic alcohols is introduced. Hydroboration of 1-halo-1-alkynes with dicyclohexylborane, reaction with t-BuLi, and transmetalation with dialkylzinc reagents generate (Z)-disubstituted vinylzinc intermediates. In situ reaction of these reagents with aldehydes in the presence of a catalyst derived from (-)-MIB generates (Z)-disubstituted allylic alcohols. It was found that the resulting allylic alcohols were racemic, most likely due to a rapid addition reaction promoted by LiX (X = Br and Cl). To suppress the LiX-promoted reaction, a series of inhibitors were screened. It was found that 20-30 mol % tetraethylethylenediamine inhibited LiCl without inhibiting the chiral zinc-based Lewis acid. In this fashion, (Z)-disubstituted allylic alcohols were obtained with up to 98% ee. The asymmetric (Z)-vinylation could be coupled with tandem diastereoselective epoxidation reactions to provide epoxy alcohols and allylic epoxy alcohols with up to three contiguous stereogenic centers, enabling the rapid construction of complex building blocks with high levels of enantio- and diastereoselectivity.

  12. Scalable and sustainable electrochemical allylic C-H oxidation

    NASA Astrophysics Data System (ADS)

    Horn, Evan J.; Rosen, Brandon R.; Chen, Yong; Tang, Jiaze; Chen, Ke; Eastgate, Martin D.; Baran, Phil S.

    2016-05-01

    New methods and strategies for the direct functionalization of C-H bonds are beginning to reshape the field of retrosynthetic analysis, affecting the synthesis of natural products, medicines and materials. The oxidation of allylic systems has played a prominent role in this context as possibly the most widely applied C-H functionalization, owing to the utility of enones and allylic alcohols as versatile intermediates, and their prevalence in natural and unnatural materials. Allylic oxidations have featured in hundreds of syntheses, including some natural product syntheses regarded as “classics”. Despite many attempts to improve the efficiency and practicality of this transformation, the majority of conditions still use highly toxic reagents (based around toxic elements such as chromium or selenium) or expensive catalysts (such as palladium or rhodium). These requirements are problematic in industrial settings; currently, no scalable and sustainable solution to allylic oxidation exists. This oxidation strategy is therefore rarely used for large-scale synthetic applications, limiting the adoption of this retrosynthetic strategy by industrial scientists. Here we describe an electrochemical C-H oxidation strategy that exhibits broad substrate scope, operational simplicity and high chemoselectivity. It uses inexpensive and readily available materials, and represents a scalable allylic C-H oxidation (demonstrated on 100 grams), enabling the adoption of this C-H oxidation strategy in large-scale industrial settings without substantial environmental impact.

  13. Structurally defined allyl compounds of main group metals: coordination and reactivity.

    PubMed

    Lichtenberg, Crispin; Okuda, Jun

    2013-05-10

    Organometallic allyl compounds are important as allylation reagents in organic synthesis, as polymerization catalysts, and as volatile metal precursors in material science. Whereas the allyl chemistry of synthetically relevant transition metals such as palladium and of the lanthanoids is well-established, that of main group metals has been lagging behind. Recent progress on allyl complexes of Groups 1, 2, and 12-16 now provides a more complete picture. This is based on a fundamental understanding of metal-allyl bonding interactions in solution and in the solid state. Furthermore, reactivity trends have been rationalized and new types of allyl-specific reactivity patterns have been uncovered. Key features include 1) the exploitation of the different types of metal-allyl bonding (highly ionic to predominantly covalent), 2) the use of synergistic effects in heterobimetallic compounds, and 3) the adjustment of Lewis acidity by variation of the charge of allyl compounds.

  14. A coupled cluster study of the spectroscopic properties and electric dipole moment functions of nitrous sulfide

    NASA Astrophysics Data System (ADS)

    Pak, Youngshang; Woods, R. Claude; Peterson, Kirk A.

    1996-05-01

    Three-dimensional near-equilibrium potential energy surfaces and dipole moment functions have been calculated for the ground state of nitrous sulfide (NNS), using a large basis set and the coupled cluster method with single and double substitutions, augmented by a perturbative estimate of triple excitations [CCSD(T)]. The CCSD(T) equilibrium bond lengths with a correlation consistent polarized valence quadruple zeta (cc-pVQZ) basis set are re(NN)=1.1284 Å and Re(NS)=1.5904 Å, which have been corrected to 1.126 and 1.581 Å, respectively, based on the results of the corresponding calculations on the NN and NS diatomics. Rotational-vibrational energy levels and the corresponding infrared intensities for NNS have been determined using variational methods with the CCSD(T)/cc-pVQZ potential energy and dipole moment functions. The calculated band origins (cm-1) ν1, ν2, and ν3 and their intensities (km/mol) at the CCSD(T)/cc-pVQZ level are 740.7/38.6, 463.1/0.01, and 2061.4/385.8, respectively. A complete set of second-order spectroscopic constants have been obtained from the ab initio potential energy surface using both the standard perturbation theory formulas and the variationally determined rovibrational energies. Comparison of the theoretical vibration-rotation interaction constants (αi) with those obtained from the published high resolution Fourier transform infrared (FTIR) spectra clearly demonstrate that the rotational quantum number (J) assignments must be revised in all the observed hot bands. A new set of spectroscopic constants for NNS, derived from a reanalysis of the published FTIR frequencies, is presented. These are in excellent agreement with our CCSD(T) predictions. Values of the quadrupole coupling constants at each nucleus are predicted using multireference configuration interaction (MRCI) with the same cc-pVQZ basis.

  15. Combined Raman-LIBS Studies on Iron Sulfides to Investigate the Effect of the LIBS Plasma on the Mineral Composition

    NASA Astrophysics Data System (ADS)

    Alsemgeest, J.; Schröder, S.; Böttger, U.; Pavlov, S. G.; Weber, I.; Greshake, A.; Knöfler, H.-R.; Altenberger, U.; Hübers, H.-W.

    2016-08-01

    Iron sulfides, analyzed under martian conditions, show alteration caused by LIBS. This means that, during robotic planetary exploration by combined LIBS-Raman, effects must be taken into account with the interpretation of post-LIBS Raman data.

  16. ESEM Studies of Colloidal Sulfur Deposition in a Natural Microbial Community from a Cold Sulfide Spring Near Ancaster, Ontario, Canada

    NASA Technical Reports Server (NTRS)

    Douglas, S.; Douglas, D.

    2000-01-01

    We have used a relatively new microscopial technique, environmental scanning electron microscopy (ESEM), together with transmission electron microscopy (TEM) and light microscopy to investigate a unique microbial community from a temperate climate, cold sulfide spring near Ancaster, Ontario, Canada.

  17. Copper-catalyzed divergent kinetic resolution of racemic allylic substrates.

    PubMed

    Pineschi, Mauro; Di Bussolo, Valeria; Crotti, Paolo

    2011-10-01

    When a racemic mixture is fully consumed the products may still be enantiomerically enriched. In particular, the regiodivergent kinetic resolution is a process in which a single chiral catalyst or reagent reacts with a racemic substrate to form regioisomers possessing an opposite configuration on the newly-formed stereogenic centers. This review reports the major advances in the field of the copper-catalyzed regiodivergent and stereodivergent kinetic resolution of allylic substrates with organometallic reagents. The chiral recognition matching phenomena found with particular allylic substrates with the absolute configuration of the chiral catalyst allows in some cases an excellent control of the regio- and stereoselectivity, sheding some light on the so-called "black-box" mechanism of a copper-catalyzed asymmetric allylic alkylation. PMID:21837639

  18. Allyl isothiocyanate affects the cell cycle of Arabidopsis thaliana

    PubMed Central

    Åsberg, Signe E.; Bones, Atle M.; Øverby, Anders

    2015-01-01

    Isothiocyanates (ITCs) are degradation products of glucosinolates present in members of the Brassicaceae family acting as herbivore repellents and antimicrobial compounds. Recent results indicate that allyl ITC (AITC) has a role in defense responses such as glutathione depletion, ROS generation and stomatal closure. In this study we show that exposure to non-lethal concentrations of AITC causes a shift in the cell cycle distribution of Arabidopsis thaliana leading to accumulation of cells in S-phases and a reduced number of cells in non-replicating phases. Furthermore, transcriptional analysis revealed an AITC-induced up-regulation of the gene encoding cyclin-dependent kinase A while several genes encoding mitotic proteins were down-regulated, suggesting an inhibition of mitotic processes. Interestingly, visualization of DNA synthesis indicated that exposure to AITC reduced the rate of DNA replication. Taken together, these results indicate that non-lethal concentrations of AITC induce cells of A. thaliana to enter the cell cycle and accumulate in S-phases, presumably as a part of a defensive response. Thus, this study suggests that AITC has several roles in plant defense and add evidence to the growing data supporting a multifunctional role of glucosinolates and their degradation products in plants. PMID:26042144

  19. 40 CFR 721.7000 - Polymer of disodium maleate, allyl ether, and ethylene oxide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Polymer of disodium maleate, allyl... New Uses for Specific Chemical Substances § 721.7000 Polymer of disodium maleate, allyl ether, and... substance identified generically as a polymer of disodium maleate, allyl ether, and ethylene oxide...

  20. 40 CFR 721.7000 - Polymer of disodium maleate, allyl ether, and ethylene oxide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Polymer of disodium maleate, allyl... New Uses for Specific Chemical Substances § 721.7000 Polymer of disodium maleate, allyl ether, and... substance identified generically as a polymer of disodium maleate, allyl ether, and ethylene oxide...

  1. 40 CFR 721.7000 - Polymer of disodium maleate, allyl ether, and ethylene oxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Polymer of disodium maleate, allyl... New Uses for Specific Chemical Substances § 721.7000 Polymer of disodium maleate, allyl ether, and... substance identified generically as a polymer of disodium maleate, allyl ether, and ethylene oxide...

  2. Trifluoromethyl sulfoxides from allylic alcohols and electrophilic SCF3 donor by [2,3]-sigmatropic rearrangement.

    PubMed

    Maeno, Mayaka; Shibata, Norio; Cahard, Dominique

    2015-04-17

    An electrophilic trifluoromethylthiolation of allylic alcohols produces the corresponding allylic trifluoromethanesulfenates, which spontaneously rearrange into trifluoromethyl sulfoxides via a [2,3]-sigmatropic rearrangement. The reaction is straightforward and proceeds in good to high yields for the preparation of various allylic trifluoromethyl sulfoxides.

  3. Enantioselective transformation of Na2SO3 into allylic sulfonic acids under Pd catalysis.

    PubMed

    Liu, Wei; Zhao, Xiao-ming; Zhang, Hong-bo; Zhang, Liang

    2015-01-14

    Pd-catalyzed asymmetric allylic sulfonation of di-aryl-substituted allylic acetates with sodium sulfite (Na2SO3) in THF-H2O at room temperature was described. This method directly provided allylic sulfonic acids in up to excellent yield and enantioselectivity. PMID:25415622

  4. 40 CFR 721.9952 - Alkoxylated aliphatic diisocyanate allyl ether (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... allyl ether (generic). 721.9952 Section 721.9952 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.9952 Alkoxylated aliphatic diisocyanate allyl ether... identified generically as alkoxylated aliphatic diisocyanate allyl ether (PMN P-00-0353) is subject...

  5. 40 CFR 721.9952 - Alkoxylated aliphatic diisocyanate allyl ether (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... allyl ether (generic). 721.9952 Section 721.9952 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.9952 Alkoxylated aliphatic diisocyanate allyl ether... identified generically as alkoxylated aliphatic diisocyanate allyl ether (PMN P-00-0353) is subject...

  6. 40 CFR 721.7000 - Polymer of disodium maleate, allyl ether, and ethylene oxide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Polymer of disodium maleate, allyl... New Uses for Specific Chemical Substances § 721.7000 Polymer of disodium maleate, allyl ether, and... substance identified generically as a polymer of disodium maleate, allyl ether, and ethylene oxide...

  7. 40 CFR 721.7000 - Polymer of disodium maleate, allyl ether, and ethylene oxide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Polymer of disodium maleate, allyl... New Uses for Specific Chemical Substances § 721.7000 Polymer of disodium maleate, allyl ether, and... substance identified generically as a polymer of disodium maleate, allyl ether, and ethylene oxide...

  8. Rapid synthesis of polyprenylated acylphloroglucinol analogs via dearomative conjunctive allylic annulation.

    PubMed

    Grenning, Alexander J; Boyce, Jonathan H; Porco, John A

    2014-08-20

    Polyprenylated acylphloroglucinols (PPAPs) are structurally complex natural products with promising biological activities. Herein, we present a biosynthesis-inspired, diversity-oriented synthesis approach for rapid construction of PPAP analogs via double decarboxylative allylation (DcA) of acylphloroglucinol scaffolds to access allyl-desoxyhumulones followed by dearomative conjunctive allylic alkylation (DCAA). PMID:25061804

  9. Oxidation, reduction, and isomerization of allyl alcohol and 1-propanol over Cu[sub 2]O(100)

    SciTech Connect

    Schulz, K.H.; Cox, D.F. )

    1993-01-21

    The reactivity of allyl alcohol and 1-propanol has been studied with TDS and XPS on the polar, Cu[sup +]-terminated, Cu[sub 2]O(100) surface. Allyl alcohol reacts on the (100) surface to give selective and nonselective oxidation products (acrolein, CO, CO[sub 2], H[sub 2]O), an isomerization product (propionaldehyde), and a reduction product (propene). 1-Propanol also reacts on the (100) surface to give selective and nonselective oxidation products (acrolein, propionaldehyde, CO, CO[sub 2], H[sub 2]O) and a reduction product (propene). Both alcohols dissociatively adsorb to form alkoxides. The alkoxide species undergo hydride elimination on the carbon [alpha] to the oxygen to form the corresponding aldehydes. The acrolein and propionaldehyde formed from the alcohols are linked by a common surface enolate intermediate which explains the similarity in C[sub 3] products observed from the two alcohols. A low-temperature reaction to propene is attributed to pathways involving C-O bond scission from unsaturated surface oxygenates to give a surface allyl. Hydrogenation of the resulting allyl produces propene at low temperature. 28 refs., 6 figs., 2 tabs.

  10. XAS Study at Mo and Co K-Edges of the Sulfidation of a CoMo / Al2O3 Hydrotreating Catalyst

    SciTech Connect

    Pichon, C.; Gandubert, A. D.; Legens, C.; Guillaume, D.

    2007-02-02

    Because of its impact on environment, the removal of sulfur is an indispensable step, called hydrotreatment, in the refining of petroleum. One of the most commonly used hydrotreating catalysts is CoMo-type catalyst which is composed of molybdenum disulfide slabs promoted by cobalt atoms (CoMoS phase) and well dispersed on a high specific area alumina. As far as the highest sulfur content allowed in gasoline and diesel is continually decreasing, more and more efficient and active hydrotreating catalysts are required. In order to optimize the reactivity of the CoMo-type catalyst in hydrotreatment, a better understanding of the processes used to produce the active phase (CoMoS slabs) of the catalyst is necessary. The study reported here deals with the sulfiding mechanism of the slabs and the influence of temperature on the phenomenon. Ex situ X-ray absorption spectroscopy (XANES and EXAFS) was used to study the evolution of the structure of CoMo-type catalyst sulfided at various temperatures (from 293 to 873 K). XAS analysis was performed at both molybdenum and cobalt K-edges to obtain a cross-characterization of the sulfidation of the slabs. It evidenced the formation of various compounds, including two molybdenum oxides, MoS3 (or MoS3-like compound) and Co9S8, at specific steps of the sulfiding process. It showed the role of intermediate played by MoS3 (or MoS3-like compound) during the formation of the slabs and the competition between the appearance of promoted slabs (CoMoS phase) and Co9S8. At last, it leaded to the proposal of a mechanism for the sulfidation of the catalyst.

  11. XAS Study at Mo and Co K-Edges of the Sulfidation of a CoMo / Al2O3 Hydrotreating Catalyst

    NASA Astrophysics Data System (ADS)

    Pichon, C.; Gandubert, A. D.; Legens, C.; Guillaume, D.

    2007-02-01

    Because of its impact on environment, the removal of sulfur is an indispensable step, called hydrotreatment, in the refining of petroleum. One of the most commonly used hydrotreating catalysts is CoMo-type catalyst which is composed of molybdenum disulfide slabs promoted by cobalt atoms (CoMoS phase) and well dispersed on a high specific area alumina. As far as the highest sulfur content allowed in gasoline and diesel is continually decreasing, more and more efficient and active hydrotreating catalysts are required. In order to optimize the reactivity of the CoMo-type catalyst in hydrotreatment, a better understanding of the processes used to produce the active phase (CoMoS slabs) of the catalyst is necessary. The study reported here deals with the sulfiding mechanism of the slabs and the influence of temperature on the phenomenon. Ex situ X-ray absorption spectroscopy (XANES and EXAFS) was used to study the evolution of the structure of CoMo-type catalyst sulfided at various temperatures (from 293 to 873 K). XAS analysis was performed at both molybdenum and cobalt K-edges to obtain a cross-characterization of the sulfidation of the slabs. It evidenced the formation of various compounds, including two molybdenum oxides, MoS3 (or MoS3-like compound) and Co9S8, at specific steps of the sulfiding process. It showed the role of intermediate played by MoS3 (or MoS3-like compound) during the formation of the slabs and the competition between the appearance of promoted slabs (CoMoS phase) and Co9S8. At last, it leaded to the proposal of a mechanism for the sulfidation of the catalyst.

  12. Sulfur and sulfides in chondrules

    NASA Astrophysics Data System (ADS)

    Marrocchi, Yves; Libourel, Guy

    2013-10-01

    The nature and distribution of sulfides within type I PO, POP and PP chondrules of the carbonaceous chondrite Vigarano (CV3) have been studied by secondary electron microscopy and electron microprobe. They occur predominantly as spheroidal blebs composed entirely of low-Ni iron sulfide (troilite, FeS) or troilite + magnetite but in less abundance in association with metallic Fe-Ni beads in opaque assemblages. Troilites are mainly located within the low-Ca pyroxene outer zone and their amounts increase with the abundance of low-Ca pyroxene within chondrules, suggesting co-crystallization of troilite and low-Ca pyroxene during high-temperature events. We show that sulfur concentration and sulfide occurrence in chondrules obey high temperature sulfur solubility and saturation laws. Depending on the fS2 and fO2 of the surrounding gas and on the melt composition, mainly the FeO content, sulfur dissolved in chondrule melts may eventually reach a concentration limit, the sulfur content at sulfide saturation (SCSS), at which an immiscible iron sulfide liquid separates from the silicate melt. The occurrence of both a silicate melt and an immiscible iron sulfide liquid is further supported by the non-wetting behavior of sulfides on silicate phases in chondrules due to the high interfacial tension between their precursor iron-sulfide liquid droplets and the surrounding silicate melt during the high temperature chondrule-forming event. The evolution of chondrule melts from PO to PP towards more silicic compositions, very likely due to high PSiO(g) of the surrounding nebular gas, induces saturation of FeS at much lower S content in PP than in PO chondrules, leading to the co-crystallization of iron sulfides and low-Ca pyroxenes. Conditions of co-saturation of low-Ca pyroxene and FeS are only achieved in non canonical environments characterized by high partial pressures of sulfur and SiO and redox conditions more oxidizing than IW-3. Fe and S mass balance calculations also

  13. Association between Daily Hydrogen Sulfide Exposure and Incidence of Emergency Hospital Visits: A Population-Based Study

    PubMed Central

    Finnbjornsdottir, Ragnhildur Gudrun; Carlsen, Hanne Krage; Thorsteinsson, Throstur; Oudin, Anna; Lund, Sigrun Helga; Gislason, Thorarinn; Rafnsson, Vilhjalmur

    2016-01-01

    Background The adverse health effects of high concentrations of hydrogen sulfide (H2S) exposure are well known, though the possible effects of low concentrations have not been thoroughly studied. The aim was to study short-term associations between modelled ambient low-level concentrations of intermittent hydrogen sulfide (H2S) and emergency hospital visits with heart diseases (HD), respiratory diseases, and stroke as primary diagnosis. Methods The study is population-based, using data from patient-, and population-registers from the only acute care institution in the Reykjavik capital area, between 1 January, 2007 and 30 June, 2014. The study population was individuals (≥18yr) living in the Reykjavik capital area. The H2S emission originates from a geothermal power plant in the vicinity. A model was used to estimate H2S exposure in different sections of the area. A generalized linear model assuming Poisson distribution was used to investigate the association between emergency hospital visits and H2S exposure. Distributed lag models were adjusted for seasonality, gender, age, traffic zones, and other relevant factors. Lag days from 0 to 4 were considered. Results The total number of emergency hospital visits was 32961 with a mean age of 70 years. In fully adjusted un-stratified models, H2S concentrations exceeding 7.00μg/m3 were associated with increases in emergency hospital visits with HD as primary diagnosis at lag 0 risk ratio (RR): 1.067; 95% confidence interval (CI): 1.024–1.111, lag 2 RR: 1.049; 95%CI: 1.005–1.095, and lag 4 RR: 1.046; 95%CI: 1.004–1.089. Among males an association was found between H2S concentrations exceeding 7.00μg/m3, and HD at lag 0 RR: 1.087; 95%CI: 1.032–1.146 and lag 4 RR: 1080; 95%CI: 1.025–1.138; and among those 73 years and older at lag 0 RR: 1.075; 95%CI: 1.014–1.140 and lag 3 RR: 1.072; 95%CI: 1.009–1.139. No associations were found with other diseases. Conclusions The study showed an association between

  14. Iridium-Catalyzed Selective Isomerization of Primary Allylic Alcohols.

    PubMed

    Li, Houhua; Mazet, Clément

    2016-06-21

    This Account presents the development of the iridium-catalyzed isomerization of primary allylic alcohols in our laboratory over the past 8 years. Our initial interest was driven by the long-standing challenge associated with the development of a general catalyst even for the nonasymmetric version of this seemingly simple chemical transformation. The added value of the aldehyde products and the possibility to rapidly generate molecular complexity from readily accessible allylic alcohols upon a redox-economical isomerization reaction were additional sources of motivation. Certainly influenced by the success story of the related isomerization of allylic amines, most catalysts developed for the selective isomerization of allylic alcohols were focused on rhodium as a transition metal of choice. Our approach has been based on the commonly accepted precept that hydrogenation and isomerization are often competing processes, with the latter being usually suppressed in favor of the former. The cationic iridium complexes [(Cy3P)(pyridine)Ir(cod)]X developed by Crabtree (X = PF6) and Pfaltz (X = BArF) are usually considered as the most versatile catalysts for the hydrogenation of allylic alcohols. Using molecular hydrogen to generate controlled amounts of the active form of these complexes but performing the reaction in the absence of molecular hydrogen enabled deviation from the typical hydrogenation manifold and favored exclusively the isomerization of allylic alcohols into aldehydes. Isotopic labeling and crossover experiments revealed the intermolecular nature of the process. Systematic variation of the ligand on the iridium center allowed us to identify the structural features beneficial for catalytic activity. Subsequently, three generations of chiral catalysts have been investigated and enabled us to reach excellent levels of enantioselectivity for a wide range of 3,3-disubstituted aryl/alkyl and alkyl/alkyl primary allylic alcohols leading to β-chiral aldehydes. The

  15. Allyl isothiocyanate induces stomatal closure in Vicia faba.

    PubMed

    Sobahan, Muhammad Abdus; Akter, Nasima; Okuma, Eiji; Uraji, Misugi; Ye, Wenxiu; Mori, Izumi C; Nakamura, Yoshimasa; Murata, Yoshiyuki

    2015-01-01

    Isothiocyanates are enzymatically produced from glucosinolates in plants, and allyl isothiocyanate (AITC) induces stomatal closure in Arabidopsis thaliana. In this study, we investigated stomatal responses to AITC in Vicia faba. AITC-induced stomatal closure accompanied by reactive oxygen species (ROS) and NO production, cytosolic alkalization and glutathione (GSH) depletion in V. faba. GSH monoethyl ester induced stomatal reopening and suppressed AITC-induced GSH depletion in guard cells. Exogenous catalase and a peroxidase inhibitor, salicylhydroxamic acid, inhibited AITC-induced stomatal closure, unlike an NAD(P)H oxidase inhibitor, diphenylene iodonium chloride. The peroxidase inhibitor also abolished the AITC-induced ROS production, NO production, and cytosolic alkalization. AITC-induced stomatal closure was suppressed by an NO scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, and an agent to acidify cytosol, butyrate. These results indicate that AITC-induced stomatal closure in V. faba as well as in A. thaliana and suggest that AITC signaling in guard cells is conserved in both plants.

  16. Sulfide Stability of Planetary Basalts

    NASA Technical Reports Server (NTRS)

    Caiazza, C. M.; Righter, K.; Gibson, E. K., Jr.; Chesley, J. T.; Ruiz, J.

    2004-01-01

    The isotopic system, 187Re 187Os, can be used to determine the role of crust and mantle in magma genesis. In order to apply the system to natural samples, we must understand variations in Re/Os concentrations. It is thought that low [Os] and [Re] in basalts can be attributed to sulfide (FeS) saturation, as Re behaves incompatibly to high degrees of evolution until sulfide saturation occurs [1]. Previous work has shown that lunar basalts are sulfide under-saturated, and mid-ocean ridge, ocean-island and Martian (shergottites) basalts are saturated [2,3]. However, little is known about arc basalts. In this study, basaltic rocks were analyzed across the Trans-Mexican Volcanic Belt.

  17. Mechanisms of hydrogen sulfide removal with steel making slag.

    PubMed

    Kim, Kyunghoi; Asaoka, Satoshi; Yamamoto, Tamiji; Hayakawa, Shinjiro; Takeda, Kazuhiko; Katayama, Misaki; Onoue, Takasumi

    2012-09-18

    In the present study, we experimentally investigated the removal of hydrogen sulfide using steel-making slag (SMS) and clarified the mechanism of hydrogen sulfide removal with the SMS. The results proved that SMS is able to remove hydrogen sulfide dissolved in water, and the maximum removal amount of hydrogen sulfide per unit weight of the SMS for 8 days was estimated to be 37.5 mg S/g. The removal processes of hydrogen sulfide were not only adsorption onto the SMS, but oxidation and precipitation as sulfur. The chemical forms of sulfide adsorbed onto the SMS were estimated to be sulfur and manganese sulfide in the ratio of 81% and 19%, respectively. It is demonstrated here that the SMS is a promising material to remediate organically enriched coastal sediments in terms of removal of hydrogen sulfide. Furthermore, using SMS is expected to contribute to development of a recycling-oriented society.

  18. Sulfide oxidation under chemolithoautotrophic denitrifying conditions.

    PubMed

    Cardoso, Ricardo Beristain; Sierra-Alvarez, Reyes; Rowlette, Pieter; Flores, Elias Razo; Gómez, Jorge; Field, Jim A

    2006-12-20

    Chemolithoautotrophic denitrifying microorganisms oxidize reduced inorganic sulfur compounds coupled to the reduction of nitrate as an electron acceptor. These denitrifiers can be applied to the removal of nitrogen and/or sulfur contamination from wastewater, groundwater, and gaseous streams. This study investigated the physiology and kinetics of chemolithotrophic denitrification by an enrichment culture utilizing hydrogen sulfide, elemental sulfur, or thiosulfate as electron donor. Complete oxidation of sulfide to sulfate was observed when nitrate was supplemented at concentrations equal or exceeding the stoichiometric requirement. In contrast, sulfide was only partially oxidized to elemental sulfur when nitrate concentrations were limiting. Sulfide was found to inhibit chemolithotrophic sulfoxidation, decreasing rates by approximately 21-fold when the sulfide concentration increased from 2.5 to 10.0 mM, respectively. Addition of low levels of acetate (0.5 mM) enhanced denitrification and sulfate formation, suggesting that acetate was utilized as a carbon source by chemolithotrophic denitrifiers. The results of this study indicate the potential of chemolithotrophic denitrification for the removal of hydrogen sulfide. The sulfide/nitrate ratio can be used to control the fate of sulfide oxidation to either elemental sulfur or sulfate.

  19. Hydrogen sulfide alleviates the aluminum-induced changes in Brassica napus as revealed by physiochemical and ultrastructural study of plant.

    PubMed

    Ali, Basharat; Qian, Ping; Sun, Rui; Farooq, Muhammad A; Gill, Rafaqat A; Wang, Jian; Azam, Muhammad; Zhou, Weijun

    2015-02-01

    In the present study, ameliorating role of hydrogen sulfide (H2S) in oilseed rape (Brassica napus L.) was studied with or without application of H2S donor sodium hydrosulfide (NaHS) (0.3 mM) in hydroponic conditions under three levels (0, 0.1 and 0.3 mM) of aluminum (Al). Results showed that addition of H2S significantly improved the plant growth, photosynthetic gas exchange, and nutrients concentration in the leaves and roots of B. napus plants under Al stress. Exogenously applied H2S significantly lowered the Al concentration in different plant parts, and reduced the production of malondialdehyde and reactive oxygen species by improving antioxidant enzyme activities in the leaves and roots under Al stress. Moreover, the present study indicated that exogenously applied H2S improved the cell structure and displayed clean mesophyll and root tip cells. The chloroplast with well-developed thylakoid membranes could be observed in the micrographs. Under the combined application of H2S and Al, a number of modifications could be observed in root tip cell, such as mitochondria, endoplasmic reticulum, and golgi bodies. Thus, it can be concluded that exogenous application of H2S under Al stress improved the plant growth, photosynthetic parameters, elements concentration, and biochemical and ultrastructural changes in leaves and roots of B. napus.

  20. Effects of tetra-arsenic tetra-sulfide on BXSB lupus-prone mice: a pilot study.

    PubMed

    Zhao, Y; Wen, G; Qiao, Z; Xu, H; Sun, Q; Huang, H; Shan, S; Mu, Z; Zhang, J

    2013-04-01

    Systemic lupus erythematosus (SLE) is an autoimmune disease of uncertain etiology that affects multiple tissues and organs. Arsenic trioxide (ATO) has been used in lupus-prone mice with a regulatory effect on immune abnormality. Tetra-arsenic tetra-sulfide (As4S4), a traditional Chinese medicine, is effective on acute promyelocytic leukemia with mild side effects than ATO. In this study, a pilot study was performed to investigate the effects and the mechanism of As4S4 on the lupus-prone BXSB mice. Improvement of monocytosis (p<0.05) in spleen and decreased serum interleukin-6 (IL-6) (p=0.0277) were observed with As4S4 treatment. As4S4-treated mice exhibited amelioration of skin, liver and renal disease with mild side effects. Histological analysis revealed that As4S4 suppressed immune complex deposition, mesangial proliferation and inflammatory cell infiltration in kidney and liver. Our study support that As4S4 selectively suppresses cutaneous lupus and nephritis in BXSB mice and might be a potential treatment for SLE.

  1. The role of diallyl sulfides and dipropyl sulfides in the in vitro antimicrobial activity of the essential oil of garlic, Allium sativum L., and leek, Allium porrum L.

    PubMed

    Casella, Sergio; Leonardi, Michele; Melai, Bernardo; Fratini, Filippo; Pistelli, Luisa

    2013-03-01

    The in vitro antibacterial activity of essential oils (EOs) obtained from fresh bulbs of garlic, Allium sativum L., and leek, Allium porrum L. ( Alliaceae), was studied. A. sativum (garlic) EO showed a good antimicrobial activity against Staphylococcus aureus (inhibition zone 14.8 mm), Pseudomonas aeruginosa (inhibition zone 21.1 mm), and Escherichia coli (inhibition zone 11.0 mm), whereas the EO of A. porrum (leek) had no antimicrobial activity. The main constituents of the garlic EO were diallyl monosulfide, diallyl disulfide (DADS), diallyl trisulfide, and diallyl tetrasulfide. The EO of A. porrum was characterized by the presence of dipropyl disulfide (DPDS), dipropyl trisulfide, and dipropyl tetrasulfide. The antimicrobial activities of the DADS and DPDS were also studied. The results obtained suggest that the presence of the allyl group is fundamental for the antimicrobial activity of these sulfide derivatives when they are present in Allium or in other species (DADS inhibition zone on S. aureus 15.9 mm, P. aeruginosa 21.9 mm, E. coli 11.4 mm).

  2. Metal-free metathesis reaction of C-chiral allylic sulfilimines with aryl isocyanates: construction of chiral nonracemic allylic isocyanates.

    PubMed

    Grange, Rebecca L; Evans, P Andrew

    2014-08-27

    We report the facile and efficient metal-free metathesis reaction of C-chiral allylic sulfilimines with aryl isocyanates. This process facilitates the room temperature construction of an array of chiral nonracemic allylic isocyanates, which are versatile intermediates for the construction of unsymmetrical ureas, carbamates, thiocarbamates and amides. Furthermore, the sulfilimine/isocyanate metathesis reaction with 4,4'-methylene diphenyl diisocyanate (4,4'-MDI) circumvents harsh reaction conditions and/or hazardous reagents employed with more classical methods for the preparation of this important functional group.

  3. Allylation of acetanilides with allyl acetate under conditions of metal-complex catalysis combined with phase-transfer catalysis

    SciTech Connect

    Lebedev, S.A.; Leonova, Yu.P.; Berestova, S.S.; Petrov, E.S.

    1988-10-20

    Acetanilides are alkylated at the nitrogen atom under the conditions of phase-transfer catalysis. For the case of the reaction of acetanilides with allyl acetate the authors showed that 2-alkenyl esters can be used for the alkylation of acetanilides under the conditions of phase-transfer catalysis in the presence of the complexes of zero valent palladium. N-Acetylskatole was obtained with a yield of 50% from N-allyl-2-bromoacetanilide by intramolecular cyclization in the presence of Od(OAc)/sub 2/ as catalyst.

  4. Complete reversal in Wacker oxidation of acetonides and cyclic carbonates of allylic diols

    SciTech Connect

    Suk-Ku Kang; Kyung-Yun Jung; Eun-Young Namkoong

    1995-12-31

    The palladium(II)-catalyzed oxidation of terminal olefins to give methyl ketones (Wacker prossess) is well established in organic synthetic reactions. However palladium(II)-catalyzed oxidation of acetonide or cyclic carbonate of terminal allylic diol afforded aldehyde or {alpha},{beta}-unsaturated aldehyde as the sole products, resulting of anti-Markovnikov hydration. Alternatively, for the internal olefins of the substituted allylic diols, (E)-allylic diol provided {beta}-keto-product, whereas (Z)-allylic diol afforded {alpha}-keto-product. The acetonides and cyclic carbonates of the substituted allylic diols yielded {beta}-keto-products and {alpha},{beta}-unsaturated ketones.

  5. Study of benzotriazole as corrosion inhibitors of carbon steel in chloride solution containing hydrogen sulfide using electrochemical impedance spectroscopy (EIS)

    NASA Astrophysics Data System (ADS)

    Solehudin, Agus; Nurdin, Isdiriayani

    2014-03-01

    Corrosion and inhibition studies on API 5LX65 carbon steel in chloride solution containing various concentrations of benzotriazole has been conducted at temperature of 70°C using Electrochemical Impedance Spectroscopy (EIS). Corroded carbon steel surface with and without inhibitor have been observed using X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), and Energy Dispersive Spectroscopy (EDS). The objectives of this research are to study the performance of benzotriazole as corrosion inhibitors. The experimental results of carbon steel corrosion in 3.5% NaCl solution containing 500 mg/l H2S at different BTAH concentrations showed that corrosion rate of carbon steel decreases with increasing of BTAH concentrations from 0 to 10 mmol/l. The inhibition efficiency of BTAH was found to be affected by its concentration. The optimum efficiency obtained of BTAH is 93% at concentration of 5 mmol/l. The result of XRD and EDS analysis reveal the iron sulfide (FeS) formation on corroded carbon steel surface without inhibitor. The EDS spectrum show the Nitrogen (N) bond on carbon steel surface inhibited by BTAH.

  6. Study of benzotriazole as corrosion inhibitors of carbon steel in chloride solution containing hydrogen sulfide using electrochemical impedance spectroscopy (EIS)

    SciTech Connect

    Solehudin, Agus; Nurdin, Isdiriayani

    2014-03-24

    Corrosion and inhibition studies on API 5LX65 carbon steel in chloride solution containing various concentrations of benzotriazole has been conducted at temperature of 70°C using Electrochemical Impedance Spectroscopy (EIS). Corroded carbon steel surface with and without inhibitor have been observed using X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), and Energy Dispersive Spectroscopy (EDS). The objectives of this research are to study the performance of benzotriazole as corrosion inhibitors. The experimental results of carbon steel corrosion in 3.5% NaCl solution containing 500 mg/l H{sub 2}S at different BTAH concentrations showed that corrosion rate of carbon steel decreases with increasing of BTAH concentrations from 0 to 10 mmol/l. The inhibition efficiency of BTAH was found to be affected by its concentration. The optimum efficiency obtained of BTAH is 93% at concentration of 5 mmol/l. The result of XRD and EDS analysis reveal the iron sulfide (FeS) formation on corroded carbon steel surface without inhibitor. The EDS spectrum show the Nitrogen (N) bond on carbon steel surface inhibited by BTAH.

  7. Sulfidation of iron at high temperatures and diffusion kinetics in ferrous sulfide

    SciTech Connect

    Danielewski, M.; Mrowec, S.; Stoklosa, A.

    1982-02-01

    The kinetics and mechanism of iron sulfidation have been studied as a function of temperature (950-1200 K) and sulfur pressure (10/sup -3/ 0.065 atm). It has been stated that a compact Fe/sub 1-y/ S scale on iron grows according to the parabolic rate law as a result of outward lattice diffusion of metal ions through cation vacancies. The activation energy of sulfidation increases with sulfur pressure and the 1/n exponent increases with temperature. This nontypical dependence of iron sulfidation kinetics on temperature and pressure results from the analogous effect of both these parameters on defect concentration in ferrous sulfide. The chemical diffusion coefficients, D/sub FeS/ , and diffusion coefficients of defects, D/sub d/ , in ferrous sulfide have been calculated on the basis of parabolic rate contacts of iron sulfidation and deviations from stoichiometry in ferrous sulfide. It has been shown that D/sub FeS/ is practically independent of cation vacancy concentration whereas the diffusion coefficient of defects depends strongly on that parameter. A comparison of self-diffusion coefficients of iron in Fe/sub 1-y/ S calculated from the kinetics of iron sulfidation to those obtained from radioisotopic studies indicates that within the range studied of temperatures and sulfur vapor pressures the outward diffusion of iron across the scale occurs preferentially along the c axis of columnar ferrous sulfide crystals.

  8. [Cu(NHC)]-Catalyzed C-H Allylation and Alkenylation of both Electron-Deficient and Electron-Rich (Hetero)arenes with Allyl Halides.

    PubMed

    Xie, Weilong; Chang, Sukbok

    2016-01-26

    New reactivity of a [Cu(NHC)] (NHC=N-heterocyclic carbene) catalyst is disclosed for the efficient C-H allylation of polyfluoroarenes using allyl halides in benzene at room temperature. The same catalyst system also promotes an isomerization-induced alkenylation of initially the generated allyl arenes when the reaction is run in tetrahydrofuran. Significantly, not only electron-deficient but also electron-rich (hetero)arenes undergo this double-bond migration process, thus leading to alkenylated products. The present system features mild reaction conditions, broad scope with respect to the arene substrates and allyl halide reactants, good functional-group tolerance, and high stereoselectivity. PMID:26695120

  9. Electrochemical Allylic Oxidation of Olefins: Sustainable and Safe.

    PubMed

    Waldvogel, Siegfried R; Selt, Maximilian

    2016-10-01

    The power you're supplying: With the application of an optimized electrochemical approach, the allylic oxidation of olefins, which is an important C-H activation process that provides access to enones, becomes a sustainable, versatile, and potent key reaction for organic synthesis.

  10. Study and modeling of the evolution of gas-liquid partitioning of hydrogen sulfide in model solutions simulating winemaking fermentations.

    PubMed

    Mouret, Jean-Roch; Sablayrolles, Jean-Marie; Farines, Vincent

    2015-04-01

    The knowledge of gas-liquid partitioning of aroma compounds during winemaking fermentation could allow optimization of fermentation management, maximizing concentrations of positive markers of aroma and minimizing formation of molecules, such as hydrogen sulfide (H2S), responsible for defects. In this study, the effect of the main fermentation parameters on the gas-liquid partition coefficients (Ki) of H2S was assessed. The Ki for this highly volatile sulfur compound was measured in water by an original semistatic method developed in this work for the determination of gas-liquid partitioning. This novel method was validated and then used to determine the Ki of H2S in synthetic media simulating must, fermenting musts at various steps of the fermentation process, and wine. Ki values were found to be mainly dependent on the temperature but also varied with the composition of the medium, especially with the glucose concentration. Finally, a model was developed to quantify the gas-liquid partitioning of H2S in synthetic media simulating must to wine. This model allowed a very accurate prediction of the partition coefficient of H2S: the difference between observed and predicted values never exceeded 4%.

  11. Allyl/propenyl phenol synthases from the creosote bush and engineering production of specialty/commodity chemicals, eugenol/isoeugenol, in Escherichia coli.

    PubMed

    Kim, Sung-Jin; Vassão, Daniel G; Moinuddin, Syed G A; Bedgar, Diana L; Davin, Laurence B; Lewis, Norman G

    2014-01-01

    The creosote bush (Larrea tridentata) harbors members of the monolignol acyltransferase, allylphenol synthase, and propenylphenol synthase gene families, whose products together are able to catalyze distinct regiospecific conversions of various monolignols into their corresponding allyl- and propenyl-phenols, respectively. In this study, co-expression of a monolignol acyltransferase with either substrate versatile allylphenol or propenylphenol synthases in Escherichia coli established that various monolignol substrates were efficiently converted into their corresponding allyl/propenyl phenols, as well as providing proof of concept for efficacious conversion in a bacterial platform. This capability thus potentially provides an alternate source to these important plant phytochemicals, whether for flavor/fragrance and fine chemicals, or ultimately as commodities, e.g., for renewable energy or other intermediate chemical purposes. Previous reports had indicated that specific and highly conserved amino acid residues 84 (Phe or Val) and 87 (Ile or Tyr) of two highly homologous allyl/propenyl phenol synthases (circa 96% identity) from a Clarkia species mainly dictate their distinct regiospecific catalyzed conversions to afford either allyl- or propenyl-phenols, respectively. However, several other allyl/propenyl phenol synthase homologs isolated by us have established that the two corresponding amino acid 84 and 87 residues are not, in fact, conserved.

  12. Fluorinated alcohols as promoters for the metal-free direct substitution reaction of allylic alcohols with nitrogenated, silylated, and carbon nucleophiles.

    PubMed

    Trillo, Paz; Baeza, Alejandro; Nájera, Carmen

    2012-09-01

    The direct allylic substitution reaction using allylic alcohols in 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) and 2,2,2-trifluoroethanol (TFE) as reaction media is described. The developed procedure is simple, works under mild conditions (rt, 50 and 70 °C), and proves to be very general, since different nitrogenated nucleophiles and carbon nucleophiles can be used achieving high yields, especially when HFIP is employed as solvent and aromatic allylic alcohols are the substrates. Thus, sulfonamides, carbamates, carboxamides, and amines can be successfully employed as nitrogen-based nucleophiles. Likewise, silylated nucleophiles such as trimethylsilylazide, allyltrimethylsilane, trimethylsilane, and trimethylsilylphenylacetylene give the corresponding allylic substitution products in high yields. Good results for the Friedel-Crafts adducts are also achieved with aromatic compounds (phenol, anisole, indole, and anilines) as nucleophiles. Particularly interesting are the results obtained with electron-rich anilines, which can behave as nitrogenated or carbon nucleophiles depending on their electronic properties and the solvent employed. In addition, 1,3-dicarbonyl compounds (acetylacetone and Meldrum's acid) are also successfully employed as soft carbon nucleophiles. Studies for mechanism elucidation are also reported, pointing toward the existence of carbocationic intermediates and two working reaction pathways for the obtention of the allylic substitution product.

  13. Development and validation of S-allyl-L-cysteine in rat plasma using a mixed-mode reversed-phase and cation-exchange LC-ESI-MS/MS method: application to pharmacokinetic studies.

    PubMed

    Lee, Sanghee; Chang, Nae In; Yoo, Miyoung; Choi, Jung Hoon; Shin, Dongbin

    2015-01-01

    S-Allyl-L-cysteine (SAC), the most abundant organosulfur compound derived from garlic, has multifunctional biological activities that occur via different mechanisms. A sensitive, rapid and simple LC-ESI-MS/MS method using a mixed-mode reversed-phase and cation-exchange column containing C18 silica particles and sulfonic acid cation-exchange particles has been developed and validated for the analysis of SAC in rat plasma. The mobile phase was optimized at 2 mM ammonium acetate buffer (pH = 3.5) and acetonitrile (75:25, v/v). The assay utilized 0.6% acetic acid in methanol to achieve simple and rapid deproteinization. Quantification was conducted using multiple reaction monitoring (MRM) of the transitions of m/z 162.0 → 145.0 for SAC. The standard curve for SAC was linear (r(2) ≥ 0.999) over a range from 5 to 2,500 ng/mL. The intra- and interday precision (relative standard deviation) of the method was not >6.0% at three quality control levels. The limit of quantification (LOQ) was 5.0 ng/mL. After being fully validated, the method was successfully applied to the pharmacokinetic monitoring of SAC in rat plasma. PMID:24668040

  14. Does the Mechanism of the Garratt-Braverman Cyclization Differ with Substrates? A Computational Study on Bispropargyl Sulfones, Sulfides, Ethers, Amines, and Methanes.

    PubMed

    Jana, Saibal; Anoop, Anakuthil

    2016-09-01

    We studied the variation in mechanism among different bispropargyl substrates-sulfone, sulfide, ether, amine, and methane-toward Garratt-Braverman (GB) cyclization using density functional theory calculations. Isomerization and cycloaddition are the key steps in the GB cyclization. To compare the reactivity among the various substrates, we computed the free energy of activation (ΔG(⧧)) for the cycloaddition and the cyclization steps, whereas we used the theoretically computed pKa values for the isomerization steps. Our results suggest that the sulfones undergo a relatively fast isomerization followed by slower cyclization, while the ethers undergo a slow isomerization followed by easy cyclization. The methanes and amines are similar to the ethers, and the sulfides showed intermediate behavior. We extended our study to unsymmetrical substrates and compare the results with experiments that suggest the isomerization to be the rate-limiting step for bispropargyl ethers, while cyclization through a diradical intermediate is crucial to the rate for the bispropargyl sulfones. On the basis of these findings, we made predictions on the selectivity of unsymmetrical bispropargyl sulfones, amines, methanes, and sulfides. This is the first detailed mechanistic study on the GB cyclization of bispropargyl substrates other than sulfones. PMID:27464253

  15. Hydrothermal ore-forming processes in the light of studies in rock- buffered systems: I. Iron-copper-zinc-lead sulfide solubility relations

    USGS Publications Warehouse

    Hemley, J.J.; Cygan, G.L.; Fein, J.B.; Robinson, G.R.; d'Angelo, W. M.

    1992-01-01

    Experimental studies, using cold-seal and extraction vessel techniques, were conducted on Fe, Pb, Zn, and Cu sulfide solubilities in chloride soultions at temperatures from 300?? to 700??C and pressures from 0.5 to 2 kbars. The solutions were buffered in pH by quartz monzonite and the pure potassium feldspar-muscovite-quartz assemblage and in fS2-fO2 largely by the assemblage pyrite-pyrrhotite-magnetite. Solubilities increase with increasing temperature and total chloride, and decrease with increasing pressure. The effect of increasing chloride concentration on solubility reflects primarily a shift to lower pH via the silicate buffer reactions. Similarity in behaviour with respect to the temperature and pressure of Fe, Zn, and Pb sulfide solubilities points to similarity in chloride speciation, and the neutral species appear to be dominant in the high-temperature region. -from Authors

  16. Textural, mineralogical and stable isotope studies of hydrothermal alteration in the main sulfide zone of the Great Dyke, Zimbabwe and the precious metals zone of the Sonju Lake Intrusion, Minnesota, USA

    USGS Publications Warehouse

    Li, C.; Ripley, E.M.; Oberthur, T.; Miller, J.D.; Joslin, G.D.

    2008-01-01

    Stratigraphic offsets in the peak concentrations of platinum-group elements (PGE) and base-metal sulfides in the main sulfide zone of the Great Dyke and the precious metals zone of the Sonju Lake Intrusion have, in part, been attributed to the interaction between magmatic PGE-bearing base-metal sulfide assemblages and hydrothermal fluids. In this paper, we provide mineralogical and textural evidence that indicates alteration of base-metal sulfides and mobilization of metals and S during hydrothermal alteration in both mineralized intrusions. Stable isotopic data suggest that the fluids involved in the alteration were of magmatic origin in the Great Dyke but that a meteoric water component was involved in the alteration of the Sonju Lake Intrusion. The strong spatial association of platinum-group minerals, principally Pt and Pd sulfides, arsenides, and tellurides, with base-metal sulfide assemblages in the main sulfide zone of the Great Dyke is consistent with residual enrichment of Pt and Pd during hydrothermal alteration. However, such an interpretation is more tenuous for the precious metals zone of the Sonju Lake Intrusion where important Pt and Pd arsenides and antimonides occur as inclusions within individual plagioclase crystals and within alteration assemblages that are free of base-metal sulfides. Our observations suggest that Pt and Pd tellurides, antimonides, and arsenides may form during both magmatic crystallization and subsolidus hydrothermal alteration. Experimental studies of magmatic crystallization and hydrothermal transport/deposition in systems involving arsenides, tellurides, antimonides, and base metal sulfides are needed to better understand the relative importance of magmatic and hydrothermal processes in controlling the distribution of PGE in mineralized layered intrusions of this type. ?? Springer-Verlag 2007.

  17. Auger electron spectroscopic study of mechanism of sulfide-accelerated corrosion of copper-nickel alloy in seawater

    NASA Astrophysics Data System (ADS)

    Schrader, Malcolm E.

    The mechanism of sulfide-induced accelerated corrosion of 90-10 copper-nickel(iron) alloy is investigated. Samples of the alloy are exposed to flowing (2.4 m/s) seawater, with and without 0 01 mg/l sulfide, for various periods of time. The resulting surfaces are examined by means of Auger electron spectroscopy coupled with inert-ion-homoardment. A detailed depth profile is thereby obtained of concentrations in the surface region of a total of nine elements. The results are consistent with the hypothesis that iron hydroxide segregates at the surface to form a protective gelatinous layer against the normal chloride-induced corrosion process. Trace sulfide interferes with formation of a good protective layer and leaves the iron hydroxide vulnerable to ultimate partial or complete debonding. When the alloy is first exposed to "pure" seawater for a prolonged period of time, however, subsequent exposure to sulfide is no longer deleterious. This is apparently due to a layer of copper-nickel salt that slowly forms over the iron hydroxide.

  18. Quenching and radical formation in the reaction of photoexcited benzophenone with thiols and thioethers (sulfides). Nanosecond flash studies

    SciTech Connect

    Inbar, S.; Linschitz, H.; Cohen, S.G.

    1982-01-01

    Laser flash measurements have been made of rate constants and primary radical yields in the reactions of triplet benzophenone with aliphatic and aromatic thiols and with dialkyl and aryl alkyl sulfides. Reaction with n-pentylthiol in benzene leads mainly to quenching, with k/sub ir/ = 9 x 10/sup 6/ M/sup -1/ s/sup -1/ and radical yield (ketyl) = 0.14; with mesitylene-2 thiol in benzene k/sub ir/ = 7 x 10/sup 8/ M/sup -1/ s/sup -1/ and hydrogen transfer is efficient, radical yield (ketyl) approx. 1.0. In reactions with both p-chlorophenyl ethyl and diisopropyl sulfides, k/sub ir/ increases and radical yield (ketyl) decreases with increasing solvent polarity. Values of k/sub ir/ are higher and those of radical yield (ketyl) are lower for the dialkyl than for the aryl alkyl sulfide. Results are discussed in terms of rapid interaction of the triplet with S, followed by quenching and/or hydrogen transfer. Quenching without hydrogen transfer occurs to a much greater extent with sulfides and aliphatic thiols than with amines.

  19. Sulfide Mineralogy and Geochemistry

    NASA Astrophysics Data System (ADS)

    Dilles, John

    2007-02-01

    Reviews in Mineralogy and Geochemistry Series, Volume 61 David J. Vaughan, Editor Geochemical Society and Mineralogical Society of America; ISBN 0-939950-73-1 xiii + 714 pp.; 2006; $40. Sulfide minerals as a class represent important minor rock-forming minerals, but they are generally known as the chief sources of many economic metallic ores. In the past two decades, sulfide research has been extended to include important roles in environmental geology of sulfide weathering and resultant acid mine drainage, as well as in geomicrobiology in which bacteria make use of sulfides for metabolic energy sources. In the latter respect, sulfides played an important role in early evolution of life on Earth and in geochemical cycling of elements in the Earth's crust and hydrosphere.

  20. [Inhibition of aflatoxin production and fungal growth on stored corn by allyl isothiocyanate vapor].

    PubMed

    Okano, Kiyoshi; Ose, Ayaka; Takai, Mitsuhiro; Kaneko, Misao; Nishioka, Chikako; Ohzu, Yuji; Odano, Masayoshi; Sekiyama, Yasushi; Mizukami, Yuichi; Nakamura, Nobuya; Ichinoe, Masakatsu

    2015-01-01

    Studies were conducted to determine the effectiveness of allyl isothiocyanate (AIT) vapor treatment with a commercial mustard seed extract (Wasaouro(®)) in controlling aflatoxin-producing fungi on stored corn. The concentration of AIT in the closed container peaked at 54.6 ng/mL on the 14th day and remained at 21.8 ng/mL on the 42nd day. AIT inhibited visible growth of aflatoxigenic molds in unsterilized corn and in sterilized corn inoculated with various aflatoxigenic fungi. However, fungi such as Aspergillus glaucus group, A. penicillioides and A. restrictus were detected by means of culture methods. PMID:25748979

  1. Thermophysical properties and reaction kinetics of γ-irradiated poly allyl diglycol carbonates nuclear track detector

    NASA Astrophysics Data System (ADS)

    Elmaghraby, Elsayed K.; Seddik, Usama

    2015-07-01

    Kinetic thermogravimetric technique was used to study the effect of gamma irradiation on the poly allyl diglycol carbonates (PADC) within the dose range from 50 to ? Gy. The approach of Coats-Redfern was used to analyze the data. Results showed that low doses around 50 Gy make the polymer slightly more resistive to heat treatment. Higher radiation doses cause severe effects in the samples accompanied by the formation of lower molecular mass species and consequent crosslinking. Results support the domination of re-polymerization and crosslinking for the γ radiation interaction PADC at dose below about ? Gy, while the situation is inverted above ? Gy in which chain secession dominates.

  2. Cadmium sulfide/copper sulfide heterojunction cell research: critical studies in materials and durability. Quarterly progress report, September 1-November 30, 1980

    SciTech Connect

    1981-02-01

    This report refers to two papers. The first describes the results of a study on the grain structure of CdS and (CdZn)S films. The other paper is a study of the band structure in heterojunctions between Cu/sub 2/S and Cd/sub 1-x/Zn/sub x/S. Ongoing material studies are focused on the optical properties of Cu/sub 2/S as influenced by oxidation-reduction heat treatments. A set of high efficiency Cu/sub 2/S/(CdZn)S cells stored in hydrogen are being monitored for changes in efficiency and nine cells have been put on test under continuous illumination.

  3. Comparative investigation of the mutagenicity of propenylic and allylic asarone isomers in the Ames fluctuation assay.

    PubMed

    Berg, Kerstin; Bischoff, Roland; Stegmüller, Simone; Cartus, Alexander; Schrenk, Dieter

    2016-07-01

    α-, β- and γ-asarone are naturally occurring phenylpropenes that occur in different plant families, mainly in Aristolochiaceae, Acoraceae and Lauraceae. Plants containing asarones are used as flavouring ingredients in alcoholic beverages (bitters), traditional phytomedicines and the rhizome of e.g. Acorus calamus is used to prepare tea. Although α- and β-asarone show a potential in the treatment of several diseases, previous studies have shown carcinogenicity in rodents (duodenum, liver). However, the mechanism of action remained unclear. Studies on the mutagenicity of propenylic α- and β-asarone are inconsistent and data on carcinogenicity and genotoxicity of allylic γ-asarone are lacking completely. Thus, the present study determined the mutagenicity of the three asarone isomers using the Ames fluctuation assay with and without exogenous metabolic activation (S9 mix) in the standard Salmonella typhimurium strains TA98 and TA100. A concentration dependent increase in mutagenicity could be verified for α- and β-asarone in strain TA100 in the presence of rat liver homogenate. The side-chain epoxides of α- and β-asarone, major metabolites formed in liver microsomes, caused mutations in TA100, supporting the hypothesis that epoxidation of the side chain plays a key role in mutagenicity of the propenylic alkenylbenzenes. The allylic γ-asarone, not undergoing detectable side-chain epoxidation in liver microsomes, was supposed to be activated via side-chain hydroxylation and further sulphonation, a typical pathway for other allylic alkenylbenzenes like estragole or methyleugenol. However, neither y-asarone nor 1'-OH-γ-asarone showed any mutagenic effect even in the human SULT-expressing Salmonella strains (TA100-hSULT1A1 and TA100-hSULT1C2), while 1'-OH-methyleugenol used as a positive control was mutagenic under these conditions. These results indicate that the propenylic asarones are genotoxic via metabolic formation of side-chain epoxides while the side

  4. Comparative investigation of the mutagenicity of propenylic and allylic asarone isomers in the Ames fluctuation assay.

    PubMed

    Berg, Kerstin; Bischoff, Roland; Stegmüller, Simone; Cartus, Alexander; Schrenk, Dieter

    2016-07-01

    α-, β- and γ-asarone are naturally occurring phenylpropenes that occur in different plant families, mainly in Aristolochiaceae, Acoraceae and Lauraceae. Plants containing asarones are used as flavouring ingredients in alcoholic beverages (bitters), traditional phytomedicines and the rhizome of e.g. Acorus calamus is used to prepare tea. Although α- and β-asarone show a potential in the treatment of several diseases, previous studies have shown carcinogenicity in rodents (duodenum, liver). However, the mechanism of action remained unclear. Studies on the mutagenicity of propenylic α- and β-asarone are inconsistent and data on carcinogenicity and genotoxicity of allylic γ-asarone are lacking completely. Thus, the present study determined the mutagenicity of the three asarone isomers using the Ames fluctuation assay with and without exogenous metabolic activation (S9 mix) in the standard Salmonella typhimurium strains TA98 and TA100. A concentration dependent increase in mutagenicity could be verified for α- and β-asarone in strain TA100 in the presence of rat liver homogenate. The side-chain epoxides of α- and β-asarone, major metabolites formed in liver microsomes, caused mutations in TA100, supporting the hypothesis that epoxidation of the side chain plays a key role in mutagenicity of the propenylic alkenylbenzenes. The allylic γ-asarone, not undergoing detectable side-chain epoxidation in liver microsomes, was supposed to be activated via side-chain hydroxylation and further sulphonation, a typical pathway for other allylic alkenylbenzenes like estragole or methyleugenol. However, neither y-asarone nor 1'-OH-γ-asarone showed any mutagenic effect even in the human SULT-expressing Salmonella strains (TA100-hSULT1A1 and TA100-hSULT1C2), while 1'-OH-methyleugenol used as a positive control was mutagenic under these conditions. These results indicate that the propenylic asarones are genotoxic via metabolic formation of side-chain epoxides while the side

  5. Branching Out: Rhodium-Catalyzed Allylation with Alkynes and Allenes.

    PubMed

    Koschker, Philipp; Breit, Bernhard

    2016-08-16

    We present a new and efficient strategy for the atom-economic transformation of both alkynes and allenes to allylic functionalized structures via a Rh-catalyzed isomerization/addition reaction which has been developed in our working group. Our methodology thus grants access to an important structural class valued in modern organic chemistry for both its versatility for further functionalization and the potential for asymmetric synthesis with the construction of a new stereogenic center. This new methodology, inspired by mechanistic investigations by Werner in the late 1980s and based on preliminary work by Yamamoto and Trost, offers an attractive alternative to other established methods for allylic functionalization such as allylic substitution or allylic oxidation. The main advantage of our methodology consists of the inherent atom economy in comparison to allylic oxidation or substitution, which both produce stoichiometric amounts of waste and, in case of the substitution reaction, require prefunctionalization of the starting material. Starting out with the discovery of a highly branched-selective coupling reaction of carboxylic acids with terminal alkynes using a Rh(I)/DPEphos complex as the catalyst system, over the past 5 years we were able to continuously expand upon this chemistry, introducing various (pro)nucleophiles for the selective C-O, C-S, C-N, and C-C functionalization of both alkynes and the double-bond isomeric allenes by choosing the appropriate rhodium/bidentate phosphine catalyst. Thus, valuable compounds such as branched allylic ethers, sulfones, amines, or γ,δ-unsaturated ketones were successfully synthesized in high yields and with a broad substrate scope. Beyond the branched selectivity inherent to rhodium, many of the presented methodologies display additional degrees of selectivity in regard to regio-, diastereo-, and enantioselective transformations, with one example even proceeding via a dynamic kinetic resolution. Many advances

  6. Temperature-programmed sulfiding of precursor cobalt oxide genesis of highly active sites on sulfided cobalt catalyst for hydrogenation and isomerization

    SciTech Connect

    Inamura, Kazuhiro; Takyu, Toshiyuki ); Okamoto, Yasuaki; Nagata, Kozo; Imanaka, Toshinobu )

    1992-02-01

    It was found that the method of sulfidation of cobalt oxide strongly affects the catalytic activities and selectivities of the resultant cobalt sulfide catalyst, as well as the calcination temperature of the cobalt oxide. When cobalt oxide was sulfided at 673 K by a temperature-programmed sulfiding method (a heating rate of 6 K/min), catalytic activities for the hydrogenation of butadiene and the isomerization of 1-butene were considerably enhanced compared with those for cobalt sulfide prepared by isothermal sulfidation at 673 K. Results of temperature-programmed sulfiding (TPS), temperature-programmed reduction (TPR), and X-ray diffraction (XRD) suggest that the catalysts showing high catalytic activities after sulfidation are partially sulfided at 673 K and consist of the unsulfided cobalt core phases (CoO or metallic Co). The sulfidation property of precursor cobalt oxides has been studied using TPS, simulating the sulfidation process of the cobalt sulfide catalysts. Two distinctly different kinds of sulfidation process are estimated by TPS measurements of the cobalt oxides. The calcination temperature of the precursor cobalt oxides strongly affects the sulfidation paths. They are differentiated in terms of the presence of a metallic Co intermediate. The relationship of the mechanism of sulfidation of the cobalt oxides to the generation of highly active sites is discussed.

  7. Impact history of the Chelyabinsk meteorite: Electron microprobe and LA-ICP-MS study of sulfides and metals

    NASA Astrophysics Data System (ADS)

    Andronikov, A. V.; Andronikova, I. E.; Hill, D. H.

    2015-12-01

    Electron microprobe and LA-ICP-MS study of sulfides and metals from two fragments of the LL5 Chelyabinsk meteorite were conducted. The fragments are impact breccias, one fragment contains both chondritic and shock vein lithologies, and the other contains shock-darkened chondritic clasts and vesicular impact melts. The chondritic lithology and shock veins display very similar opaque mineral compositions. The mineral compositions in the impact-melt breccias are distinctly different. The brecciated state of the Chelyabinsk meteorite suggests strong involvement of shock-related processes during the evolution of the parent body. Multiple heavy impact events occurred on the parent asteroid and on the Chelyabinsk meteoroid itself over the time period from ca. 4.5 Ga until ca. 1.2 Ma. The shock veins were produced in situ on the parent body. The impact-melt breccias could have formed because of the dramatic impact to the parent LL-chondrite body that could be partly disintegrated. The fragment containing shock-darkened chondritic clasts and vesicular impact melt lithologies preserves a record of melting, volatilization, partial degassing, and quenching of the molten material. The abundance and size (up to 1 mm) of the vesicles suggest that the impact melt must have been buried at some depth after formation. After impact and subsequent melting occurred, the impact-induced pressure on the shallow asteroid interior was released that caused "boiling" of volatiles and generation of S-rich bubbles. Such an impact excavated down to depths of the body generating multiple fragments with complicated histories. These fragments reaccumulated into a gravitational aggregate and formed the parental meteoroid for the Chelyabinsk meteorite.

  8. Nanostructured lead sulfide: synthesis, structure and properties

    NASA Astrophysics Data System (ADS)

    Sadovnikov, S. I.; Gusev, A. I.; Rempel, A. A.

    2016-07-01

    The theoretical and experimental results of recent studies dealing with nanostructured lead sulfide are summarized and analyzed. The key methods for the synthesis of nanostructured lead sulfide are described. The crystal structure of PbS in nanopowders and nanofilms is discussed. The influence of the size of nanostructure elements on the optical and thermal properties of lead sulfide is considered. The dependence of the band gap of PbS on the nanoparticle (crystallite) size for powders and films is illustrated. The bibliography includes 222 references.

  9. Cadmium sulfide/copper sulfide heterojunction cell research. Critical studies in materials and durability. Annual progress report, July 1, 1979-August 31, 1980

    SciTech Connect

    1981-01-01

    A summary of the structural and morphological features of CdS and (CdZn)S layers and their heterojunctions with Cu/sub 2/S is presented. The growth of the Cu/sub 2/S layer has been studied as a function of time for both the solution and solid state process using transmission electron microscopy. Preliminary observations have also been made on vapor and sputter deposited Cu/sub 2/S layers. The effect of oxidation and reduction heat treatments on the optical properties of Cu/sub 2/S are reported. Changes of cell performance with time for cells loaded to various points in the power quadrant are described.

  10. Deep level study of cadmium sulfide/cadmium telluride solar cells

    NASA Astrophysics Data System (ADS)

    Komin, Valery Vitalyevich

    The goal of this project is to develop a reliable approach to characterize defects in CdTe/CdS solar cells, taking into account the requirements dictated by the polycrystallinity of the device materials, to characterize solar cells prepared in different processing conditions, to develop an understanding on how processing variations correlate with changes in the overall device performance and stability, and to develop recommendations on the optimization of processing conditions based on this analysis. Polycrystalline CdTe/CdS solar cells were studied using double boxcar deep level transient spectroscopy (DLTS) and correlation DLTS measurements to investigate the effect of the post-growth CdCl2 heat treatment, and the effect of the HgTe:Cu-doped graphite and Ni2P-based back contacts. The limitations of each deep-level characterization technique dictated by the polycrystalline nature of the CdTe/CdS heterostructure, were taken in consideration. Dark C-V, dark and illuminated J-V measurements were performed in order to monitor changes in the solar cell parameters during the deep level studies. To avoid issues associated with the metastability of some defects, all experiments were performed in the dark. Twelve traps were detected in the temperature range from 90K to 360K. Preliminary solar cell simulations using AMPS-1D were used to help understand the role of these traps in the current transport mechanism and the impact of their presence on the overall device performance. A donor-like defect with activation energy EA = 0.140 eV was identified as a chlorine-related DX2-state of (VCd2--ClTe+) complex. Its presence in the CdTe layer was associated with significant degradation of overall solar cell performance. An acceptor-like defect with activation energy EA = 0.350 was identified as a defect Cu Cd- or complex (Cui+-2Cu Cd-)-. Recommendations for processing condition optimization are made based on the results of this study.

  11. Copper-Catalyzed Oxidative Amination and Allylic Amination of Alkenes

    PubMed Central

    Liwosz, Timothy W.; Chemler, Sherry R.

    2014-01-01

    Enamines and enamides are useful synthetic intermediates and common components of bioactive compounds. A new protocol for their direct synthesis by a net alkene C–H amination and allylic amination by using catalytic CuII in the presence of MnO2 is reported. Reactions between N-aryl sulfonamides and vinyl arenes furnish enamides, allylic amines, indoles, benzothiazine dioxides, and dibenzazepines directly and efficiently. Control experiments further showed that MnO2 alone can promote the reaction in the absence of a copper salt, albeit with lower efficiency. Mechanistic probes support the involvement of nitrogen-radical intermediates. This method is ideal for the synthesis of enamides from 1,1-disubstituted vinyl arenes, which are uncommon substrates in existing oxidative amination protocols. PMID:23878099

  12. Radiation initiated copolymerization of allyl alcohol with acrylonitrile

    NASA Astrophysics Data System (ADS)

    Şolpan, Dilek; Güven, Olgun

    1996-07-01

    Copolymerization of allyl alcohol (AA) with acrylonitrile (AN) initiated by γ-rays has been investigated to determine the respective reactivity ratios. Three different experimental techniques, namely Fourier Transform Infrared (FTIR), Ultraviolet (UV/vis) and elemental analysis (EA) have been used for the determination of copolymer compositions. Fineman-Ross (FR), Kelen-Tüdös (KT), Non-Linear Least Square (NLLS) Analysis and Q-e methods have been applied to the three sets of experimental data. It has been concluded that data obtained from elemental analysis as applied to the Non-Linear Least Square approach gave the most reliable reactivity ratios as 2.09 and 0.40 for acrylonitrile and allyl alcohol, respectively.

  13. ION EXCHANGE SUBSTANCES BY SAPONIFICATION OF ALLYL PHOSPHATE POLYMERS

    DOEpatents

    Kennedy, J.

    1959-04-14

    An ion exchange resin having a relatively high adsorption capacity tor uranyl ion as compared with many common cations is reported. The resin comprises an alphyl-allyl hydrogen phosphate polymer, the alphyl group being either allyl or a lower alkyl group having up to 5 carbon atoins. The resin is prepared by polymerizing compounds such as alkyl-diallyl phosphate and triallyl phosphate in the presence of a free radical generating substance and then partially hydrolyzing the resulting polymer to cause partial replacement of organic radicals by cations. A preferred free radical gencrating agent is dibenzoyl peroxide. The partial hydrolysis is brought about by refluxing the polymer with concentrated aqueous NaOH for three or four hours.

  14. Study of the active surface on titanium oxide catalysts for the oxidation of hydrogen sulfide

    SciTech Connect

    Khanmamedov, T.K.; Kalinkin, A.V.; Rakhimova, N.R.

    1989-02-01

    A study was carried out on the change in the composition of a Ti-Mo-W catalyst depending on the conditions for their treatment by H/sub 2/S-SO/sub 2/ and H/sub 2/S-O/sub 2/ gas mixtures, which serve as models for the technological gases in Klaus apparatuses and the direct catalytic oxidation of H/sub 2/S. X-ray photoelectron spectroscopy was used to establish the formation of sulfur as S/sup 2/minus// and S/sup 6+/ on the surface. The presence of S/sup 6+/ along with the changes in E/sub b/ of the electrons in the T-Mo-W catalyst indicates the formation of MoS/sub 2/ and TiO(SO/sub 4/) species.

  15. Study of the effects of gaseous environments on sulfidation attack of superalloys

    NASA Technical Reports Server (NTRS)

    Smeggil, J. G.; Bornstein, N. S.

    1977-01-01

    Studies were conducted to examine the effect of the gaseous corrodents NaCl, HCl, and NaOH on the high temperature oxidation and Na2SO4-induced corrosion behavior of the alumina former NiAl, the chromia former Ni-25 wt.% Cr, elemental Cr, and the superalloy B-1900. Experiments were conducted at 900 and 1050 C in air in the presence and absence of the gaseous corrodents. Effects involving both reaction rates and microstructural changes in oxide morphology were observed due to the presence of these corrodents at levels anticipated to be present in operating industrial and marine gas turbines. The effect of gaseous NaCl, HCl, and possibly NaOH on NiAl in simple oxidation was to remove aluminum from below the protective alumina layer and to simultaneously weaken the adherence of the protective alumina oxide scale to the substrate. The aluminum removed from below the oxide scale was redeposited on its surface as alpha-Al2O3 whiskers. With respect to the chromia formers, gaseous NaCl and HCl promoted breakaway oxidation kinetics and changes in the microstructures of the oxide scales.

  16. Copper-catalyzed trifluoromethylation of trisubstituted allylic and homoallylic alcohols.

    PubMed

    Lei, Jian; Liu, Xiaowu; Zhang, Shaolin; Jiang, Shuang; Huang, Minhao; Wu, Xiaoxing; Zhu, Qiang

    2015-04-27

    An efficient copper-catalyzed trifluoromethylation of trisubstituted allylic and homoallylic alcohols with Togni's reagent has been developed. This strategy, accompanied by a double-bond migration, leads to various branched CF3-substituted alcohols by using readily available trisubstituted cyclic/acyclic alcohols as substrates. Moreover, for alcohols in which β-H elimination is prohibited, CF3-containing oxetanes are isolated as the sole product. PMID:25810003

  17. Petasis Borono-Mannich reaction and allylation of carbonyl compounds via transient allyl boronates generated by palladium-catalyzed substitution of allyl alcohols. an efficient one-pot route to stereodefined alpha-amino acids and homoallyl alcohols.

    PubMed

    Selander, Nicklas; Kipke, Andreas; Sebelius, Sara; Szabó, Kalman J

    2007-11-01

    An efficient one-pot procedure was designed by integration of the pincer-complex-catalyzed borylation of allyl alcohols in the Petasis borono-Mannich reaction and in allylation of aldehydes and ketones. These procedures are suitable for one-pot synthesis of alpha-amino acids and homoallyl alcohols from easily available allyl alcohol, amine, aldehyde, or ketone substrates. In the presented transformations, the active allylating agents are in situ generated allyl boronic acid derivatives. These transient intermediates are proved to be reasonably acid-, base-, alcohol-, water-, and air-stable species, which allows a high level of compatibility with the reaction conditions of the allylation of various aldehyde/ketone and imine electrophiles. The boronate source of the reaction is diboronic acid or in situ hydrolyzed diboronate ester ensuring that the waste product of the reaction is nontoxic boric acid. The regio- and stereoselectivity of the reaction is excellent, as almost all products form as single regio- and stereoisomers. The described procedure is suitable to create quaternary carbon centers in branched allylic products without formation of the corresponding linear allylic isomers. Furthermore, products comprising three stereocenters were formed as single products without formation of other diastereomers. Because of the highly disciplined consecutive processes, up to four-step, four-component transformations could be performed selectively as a one-pot sequence. For example, stereodefined pyroglutamic acid could be prepared from a simple allyl alcohol, a commercially available amine, and glyoxylic acid in a one-step procedure. The presented method also grants an easy access to stereodefined 1,7-dienes that are useful substrates for Grubbs ring-closing metathesis.

  18. Pd(Quinox)-Catalyzed Allylic Relay Suzuki Reactions of Secondary Homostyrenyl Tosylates via Alkene-Assisted Oxidative Addition.

    PubMed

    Stokes, Benjamin J; Bischoff, Amanda J; Sigman, Matthew S

    2014-06-01

    Pd-catalyzed allylic relay Suzuki cross-coupling reactions of secondary alkyl tosylates, featuring a sterically-hindered oxidative addition and precise control of β-hydride elimination, are reported. The identification of a linear free energy relationship between the relative rates of substrate consumption and the electronic nature of the substrate alkene suggests that the oxidative addition requires direct alkene involvement. A study of the effect of chain length on the reaction outcome supports a chelation-controlled oxidative addition.

  19. Low-temperature synthesis of allyl dimethylamine by selective heating under microwave irradiation used for water treatment

    NASA Astrophysics Data System (ADS)

    Tian, Binghui; Luan, Zhaokun; Li, Mingming

    2005-08-01

    Low-temperature synthesis of allyl dimethylamine (ADA) by selective heating under microwave irradiation (MI) used for water treatment is investigated. The effect of MI, ultrasound irradiation (UI) and conventional heating on yield of ADA, reaction time and the flocculation efficiency of polydiallyl dimethylammunion chloride (PDADMAC) prepared form ADA were studied. The results show that by selective heating at low temperature, MI not only increases yield of ADA and reduces reaction time, but also greatly enhances the flocculation efficiency of PDADMAC.

  20. Regiochemical control in the metal-catalyzed transposition of allylic silyl ethers.

    PubMed

    Hansen, Eric C; Lee, Daesung

    2006-06-28

    A novel mode of regiochemical control over the allylic [1,3]-transposition of silyloxy groups catalyzed by Re2O7 has been developed. This strategy relies on a cis-oriented vinyl boronate, generated from the Alder-ene reaction of homoallylic silyl ethers and alkynyl boronates, to trap out the allylic hydroxyl group. The resulting cyclic boronic acids are excellent partners for cross-coupling reactions. High chirality transfer is observed for the rearrangement of enantioenriched allylic silyl ethers.

  1. Gold(I)-Assisted α-Allylation of Enals and Enones with Alcohols.

    PubMed

    Mastandrea, Marco Michele; Mellonie, Niall; Giacinto, Pietro; Collado, Alba; Nolan, Steven P; Miscione, Gian Pietro; Bottoni, Andrea; Bandini, Marco

    2015-12-01

    The intermolecular α-allylation of enals and enones occurs by the condensation of variously substituted allenamides with allylic alcohols. Cooperative catalysis by [Au(ItBu)NTf2] and AgNTf2 enables the synthesis of a range of densely functionalized α-allylated enals, enones, and acyl silanes in good yield under mild reaction conditions. DFT calculations support the role of an α-gold(I) enal/enone as the active nucleophilic species.

  2. Preparation of aliphatic ketones through a ruthenium-catalyzed tandem cross-metathesis/allylic alcohol isomerization.

    PubMed

    Finnegan, David; Seigal, Benjamin A; Snapper, Marc L

    2006-06-01

    Grubbs' 2nd generation and Hoveyda-Grubbs' ruthenium alkylidenes are shown to be effective catalysts for cross-metatheses of allylic alcohols with cyclic and acyclic olefins, as well as isomerization of the resulting allylic alcohols to alkyl ketones. The net result of this new tandem methodology is a single-flask process that provides highly functionalized, ketone-containing products from simple allylic alcohol precursors. [reaction: see text

  3. Ore mineralogy and sulfur isotope study of the massive sulfide deposit of Filon Norte, Tharsis Mine, Spain

    NASA Astrophysics Data System (ADS)

    Kase, K.; Yamamoto, M.; Nakamura, T.; Mitsuno, C.

    1990-10-01

    The volcanogenic massive sulfide deposit of Filon Norte at Tharsis is hosted by carbonaceous black slate and connected only partly with stockwork veins. The massive ores are usually composed of fine-grained pyrite with subordinate amounts of sphalerite, chalcopyrite, galena and arsenopyrite. Monoclinic pyrrhotite sometimes occurs in massive pyritic ores in the apparently middle and upper horizons of the orebody, and siderite-rich ores are interstratified with compact pyritic ores in the apparently lower horizons. From the occurrence of monoclinic pyrrhotite, together with the FeS contents of sphalerite mostly ranging from 11 to 16 mol %, it is inferred that the sulfide minerals of the massive orebody were precipitated in euxinic muds on the sea-floor at temperatures below 250°C. The negatively shifted, highly variable δ 34S values of the massive ores and their close similarity to those of the underlying black slates strongly suggest that the sulfide sulfur of the massive orebody and the slates is cognate and biogenic.

  4. The pure rotational spectrum of a Claisen rearrangement precursor Allyl Phenyl Ether using CP-FTMW spectroscopy

    NASA Astrophysics Data System (ADS)

    Grubbs, G. S.; Frank, Derek S.; Obenchain, Daniel A.; Cooke, S. A.; Novick, Stewart E.

    2016-06-01

    The pure rotational spectrum of a Claisen rearrangement precursor, Allyl Phenyl Ether (APE), has been measured on a chirped pulse Fourier transform microwave (CP-FTMW) spectrometer in the 8-14 GHz region. Rotational and centrifugal distortion constants for multiple conformations have been determined and are reported for the first time. This is the first study of a phenyl-containing ether where multiple conformers were experimentally observed all within their ground vibrational states. Quantum chemical calculations have been performed to isolate low energy geometries of APE and are implemented to aid in spectral assignment. Other structural parameters such as planar moments and inertial defects for the Allyl Phenyl Ether conformers are presented and compared to similar molecules.

  5. Os and S isotope studies of ultramafic rocks in the Duke Island Complex, Alaska: variable degrees of crustal contamination of magmas in an arc setting and implications for Ni-Cu-PGE sulfide mineralization

    NASA Astrophysics Data System (ADS)

    Stifter, Eric C.; Ripley, Edward M.; Li, Chusi

    2016-03-01

    The Duke Island Complex is one of the several "Ural-Alaskan" intrusions of Cretaceous age that occur along the coast of SE Alaska. Significant quantities of magmatic Ni-Cu-PGE sulfide mineralization are locally found in the complex, primarily within olivine clinopyroxenites. Sulfide mineralization is Ni-poor, consistent with petrologic evidence which indicates that sulfide saturation was reached after extensive olivine crystallization. Olivine clinopyroxenites were intruded by magmas that produced sulfide-poor, adcumulate dunites. As part of a study to investigate the potential for Ni-rich sulfide mineralization in association with the dunites, a Re-Os and S isotope study of the dunites, as well as sulfide mineralization in the olivine clinopyroxenites, was initiated. Importantly, recent drilling in the complex identified the presence of sulfidic and carbonaceous country rocks that may have been involved in the contamination of magmas and generation of sulfide mineralization. γOs (110 Ma) values of two sulfidic country rocks are 1022 and 2011. δ34S values of the country rocks range from -2.6 to -16.1 ‰. 187Os/188Os ratios of sulfide minerals in the mineralization hosted by olivine clinopyroxenites are variable and high, with γOs (110 Ma) values between 151 and 2059. Extensive interaction with Re-rich sedimentary country rocks is indicated. In contrast, γOs (110 Ma) values of the dunites are significantly lower, ranging between 2 and 16. 187Os/188Os ratios increase with decreasing Os concentration. This inverse relation is similar to that shown by ultramafic rocks from several arc settings, as well as altered abyssal dunites and peridotites. The relation may be indicative of magma derivation from a sub-arc mantle that had experienced metasomatism via slab-derived fluids. Alternatively, the relation may be indicative of minor contamination of magma by crustal rocks with low Os concentrations but high 187Os/188Os ratios. A third alternative is that the low Os

  6. Os and S isotope studies of ultramafic rocks in the Duke Island Complex, Alaska: variable degrees of crustal contamination of magmas in an arc setting and implications for Ni-Cu-PGE sulfide mineralization

    NASA Astrophysics Data System (ADS)

    Stifter, Eric C.; Ripley, Edward M.; Li, Chusi

    2016-10-01

    The Duke Island Complex is one of the several "Ural-Alaskan" intrusions of Cretaceous age that occur along the coast of SE Alaska. Significant quantities of magmatic Ni-Cu-PGE sulfide mineralization are locally found in the complex, primarily within olivine clinopyroxenites. Sulfide mineralization is Ni-poor, consistent with petrologic evidence which indicates that sulfide saturation was reached after extensive olivine crystallization. Olivine clinopyroxenites were intruded by magmas that produced sulfide-poor, adcumulate dunites. As part of a study to investigate the potential for Ni-rich sulfide mineralization in association with the dunites, a Re-Os and S isotope study of the dunites, as well as sulfide mineralization in the olivine clinopyroxenites, was initiated. Importantly, recent drilling in the complex identified the presence of sulfidic and carbonaceous country rocks that may have been involved in the contamination of magmas and generation of sulfide mineralization. γOs (110 Ma) values of two sulfidic country rocks are 1022 and 2011. δ34S values of the country rocks range from -2.6 to -16.1 ‰. 187Os/188Os ratios of sulfide minerals in the mineralization hosted by olivine clinopyroxenites are variable and high, with γOs (110 Ma) values between 151 and 2059. Extensive interaction with Re-rich sedimentary country rocks is indicated. In contrast, γOs (110 Ma) values of the dunites are significantly lower, ranging between 2 and 16. 187Os/188Os ratios increase with decreasing Os concentration. This inverse relation is similar to that shown by ultramafic rocks from several arc settings, as well as altered abyssal dunites and peridotites. The relation may be indicative of magma derivation from a sub-arc mantle that had experienced metasomatism via slab-derived fluids. Alternatively, the relation may be indicative of minor contamination of magma by crustal rocks with low Os concentrations but high 187Os/188Os ratios. A third alternative is that the low Os

  7. Hot water-promoted S(N)1 solvolysis reactions of allylic and benzylic alcohols.

    PubMed

    Xu, Zhao-Bing; Qu, Jin

    2013-01-01

    During the studies of hydrolysis of epoxides in water, we found that the hydrolysis of (-)-α-pinene oxide at 20 °C gave enantiomerically pure trans-(-)-sobrerol, whereas the same reaction in water heated at reflux unexpectedly gave a racemic mixture of trans- and cis-sobrerol (trans/cis = 6:4). We have examined this remarkable difference in detail and found that hot water, whose behavior is quite different compared with room- or high-temperature water, could promote S(N)1 solvolysis reactions of allylic alcohols and thus caused the racemization of trans-(-)-sobrerol. The effect of reaction temperature, the addition of organic co-solvent, and the concentration of the solute on the rate of the racemization of trans-(-)-sobrerol were further examined to understand the role that hot water played in the reaction. It was proposed that the catalytic effects of hot water are owing to its mild acidic characteristic, thermal activation, high ionizing power, and better solubility of organic reactant. Further investigation showed that the racemization of other chiral allylic/benzylic alcohols could efficiently proceed in hot water.

  8. Iron complexes of tetramine ligands catalyse allylic hydroxyamination via a nitroso–ene mechanism

    PubMed Central

    Porter, David; Poon, Belinda M-L

    2015-01-01

    Summary Iron(II) complexes of the tetradentate amines tris(2-pyridylmethyl)amine (TPA) and N,N′-bis(2-pyridylmethyl)-N,N′-dimethylethane-1,2-diamine (BPMEN) are established catalysts of C–O bond formation, oxidising hydrocarbon substrates via hydroxylation, epoxidation and dihydroxylation pathways. Herein we report the capacity of these catalysts to promote C–N bond formation, via allylic amination of alkenes. The combination of N-Boc-hydroxylamine with either FeTPA (1 mol %) or FeBPMEN (10 mol %) converts cyclohexene to the allylic hydroxylamine (tert-butyl cyclohex-2-en-1-yl(hydroxy)carbamate) in moderate yields. Spectroscopic studies and trapping experiments suggest the reaction proceeds via a nitroso–ene mechanism, with involvement of a free N-Boc-nitroso intermediate. Asymmetric induction is not observed using the chiral tetramine ligand (+)-(2R,2′R)-1,1′-bis(2-pyridylmethyl)-2,2′-bipyrrolidine ((R,R′)-PDP). PMID:26734101

  9. Palladium/N-heterocyclic carbene catalysed regio and diastereoselective reaction of ketones with allyl reagents via inner-sphere mechanism

    DOE PAGESBeta

    Bai, Da -Chang; Yu, Fei -Le; Wang, Wan -Ying; Chen, Di; Li, Hao; Liu, Qing -Rong; Ding, Chang -Hua; Chen, Bo; Hou, Xue -Long

    2016-06-10

    The palladium-catalysed allylic substitution reaction is one of the most important reactions in transition-metal catalysis and has been well-studied in the past decades. Most of the reactions proceed through an outer-sphere mechanism, affording linear products when monosubstituted allyl reagents are used. Here, we report an efficient Palladium-catalysed protocol for reactions of beta-substituted ketones with monosubstituted allyl substrates, simply by using N-heterocyclic carbene as ligand, leading to branched products with up to three contiguous stereocentres in a (syn, anti)-mode with excellent regio and diastereoselectivities. The scope of the protocol in organic synthesis has been examined preliminarily. As a result, mechanistic studiesmore » by both experiments and density functional theory ( DFT) calculations reveal that the reaction proceeds via an inner-sphere mechanism-nucleophilic attack of enolate oxygen on Palladium followed by C-C bond-forming [3,3']-reductive elimination.« less

  10. Synchrotron Photoionization Mass Spectrometry Measurements of Kinetics and Product Formation in the Allyl Radical (H2CCHCH2)Self Reaction

    NASA Technical Reports Server (NTRS)

    Selby, Talitha M.; Melini, giovanni; Goulay, Fabien; Leone, Stephen R.; Fahr, Askar; Taatjes, Craig A.; Osborn, David L.

    2008-01-01

    Product channels for the self-reaction of the resonance-stabilized allyl radical, C3H5 + C3H5, have been studied with isomeric specificity at temperatures from 300-600 K and pressures from 1-6 Torr using time-resolved multiplexed photoionization mass spectrometry. Under these conditions 1,5-hexadiene was the only C6H10 product isomer detected. The lack of isomerization of the C6H10 product is in marked contrast to the C6H6 product in the related C3H3 + C3H3 reaction, and is due to the more saturated electronic structure of the C6H10 system. The disproportionation product channel, yielding allene + propene, was also detected, with an upper limit on the branching fraction relative to recombination of 0.03. Analysis of the allyl radical decay at 298 K yielded a total rate coefficient of (2.7 +/- 0.8) x 10(exp -11) cu cm/molecule/s, in good agreement with pre.vious experimental measurements using ultraviolet kinetic absorption spectroscopy and a recent theoretical determination using variable reaction coordinate transition state theory. This result provides independent indirect support for the literature value of the allyl radical ultraviolet absorption cross-section near 223 nm.

  11. Directed Growth of Polymer Nanorods Using Surface-Initiated Ring-Opening Polymerization of N-Allyl N-Carboxyanhydride.

    PubMed

    Lu, Lu; Lahasky, Samuel H; Zhang, Donghui; Garno, Jayne C

    2016-02-17

    A stepwise chemistry route was used to prepare arrays of polymer nanostructures of poly(N-allyl glycine) on Si(111) using particle lithography. The nanostructures were used for studying surface reactions with advanced measurements of atomic force microscopy (AFM). In the first step to fabricate the surface platform, isolated nanopores were prepared within a thin film of octadecyltrichlorosilane (OTS). The OTS served as a surface resist, and the areas of nanopores provided multiple, regularly shaped sites for further reaction. An initiator, (3-aminopropyl)triethoxysilane (APTES), was grown selectively inside the nanopores to define sites for polymerization. The initiator attached selectively to the sites of nanopores indicating OTS prevented nonspecific adsorption. Surface-initiated ring-opening polymerization of N-allyl N-carboxyanhydride with APTES produced polymer nanorods on the nanodots of APTES presenting amine functional groups. The surface changes for each step were monitored using high resolution atomic force microscopy (AFM). Slight variations in the height of the poly(N-allyl glycine) nanorods were observed which scale correspondingly to the initial dimensions of nanopores. The distance between adjacent polymer nanorods was controlled by the size of mesoparticle masks used in the experiment. This surface platform has potential application in biotechnology for smart coatings or biosensors. PMID:26789943

  12. Alpha-hydroxyalkyl heterocycles via chiral allylic boronates: Pd-catalyzed borylation leading to a formal enantioselective isomerization of allylic ether and amine.

    PubMed

    Lessard, Stéphanie; Peng, Feng; Hall, Dennis G

    2009-07-22

    An efficient catalytic enantioselective preparation of synthetically useful pyranyl and piperidinyl allylic boronates was achieved via a palladium-catalyzed borylation/isomerization reaction on the corresponding alkenyl triflates. The influence of the base and solvent was found to be crucial on the regio- and enantioselectivity of this reaction. The overall borylation process constitutes a successful example of formal asymmetric isomerization of allylic ether/amine. The resulting allylic boronate reagents add to various aldehydes in a one-pot process to give synthetically useful alpha-hydroxyalkyl derivatives in high stereoselectivity. PMID:19552416

  13. Enhanced reductive dechlorination of trichloroethylene by sulfidated nanoscale zerovalent iron.

    PubMed

    Rajajayavel, Sai Rajasekar C; Ghoshal, Subhasis

    2015-07-01

    Direct injection of reactive nanoscale zerovalent iron particles (NZVI) is considered to be a promising approach for remediation of aquifers contaminated by chlorinated organic pollutants. In this study we show that the extent of sulfidation of NZVI enhances the rate of dechlorination of trichloroethylene (TCE) compared to that by unamended NZVI, and the enhancement depends on the Fe/S molar ratio. Experiments where TCE was reacted with NZVI sulfidated to different extents (Fe/S molar ratios 0.62-66) showed that the surface-area normalized first-order TCE degradation rate constant increased up to 40 folds compared to non-sulfidated NZVI. Fe/S ratios in the range of 12-25 provided the highest TCE dechlorination rates, and rates decreased at both higher and lower Fe/S. In contrast, sulfidated NZVI exposed to water in the absence of TCE showed significantly lower hydrogen evolution rate (2.75 μmol L(-1) h(-1)) compared to that by an unamended NZVI (6.92 μmol L(-1) h(-1)), indicating that sulfidation of NZVI suppressed corrosion reactions with water. Sulfide (HS(-)) ions reacted rapidly with NZVI and X-ray photoelectron spectroscopy analyses showed formation of a surface layer of FeS and FeS2. We propose that more electrons are preferentially conducted from sulfidated NZVI than from unamended NZVI to TCE, likely because of greater binding of TCE on the reactive sites of the iron sulfide outer layer. Resuspending sulfidated NZVI in sulfide-free or sulfide containing solutions altered the TCE degradation rate constants because of changes in the FeS layer thickness. Sulfidated NZVI maintained its high reactivity in the presence of multiple mono and divalent ions and with polyelectrolyte coatings. Thus, sulfide ions in groundwater can significantly alter NZVI reactivity.

  14. Mineralogical studies of sulfide samples and volatile concentrations of basalt glasses from the southern Juan de Fuca Ridge.

    USGS Publications Warehouse

    Brett, R.; Evans, H.T.; Gibson, E.K.; Hedenquist, J.W.; Wandless, M.-V.; Sommer, M.A.

    1987-01-01

    Specifically considers unusual minerals and geothermometric relations not previously covered. Equilibrium, if attained at all, during deposition of most sulfides was a transient event over a few tens of micrometers at most and was perturbed by rapid temperature and compositional changes of the circulating fluid. Two new minerals were found: one, a hydrated Zn, Fe hydroxy-chlorosulfate, and the other, a (Mn, Mg, Fe) hydroxide or hydroxy-hydrate. Both were formed at relatively low temperatures. Lizardite, starkeyite, and anatase were found for the first time in such an environment.-from Authors

  15. Marine diagenesis of hydrothermal sulfide

    SciTech Connect

    Moammar, M.O.

    1985-01-01

    An attempt is made to discuss the artificial and natural oxidation and hydrolysis of hydrothermal sulfide upon interaction with normal seawater. Synthetic and natural ferrosphalerite particles used in kinetic oxidation and hydrolysis studies in seawater develop dense, crystalline coatings consisting of ordered and ferrimagnetic delta-(Fe, Zn)OOH. Due to the formation of this reactive diffusion barrier, the release of Zn into solution decreases rapidly, and sulfide oxidation is reduced to a low rate determined by the diffusion of oxygen through the oxyhydroxide film. This also acts as an efficient solvent for ions such as Zn/sup 2 +/, Ca/sup 2 +/, and possibly Cd/sup 2 +/, which contribute to the stabilization of the delta-FeOOH structure. The oxidation of sulfide occurs in many seafloor spreading areas, such as 21/sup 0/N on the East Pacific Ridge. In these areas the old surface of the sulfide chimneys are found to be covered by an orange stain, and sediment near the base of nonactive vents is also found to consist of what has been referred to as amorphous iron oxide and hydroxide. This thesis also discusses the exceedingly low solubility of zinc in seawater, from delta-(Fe, Zn)OOH and the analogous phase (zinc-ferrihydroxide) and the zinc exchange minerals, 10-A manganate and montmorillonite. The concentrations of all four are of the same magnitude (16, 36.4, and 12 nM, respectively) as the zinc concentration in deep ocean water (approx. 10 nM), which suggests that manganates and montmorillonite with iron oxyhydroxides control zinc concentration in the deep ocean.

  16. A comprehensive study on photocatalytic activity of supported Ni/Pb sulfide and oxide systems onto natural zeolite nanoparticles.

    PubMed

    Babaahamdi-Milani, Majid; Nezamzadeh-Ejhieh, Alireza

    2016-11-15

    The Ni(II)-Pb(II) exchanged clinoptilolite nanoparticles (NCP) were transformed to corresponding oxides and sulfides via calcination and sulfiding processes, respectively. The obtained catalysts were characterized by XRD, FT-IR, TEM and DRS and used in photodegradation of p-nitrophenol (4-NP) aqueous solution under Hg-lamp irradiation. Results showed considerable increase in activity of the coupled semiconductors with respect to monocomponent one. In NiO-PbO-NCP system, conduction band (CB) of NiO is enough negative for easily migration of photogenerated electrons to CB-PbO level, while such phenomena take place from more negative CB-PbS level to CB-NiS level in NiS-PbS-NCP. These phenomena significantly prevented from electron-hole recombination which increased photocatalytic activity of the coupled semiconductors. Best photodegradation activities obtained by NiO1.3%-PbO14.7%-NCP and NiS2.1%-PbS10.0%-NCP, confirming semiconductors' mass-ratio dependence of the photocatalytic process. The supported coupled semiconductors showed blue shifts in band gap energies with respect to the bulk semiconductors which confirm formation of semiconductors nanoparticles inside the zeolite framework. The highest degradation percentage of 4-NP was obtained at: 0.5gL(-1) photocatalysts, 15mgL(-1) 4-NP at pH 7.5.

  17. A comprehensive study on photocatalytic activity of supported Ni/Pb sulfide and oxide systems onto natural zeolite nanoparticles.

    PubMed

    Babaahamdi-Milani, Majid; Nezamzadeh-Ejhieh, Alireza

    2016-11-15

    The Ni(II)-Pb(II) exchanged clinoptilolite nanoparticles (NCP) were transformed to corresponding oxides and sulfides via calcination and sulfiding processes, respectively. The obtained catalysts were characterized by XRD, FT-IR, TEM and DRS and used in photodegradation of p-nitrophenol (4-NP) aqueous solution under Hg-lamp irradiation. Results showed considerable increase in activity of the coupled semiconductors with respect to monocomponent one. In NiO-PbO-NCP system, conduction band (CB) of NiO is enough negative for easily migration of photogenerated electrons to CB-PbO level, while such phenomena take place from more negative CB-PbS level to CB-NiS level in NiS-PbS-NCP. These phenomena significantly prevented from electron-hole recombination which increased photocatalytic activity of the coupled semiconductors. Best photodegradation activities obtained by NiO1.3%-PbO14.7%-NCP and NiS2.1%-PbS10.0%-NCP, confirming semiconductors' mass-ratio dependence of the photocatalytic process. The supported coupled semiconductors showed blue shifts in band gap energies with respect to the bulk semiconductors which confirm formation of semiconductors nanoparticles inside the zeolite framework. The highest degradation percentage of 4-NP was obtained at: 0.5gL(-1) photocatalysts, 15mgL(-1) 4-NP at pH 7.5. PMID:27427895

  18. Cobalt-catalyzed chelation assisted C-H allylation of aromatic amides with unactivated olefins.

    PubMed

    Yamaguchi, Takuma; Kommagalla, Yadagiri; Aihara, Yoshinori; Chatani, Naoto

    2016-08-01

    The cobalt-catalyzed chelation assisted ortho C-H allylation of aromatic amides with unactivated aliphatic alkenes is reported. The reaction proceeds in air under mild reaction conditions, providing allylated products in good to excellent yields with high E-selectivities. This operationally simple method shows a high functional group tolerance.

  19. Allyl sulphides in olefin metathesis: catalyst considerations and traceless promotion of ring-closing metathesis.

    PubMed

    Edwards, Grant A; Culp, Phillip A; Chalker, Justin M

    2015-01-11

    Allyl sulphides are reactive substrates in ruthenium-catalysed olefin metathesis reactions, provided each substrate is matched with a suitable catalyst. A profile of catalyst activity is described, along with the first demonstration of allyl sulphides as traceless promoters in relayed ring-closing metathesis reactions. PMID:25410944

  20. Allyl sulphides in olefin metathesis: catalyst considerations and traceless promotion of ring-closing metathesis.

    PubMed

    Edwards, Grant A; Culp, Phillip A; Chalker, Justin M

    2015-01-11

    Allyl sulphides are reactive substrates in ruthenium-catalysed olefin metathesis reactions, provided each substrate is matched with a suitable catalyst. A profile of catalyst activity is described, along with the first demonstration of allyl sulphides as traceless promoters in relayed ring-closing metathesis reactions.

  1. Pd-catalyzed cascade allylic alkylation and dearomatization reactions of indoles with vinyloxirane.

    PubMed

    Gao, Run-Duo; Xu, Qing-Long; Dai, Li-Xin; You, Shu-Li

    2016-09-14

    We have developed Pd-catalyzed intermolecular Friedel-Crafts-type allylic alkylation and allylic dearomatization reactions of substituted indoles bearing a nucleophilic group with vinyloxirane, providing an efficient method to synthesize structurally diverse tetrahydrocarboline and spiroindolenine derivatives under mild conditions. PMID:27511802

  2. Magnetic silica supported palladium catalyst: synthesis of allyl aryl ethers in water

    EPA Science Inventory

    A simple and benign procedure for the synthesis of aryl allyl ethers has been developed using phenols, allyl acetates and magnetically recyclable silica supported palladium catalyst in water; performance of reaction in air and easy separation of the catalyst using an external mag...

  3. Aerobic oxidation of methyl p-tolyl sulfide catalyzed by a remarkably labile heteroscorpionate RuII-aqua complex, fac-[RuII(H2O)(dpp)(tppm)]2+.

    PubMed

    Huynh, My Hang V; Witham, Laura M; Lasker, Joanne M; Wetzler, Modi; Mort, Brendan; Jameson, Donald L; White, Peter S; Takeuchi, Kenneth J

    2003-01-15

    fac-[RuII(Cl)(dpp)(L3)]+ (L3 = tris(pyrid-2-yl)methoxymethane (tpmm) = [1A]+ and tris(pyrid-2-yl)pentoxymethane (tppm) = [1B]+ and dpp = di(pyrazol-1-yl)propane) rapidly undergo ligand substitution with water to form fac-[RuII(H2O)(dpp)(L3)]2+ (L3 = tpmm = [2A]2+ and tppm = [2B]2+). In the structure of [2A]2+, the distorted octahedral arrangement of ligands around Ru is evident by a long Ru(1)-O(40) of 2.172(3) A and a large angle O(40)-Ru(1)-N(51) of 96.95(14) degrees . The remarkably short distance between O(40) of H2O and H(45a) of dpp confirms the heteroscorpionate ligand effect of dpp on H2O. [2B]2+ aerobically catalyzes methyl p-tolyl sulfide to methyl p-tolyl sulfoxide in 1,2-dichlorobenzene at 25.0 +/- 0.1 degrees C under 11.4 psi of O2. Experimental facts in support of this aerobic sulfide oxidation are the absence of H2O2 and the oxidative reactivity of the putative Ru(IV)-oxo intermediate toward methyl p-tolyl sulfide, 2-propanol, and allyl alcohol. This study provides the first documented example of aerobic-sulfide oxidation catalyzed by the remarkably labile heteroscorpionate Ru(II)-aqua complex without the formation of a highly reactive peroxide as an intermediate.

  4. Microaeration for hydrogen sulfide removal in UASB reactor.

    PubMed

    Krayzelova, Lucie; Bartacek, Jan; Kolesarova, Nina; Jenicek, Pavel

    2014-11-01

    The removal of hydrogen sulfide from biogas by microaeration was studied in Up-flow Anaerobic Sludge Blanket (UASB) reactors treating synthetic brewery wastewater. A fully anaerobic UASB reactor served as a control while air was dosed into a microaerobic UASB reactor (UMSB). After a year of operation, sulfur balance was described in both reactors. In UASB, sulfur was mainly presented in the effluent as sulfide (49%) and in biogas as hydrogen sulfide (34%). In UMSB, 74% of sulfur was detected in the effluent (41% being sulfide and 33% being elemental sulfur), 10% accumulated in headspace as elemental sulfur and 9% escaped in biogas as hydrogen sulfide. The efficiency of hydrogen sulfide removal in UMSB was on average 73%. Microaeration did not cause any decrease in COD removal or methanogenic activity in UMSB and the elemental sulfur produced by microaeration did not accumulate in granular sludge. PMID:25270045

  5. Highly efficient redox isomerization of allylic alcohols at ambient temperature catalyzed by novel ruthenium-cyclopentadienyl complexes--new insight into the mechanism.

    PubMed

    Martín-Matute, Belén; Bogár, Krisztián; Edin, Michaela; Kaynak, F Betül; Bäckvall, Jan-E

    2005-10-01

    A range of ruthenium cyclopentadienyl (Cp) complexes have been prepared and used for isomerization of allylic alcohols to the corresponding saturated carbonyl compounds. Complexes bearing CO ligands show higher activity than those with PPh3 ligands. The isomerization rate is highly affected by the substituents on the Cp ring. Tetra(phenyl)methyl-substituted catalysts rapidly isomerize allylic alcohols under very mild reaction conditions (ambient temperature) with short reaction times. Substituted allylic alcohols have been isomerized by employing Ru-Cp complexes. A study of the isomerization catalyzed by [Ru(Ph5Cp)(CO)2H] (14) indicates that the isomerization catalyzed by ruthenium hydrides partly follows a different mechanism than that of ruthenium halides activated by KOtBu. Furthermore, the lack of ketone exchange when the isomerization was performed in the presence of an unsaturated ketone (1 equiv), different from that obtained by dehydrogenation of the starting allylic alcohol, supports a mechanism in which the isomerization takes place within the coordination sphere of the ruthenium catalyst. PMID:16028298

  6. Radiogenic and stable isotope study of the Dyumptaley and Binyuda ultramafic-mafic intrusions and associated Ni-Cu-PGE sulfide ores (Russian Arctic)

    NASA Astrophysics Data System (ADS)

    Malich, Kreshimir; Badanina, Inna; Belousova, Elena; Pearson, Norman; Romanov, Andrey; Sluzhenikin, Sergey

    2014-05-01

    It is commonly assumed that ultramafic-mafic intrusions and associated PGE-Cu-Ni sulphide deposits of Northern Siberia represent a small component of a major episode of mafic activity at ~250 Ma, which included formation of the most extensive flood-basalt province on Earth [1]. Recent studies, however, advocated protracted evolution of the ore-forming magmas parent to the Noril'sk-type intrusions [2, 3, etc.]. Understanding the processes behind the formation of economically important ore deposits is crucial for locating additional deposits in areas that have not been previously considered. This study, therefore, aimed to provide isotope-geochemical fingerprinting to be used in exploration for Ni-Cu-PGE sulfide ores. We firstly present geochronological and Hf-Nd-Sr-Cu-S isotope data for the same suite of lithologies and associated PGE-Cu-Ni sulphide ores from the Dyumptaley and Binyuda ultramafic-mafic intrusions located in the limits of the Taimyr Peninsula (Russian Arctic). The rocks investigated comprise sulphide-rich varieties of ferrogabbro (i.e. gabbro abnormally high in Fe) and melanocratic troctolite occurring in bottom parts of the Dyumptaley and Binyuda intrusions, respectively. Zircons are characterized by similar U-Pb ages (256.2±0.9 Ma at Dyumtaley, and 245.7±12 Ma at Binyuda). In contrast, silicate materials show distinct Hf-Nd-Sr isotope signatures (ɛHf=8.3±3.7, ɛNd=3.5±0.7 and 87Sr/86Sri=0.70493±0.00021 at Dyumptaley, and ɛHf=-5.2±0.6, ɛNd=-3.4±0.3 and 87Sr/86Sri=0.70585±0.00004 at Binyuda). The determined Hf-Nd-Sr variability is interpreted to represent a primary source signature of the lithological units. An important role of the juvenile component is clearly pronounced for the Dyumptaley intrusion, whereas a major contribution from a SCLM or essentially crustal source is inferred for the Binyuda intrusion. These signatures clearly manifest deviation from those typical of the ore-bearing intrusions from the Noril'sk Province

  7. Activity studies of sesquiterpene oxides and sulfides from the plant Hyptis suaveolens (Lamiaceae) and its repellency on Ixodes ricinus (Acari: Ixodidae).

    PubMed

    Ashitani, T; Garboui, S S; Schubert, F; Vongsombath, C; Liblikas, I; Pålsson, K; Borg-Karlson, A-K

    2015-12-01

    Hyptis suaveolens (Lamiaceae), a plant traditionally used as a mosquito repellent, has been investigated for repellent properties against nymphs of the tick Ixodes ricinus. Essential oils and volatile compounds of fresh and dried leaves, from plants originating from Laos and Guinea-Bissau, were identified by GC-MS and tested in a tick repellency bioassay. All the essential oils were strongly repellent against the ticks, even though the main volatile constituents differed in their proportions of potentially tick repellent chemicals. (+)/(-)-sabinene were present in high amounts in all preparations, and dominated the emission from dry and fresh leaves together with 1,8-cineol and α-phellandrene. 1,8-Cineol and sabinene were major compounds in the essential oils from H. suaveolens from Laos. Main compounds in H. suaveolens from Guinea-Bissau were (-)-sabinene, limonene and terpinolene. Among the sesquiterpene hydrocarbons identified, α-humulene exhibited strong tick repellency (96.8 %). Structure activity studies of oxidation or sulfidation products of germacrene D, α-humulene and β-caryophyllene, showed increased tick repellent activity: of mint sulfide (59.4 %), humulene-6,7-oxide (94.5 %) and caryophyllene-6,7-oxide (96.9 %). The substitution of oxygen with sulfur slightly lowered the repellency. The effects of the constituents in the oils can then be regarded as a trade off between the subsequently lower volatility of the sesquiterpene derivatives compared to the monoterpenes and may thus increase their potential usefulness as tick repellents. PMID:26385208

  8. Limitation of Sulfide Capacity Concept for Molten Slags

    NASA Astrophysics Data System (ADS)

    Jung, In-Ho; Moosavi-Khoonsari, Elmira

    2016-04-01

    The sulfide capacity concept has been widely used in pyrometallurgy to define sulfur removal capacities of slags. Typically, the sulfide capacity is considered to be a unique slag property depending only on temperature regardless of partial pressures of oxygen and sulfur. In the present study, it is demonstrated that sulfide capacities of slags in particular those of Na2O-containing slags can vary with partial pressures of oxygen and sulfur due to large solubility of sulfide in Na2O-containing slag systems.

  9. Oxidative addition of allylic halides to ruthenium(II) compounds. Preparation, reactions, and X-ray crystallographic structure of ruthenium(IV)-allyl complexes

    SciTech Connect

    Nagashima, Hideo; Mukai, Katsunori; Shiota, Yusuke; Yamaguchi, Keitaro; Ara, Kenichi; Fukahori, Takahiko; Itoh, Kenji ); Suzuki, Hiroharu; Akita, Munetaka; Moro-oka, Yoshihiko )

    1990-03-01

    The oxidative addition of allylic halides to (C{sub 5}R{sub 5})RuL{sub 2}X (R = H, Me; L = CO, PPh{sub 3}) gave new Ru(IV)-{eta}{sup 3}-allyl complexes, (C{sub 5}R{sub 5})RuX{sub 2}({eta}{sup 3}-allyl). An X-ray structure determination was carried out on (C{sub 5}Me{sub 5})RuBr{sub 2}({eta}{sup 3}-C{sub 3}H{sub 5}), indicating a pseudo-piano-stool structure having two Br atoms and two terminal carbons of the endo-{eta}{sup 3}-allyl ligand located at the basal positions. There is a crystal mirror plane bisecting the pentamethylcyclopentadienyl and the {pi}-allyl ligands. Crystal data: orthorhombic, space group P2{sub 1}2{sub 1}2{sub 1}, a = 22.738 (1) {angstrom}, b = 13.367 (7) {angstrom}, c = 9.383 (1) {angstrom}, Z = 4., data refined to R = 0.0695. Its {sup 1}H and {sup 13}C NMR spectra showed symmetric allyl signals, supporting that the above-described piano-stool structure is maintained even in solution.

  10. SULFIDE METHOD PLUTONIUM SEPARATION

    DOEpatents

    Duffield, R.B.

    1958-08-12

    A process is described for the recovery of plutonium from neutron irradiated uranium solutions. Such a solution is first treated with a soluble sullide, causing precipitation of the plutoniunn and uraniunn values present, along with those impurities which form insoluble sulfides. The precipitate is then treated with a solution of carbonate ions, which will dissolve the uranium and plutonium present while the fission product sulfides remain unaffected. After separation from the residue, this solution may then be treated by any of the usual methods, such as formation of a lanthanum fluoride precipitate, to effect separation of plutoniunn from uranium.

  11. Adherence of sulfide mineral layers produced by corrosion of copper alloys

    SciTech Connect

    McNeil, M.B. . Office of Research); Amos, A.L.; Woods, T.L. . Dept. of Geology)

    1993-09-01

    Sulfiding corrosion of copper alloys can occur from microbiologically induced corrosion (MIC) mechanisms involving sulfate reducing bacteria (SRB) or from exposure to bulk waters containing reduced sulfur (S) species of microbiological, industrial, or geologic origin. The sulfide minerals produced generally are nonadherent. Under some circumstances, adherent sulfide layers can form and offer a degree of protection against further attack. Test were conducted in sterile synthetic seawater with various levels of dissolved sulfide, and the structure of the corrosion products was examined. Results, combined with MIC observations from literature and geochemical studies of copper sulfide paragenesis, revealed the nature of the reactions that produce dense, relatively protective sulfides.

  12. Biology and therapeutic potential of hydrogen sulfide and hydrogen sulfide-releasing chimeras

    PubMed Central

    Kashfi, Khosrow; Olson, Kenneth R.

    2012-01-01

    Hydrogen sulfide, H2S, is a colorless gas with a strong odor that until recently was only considered to be a toxic environmental pollutant with little or no physiological significance. However, the past few years have demonstrated its role in many biological systems and it is becoming increasingly clear that H2S is likely to join nitric oxide (NO) and carbon monoxide (CO) as a major player in mammalian biology. In this review, we have provided an overview of the chemistry and biology of H2S and have summarized the chemistry and biological activity of some natural and synthetic H2S-donating compounds. The naturally occurring compounds discussed include, garlic, sulforaphane, erucin, and iberin. The synthetic H2S donors reviewed include, GYY4137; cysteine analogs; S-propyl cysteine, S-allyl cysteine, S-propargyl cysteine, and N-acetyl cysteine. Dithiolethione and its NSAID and other chimeras such as, L-DOPA, sildenafil, aspirin, diclofenac, naproxen, ibuprofen, indomethacin, and mesalamine have also been reviewed in detail. The newly reported NOSH-aspirin that releases both NO and H2S has also been discussed. PMID:23103569

  13. Zinc sulfide liquefaction catalyst

    DOEpatents

    Garg, Diwakar

    1984-01-01

    A process for the liquefaction of carbonaceous material, such as coal, is set forth wherein coal is liquefied in a catalytic solvent refining reaction wherein an activated zinc sulfide catalyst is utilized which is activated by hydrogenation in a coal derived process solvent in the absence of coal.

  14. [Biochemical parameters of blood and morpho-functional state of the liver of experimental animals by the actions of lead sulfide nanoparticles in different time study].

    PubMed

    Omel'chuk, S T; Aleksiĭchuk, V D; Sokurenko, L M

    2014-01-01

    Biochemical studies revealed that alanine aminotransferase levels changing first during short action (30 injections) of lead sulfide nanoparticles of size 10 and 30 nm, and the ionic form of a 400 nm lead while the growth of both enzymes (aspartate aminotransferase and alanine aminotransferase) activity during long-term exposure (60 injections) is the same intensity. It it confirmed by the value of de Ritis coefficient, which is statistically the same as control. Morphological studies also confirm these data--degenerative changes of hepatocytes, reactive changes of the stroma and vascular responses were detected. It is shown that the severity of metabolic and morphological damages in the liver increased with prolonging the duration of lead nanoparticles intake.

  15. Enantioselective functionalization of allylic C-H bonds following a strategy of functionalization and diversification.

    PubMed

    Sharma, Ankit; Hartwig, John F

    2013-11-27

    We report the enantioselective functionalization of allylic C-H bonds in terminal alkenes by a strategy involving the installation of a temporary functional group at the terminal carbon atom by C-H bond functionalization, followed by the catalytic diversification of this intermediate with a broad scope of reagents. The method consists of a one-pot sequence of palladium-catalyzed allylic C-H bond oxidation under neutral conditions to form linear allyl benzoates, followed by iridium-catalyzed allylic substitution. This overall transformation forms a variety of chiral products containing a new C-N, C-O, C-S, or C-C bond at the allylic position in good yield with a high branched-to-linear selectivity and excellent enantioselectivity (ee ≤97%). The broad scope of the overall process results from separating the oxidation and functionalization steps; by doing so, the scope of nucleophile encompasses those sensitive to direct oxidative functionalization. The high enantioselectivity of the overall process is achieved by developing an allylic oxidation that occurs without acid to form the linear isomer with high selectivity. These allylic functionalization processes are amenable to an iterative sequence leading to (1,n)-functionalized products with catalyst-controlled diastereo- and enantioselectivity. The utility of the method in the synthesis of biologically active molecules has been demonstrated.

  16. Cp-Ftmw Spectroscopy of a Claisen Rearrangement Precursor Allyl Phenyl Ether

    NASA Astrophysics Data System (ADS)

    Grubbs, G. S., II; Frank, Derek S.; Obenchain, Daniel A.; Cooke, S. A.; Novick, Stewart E.

    2016-06-01

    The pure rotational spectrum of a Claisen rearrangement precursor, allyl phenyl ether (APE), has been measured on a chirped pulse Fourier transform microwave (CP-FTMW) spectrometer in the 8-14 GHz region. Rotational and centrifugal distortion constants for multiple conformations have been determined for the first time and will be discussed. This is the first study of a phenyl-containing ether where multiple conformers were experimentally observed all within their ground vibrational states. Quantum chemical calculations have been performed to isolate low energy geometries of APE and are implemented to aid in spectral assignment. Other structural parameters such as planar moments and inertial defects for the APE conformers are presented and compared to similar molecules for discussion.

  17. Antiangiogenic and proapoptotic activities of allyl isothiocyanate inhibit ascites tumor growth in vivo.

    PubMed

    Kumar, Akhilesh; D'Souza, Saritha S; Tickoo, Sanjay; Salimath, Bharathi P; Singh, H B

    2009-03-01

    The authors investigate the antiangiogenic and proapoptotic effects of mustard essential oil containing allyl isothiocyanate (AITC) and explore its mechanism of action on Ehrlich ascites tumor (EAT) cells. Swiss albino mice transplanted with EAT cells were used to study the effect of AITC. AITC was effective at a concentration of 10 mum as demonstrated by the inhibition of proliferation of EAT cells when compared with the normal HEK293 cells. It significantly reduced ascites secretion and tumor cell proliferation by about 80% and inhibited vascular endothelial growth factor expression in tumor-bearing mice in vivo. It also reduced vessel sprouting and exhibited potent antiangiogenic activity in the chorioallantoic membrane and cornea of the rat. AITC arrested the growth of EAT cells by inducing apoptosis and effectively arrested cell cycle progression at the G1 phase. The results clearly suggest that AITC inhibits tumor growth by both antiangiogenic and proapoptotic mechanisms.

  18. Mechanism of oxidation of allyl alcohol on a V-Mo oxide catalyst

    SciTech Connect

    Makarova, M.A.; Rozentuller, B.V.; Krylov, O.V.

    1989-01-01

    The kinetics of oxidation of allyl alcohol by oxygen on a V-Mo oxide catalyst have been studied in situ by EPR. It has been found that during the course of the reaction V ions within the bulk volume of the catalyst undergo redox conversions, V/sup 4+/ /yields/ V/sup 5+/. At elevated temperatures (213/degree/C) the process kinetics can be described very well in terms of an oxidation-reduction scheme which takes into account reactions occurring within the catalyst bulk, and that the rate of acrolein formation is linearly related to the concentration (V/sup 4+/) in the catalyst volume. At lower temperatures this relationship is disrupted, and the rate of acrolein formation is no longer dependent on the O/sub 2/ pressure. In order to account for these effects the authors have proposed a stepwise scheme, which incorporates an oxygen activation step.

  19. Catalytic asymmetric carbon-carbon bond formation via allylic alkylations with organolithium compounds

    NASA Astrophysics Data System (ADS)

    Pérez, Manuel; Fañanás-Mastral, Martín; Bos, Pieter H.; Rudolph, Alena; Harutyunyan, Syuzanna R.; Feringa, Ben L.

    2011-05-01

    Carbon-carbon bond formation is the basis for the biogenesis of nature's essential molecules. Consequently, it lies at the heart of the chemical sciences. Chiral catalysts have been developed for asymmetric C-C bond formation to yield single enantiomers from several organometallic reagents. Remarkably, for extremely reactive organolithium compounds, which are among the most broadly used reagents in chemical synthesis, a general catalytic methodology for enantioselective C-C formation has proven elusive, until now. Here, we report a copper-based chiral catalytic system that allows carbon-carbon bond formation via allylic alkylation with alkyllithium reagents, with extremely high enantioselectivities and able to tolerate several functional groups. We have found that both the solvent used and the structure of the active chiral catalyst are the most critical factors in achieving successful asymmetric catalysis with alkyllithium reagents. The active form of the chiral catalyst has been identified through spectroscopic studies as a diphosphine copper monoalkyl species.

  20. Divergent C—H Insertion–Cyclization Cascades of N‐Allyl Ynamides

    PubMed Central

    Adcock, Holly V.; Chatzopoulou, Elli

    2015-01-01

    Abstract Gold carbene reactivity patterns were accessed by ynamide insertion into a C(sp3)—H bond. A substantial increase in molecular complexity occurred through the cascade polycyclization of N‐allyl ynamides to form fused nitrogen‐heterocycle scaffolds. Exquisite selectivity was observed despite several competing pathways in an efficient gold‐catalyzed synthesis of densely functionalized C(sp3)‐rich polycycles and a copper‐catalyzed synthesis of fused pyridine derivatives. The respective gold–keteniminium and ketenimine activation pathways have been explored through a structure–reactivity study, and isotopic labeling identified turnover‐limiting C—H bond‐cleavage in both processes. PMID:26515958

  1. Sulfide capacities of fayalite-base slags

    NASA Astrophysics Data System (ADS)

    Simeonov, S. R.; Sridhar, R.; Toguri, J. M.

    1995-04-01

    The sulfide capacities of fayalite-base slags were measured by a gas-slag equilibration technique under controlled oxygen and sulfur potentials similar to those encountered in the pyrometallurgical processing of nonferrous metals. The oxygen pressure range was from 10-9.5 to 10-11 MPa and the sulfur pressure range from 10-3 to 10-4.5 MPa, over a temperature range of 1473 to 1623 K. The slags studied were FeO-SiO2 at silica saturation and those with addition of CaO, MgO, and Al2O3 to determine their effect on sulfide capacities. For these slags, the sulfide capacities were found to vary from 10-3.3 to 10-5. The sulfide capacities increased with increasing temperature from 1473 to 1623 K. A comparison of the reported plant data on sulfur content of industrial slags shows good agreement with the present experimental results. The present data will be useful in estimating metal losses in slag due to metal sulfide entrainment in nonferrous smelters.

  2. Phase Engineering of 2D Tin Sulfides.

    PubMed

    Mutlu, Zafer; Wu, Ryan J; Wickramaratne, Darshana; Shahrezaei, Sina; Liu, Chueh; Temiz, Selcuk; Patalano, Andrew; Ozkan, Mihrimah; Lake, Roger K; Mkhoyan, K A; Ozkan, Cengiz S

    2016-06-01

    Tin sulfides can exist in a variety of phases and polytypes due to the different oxidation states of Sn. A subset of these phases and polytypes take the form of layered 2D structures that give rise to a wide host of electronic and optical properties. Hence, achieving control over the phase, polytype, and thickness of tin sulfides is necessary to utilize this wide range of properties exhibited by the compound. This study reports on phase-selective growth of both hexagonal tin (IV) sulfide SnS2 and orthorhombic tin (II) sulfide SnS crystals with diameters of over tens of microns on SiO2 substrates through atmospheric pressure vapor-phase method in a conventional horizontal quartz tube furnace with SnO2 and S powders as the source materials. Detailed characterization of each phase of tin sulfide crystals is performed using various microscopy and spectroscopy methods, and the results are corroborated by ab initio density functional theory calculations. PMID:27099950

  3. Phase Engineering of 2D Tin Sulfides.

    PubMed

    Mutlu, Zafer; Wu, Ryan J; Wickramaratne, Darshana; Shahrezaei, Sina; Liu, Chueh; Temiz, Selcuk; Patalano, Andrew; Ozkan, Mihrimah; Lake, Roger K; Mkhoyan, K A; Ozkan, Cengiz S

    2016-06-01

    Tin sulfides can exist in a variety of phases and polytypes due to the different oxidation states of Sn. A subset of these phases and polytypes take the form of layered 2D structures that give rise to a wide host of electronic and optical properties. Hence, achieving control over the phase, polytype, and thickness of tin sulfides is necessary to utilize this wide range of properties exhibited by the compound. This study reports on phase-selective growth of both hexagonal tin (IV) sulfide SnS2 and orthorhombic tin (II) sulfide SnS crystals with diameters of over tens of microns on SiO2 substrates through atmospheric pressure vapor-phase method in a conventional horizontal quartz tube furnace with SnO2 and S powders as the source materials. Detailed characterization of each phase of tin sulfide crystals is performed using various microscopy and spectroscopy methods, and the results are corroborated by ab initio density functional theory calculations.

  4. Effect of sulfide ions on complement factor C3.

    PubMed Central

    Granlund-Edstedt, M; Johansson, E; Claesson, R; Carlsson, J

    1991-01-01

    In infected sites such as the gingival pockets of patients with periodontal disease, sulfide levels up to 1 mmol/liter may be reached. There is little information, however, on how sulfide may interact with the host defense. In a previous study (R. Claesson, M. Granlund-Edstedt, S. Persson, and J. Carlsson, Infect. Immun. 57:2776-2781, 1989), it was shown that polymorphonuclear leukocytes were able to kill bacteria in the presence of 1 mM sulfide. However, sulfide seemed to interfere with the opsonization of the bacteria. It has been claimed that sulfide may be toxic by splitting disulfide bonds of proteins. In the present study, serum was exposed to 2 mM sulfide under anaerobic conditions, and the capacity of sulfide to split disulfide bonds of 10 serum proteins involved in opsonization was evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunodetection of the proteins after blotting. Sulfide had a low capacity to split the disulfide bonds of most proteins. Sulfide had, however, a pronounced effect on the complement component C3 in the form of C3bi. Sulfide released the C-terminal region of the alpha chain from C3bi. When C3 opsonizes bacteria, it is this region of C3bi which binds to complement receptor 3 (CR3) of the polymorphonuclear leukocytes. If sulfide has the same effect on C3bi deposited on the bacterial surface as it has on C3bi in solution, it will annihilate the very important contribution of C3bi to opsonization. Images PMID:1987085

  5. Studies of high temperature ternary phases in mixed-metal-rich early transition metal sulfide and phosphide systems

    SciTech Connect

    Marking, G.A.

    1994-01-04

    Investigations of ternary mixed early transition metal-rich sulfide and phosphide systems resulted in the discovery of new structures and new phases. A new series of Zr and Hf - group V transition metal - sulfur K-phases was synthesized and crystallographically characterized. When the group V transition metal was Nb or Ta, the unit cell volume was larger than any previously reported K-phase. The presence of adventitious oxygen was determined in two K-phases through a combination of neutron scattering and X-ray diffraction experiments. A compound Hf{sub 10}Ta{sub 3}S{sub 3} was found to crystallize in a new-structure type similar to the known gamma brasses. This structure is unique in that it is the only reported {open_quotes}stuffed{close_quotes} gamma-brass type structure. The metal components, Hf and Ta, are larger in size and more electropositive than the metals found in normal gamma brasses (e.g. Cu and Zn) and because of the larger metallic radii, sulfur can be incorporated into the structure where it plays an integral role in stabilizing this phase relative to others. X-ray single-crystal, X-ray powder and neutron powder refinements were performed on this structure. A new structure was found in the ternary Nb-Zr-P system which has characteristics in common with many known early transition metal-rich sulfides, selenides, and phosphides. This structure has the simplest known interconnection of the basic building blocks known for this structural class. Anomalous scattering was a powerful tool for differentiating between Zr and Nb when using Mo K{alpha} X-radiation. The compounds ZrNbP and HfNbP formed in the space group Prima with the simple Co{sub 2}Si structure which is among the most common structures found for crystalline solid materials. Solid solution compounds in the Ta-Nb-P, Ta-Zr-P, Nb-Zr-P, Hf-Nb-P, and Hf-Zr-S systems were crystallographically characterized. The structural information corroborated ideas about bonding in metal-rich compounds.

  6. Thermodynamics of Complex Sulfide Inclusion Formation in Ca-Treated Al-Killed Structural Steel

    NASA Astrophysics Data System (ADS)

    Guo, Yin-tao; He, Sheng-ping; Chen, Gu-jun; Wang, Qian

    2016-08-01

    Controlling the morphology of the sulfide inclusion is of vital importance in enhancing the properties of structural steel. Long strip-shaped sulfides in hot-rolled steel can spherize when, instead of the inclusion of pure single-phase MnS, the guest is a complex sulfide, such as an oxide-sulfide duplex and a solid-solution sulfide particle. In this study, the inclusions in a commercial rolled structural steel were investigated. Spherical and elongated oxide-sulfide duplex as well as single-phase (Mn,Ca)S solid solution inclusions were observed in the steel. A thermodynamic equilibrium between the oxide and sulfide inclusions was proposed to understand the oxide-sulfide duplex inclusion formation. Based on the equilibrium solidification principle, thermodynamic discussions on inclusion precipitation during the solidification process were performed for both general and resulfurized structural steel. The predicted results of the present study agreed well with the experimental ones.

  7. Oxygen Demand of Fresh and Stored Sulfide Solutions and Sulfide-Rich Constructed Wetland Effluent.

    PubMed

    Chan, Carolyn; Farahbakhsh, Khosrow

    2015-08-01

    This study investigated the contribution of hydrogen sulfide to biological oxygen demand (BOD5) and chemical oxygen demand (COD) in wastewater effluents, and documented the effect of storage times and conditions on the BOD5 and COD of pH-adjusted sodium sulfide solutions as well as graywater wetland effluent. Initial COD measurements of sulfide solutions were 84-89% of the theoretical oxygen demand (ThOD), 1.996 mg O2/mg S, whereas unseeded BOD5 measurements were 55-77%. For sulfide solutions, all storage conditions led to declines of >15% (COD, BOD5), and >31% (sulfide). For wetland effluent, storage without headspace was effective in reducing COD losses (3.7%), compared to storage with headspace (17%), and affected changes in turbidity, UVA-254 and pH. The results suggest that storage times and conditions should be controlled and reported when reporting BOD5 and COD of sulfide-rich samples. Wetland models representing sulfate reduction as a method of COD removal may need to be reconsidered. PMID:26237688

  8. Evidence supporting biologically mediated sulfide oxidation in hot spring ecosystems

    NASA Astrophysics Data System (ADS)

    Cox, A. D.; Shock, E.

    2011-12-01

    The sulfide concentration of fluids in hydrothermal ecosystems is one of several factors determining the transition to microbial photosynthesis (Cox et al., 2011, Chem. Geol. 280, 344-351). To investigate the loss of sulfide in Yellowstone hot spring systems, measurements of total dissolved sulfide with respect to time were made in incubation experiments conducted on 0.2-micron filtered (killed controls) vs. unfiltered hot spring water at locations with three different pH:sulfide combinations (pH 2.5 with 50 μM sulfide, 5.2 with 5.6 μM sulfide, and 8.3 with 86 μM sulfide). At the higher pH values, the experiments yielded similar rates of sulfide loss in filtered and unfiltered water of approximately 0.8 (pH 5.2) and 7.6 nmol sulfide L-1s-1 (pH 8.3). At the acidic spring, the unfiltered water lost sulfide at a rate 1.6 times that of the filtered water (8.2 vs. 5 nmol sulfide L-1s-1). These results suggest that the pelagic biomass at the pH 5.2 and 8.3 springs may not affect sulfide loss, whereas in the pH 2.5 spring there appears to be an effect. In addition, the incubation of filamentous biomass with unfiltered water increased the rate of sulfide loss by approximately two-fold at a pH of 2.5 (59 vs. 31 nmol L-1s-1; Cox et al., 2011), five-fold at a pH of 5.2 (3.9 vs. 0.8 nmol sulfide L-1s-1), and barely increased the rate of sulfide loss at a pH of 8.3 (9.1 vs. 8.4 nmol sulfide L-1s-1). Sulfide is predominately present as HS- at a pH of 8.3, which may not be taken up as easily by microorganisms as the H2S (aq) that dominates sulfide speciation at pH 2.5 and 5.2. That the loss of sulfide at acidic pH is due to biotic rather than abiotic factors is further supported by studies with whole mat samples that show greater sulfide consumption than killed controls (D'Imperio et al., 2008, AEM 74, 5802-5808). Taken together, the results of these experiments suggest that the majority of sulfide oxidation occurs in the filamentous biomass of hot spring ecosystems, although

  9. Scanning electrochemical microscopy studies of micropatterned copper sulfide (CuxS) thin films fabricated by a wet chemistry method

    PubMed Central

    Chen, Miao; Zhao, Jing; Zhao, Xiaocui

    2011-01-01

    Patterned copper sulfide (CuxS) microstructures on Si (1 1 1) wafers were successfully fabricated by a relatively simple solution growth method using copper sulfate, ethylenediaminetetraacetate and sodium thiosulfate aqueous solutions as precursors. The CuxS particles were selectively deposited on a patterned self-assembled monolayer of 3-aminopropyltriethoxysilane regions created by photolithography. To obtain high quality CuxS films, preparative conditions such as concentration, proportion, pH and temperature of the precursor solutions were optimized. Various techniques such as optical microscopy, atomic force microscopy (AFM), X-ray diffraction, optical absorption and scanning electrochemical microscopy (SECM) were employed to examine the topography and properties of the micro-patterned CuxS films. Optical microscopy and AFM results indicated that the CuxS micro-pattern possessed high selectivity and clear edge resolution. From combined X-ray diffraction analysis and optical band gap calculations we conclude that Cu9S5 (digenite) was the main phase within the resultant CuxS film. Both SECM image and cyclic voltammograms confirmed that the CuxS film had good electrical conductivity. Moreover, from SECM approach curve analysis, the apparent electron-transfer rate constant (k) in the micro-pattern of CuxS dominated surface was estimated as 0.04 cm/s. The SECM current map showed high edge acuity of the micro-patterned CuxS. PMID:21785491

  10. Scanning electrochemical microscopy studies of micropatterned copper sulfide (Cu(x)S) thin films fabricated by a wet chemistry method.

    PubMed

    Chen, Miao; Zhao, Jing; Zhao, Xiaocui

    2011-05-30

    Patterned copper sulfide (Cu(x)S) microstructures on Si (1 1 1) wafers were successfully fabricated by a relatively simple solution growth method using copper sulfate, ethylenediaminetetraacetate and sodium thiosulfate aqueous solutions as precursors. The Cu(x)S particles were selectively deposited on a patterned self-assembled monolayer of 3-aminopropyltriethoxysilane regions created by photolithography. To obtain high quality Cu(x)S films, preparative conditions such as concentration, proportion, pH and temperature of the precursor solutions were optimized. Various techniques such as optical microscopy, atomic force microscopy (AFM), X-ray diffraction, optical absorption and scanning electrochemical microscopy (SECM) were employed to examine the topography and properties of the micro-patterned Cu(x)S films. Optical microscopy and AFM results indicated that the Cu(x)S micro-pattern possessed high selectivity and clear edge resolution. From combined X-ray diffraction analysis and optical band gap calculations we conclude that Cu(9)S(5) (digenite) was the main phase within the resultant Cu(x)S film. Both SECM image and cyclic voltammograms confirmed that the Cu(x)S film had good electrical conductivity. Moreover, from SECM approach curve analysis, the apparent electron-transfer rate constant (k) in the micro-pattern of Cu(x)S dominated surface was estimated as 0.04 cm/s. The SECM current map showed high edge acuity of the micro-patterned Cu(x)S.

  11. Study on the mesocarbon microbeads/polyphenylene sulfide composite bipolar plates applied for proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Yang, Tao; Shi, Pengfei

    Thermoplastic/graphite composite bipolar plates based on polyphenylene sulfide (PPS) and mesocarbon microbeads (MCMB) were prepared by compression molding at a pressure of 40 MPa and 400 °C. Electrical conductivity, bulk density, flexural strength, water and ethanol absorption were determined as function of PPS content. The influences of molding time, actived carbon and carbon fiber on the properties of the composite bipolar plates were investigated, the cross section of the composite plates were analyzed by scanning electron microscope (SEM). We found that the optimized PPS content is 20 wt% and the required molding time is 30 min. In particular, the composite plates containing 20 wt% PPS demonstrated in-plane conductivity as high as 133.7 S cm -1, through-plane conductivity 21.37 S cm -1, in addition to showing the value of density, flexural strength, water and ethanol absorption as 1.98 g cm -3, 38.82 MPa, 0.0409 and 0.352 g cm -3. The addition of actived carbon degraded all the performance of the bipolar plate, while addition of carbon fiber improved almost all the performance of bipolar plate except bulk density and through-plane conductivity. The performances of fuel cell with this composite bipolar plate were tested, no distinct variation occurred after the composite plates operating in fuel cell. These data indicates the chemical and mechanical stability of the composite plates and their potential application in fuel cell.

  12. Copper-Catalyzed Oxidative Dehydrogenative Carboxylation of Unactivated Alkanes to Allylic Esters via Alkenes

    PubMed Central

    2015-01-01

    We report copper-catalyzed oxidative dehydrogenative carboxylation (ODC) of unactivated alkanes with various substituted benzoic acids to produce the corresponding allylic esters. Spectroscopic studies (EPR, UV–vis) revealed that the resting state of the catalyst is [(BPI)Cu(O2CPh)] (1-O2CPh), formed from [(BPI)Cu(PPh3)2], oxidant, and benzoic acid. Catalytic and stoichiometric reactions of 1-O2CPh with alkyl radicals and radical probes imply that C–H bond cleavage occurs by a tert-butoxy radical. In addition, the deuterium kinetic isotope effect from reactions of cyclohexane and d12-cyclohexane in separate vessels showed that the turnover-limiting step for the ODC of cyclohexane is C–H bond cleavage. To understand the origin of the difference in products formed from copper-catalyzed amidation and copper-catalyzed ODC, reactions of an alkyl radical with a series of copper–carboxylate, copper–amidate, and copper–imidate complexes were performed. The results of competition experiments revealed that the relative rate of reaction of alkyl radicals with the copper complexes follows the trend Cu(II)–amidate > Cu(II)–imidate > Cu(II)–benzoate. Consistent with this trend, Cu(II)–amidates and Cu(II)–benzoates containing more electron-rich aryl groups on the benzamidate and benzoate react faster with the alkyl radical than do those with more electron-poor aryl groups on these ligands to produce the corresponding products. These data on the ODC of cyclohexane led to preliminary investigation of copper-catalyzed oxidative dehydrogenative amination of cyclohexane to generate a mixture of N-alkyl and N-allylic products. PMID:25389772

  13. Copper-catalyzed oxidative dehydrogenative carboxylation of unactivated alkanes to allylic esters via alkenes.

    PubMed

    Tran, Ba L; Driess, Matthias; Hartwig, John F

    2014-12-10

    We report copper-catalyzed oxidative dehydrogenative carboxylation (ODC) of unactivated alkanes with various substituted benzoic acids to produce the corresponding allylic esters. Spectroscopic studies (EPR, UV-vis) revealed that the resting state of the catalyst is [(BPI)Cu(O2CPh)] (1-O2CPh), formed from [(BPI)Cu(PPh3)2], oxidant, and benzoic acid. Catalytic and stoichiometric reactions of 1-O2CPh with alkyl radicals and radical probes imply that C-H bond cleavage occurs by a tert-butoxy radical. In addition, the deuterium kinetic isotope effect from reactions of cyclohexane and d12-cyclohexane in separate vessels showed that the turnover-limiting step for the ODC of cyclohexane is C-H bond cleavage. To understand the origin of the difference in products formed from copper-catalyzed amidation and copper-catalyzed ODC, reactions of an alkyl radical with a series of copper-carboxylate, copper-amidate, and copper-imidate complexes were performed. The results of competition experiments revealed that the relative rate of reaction of alkyl radicals with the copper complexes follows the trend Cu(II)-amidate > Cu(II)-imidate > Cu(II)-benzoate. Consistent with this trend, Cu(II)-amidates and Cu(II)-benzoates containing more electron-rich aryl groups on the benzamidate and benzoate react faster with the alkyl radical than do those with more electron-poor aryl groups on these ligands to produce the corresponding products. These data on the ODC of cyclohexane led to preliminary investigation of copper-catalyzed oxidative dehydrogenative amination of cyclohexane to generate a mixture of N-alkyl and N-allylic products. PMID:25389772

  14. Rhodium-Catalyzed Regiodivergent Hydrothiolation of Allyl Amines and Imines.

    PubMed

    Kennemur, Jennifer L; Kortman, Gregory D; Hull, Kami L

    2016-09-14

    The regiodivergent Rh-catalyzed hydrothiolation of allyl amines and imines is presented. Bidentate phosphine ligands with larger natural bite angles (βn ≥ 99°), for example, DPEphos, dpph, or L1, promote a Markovnikov-selective hydrothiolation in up to 88% yield and >20:1 regioselectivity. Conversely, when smaller bite angle ligands (βn ≤ 86°), for example, dppbz or dppp, are employed, the anti-Markovnikov product is formed in up to 74% yield and >20:1 regioselectivity. Initial mechanistic investigations are performed and are consistent with an oxidative addition/olefin insertion/reductive elimination mechanism for each regioisomeric pathway. We hypothesize that the change in regioselectivity is an effect of diverging coordination spheres to favor either Rh-S or Rh-H insertion to form the branched or linear isomer, respectively. PMID:27547858

  15. Sulfide detoxification in plant mitochondria.

    PubMed

    Birke, Hannah; Hildebrandt, Tatjana M; Wirtz, Markus; Hell, Rüdiger

    2015-01-01

    In contrast to animals, which release the signal molecule sulfide in small amounts from cysteine and its derivates, phototrophic eukaryotes generate sulfide as an essential intermediate of the sulfur assimilation pathway. Additionally, iron-sulfur cluster turnover and cyanide detoxification might contribute to the release of sulfide in mitochondria. However, sulfide is a potent inhibitor of cytochrome c oxidase in mitochondria. Thus, efficient sulfide detoxification mechanisms are required in mitochondria to ensure adequate energy production and consequently survival of the plant cell. Two enzymes have been recently described to catalyze sulfide detoxification in mitochondria of Arabidopsis thaliana, O-acetylserine(thiol)lyase C (OAS-TL C), and the sulfur dioxygenase (SDO) ethylmalonic encephalopathy protein 1 (ETHE1). Biochemical characterization of sulfide producing and consuming enzymes in mitochondria of plants is fundamental to understand the regulatory network that enables mitochondrial sulfide homeostasis under nonstressed and stressed conditions. In this chapter, we provide established protocols to determine the activity of the sulfide releasing enzyme β-cyanoalanine synthase as well as sulfide-consuming enzymes OAS-TL and SDO. Additionally, we describe a reliable and efficient method to purify OAS-TL proteins from plant material.

  16. Percutaneous absorption of selenium sulfide

    SciTech Connect

    Farley, J.; Skelly, E.M.; Weber, C.B.

    1986-01-01

    The purpose of this study was to determine selenium levels in the urine of Tinea patients before and after overnight application of a 2.5% selenium sulfide lotion. Selenium was measured by atomic absorption spectroscopy (AAS). Hydride generation and carbon rod atomization were studied. It was concluded from this study that selenium is absorbed through intact skin. Selenium is then excreted, at least partially, in urine, for at least a week following treatment. The data show that absorption and excretion of selenium vary on an individual basis. Selenium levels in urine following a single application of selenium sulfide lotion do not indicate that toxic amounts of selenium are being absorbed. Repeated treatments with SeS/sub 2/ result in selenium concentrations in urine which are significantly higher than normal. Significant matrix effects are observed in the carbon rod atomization of urine samples for selenium determinations, even in the presence of a matrix modifier such as nickel. The method of standard additions is required to obtain accurate results in the direct determination of selenium in urine by carbon rod AAS.

  17. Geothermal hydrogen sulfide removal

    SciTech Connect

    Urban, P.

    1981-04-01

    UOP Sulfox technology successfully removed 500 ppM hydrogen sulfide from simulated mixed phase geothermal waters. The Sulfox process involves air oxidation of hydrogen sulfide using a fixed catalyst bed. The catalyst activity remained stable throughout the life of the program. The product stream composition was selected by controlling pH; low pH favored elemental sulfur, while high pH favored water soluble sulfate and thiosulfate. Operation with liquid water present assured full catalytic activity. Dissolved salts reduced catalyst activity somewhat. Application of Sulfox technology to geothermal waters resulted in a straightforward process. There were no requirements for auxiliary processes such as a chemical plant. Application of the process to various types of geothermal waters is discussed and plans for a field test pilot plant and a schedule for commercialization are outlined.

  18. Ultrafine particles derived from mineral processing: A case study of the Pb-Zn sulfide ore with emphasis on lead-bearing colloids.

    PubMed

    Mikhlin, Yuri; Vorobyev, Sergey; Romanchenko, Alexander; Karasev, Sergey; Karacharov, Anton; Zharkov, Sergey

    2016-03-01

    Although mining and mineral processing industry is a vast source of heavy metal pollutants, the formation and behavior of micrometer- and nanometer-sized particles and their aqueous colloids entered the environment from the technological media has received insufficient attention to date. Here, the yield and characteristics of ultrafine mineral entities produced by routine grinding of the Pb-Zn sulfide ore (Gorevskoe ore deposit, Russia) were studied using laser diffraction analysis (LDA), dynamic light scattering (DLS) and zeta potential measurement, microscopy, X-ray photoelectron spectroscopy, with most attention given to toxic lead species. It was revealed, in particular, that the fraction of particles less that 1 μm in the ground ore typical reaches 0.4 vol. %. The aquatic particles in supernatants were micrometer size aggregates with increased content of zinc, sulfur, calcium as compared with the bulk ore concentrations. The hydrodynamic diameter of the colloidal species decreased with time, with their zeta potentials remaining about -12 mV. The colloids produced from galena were composed of 20-50 nm PbS nanoparticles associated with lead sulfate and thiosulfate, while the surface oxidation products at precipitated galena were largely lead oxyhydroxides. The size and zeta potential of the lead-bearing colloids decreased with time down to about 100 nm and from -15 mV to -30 mV, respectively. And, conversely, lead sulfide nanoparticles were mobilized before the aggregates during redispersion of the precipitates in fresh portions of water. The potential environmental impact of the metal-bearing colloids, which is due to the large-scale production and relative stability, is discussed.

  19. Ultrafine particles derived from mineral processing: A case study of the Pb-Zn sulfide ore with emphasis on lead-bearing colloids.

    PubMed

    Mikhlin, Yuri; Vorobyev, Sergey; Romanchenko, Alexander; Karasev, Sergey; Karacharov, Anton; Zharkov, Sergey

    2016-03-01

    Although mining and mineral processing industry is a vast source of heavy metal pollutants, the formation and behavior of micrometer- and nanometer-sized particles and their aqueous colloids entered the environment from the technological media has received insufficient attention to date. Here, the yield and characteristics of ultrafine mineral entities produced by routine grinding of the Pb-Zn sulfide ore (Gorevskoe ore deposit, Russia) were studied using laser diffraction analysis (LDA), dynamic light scattering (DLS) and zeta potential measurement, microscopy, X-ray photoelectron spectroscopy, with most attention given to toxic lead species. It was revealed, in particular, that the fraction of particles less that 1 μm in the ground ore typical reaches 0.4 vol. %. The aquatic particles in supernatants were micrometer size aggregates with increased content of zinc, sulfur, calcium as compared with the bulk ore concentrations. The hydrodynamic diameter of the colloidal species decreased with time, with their zeta potentials remaining about -12 mV. The colloids produced from galena were composed of 20-50 nm PbS nanoparticles associated with lead sulfate and thiosulfate, while the surface oxidation products at precipitated galena were largely lead oxyhydroxides. The size and zeta potential of the lead-bearing colloids decreased with time down to about 100 nm and from -15 mV to -30 mV, respectively. And, conversely, lead sulfide nanoparticles were mobilized before the aggregates during redispersion of the precipitates in fresh portions of water. The potential environmental impact of the metal-bearing colloids, which is due to the large-scale production and relative stability, is discussed. PMID:26761598

  20. Acute inhalation toxicity of carbonyl sulfide

    SciTech Connect

    Benson, J.M.; Hahn, F.F.; Barr, E.B.

    1995-12-01

    Carbonyl sulfide (COS), a colorless gas, is a side product of industrial procedures sure as coal hydrogenation and gasification. It is structurally related to and is a metabolite of carbon disulfide. COS is metabolized in the body by carbonic anhydrase to hydrogen sulfide (H{sub 2}S), which is thought to be responsible for COS toxicity. No threshold limit value for COS has been established. Results of these studies indicate COS (with an LC{sub 50} of 590 ppm) is slightly less acutely toxic than H{sub 2}S (LC{sub 50} of 440 ppm).

  1. Sulfide and methane production in sewer sediments.

    PubMed

    Liu, Yiwen; Ni, Bing-Jie; Ganigué, Ramon; Werner, Ursula; Sharma, Keshab R; Yuan, Zhiguo

    2015-03-01

    Recent studies have demonstrated significant sulfide and methane production by sewer biofilms, particularly in rising mains. Sewer sediments in gravity sewers are also biologically active; however, their contribution to biological transformations in sewers is poorly understood at present. In this study, sediments collected from a gravity sewer were cultivated in a laboratory reactor fed with real wastewater for more than one year to obtain intact sediments. Batch test results show significant sulfide production with an average rate of 9.20 ± 0.39 g S/m(2)·d from the sediments, which is significantly higher than the areal rate of sewer biofilms. In contrast, the average methane production rate is 1.56 ± 0.14 g CH4/m(2)·d at 20 °C, which is comparable to the areal rate of sewer biofilms. These results clearly show that the contributions of sewer sediments to sulfide and methane production cannot be ignored when evaluating sewer emissions. Microsensor and pore water measurements of sulfide, sulfate and methane in the sediments, microbial profiling along the depth of the sediments and mathematical modelling reveal that sulfide production takes place near the sediment surface due to the limited penetration of sulfate. In comparison, methane production occurs in a much deeper zone below the surface likely due to the better penetration of soluble organic carbon. Modelling results illustrate the dependency of sulfide and methane productions on the bulk sulfate and soluble organic carbon concentrations can be well described with half-order kinetics.

  2. Effect of Allyl Isothiocyanate on developmental toxicity in exposed Xenopus laevis embryos

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The pungent natural compound allyl isothiocyanate isolated from the seeds of Cruciferous (Brassica) plants such as mustard is reported to exhibit numerous beneficial health-promoting antimicrobial, antifungal, anticarcinogenic, cardioprotective, and neuroprotective properties. Because it is also re...

  3. Total Synthesis of Enantiopure (+)-γ -Lycorane Using Highly Efficient Pd-Catalyzed Asymmetric Allylic Alkylation

    PubMed Central

    Chapsal, Bruno D.; Ojima, Iwao

    2008-01-01

    Highly efficient short total synthesis of γ -lycorane (>99% ee, 41% overall yield) was achieved by using the asymmetric allylic alkylation in the key step catalyzed by palladium complexes with novel chiral biphenol-based monodentate phosphoramidite ligands. PMID:16562900

  4. O-allyl decoration on alpha-glucan isolated from the haloalkaliphilic Halomonas pantelleriensis bacterium.

    PubMed

    Corsaro, Maria Michela; Gambacorta, Agata; Lanzetta, Rosa; Nicolaus, Barbara; Pieretti, Giuseppina; Romano, Ida; Parrilli, Michelangelo

    2007-07-01

    An alpha-glucan containing the unprecedented peculiar O-allyl substituent was isolated from the haloalkaliphilic Gram-negative Halomonas pantelleriensis bacterium. Its dextran-like structure was deduced from chemical degradative and spectroscopic methods.

  5. Expanding the scope of Metal-Free enantioselective allylic substitutions: Anthrones

    PubMed Central

    Ceban, Victor; Tauchman, Jiří; Meazza, Marta; Gallagher, Greg; Light, Mark E.; Gergelitsová, Ivana; Veselý, Jan; Rios, Ramon

    2015-01-01

    The highly enantioselective asymmetric allylic alkylation of Morita–Baylis–Hillman carbonates with anthrones is presented. The reaction is simply catalyzed by cinchona alkaloid derivatives affording the final alkylated products in good yields and excellent enantioselectivities. PMID:26592555

  6. Effect of palladium on sulfide tarnishing of noble metal alloys.

    PubMed

    Suoninen, E; Herø, H; Minni, E

    1985-10-01

    Electron spectroscopic studies of Au-Ag-Cu alloys of the type used for dental castings show that small additions (less than or equal to 3 wt%) of palladium reduce essentially the thickness of the sulfide layer formed on surfaces of samples treated in aqueous Na2S solutions. Relative to silver, palladium does not enrich in the sulfide, but statistically significant enrichment is found immediately below the sulfide layer. This enrichment probably takes place during the exposure of the substrate surface to atmosphere before the sulfiding treatment. The mechanism of the impeding effect of palladium on sulfiding is assumed to be a decrease in diffusion from the bulk alloy to the surface due to the enriched layer. The effect cannot be explained by changes in the electronic structure of the alloy due to palladium alloying.

  7. Enzyme- and ruthenium-catalyzed dynamic kinetic resolution of functionalized cyclic allylic alcohols.

    PubMed

    Lihammar, Richard; Millet, Renaud; Bäckvall, Jan-E

    2013-12-01

    Enantioselective synthesis of functionalized cyclic allylic alcohols via dynamic kinetic resolution has been developed. Cyclopentadienylruthenium catalysts were used for the racemization, and lipase PS-IM or CALB was employed for the resolution. By optimization of the reaction conditions the formation of the enone byproduct was minimized, making it possible to prepare a range of optically active functionalized allylic alcohols in good yields and high ee's.

  8. Palladium-Catalyzed Asymmetric Allylic Alkylations with Toluene Derivatives as Pronucleophiles.

    PubMed

    Mao, Jianyou; Zhang, Jiadi; Jiang, Hui; Bellomo, Ana; Zhang, Mengnan; Gao, Zidong; Dreher, Spencer D; Walsh, Patrick J

    2016-02-12

    The first two highly enantioselective palladium-catalyzed allylic alkylations with benzylic nucleophiles, activated with Cr(CO)3 , have been developed. These methods enable the enantioselective synthesis of α-2-propenyl benzyl motifs, which are important scaffolds in natural products and pharmaceuticals. A variety of cyclic and acyclic allylic carbonates are competent electrophilic partners furnishing the products in excellent enantioselectivity (up to 99 % ee and 92 % yield). This approach was employed to prepare a nonsteroidal anti-inflammatory drug analogue.

  9. DABO Boronate Promoted Conjugate Allylation of α,β-Unsaturated Aldehydes Using Copper(II) Catalysis.

    PubMed

    Roest, Pjotr C; Michel, Nicholas W M; Batey, Robert A

    2016-08-01

    The first catalytic method for the selective 1,4-conjugate allylation of α,β-unsaturated aldehydes is reported. The method employs an air-stable diethanolamine-complexed boronic acid (DABO boronate) as the allyl transfer reagent and promotes conjugate addition over 1,2-addition. A variety of aryl- and alkyl-substituted enals are tolerated, providing δ,ε-unsaturated aldehyde products in good yields and selectivities under mild conditions. PMID:27362535

  10. Luminal sulfide and large intestine mucosa: friend or foe?

    PubMed

    Blachier, François; Davila, Anne-Marie; Mimoun, Sabria; Benetti, Pierre-Henri; Atanasiu, Calina; Andriamihaja, Mireille; Benamouzig, Robert; Bouillaud, Frédéric; Tomé, Daniel

    2010-07-01

    Hydrogen sulfide (H(2)S) is present in the lumen of the human large intestine at millimolar concentrations. However, the concentration of free (unbound) sulfide is in the micromolar range due to a large capacity of fecal components to bind the sulfide. H(2)S can be produced by the intestinal microbiota from alimentary and endogenous sulfur-containing compounds including amino acids. At excessive concentration, H(2)S is known to severely inhibit cytochrome c oxidase, the terminal oxidase of the mitochondrial electron transport chain, and thus mitochondrial oxygen (O(2)) consumption. However, the concept that sulfide is simply a metabolic troublemaker toward colonic epithelial cells has been challenged by the discovery that micromolar concentration of H(2)S is able to increase the cell respiration and to energize mitochondria allowing these cells to detoxify and to recover energy from luminal sulfide. The main product of H(2)S metabolism by the colonic mucosa is thiosulfate. The enzymatic activities involved in sulfide oxidation by the colonic epithelial cells appear to be sulfide quinone oxidoreductase considered as the first and rate-limiting step followed presumably by the action of sulfur dioxygenase and rhodanese. From clinical studies with human volunteers and experimental works with rodents, it appears that H(2)S can exert mostly pro- but also anti-inflammatory effects on the colonic mucosa. From the available data, it is tempting to propose that imbalance between the luminal concentration of free sulfide and the capacity of colonic epithelial cells to metabolize this compound will result in an impairment of the colonic epithelial cell O(2) consumption with consequences on the process of mucosal inflammation. In addition, endogenously produced sulfide is emerging as a prosecretory neuromodulator and as a relaxant agent toward the intestinal contractibility. Lastly, sulfide has been recently described as an agent involved in nociception in the large intestine

  11. Experimental and theoretical studies of the reaction of the OH radical with alkyl sulfides: 3. Kinetics and mechanism of the OH initiated oxidation of dimethyl, dipropyl, and dibutyl sulfides: reactivity trends in the alkyl sulfides and development of a predictive expression for the reaction of OH with DMS.

    PubMed

    Williams, M B; Campuzano-Jost, P; Hynes, A J; Pounds, A J

    2009-06-18

    A pulsed laser photolysis-pulsed laser-induced fluorescence technique has been employed to measure rate coefficients for the OH-initiated oxidation of dimethyl sulfide (DMS), its deuterated analog (DMS-d(6)), dipropyl sulfide (DPS), and dibutyl sulfide (DBS). Effective rate coefficients have been measured as a function of the partial pressure of O(2) over the temperature range of 240-295 K and at 200 and 600 Torr total pressure. We report the first observations of an O(2) enhancement in the effective rate coefficients for the reactions of OH with DPS and DBS. All observations are consistent with oxidation proceeding via a two-channel oxidation mechanism involving abstraction and addition channels. Structures and thermochemistry of the DPSOH and DBSOH adducts were calculated. Calculated bond strengths of adducts increase with alkyl substitution but are comparable to that of the DMSOH adduct and are consistent with experimental observations. Reactivity trends across the series of alkyl sulfide (C(2)-C(8)) reactions are analyzed. All reactions proceed via a two-channel mechanism involving either an H-atom abstraction or the formation of an OH adduct that can then react with O(2). Measurements presented in this work, in conjunction with previous measurements, have been used to develop a predictive expression for the OH-initiated oxidation of DMS. This expression is based on the elementary rate coefficients in the two-channel mechanism. The expression can calculate the effective rate coefficient for the reaction of OH with DMS over the range of 200-300 K, 0-760 Torr, and 0-100% partial pressure of O(2). This expression expands on previously published work but is applicable to DMS oxidation throughout the troposphere.

  12. Hydrogen sulfide intoxication.

    PubMed

    Guidotti, Tee L

    2015-01-01

    Hydrogen sulfide (H2S) is a hazard primarily in the oil and gas industry, agriculture, sewage and animal waste handling, construction (asphalt operations and disturbing marshy terrain), and other settings where organic material decomposes under reducing conditions, and in geothermal operations. It is an insoluble gas, heavier than air, with a very low odor threshold and high toxicity, driven by concentration more than duration of exposure. Toxicity presents in a unique, reliable, and characteristic toxidrome consisting, in ascending order of exposure, of mucosal irritation, especially of the eye ("gas eye"), olfactory paralysis (not to be confused with olfactory fatigue), sudden but reversible loss of consciousness ("knockdown"), pulmonary edema (with an unusually favorable prognosis), and death (probably with apnea contributing). The risk of chronic neurcognitive changes is controversial, with the best evidence at high exposure levels and after knockdowns, which are frequently accompanied by head injury or oxygen deprivation. Treatment cannot be initiated promptly in the prehospital phase, and currently rests primarily on supportive care, hyperbaric oxygen, and nitrite administration. The mechanism of action for sublethal neurotoxicity and knockdown is clearly not inhibition of cytochrome oxidase c, as generally assumed, although this may play a role in overwhelming exposures. High levels of endogenous sulfide are found in the brain, presumably relating to the function of hydrogen sulfide as a gaseous neurotransmitter and immunomodulator. Prevention requires control of exposure and rigorous training to stop doomed rescue attempts attempted without self-contained breathing apparatus, especially in confined spaces, and in sudden release in the oil and gas sector, which result in multiple avoidable deaths. PMID:26563786

  13. Monitoring sulfide and sulfate-reducing bacteria

    SciTech Connect

    Tanner, R.S.

    1995-12-31

    Simple yet precise and accurate methods for monitoring sulfate-reducing bacteria (SRB) and sulfide remain useful for the study of bacterial souring and corrosion. Test kits are available to measure sulfide in field samples. A more precise methylene blue sulfide assay for both field and laboratory studies is described here. Improved media, compared to that in API RP-38, for enumeration of SRB have been formulated. One of these, API-RST, contained cysteine (1.1 mM) as a reducing agent, which may be a confounding source of sulfide. While cysteine was required for rapid enumeration of SRB from environmental samples, the concentration of cysteine in medium could be reduced to 0.4 mM. It was also determined that elevated levels of yeast extract (>1 g/liter) could interfere with enumeration of SRB from environmental samples. The API-RST medium was modified to a RST-11 medium. Other changes in medium composition, in addition to reduction of cysteine, included reduction of the concentration of phosphate from 3.4 mM to 2.2 mM, reduction of the concentration of ferrous iron from 0.8 mM to 0.5 mM and preparation of a stock mineral solution to ease medium preparation. SRB from environmental samples could be enumerated in a week in this medium.

  14. Electrophilic reactions of group-VI element halides. VIII. Reactions of selenium and tellurium tetrahalides with allyl cinnamate

    SciTech Connect

    Lendel, V.G.; Sani, A.Yu.; Balog, I.M.; Migalina, Yu.V.; Kornilov, M.Yu.; Turov, A.V.

    1988-02-20

    It was shown that, as a result of two-phase selenohalogenation or tellurohalogenation of allyl cinnamate at /minus/30 C, addition took place at the C/doteq/C bond of the allyl group; the C=C bond of the cinnamoyl moiety remained uninvolved. Selenium tetrahalides were added to allyl cinnamate in accordance with the Markownikoff rule, forming adducts with 1:2 composition; tellurium tetrahalides formed products of rearrangement of the adducts with a 1:1 composition.

  15. Structure and stability of acrolein and allyl alcohol networks on Ag(111) from density functional theory based calculations with dispersion corrections

    NASA Astrophysics Data System (ADS)

    Ferullo, Ricardo M.; Branda, Maria Marta; Illas, Francesc

    2013-11-01

    The interaction of acrolein and allyl alcohol with the Ag(111) surface has been studied by means of periodic density functional theory based calculations including explicitly dispersion terms. Different coverage values have been explored going from isolated adsorbed molecules to isolated dimers, interacting dimers or ordered overlayers. The inclusion of the dispersion terms largely affects the calculated values of the adsorption energy and also the distance between adsorbed molecule and the metallic surface but much less the adsorbate-adsorbate interactions. Owing to the large dipole moment of acrolein, the present calculations predict that at high coverage this molecule forms a stable extensive two-dimensional network on the surface, caused by the alignment of the adsorbate dipoles. For the case of allyl alcohol, dimers and complex networks exhibit similar stability.

  16. Actinide sulfides in the gas phase: experimental and theoretical studies of the thermochemistry of AnS (An = Ac, Th, Pa, U, Np, Pu, Am and Cm).

    PubMed

    Pereira, Cláudia C L; Marsden, Colin J; Marçalo, Joaquim; Gibson, John K

    2011-07-28

    The gas-phase thermochemistry of actinide monosulfides, AnS, was investigated experimentally and theoretically. Fourier transform ion cyclotron resonance mass spectrometry was employed to study the reactivity of An(+) and AnO(+) (An = Th, Pa, U, Np, Pu, Am and Cm) with CS(2) and COS, as well as the reactivity of the produced AnS(+) with oxidants (COS, CO(2), CH(2)O and NO). From these experiments, An(+)-S bond dissociation energies could be bracketed. Density functional theory studies of the energetics of neutral and monocationic AnS (An = Ac, Th, Pa, U, Np, Pu, Am and Cm) provided values for bond dissociation energies and ionization energies; the computed energetics of neutral and monocationic AnO were also obtained for comparison. The theoretical data, together with comparisons with known An(+)-O bond dissociation energies and M(+)-S and M(+)-O dissociation energies for the early transition metals, allowed for the refining of the An(+)-S bond dissociation energy ranges obtained from experiment. Examination of the reactivity of AnS(+) with dienes, coupled to comparisons with reactivities of the AnO(+) analogues, systematic considerations and the theoretical results, allowed for the estimation of the ionization energies of the AnS; the bond dissociation energies of neutral AnS were consequently derived. Estimates for the case of AcS were also made, based on correlations of the data for the other An and the electronic energetics of neutral and ionic An. The nature of the bonding in the elementary molecular actinide chalcogenides (oxides and sulfides) is discussed, based on both the experimental data and the computed electronic structures. DFT calculations of ionization energies for the actinide atoms and the diatomic sulfides and oxides are relatively reliable, but the calculation of bond dissociation energies is not uniformly satisfactory, either with DFT or CCSD(T). A key conclusion from both the experimental and theoretical results is that the 5f electrons do not

  17. Actinide sulfides in the gas phase: experimental and theoretical studies of the thermochemistry of AnS (An = Ac, Th, Pa, U, Np, Pu, Am and Cm).

    PubMed

    Pereira, Cláudia C L; Marsden, Colin J; Marçalo, Joaquim; Gibson, John K

    2011-07-28

    The gas-phase thermochemistry of actinide monosulfides, AnS, was investigated experimentally and theoretically. Fourier transform ion cyclotron resonance mass spectrometry was employed to study the reactivity of An(+) and AnO(+) (An = Th, Pa, U, Np, Pu, Am and Cm) with CS(2) and COS, as well as the reactivity of the produced AnS(+) with oxidants (COS, CO(2), CH(2)O and NO). From these experiments, An(+)-S bond dissociation energies could be bracketed. Density functional theory studies of the energetics of neutral and monocationic AnS (An = Ac, Th, Pa, U, Np, Pu, Am and Cm) provided values for bond dissociation energies and ionization energies; the computed energetics of neutral and monocationic AnO were also obtained for comparison. The theoretical data, together with comparisons with known An(+)-O bond dissociation energies and M(+)-S and M(+)-O dissociation energies for the early transition metals, allowed for the refining of the An(+)-S bond dissociation energy ranges obtained from experiment. Examination of the reactivity of AnS(+) with dienes, coupled to comparisons with reactivities of the AnO(+) analogues, systematic considerations and the theoretical results, allowed for the estimation of the ionization energies of the AnS; the bond dissociation energies of neutral AnS were consequently derived. Estimates for the case of AcS were also made, based on correlations of the data for the other An and the electronic energetics of neutral and ionic An. The nature of the bonding in the elementary molecular actinide chalcogenides (oxides and sulfides) is discussed, based on both the experimental data and the computed electronic structures. DFT calculations of ionization energies for the actinide atoms and the diatomic sulfides and oxides are relatively reliable, but the calculation of bond dissociation energies is not uniformly satisfactory, either with DFT or CCSD(T). A key conclusion from both the experimental and theoretical results is that the 5f electrons do not

  18. Allylic and Allenic Halide Synthesis via NbCl5- and NbBr5-Mediated Alkoxide Rearrangements

    PubMed Central

    Ravikumar, P. C.; Yao, Lihua; Fleming, Fraser F.

    2009-01-01

    Addition of NbCl5, or NbBr5, to a series of magnesium, lithium, or potassium allylic or propargylic alkoxides directly provides allylic or allenic halides. Halogenation formally occurs through a metalla-halo-[3,3] rearrangement although concerted, ionic, and direct displacement mechanisms appear to operate competitively. Transposition of the olefin is equally effective for allylic alkoxides prepared by nucleophilic addition, deprotonation, or reduction. Experimentally, the niobium pentahalide halogenations are rapid, afford essentially pure E-allylic or allenic halides after extraction, and are applicable to a range of aliphatic and aromatic alcohols, aldehydes, and ketones. PMID:19739606

  19. Allylic and allenic halide synthesis via NbCl(5)- and NbBr(5)-mediated alkoxide rearrangements.

    PubMed

    Ravikumar, P C; Yao, Lihua; Fleming, Fraser F

    2009-10-01

    Addition of NbCl(5) or NbBr(5) to a series of magnesium, lithium, or potassium allylic or propargylic alkoxides directly provides allylic or allenic halides. Halogenation formally occurs through a metalla-halo-[3,3] rearrangement, although concerted, ionic, and direct displacement mechanisms appear to operate competitively. Transposition of the olefin is equally effective for allylic alkoxides prepared by nucleophilic addition, deprotonation, or reduction. Experimentally, the niobium pentahalide halogenations are rapid, afford essentially pure (E)-allylic or -allenic halides after extraction, and are applicable to a range of aliphatic and aromatic alcohols, aldehydes, and ketones. PMID:19739606

  20. Field method for sulfide determination

    SciTech Connect

    Wilson, B L; Schwarser, R R; Chukwuenye, C O

    1982-01-01

    A simple and rapid method was developed for determining the total sulfide concentration in water in the field. Direct measurements were made using a silver/sulfide ion selective electrode in conjunction with a double junction reference electrode connected to an Orion Model 407A/F Specific Ion Meter. The method also made use of a sulfide anti-oxidant buffer (SAOB II) which consists of ascorbic acid, sodium hydroxide, and disodium EDTA. Preweighed sodium sulfide crystals were sealed in air tight plastic volumetric flasks which were used in standardization process in the field. Field standards were prepared by adding SAOB II to the flask containing the sulfide crystals and diluting it to the mark with deionized deaerated water. Serial dilutions of the standards were used to prepare standards of lower concentrations. Concentrations as low as 6 ppB were obtained on lake samples with a reproducibility better than +- 10%.

  1. [Hydrogen sulfide and penile erection].

    PubMed

    Huang, Yi-Ming; Cheng, Yong; Jiang, Rui

    2012-09-01

    Hydrogen sulfide (H2S) is the third type of active endogenous gaseous signal molecule following nitric oxide (NO) and carbon monoxide (CO). In mammalians, H2S is mainly synthesized by two proteases, cystathionine-beta-synthase (CBS) and cystathionine-gamma-lyase (CSE). H2S plays an essential function of physiological regulation in vivo, and promotes penile erection by acting on the ATP-sensitive potassium channels to relax the vascular smooth muscle as well as by the synergistic effect with testosterone and NO to relax the corpus cavernosum smooth muscle (CCSM). At present, the selective phosphodiesterase type 5 (PDE5) inhibitor is mainly used for the treatment of erectile dysfunction (ED), but some ED patients fail to respond. Therefore, further studies on the mechanism of H2S regulating penile erection may provide a new way for the management of erectile dysfunction.

  2. Atomic layer deposition of metal sulfide materials.

    PubMed

    Dasgupta, Neil P; Meng, Xiangbo; Elam, Jeffrey W; Martinson, Alex B F

    2015-02-17

    CONSPECTUS: The field of nanoscience is delivering increasingly intricate yet elegant geometric structures incorporating an ever-expanding palette of materials. Atomic layer deposition (ALD) is a powerful driver of this field, providing exceptionally conformal coatings spanning the periodic table and atomic-scale precision independent of substrate geometry. This versatility is intrinsic to ALD and results from sequential and self-limiting surface reactions. This characteristic facilitates digital synthesis, in which the film grows linearly with the number of reaction cycles. While the majority of ALD processes identified to date produce metal oxides, novel applications in areas such as energy storage, catalysis, and nanophotonics are motivating interest in sulfide materials. Recent progress in ALD of sulfides has expanded the diversity of accessible materials as well as a more complete understanding of the unique chalcogenide surface chemistry. ALD of sulfide materials typically uses metalorganic precursors and hydrogen sulfide (H2S). As in oxide ALD, the precursor chemistry is critical to controlling both the film growth and properties including roughness, crystallinity, and impurity levels. By modification of the precursor sequence, multicomponent sulfides have been deposited, although challenges remain because of the higher propensity for cation exchange reactions, greater diffusion rates, and unintentional annealing of this more labile class of materials. A deeper understanding of these surface chemical reactions has been achieved through a combination of in situ studies and quantum-chemical calculations. As this understanding matures, so does our ability to deterministically tailor film properties to new applications and more sophisticated devices. This Account highlights the attributes of ALD chemistry that are unique to metal sulfides and surveys recent applications of these materials in photovoltaics, energy storage, and photonics. Within each application

  3. Removal of sulfur fumes by metal sulfide sorbents.

    PubMed

    Chung, Jae Bin; Ziang, Zhidong; Chung, Jong Shik

    2002-07-01

    Removal of sulfur by a transition metal is studied at temperatures of 300-350 degrees C. Among various metal sulfides tested, only metal sulfides of iron, cobalt, and nickel can remove sulfur fumes as they are transformed into disulfides in the presence of sulfur vapor. The disulfide form can be regenerated into FeS, Co9S8, and Ni3S2, respectively, using hydrogen gas at 350-400 degrees C. These two reactions of deep sulfidation with sulfur and reduction with hydrogen can be utilized for the removal of sulfur fumes in a process stream and an emission gas.

  4. Anodic oxidation of sulfide ions in molten lithium fluoride

    SciTech Connect

    Lloyd, C.L.; Gilbert, J.B. II . Applied Research Lab.)

    1994-10-01

    The study of sulfur and sulfide oxidation in molten salt systems is of current interest in high energy battery, and metallurgical applications. Cyclic voltammetry experiments have been performed on lithium sulfide in a lithium fluoride electrolyte at 1,161 K using a graphite working electrode and a platinum quasi-reference electrode. Two distinct oxidation mechanisms are observed for the sulfide ions. The first oxidation produces sulfur and at a higher potential a disulfide species is proposed to have formed. Both oxidations appear to be reversible and diffusion controlled.

  5. Lanthanide Sensitization in II–VI Semiconductor Materials: A Case Study with Terbium (III) and Europium (III) in Zinc Sulfide Nanoparticles

    PubMed Central

    Mukherjee, Prasun; Shade, Chad M.; Yingling, Adrienne M.; Lamont, Daniel N.; Waldeck, David H.; Petoud, Stéphane

    2010-01-01

    This work explores the sensitization of luminescent lanthanide Tb3+ and Eu3+ cations by the electronic structure of zinc sulfide (ZnS) semiconductor nanoparticles. Excitation spectra collected, while monitoring the lanthanide emission bands, reveals that the ZnS nanoparticles act as an antenna for the sensitization of Tb3+ and Eu3+. The mechanism of lanthanide ion luminescence sensitization is rationalized in terms of an energy and charge transfer between trap sites and is based on a semi-empirical model, proposed by Dorenbos and coworkers, 1–6 to describe the energy level scheme. This model implies that the mechanisms of luminescence sensitization of Tb3+ and Eu3+ in ZnS nanoparticles are different; namely Tb3+ acts as a hole trap, while Eu3+ acts as an electron trap. Further testing of this model is made by extending the studies from ZnS nanoparticles to other II–VI semiconductor materials; namely, CdSe, CdS, and ZnSe. PMID:21090795

  6. Rearrangements of Allylic Sulfinates to Sulfones: A Mechanistic Study

    ERIC Educational Resources Information Center

    Ball, David B.; Mollard, Paul; Voigtritter, Karl R.; Ball, Jenelle L.

    2010-01-01

    Most current organic chemistry textbooks are organized by functional groups and those of us who teach organic chemistry use functional-group organization in our courses but ask students to learn organic chemistry from a mechanistic approach. To enrich and extend the chemical understanding and knowledge of pericyclic-type reactions for chemistry…

  7. Multidirectional Time-Dependent Effect of Sinigrin and Allyl Isothiocyanate on Metabolic Parameters in Rats

    PubMed Central

    2010-01-01

    Sinigrin (SIN) and allyl isothiocyanate (AITC) are compounds found in high concentrations in Brassica family vegetables, especially in Brussels sprouts. Recently, they have been used as a nutrition supplement for their preventive and medicinal effect on some types of cancer and other diseases. In this research, nutritional significance of parent glucosinolate sinigrin 50 μmol/kg b. w./day and its degradation product allyl isothiocyanate 25 μmol/kg b. w./day and 50 μmol/kg b. w./day was studied by the evaluation of their influence on some parameters of carbohydrate and lipid metabolism in an animal rat model in vivo after their single (4 h) and 2 weeks oral administration. Additionally, the aim of this trial was to evaluate the direct action of AITC on basal and epinephrine-induced lipolysis in isolated rat adipocytes at concentration 1 μM, 10 μM and 100 μM in vitro. Sole AITC after 4 h of its ingestion caused liver triacylglycerols increment at both doses and glycaemia only at the higher dose. Multiple SIN treatment showed its putative bioconversion into AITC. It was found that SIN and AITC multiple administration in the same way strongly disturbed lipid and carbohydrate homeostasis, increasing esterified and total cholesterol, free fatty acids and lowering tracylglycerols in the blood serum. Additionally, AITC at both doses elevated insulinaemia and liver glycogen enhancement. The in vitro experiment revealed that AITC potentiated basal lipolysis process at 10 μM, and had stimulatory effect on epinephrine action at 1 μM and 10 μM. The results of this study demonstrated that the effect of SIN and AITC is multidirectional, indicating its impact on many organs like liver as well as pancreas, intestine in vivo action and rat adipocytes in vitro. Whilst consumption of cruciferous vegetables at levels currently considered “normal” seems to be beneficial to human health, this data suggest that any large increase in intake could conceivably lead

  8. XAFS study on the sulfidation mechanisms of Co-Mo catalysts supported on activated carbon and alumina: effect of complexing agent.

    PubMed

    Tsuji, K; Umeki, T; Yokoyama, Y; Kitada, T; Iwanami, Y; Nonaka, O; Shimada, H; Matsubayashi, N; Nishijima, A; Nomura, M

    2001-03-01

    The effect of nitrilotriacetic acid (NTA) as a complexing agent on the sulfidation mechanisms of Co-Mo catalysts supported on activated carbon and alumina was examined by the XAFS technique. The XAFS results revealed that NTA interacted with Co atoms and formed the Co-NTA interaction, while it showed almost no influence on the local structures around Mo atoms. The Co-NTA interaction suppressed the aggregation of cobalt atoms and the interaction between cobalt and alumina during sulfiding, and consequently promoted the formation of the Co-Mo-S phase.

  9. Micro-aeration for hydrogen sulfide removal from biogas

    NASA Astrophysics Data System (ADS)

    Duangmanee, Thanapong

    The presence of sulfur compounds (e.g. protein, sulfate, thiosulfate, sulfite, etc.) in the feed stream generates highly corrosive and odorous hydrogen sulfide during anaerobic digestion. The high sulfide level in the biogas stream is not only poisonous to many novel metal catalysts employed in thermo-catalytic processes but also reduces the quality of methane to produce renewable energy. This study used an innovative, low-maintenance, low-cost biological sulfide removal technology to remove sulfides simultaneously from both gas and liquid phase. ORP (Oxidation-Reduction-Potential) was used as the controlling parameter to precisely regulate air injection to the sulfide oxidizing unit (SOU). The microaeration technique provided just enough oxygen to partially oxidize sulfides to elemental sulfur without inhibiting methanogenesis. The SOU was equipped with a diffuser at the bottom for the dispersion of sulfide-laden biogas and injected air throughout the column. The SOU can be operated as a standalone unit or coupled with an anaerobic digester to simultaneously remove sulfide from the biogas and effluent. The integrated system was capable of reducing hydrogen sulfide in biogas from 2,450 to less than 2 ppmV with minimal sulfate production at the highest available sulfide loading rate of 0.24 kg/m3-day. More than 98% of sulfide removed was recovered as elemental sulfur. However, the standalone SOU was able to operate at high hydrogen sulfide loading of 1.46 kg/m 3-day at inlet sulfide concentration of 3000 ppmV and reduce the off-gas hydrogen sulfide concentrations to less than 10 ppmV. The experiment also revealed that the ORP controlled aeration was sensitive enough to prevent oxygen overdosing (dampening effect) during unexpected surges of aeration. Using generalized linear regression, a model predicting output H2S concentration based on input H2S concentrations, SOU medium heights, and biogas flow rates, was derived. With 95% confidence, output H2S concentration

  10. Enhanced Mantle Conductivity from Sulfides beneath the Sierra Nevada?

    NASA Astrophysics Data System (ADS)

    Park, S. K.

    2002-12-01

    A region of enhanced mantle conductivity (0.03-0.1 S/m) beneath the southern Sierra Nevada, where elevations of over 4000 m are found, has been attributed previously to 3-5% basaltic melt (Park et al., 1996) and to a mix of basaltic and sulfide melt (Ducea and Park, 2000). Because the sulfide melt is assumed to have similar conductivities to its solid counterpart (10,000 S/m), very small amounts (< 0.1%) of sulfide are needed in order to reduce the bulk conductivity from matrix values of about 0.003 S/m or even that of the matrix-basalt melt mix to the values observed. Basaltic melt percentages of less than 1% are needed in the presence of ~0.1% sulfide melt in order to match the observed mantle values. Xenoliths from the Holocene basalts in the Big Pine Volcanic Field contain 0.06-0.4% sulfide, so the estimated values are reasonable. Given the lack of evidence for volumetrically extensive, young (< 10 Ma) basaltic volcanism, calculated residence times of approximately 100 Ka for 3-5% partial melt, the short (about 300 Ka) times needed to develop connected pathways for the basalt, and the young extension of the adjacent Basin and Range province, a mixed melt with both basalt and sulfides seems more reasonable. This conclusion presupposes that the sulfide melt is somehow interconnected in the mantle. Models in which the matrix, the basaltic melt, and the sulfide melt each form interconnected, interlaced networks leads to much higher predictions of mantle conductivity; the sulfide melt fraction must be discontinuous in order to lower bulk conductivity. Petrological studies of sulfide-silicate systems confirm this conclusion; sulfide melts form isolated blebs on the surfaces of olivine within interconnected basaltic melt channels (Holzheid et al., 2000). Simple series-parallel models of ~1% continuous basaltic melt and ~0.01% discontinuous sulfide melt provide bulk conductivities comparable to the observed mantle values. More complicated equivalent media and Hashin

  11. Prevention of sulfide oxidation in sulfide-rich waste rock

    NASA Astrophysics Data System (ADS)

    Nyström, Elsa; Alakangas, Lena

    2015-04-01

    The ability to reduce sulfide oxidation in waste rock after mine closure is a widely researched area, but to reduce and/or inhibit the oxidation during operation is less common. Sulfide-rich (ca 30 % sulfur) waste rock, partially oxidized, was leached during unsaturated laboratory condition. Trace elements such as As and Sb were relatively high in the waste rock while other sulfide-associated elements such as Cu, Pb and Zn were low compared to common sulfide-rich waste rock. Leaching of unsaturated waste rock lowered the pH, from around six down to two, resulting in continuously increasing element concentrations during the leaching period of 272 days. The concentrations of As (65 mg/L), Cu (6.9 mg/L), Sb (1.2 mg/L), Zn (149 mg/L) and S (43 g/L) were strongly elevated at the end of the leaching period. Different alkaline industrial residues such as slag, lime kiln dust and cement kiln dust were added as solid or as liquid to the waste rock in an attempt to inhibit sulfide oxidation through neo-formed phases on sulfide surfaces in order to decrease the mobility of metals and metalloids over longer time scale. This will result in a lower cost and efforts of measures after mine closure. Results from the experiments will be presented.

  12. Sulfur isotope characteristics of metamorphosed Zn-Cu volcanogenic massive sulfides in the Areachap Group, Northern Cape Province, South Africa

    NASA Astrophysics Data System (ADS)

    Bailie, Russell; Gutzmer, Jens; Strauss, Harald; Stüeken, Eva; McClung, Craig

    2010-06-01

    Zn- and Cu-rich massive sulfide ores of volcanogenic origin [volcanogenic massive sulfide (VMS) deposits] occur as stratiform/stratabound lenses of variable size hosted by gneisses, amphibolites, and schists of the Areachap Group, in the Northern Cape Province of South Africa. The Areachap Group represents the highly deformed and metamorphosed remnants of a Mesoproterozoic volcanic arc that was accreted onto the western margin of the Kaapvaal Craton during the ˜1.0-1.2 Ga Namaquan Orogeny. Sulfur isotope data (δ34S) are presented for 57 sulfide separates and one barite sample from five massive sulfide occurrences in the Areachap Group. Although sulfides from each site have distinct sulfur isotope values, all δ34S values fall within a very limited range (3.0‰ to 8.5‰). Barite has a δ34S value of 18.5‰, very different from that of associated sulfides. At one of the studied sites (Kantienpan), a distinct increase in δ34S of sulfides is observed from the massive sulfide lens into the disseminated sulfides associated with a distinct footwall alteration zone. Sulfide-sulfide and sulfide-barite mineral pairs which recrystallized together during amphibolite- and lower granulite facies metamorphism are not in isotopic equilibrium. Sulfur isotope characteristics of sulfides and sulfates of the Zn-Cu ores in the Areachap Group are, however, very similar to base metal sulfide accumulations associated with modern volcanic arcs and unsedimented mid-ocean ridges. It is thus concluded that profound recrystallization and textural reconstitution associated with high-grade regional metamorphism of the massive sulfide ores of the Areachap Group did not result in extensive sulfur isotopic homogenization. This is similar to observations in other metamorphosed VMS deposit districts and confirms that massive sulfide ores remain effectively a closed system for sulfur isotopes for both sulfides and sulfates during metamorphism.

  13. Massive sulfide exploration models of the Iberian Pyrite Belt Neves Corvo mine region, based in a 3D geological, geophysical and geochemical ProMine study

    NASA Astrophysics Data System (ADS)

    Inverno, Carlos; Matos, João Xavier; Rosa, Carlos; Mário Castelo-Branco, José; Granado, Isabel; Carvalho, João; João Baptista, Maria; Represas, Patrícia; Pereira, Zélia; Oliveira, Tomás; Araujo, Vitor

    2013-04-01

    The Iberian Pyrite Belt (IPB) hosts one of the largest concentrations of massive sulfides in the Earth's crust. This highly productive VMS belt contains more than 85 massive sulfide deposits, totalling an estimate of 1600 Mt of massive ore and about 250 Mt of stockwork ore (Leistel et al., 1998; Oliveira et al., 2005; Tornos, 2006). Included in the South Portuguese Zone the IPB is represented by the Phyllite-Quartzite Group (PQG) composed of shales and quartzites of late Devonian age followed by the Volcanic-Sedimentary Complex (VSC) a submarine succession of sediments and felsic and basic volcanic rocks (late Famennian-late Viséan age). Above the IPB a turbidite sedimentary unit occurs being represented by the Baixo Alentejo Flysch Group (BAFG). The ore deposits are hosted by felsic volcanic rocks and sediments that are dominant in the lower part of the VSC succession. The Neves Corvo (ProMine, EU FP7) project area is focused on the Neves Corvo deposit, an active copper mine. The project area is located between the Messejana Fault and the Portuguese/Spanish border which has been selected for the 3D geological and geophysical modelling study, based on high exploration potential of the Neves Corvo area (Oliveira et al. 2006, Relvas et al. 2006, Pereira et al. 2008, Rosa et al. 2008, Matos et al. 2011, Oliveira et al. 2013). In this study existing LNEG and AGC geological, geophysical and geochemistry databases were considered. New surveys were done: i) - A physical volcanology and palynostratigraphic age data study and log of the Cotovio drill-hole core (1,888 m, drilled by AGC). ii) - Interpretation of 280 km of Squid TEM performed by AGC. Based on the TEM data, significant conductors have been identified related with: shallow conductive cover, graphitic shale, black shale and sulphide mineralizations. The most important TEM conductors are related with the Neves Corvo massive sulphides lenses (1-10 Ωm). iii) - Ground and residual gravimetry studies including

  14. Regiodivergent Addition of Phenols to Allylic Oxides: Control of 1,2 and 1,4-Additions for Cyclitol Synthesis**

    PubMed Central

    Moschitto, Matthew J.; Vaccarello, David N.; Lewis, Chad A.

    2015-01-01

    Control of 1,2- and 1,4-addition of substituted phenols to allylic oxides is achieved by intercepting palladium π-allyl complexes. The interconversion of palladium complexes results in the total synthesis of MK7607, cyathiformine B type, streptol, and a new cyclitol. PMID:25533617

  15. Highly Regio-, Diastereo-, and Enantioselective Mannich Reaction of Allylic Ketones and Cyclic Ketimines: Access to Chiral Benzosultam.

    PubMed

    Qiao, Baokun; Huang, Yin-Jun; Nie, Jing; Ma, Jun-An

    2015-09-18

    An organocatalytic asymmetric Mannich reaction of allylic ketones with cyclic N-sulfonyl α-iminoester has been developed. By using a saccharide-derived chiral tertiary amino-thiourea catalyst, a range of allylic ketones and N-sulfonyl ketimines reacted smoothly to afford tetrasubstituted α-amino esters in high yields with good to excellent regio-, diastero-, and enantioselectivities. PMID:26335386

  16. Formation of gas-phase. pi. -allyl radicals from propylene over bismuth oxide and. gamma. -bismuth molybdate catalysts

    SciTech Connect

    Martir, W.; Lunsford, J.H.

    1981-07-01

    Gas-phase ..pi..-allyl radicals were produced when propylene reacted over Bi/sub 2/O/sub 3/ and ..gamma..-bismuth molybdate catalysts at 723 K. The pressure in the catalyst zone was varied between 5 x 10/sup -3/ and 1 torr. The radicals were detected by EPR spectroscopy together with a matrix isolation technique in which argon was used as the diluent. The matrix was formed on a sapphire rod at 12 K which was located 33-cm downstream from the catalyst. Bismuth oxide was more effective in the production of gas-phase allyl radicals than ..gamma..-bismuth molybdate. By contrast ..cap alpha..-bismuth molybdate was ineffective in forming allyl radicals and MoO/sub 3/ acted as a sink for radicals which were produced elsewhere in the system. Comparison of the ..pi..-allyl radical and the stable product concentrations over Bi/sub 2/O/sub 3/ revealed that gas-phase radical recombination reactions served as a major pathway for the formation of 1,5-hexadiene. Addition of small amounts of gas-phase oxygen increased the concentration of allyl radicals, and at greater oxygen levels allyl peroxy radicals were detected. Because of the effect of temperature on the equilibrium between allyl and allyl peroxy radicals, the latter product must be formed in the cooler part of the system.

  17. Apparatus for use in sulfide chemiluminescence detection

    DOEpatents

    Spurlin, S.R.; Yeung, E.S.

    1987-01-06

    A method is described for chemiluminescently determining a sulfide which is either hydrogen sulfide or methyl mercaptan by reacting the sulfide with chlorine dioxide at low pressure and under conditions which allow a longer reaction time in emission of a single photon for every two sulfide containing species, and thereafter, chemiluminescently detecting and determining the sulfide. The invention also relates not only to the detection method, but the novel chemical reaction and a specifically designed chemiluminescence detection cell for the reaction. 4 figs.

  18. Apparatus for use in sulfide chemiluminescence detection

    DOEpatents

    Spurlin, Stanford R.; Yeung, Edward S.

    1987-01-01

    A method of chemiluminescently determining a sulfide which is either hydrogen sulfide or methyl mercaptan by reacting the sulfide with chlorine dioxide at low pressure and under conditions which allow a longer reaction time in emission of a single photon for every two sulfide containing species, and thereafter, chemiluminescently detecting and determining the sulfide. The invention also relates not only to the detection method, but the novel chemical reaction and a specifically designed chemiluminescence detection cell for the reaction.

  19. Synthesis of 3-fluoropyrrolidines and 4-fluoropyrrolidin-2-ones from allylic fluorides.

    PubMed

    Combettes, Lorraine E; Schuler, Marie; Patel, Rakesh; Bonillo, Baltasar; Odell, Barbara; Thompson, Amber L; Claridge, Tim D W; Gouverneur, Véronique

    2012-10-01

    Various 3-fluoropyrrolidines and 4-fluoropyrrolidin-2-ones were prepared by 5-exo-trig iodocyclisation from allylic fluorides bearing a pending nitrogen nucleophile. These bench-stable precursors were made accessible upon electrophilic fluorination of the corresponding allylsilanes. The presence of the allylic fluorine substituent induces syn-stereocontrol upon iodocyclisation with diastereomeric ratios ranging from 10:1 to > 20:1 for all N-tosyl-3-fluoropent-4-en-1-amines and amides. The sense and level of stereocontrol is strikingly similar to the corresponding iodocyclisation of structurally related allylic fluorides bearing pending oxygen nucleophiles. These results suggest that the syn selectivity observed upon ring closure involves I(2)-π complexes with the fluorine positioned inside.

  20. Synergistic effect of allyl isothiocyanate (AITC) on cisplatin efficacy in vitro and in vivo

    PubMed Central

    Ling, Xiang; Westover, David; Cao, Felicia; Cao, Shousong; He, Xiang; Kim, Hak-Ryul; Zhang, Yuesheng; Chan, Daniel CF; Li, Fengzhi

    2015-01-01

    Although in vitro studies have shown that isothiocyanates (ITCs) can synergistically sensitize cancer cells to cisplatin treatment, the underlying mechanisms have not been well defined, and there are no in vivo demonstrations of this synergy. Here, we report the in vitro and in vivo data for the combination of allyl isothiocyanate (AITC), one of the most common naturally occurring ITCs, with cisplatin. Our study revealed that cisplatin and AITC combination synergistically inhibits cancer cell growth and colony formation, and enhances apoptosis in association with the downregulation of antiapoptotic proteins Bcl-2 and survivin. Importantly, the in vivo combination treatment suppresses human tumor growth in animal models without observable increases in toxicity (body weight loss) in comparison with single agent treatment. Furthermore, our data revealed that addition of AITC to cisplatin treatment changes the profile of G2/M arrest (e.g. increase in M phase cell number) and significantly extends the duration of G2/M arrest in comparison with cisplatin treatment alone. To explore the underlying mechanism, we found that AITC treatment rapidly depletes b-tubulin. Combination of AITC and cisplatin inhibits the expression of G2/M checkpoint-relevant proteins including CDC2, cyclin B1 and CDC25. Together, our findings reveal a novel mechanism for AITC enhancing cisplatin efficacy and provides the first in vivo evidence to support ITCs as potential candidates for developing new regimens to overcome platinum resistance. PMID:26396928

  1. Protective effect of allyl methyl disulfide on acetaminophen-induced hepatotoxicity in mice.

    PubMed

    Zhang, Yongchun; Zhang, Fang; Wang, Kaiming; Liu, Guangpu; Yang, Min; Luan, Yuxia; Zhao, Zhongxi

    2016-04-01

    Multiple sulfur compounds of garlic have shown versatile medicinal activities in the prevention and treatment of various diseases. Allyl methyl disulfide (AMDS) was identified as one of the bioactive components in fresh garlic paste in our previous study. The purpose of this study was to investigate the hepatoprotective effect of AMDS against acetaminophen (APAP)-induced acute liver damage in mice. Results reveal that AMDS significantly alleviates APAP-induced elevation of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) levels in mice. Furthermore, AMDS significantly (p < 0.05) reduced the maleic dialdehyde (MDA) level in liver tissues and restored the activities of antioxidant enzymes SOD, GSH-PX and GSH towards normal levels. IL-6 and TNF-alpha (TNF-α) levels in the serum and liver were clearly increased by acetaminophen-damage (p < 0.05) and AMDS intake significantly suppressed acetaminophen-induced increase of the two cytokines (p < 0.05). The immunohistochemical and pathological analyses showed that AMDS could ameliorate the liver injury through the strong attenuation of the CD45 expression and HNE formation. All the results indicate that AMDS had the ability to protect hepatocytes from APAP-induced liver damage.

  2. The effects of allyl isovalerate on the hematopoietic and immunologic systems in rodents.

    PubMed

    Hong, H L; Huff, J E; Luster, M I; Maronpot, R R; Dieter, M P; Hayes, H T; Boorman, G A

    1988-05-01

    Female B6C3F1 mice plus male and female Fischer 344/N rats were gavaged with allyl isovalerate (AIV) in corn oil at 0, 31, 62, or 125 (mice) and 0, 31, 62, 125, or 250 (rats) mg/kg body weight for five daily exposures per week for a 2-week period. Hematologic, immunologic, and histopathologic studies were performed 48 to 72 hr following the final treatment. AIV exposure had no effect on hematology or bone marrow cellularity in mice or rats. AIV exposure at 250 mg/kg was toxic to rats causing reduced weight gain and hepatotoxicity. In vivo and in vitro studies revealed that pluripotent hematopoietic stem cells (CFU-S) and granulocyte-macrophage progenitors (CFU-GM) in the bone marrow were decreased in the treated mice. Hematopoietic suppression was correlated with the reduction in the hexose monophosphate shunt metabolism of bone marrow cells but the Embden-Meyerhof pathway and tricarboxylic acid pathway enzymes did not appear to be affected. Examination of host resistance following Plasmodium and Listeria challenge did not demonstrate significant differences between treated and control mice, nor were there other effects on the immune system. This suggests that the myelotoxic effects were minimal and of a degree that would not alter host resistance.

  3. Platinum metals magmatic sulfide ores.

    PubMed

    Naldrett, A J; Duke, J M

    1980-06-27

    Platinum-group elements (PGE) are mined predominantly from deposits that have formed by the segregation of molten iron-nickel-copper sulfides from silicate magmas. The absolute concentrations of PGE in sulfides from different deposits vary over a range of five orders of magnitude, whereas those of other chalcophile elements vary by factors of only 2 to 100. However, the relative proportions of the different PGE in a given deposit are systematically related to the nature of the parent magma. The absolute and relative concentrations of PGE in magmatic sulfides are explained in terms of the degree of partial melting of mantle peridotite required to produce the parent magma and the processes of batch equilibration and fractional segregation of sulfides. The Republic of South Africa and the U.S.S.R. together possess more than 97 percent of the world PGE reserves, but significant undeveloped resources occur in North America. The Stillwater complex in Montana is perhaps the most important example.

  4. Study of the Susceptibility of Oxygen-Free Phosphorous Doped Copper to Corrosion in Simulated Groundwater in the Presence of Chloride and Sulfide

    SciTech Connect

    Escobar, Ivan; Lamas, Claudia; Werme, Lars |; Oversby, Virginia

    2007-07-01

    Oxygen free high conductivity copper, doped with phosphorus (Cu OFP) has been chosen as the material for the fabrication of high level nuclear waste containers in Sweden. This material will be the corrosion barrier for spent fuel in the environment of a deep geological repository in granitic rock. The service life of this container is expected to exceed 1,000,000 years. During this time, which includes several glaciations, water of different compositions, including high concentration of chloride ions, will contact the copper surface. This work reports a study of the susceptibility of Cu OFP to corrosion when chloride ions are present, in deionized water (DW) and in synthetic groundwater (SGW). The techniques used were electrochemical methods such as corrosion potential evolution and Tafel curves. The system was studied with Electrochemical Impedance Spectroscopy (EIS). We also used as characterization techniques Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). The main conclusions are that copper is more susceptible to corrosion at high chloride ion concentration. When the chloride concentration is low, it is possible to form copper chloride crystals, but at the highest concentration, copper chloride complexes are formed, leaving the copper surface without deposits. When the chloride concentration is low (<0.1 M) the corrosion process is mainly controlled by diffusion, while at higher concentrations (0.1 M to 1 M) corrosion is controlled by charge transfer processes. At low concentration of sulfide (<3 . 10{sup -5} M), copper corrosion in the presence of chloride is controlled by diffusional processes, while at higher concentrations corrosion is controlled by charge transfer processes. (authors)

  5. A search for stratiform massive-sulfide exploration targets in Appalachian Devonian rocks; a case study using computer-assisted attribute-coincidence mapping

    USGS Publications Warehouse

    Wedow, Helmuth

    1983-01-01

    The empirical model for sediment-associated, stratiform, exhalative, massive-sulfide deposits presented by D. Large in 1979 and 1980 has been redesigned to permit its use in a computer-assisted search for exploration-target areas in Devonian rocks of the Appalachian region using attribute-coincidence mapping (ACM). Some 36 gridded-data maps and selected maps derived therefrom were developed to show the orthogonal patterns, using the 7-1/2 minute quadrangle as an information cell, of geologic data patterns relevant to the empirical model. From these map and data files, six attribute-coincidence maps were prepared to illustrate both variation in the application of ACM techniques and the extent of possible significant exploration-target areas. As a result of this preliminary work in ACM, four major (and some lesser) exploration-target areas needing further study and analysis have been defined as follows: 1) in western and central New York in the outcrop area of lowermost Upper Devonian rocks straddling the Clarendon-Linden fault; 2) in western Virginia and eastern West Virginia in an area largely coincident with the well-known 'Oriskany' Mn-Fe ores; 3) an area in West Virginia, Maryland, and Virginia along and nearby the trend of the Alabama-New York lineament of King and Zietz approximately between 38- and 40-degrees N. latitude; and 4) an area in northeastern Ohio overlying an area coincident with a significant thickness of Silurian salt and high modern seismic activity. Some lesser, smaller areas suggested by relatively high coincidence may also be worthy of further study.

  6. Sulfide-mediated dehydrative glycosylation.

    PubMed

    Nguyen, H M; Chen, Y; Duron, S G; Gin, D Y

    2001-09-12

    The development of a new method for glycosylation with 1-hydroxy glycosyl donors employing dialkyl sulfonium reagents is described. The process employs the reagent combination of a dialkyl sulfide and triflic anhydride to effect anomeric bond constructions. This controlled dehydrative coupling of various C(1)-hemiacetal glycosyl donors and nucleophilic acceptors proceeds by way of a sulfide-to-sulfoxide oxidation process in which triflic anhydride serves as the oxidant.

  7. Sulfiding of cobalt molybdate catalysts: characterization by Raman spectroscopy

    SciTech Connect

    Schrader, G.L.; Cheng, C.P.

    1984-02-01

    In situ laser Raman spectroscopic studies of the sulfiding of cobalt molybdate hydrodesulfurization catalysts were performed. Sulfiding in 10% H/sub 2/S/H/sub 2/ at 400/sup 0/C resulted in the formation of stable MoS/sub 2/ structures after 2h. However, the Raman spectra indicated that small crystallites or surface layers of perhaps distorted MoS/sub 2/ were present. Stepwise sulfiding of samples to 150, 250, and 350/sup 0/C permitted intermediate stages of sulfiding to be examined. Differences were observed for the relative rates of reduction versus sulfur incorporation for CoMoO/sub 4/, Co/sub 3/O/sub 4/, MoO/sub 3/, and aggregated or polymeric molybdate phases. Cobalt tended to increase the extent of reduction of the catalyst. A previously described model is extended to include the role of cobalt.

  8. A Combinatorial Approach to Determine Mechanisms of Atmospheric Copper Sulfidation

    SciTech Connect

    BARBOUR,J. CHARLES; BRAITHWAITE,JEFFREY W.; COPELAND,ROBERT GUILD; DUNN,ROBERTO G.; MINOR,KENNETH G.; MISSERT,NANCY A.; NELSON,JEFFREY S.; SULLIVAN,JOHN P.

    1999-10-07

    Parallel microscopic experimentation (the combinatorial approach often used in solid-state science) was applied to characterize atmospheric copper corrosion behavior. Specifically, this technique permitted relative sulfidation rates to be determined for copper containing different levels of point defects and impurities (In, Al, O, and D). Corrosion studies are inherently difficult because of complex interactions between material interfaces and the environment. The combinatorial approach was demonstrated using micron-scale Cu lines that were exposed to a humid air environment containing sub-ppm levels of H{sub 2}S. The relative rate of Cu{sub 2}S growth was determined by measuring the change in resistance of the line. The data suggest that vacancy trapping by In and Al impurities slow the sulfidation rate. Increased sulfidation rates were found for samples containing excess point defects or deuterium. Furthermore, the sulfidation rate of 14 {micro}m wide Cu lines was increased above that for planar films.

  9. The hydrogen sulfide metabolite trimethylsulfonium is found in human urine

    NASA Astrophysics Data System (ADS)

    Lajin, Bassam; Francesconi, Kevin A.

    2016-06-01

    Hydrogen sulfide is the third and most recently discovered gaseous signaling molecule following nitric oxide and carbon monoxide, playing important roles both in normal physiological conditions and disease progression. The trimethylsulfonium ion (TMS) can result from successive methylation reactions of hydrogen sulfide. No report exists so far about the presence or quantities of TMS in human urine. We developed a method for determining TMS in urine using liquid chromatography-electrospray ionization-triple quadrupole mass spectrometry (LC-ESI-QQQ), and applied the method to establish the urinary levels of TMS in a group of human volunteers. The measured urinary levels of TMS were in the nanomolar range, which is commensurate with the steady-state tissue concentrations of hydrogen sulfide previously reported in the literature. The developed method can be used in future studies for the quantification of urinary TMS as a potential biomarker for hydrogen sulfide body pools.

  10. Micro-PIXE Analysis of Trace Elements in Sulfides

    SciTech Connect

    Hickmott, D.D.; Wetteland, C.; Stimac, J.; Larocque, A.C.L.; Brearley, A.

    2003-08-26

    Micro-scale Proton-induced X-ray Emission (PIXE) of trace elements (TE) in sulfides provides insights into geologic processes including magmatic system evolution, ore forming events, and fluid-flow processes. The Los Alamos nuclear microprobe was used to determine TE concentrations and ratios in sulfides from diverse geologic environments including hydrothermal ore deposits, coal seams, and metamorphic rocks. Pyrrhotite (Po) from silicic volcanics contains high Cu and Ni; Po from the Clear Lake volcanic field has higher Mo than does Po from other volcanic fields. Coal pyrites contain high Cu, As, Se, Mo and Pb, and show high As/Se and Mo/Se in marine influenced sulfides from the Lower Kittanning coal, but not in other marine-influenced coals. Sulfides are amenable to micro-PIXE studies because of the difficulties in obtaining the homogeneous standards required for many other TE microanalytical techniques.

  11. Optimization of biological sulfide removal in a CSTR bioreactor.

    PubMed

    Roosta, Aliakbar; Jahanmiri, Abdolhossein; Mowla, Dariush; Niazi, Ali; Sotoodeh, Hamidreza

    2012-08-01

    In this study, biological sulfide removal from natural gas in a continuous bioreactor is investigated for estimation of the optimal operational parameters. According to the carried out reactions, sulfide can be converted to elemental sulfur, sulfate, thiosulfate, and polysulfide, of which elemental sulfur is the desired product. A mathematical model is developed and was used for investigation of the effect of various parameters on elemental sulfur selectivity. The results of the simulation show that elemental sulfur selectivity is a function of dissolved oxygen, sulfide load, pH, and concentration of bacteria. Optimal parameter values are calculated for maximum elemental sulfur selectivity by using genetic algorithm as an adaptive heuristic search. In the optimal conditions, 87.76% of sulfide loaded to the bioreactor is converted to elemental sulfur.

  12. The hydrogen sulfide metabolite trimethylsulfonium is found in human urine

    PubMed Central

    Lajin, Bassam; Francesconi, Kevin A.

    2016-01-01

    Hydrogen sulfide is the third and most recently discovered gaseous signaling molecule following nitric oxide and carbon monoxide, playing important roles both in normal physiological conditions and disease progression. The trimethylsulfonium ion (TMS) can result from successive methylation reactions of hydrogen sulfide. No report exists so far about the presence or quantities of TMS in human urine. We developed a method for determining TMS in urine using liquid chromatography-electrospray ionization-triple quadrupole mass spectrometry (LC-ESI-QQQ), and applied the method to establish the urinary levels of TMS in a group of human volunteers. The measured urinary levels of TMS were in the nanomolar range, which is commensurate with the steady-state tissue concentrations of hydrogen sulfide previously reported in the literature. The developed method can be used in future studies for the quantification of urinary TMS as a potential biomarker for hydrogen sulfide body pools. PMID:27247020

  13. Azo dye decolorization assisted by chemical and biogenic sulfide.

    PubMed

    Prato-Garcia, Dorian; Cervantes, Francisco J; Buitrón, Germán

    2013-04-15

    The effectiveness of chemical and biogenic sulfide in decolorizing three sulfonated azo dyes and the robustness of a sulfate-reducing process for simultaneous decolorization and sulfate removal were evaluated. The results demonstrated that decolorization of azo dyes assisted by chemical sulfide and anthraquinone-2,6-disulfonate (AQDS) was effective. In the absence of AQDS, biogenic sulfide was more efficient than chemical sulfide for decolorizing the azo dyes. The performance of sulfate-reducing bacteria in attached-growth sequencing batch reactors suggested the absence of competition between the studied azo dyes and the sulfate-reducing process for the reducing equivalents. Additionally, the presence of chemical reduction by-products had an almost negligible effect on the sulfate removal rate, which was nearly constant (94%) after azo dye injection.

  14. Distribution and solubility limits of trace elements in hydrothermal black smoker sulfides: An in-situ LA-ICP-MS study

    NASA Astrophysics Data System (ADS)

    Wohlgemuth-Ueberwasser, Cora C.; Viljoen, Fanus; Petersen, Sven; Vorster, Clarisa

    2015-06-01

    The key for understanding the trace metal inventory of currently explored VHMS deposits lies in the understanding of trace element distribution during the formation of these deposits on the seafloor. Recrystallization processes already occurring at the seafloor might liberate trace elements to later hydrothermal alteration and removement. To investigate the distribution and redistribution of trace elements we analyzed sulfide minerals from 27 black smoker samples derived from three different seafloor hydrothermal fields: the ultramafic-hosted Logatchev hydrothermal field on the Mid-Atlantic Ridge, the basaltic-hosted Turtle Pits field on the mid-atlantic ridge, and the felsic-hosted PACMANUS field in the Manus basin (Papua New Guinea). The sulfide samples were analyzed by mineral liberation analyser for the modal abundances of sulfide minerals, by electron microprobe for major elements and by laser ablation-inductively coupled plasma-mass spectrometry for As, Sb, Se, Te, and Au. The samples consist predominantly of chalcopyrite, sphalerite, pyrite, galena and minor isocubanite as well as inclusions of tetrahedrite-tennantite. Laser ablation spectra were used to evaluate the solubility limits of trace elements in different sulfide minerals at different textures. The solubility of As, Sb, and Au in pyrite decreases with increasing degree of recrystallization. When solubility limits are reached these elements occur as inclusions in the different sulfide phases or they are expelled from the mineral phase. Most ancient VHMS deposits represent felsic or bimodal felsic compositions. Samples from the felsic-hosted PACMANUS hydrothermal field at the Pual ridge (Papua New Guinea) show high concentrations of Pb, As, Sb, Bi, Hg, and Te, which is likely the result of an additional trace element contribution derived from magmatic volatiles. Co-precipitating pyrite and chalcopyrite are characterized by equal contents of Te, while chalcopyrite that replaced pyrite (presumably

  15. Stereodivergent α-allylation of linear aldehydes with dual iridium and amine catalysis.

    PubMed

    Krautwald, Simon; Schafroth, Michael A; Sarlah, David; Carreira, Erick M

    2014-02-26

    We describe the fully stereodivergent, dual catalytic α-allylation of linear aldehydes. The reaction proceeds via direct iridium-catalyzed substitution of racemic allylic alcohols with enamines generated in situ. The use of an Ir(P,olefin) complex and a diarylsilyl prolinol ether as catalysts in the presence of dimethylhydrogen phosphate as the promoter proved to be crucial for achieving high enantio- and diastereoselectivity (>99% ee, up to >20:1 dr). The utility of the method is demonstrated in a concise enantioselective synthesis of the antidepressant (-)-paroxetine. PMID:24506196

  16. Stereodivergent Dual Catalytic α-Allylation of Protected α-Amino- and α-Hydroxyacetaldehydes.

    PubMed

    Sandmeier, Tobias; Krautwald, Simon; Zipfel, Hannes F; Carreira, Erick M

    2015-11-23

    Fully stereodivergent dual-catalytic α-allylation of protected α-amino- and α-hydroxyacetaldehydes is achieved through iridium- and amine-catalyzed substitution of racemic allylic alcohols with chiral enamines generated in situ. The operationally simple method furnishes useful aldehyde building blocks in good yields, more than 99% ee, and with d.r. values greater than 20:1 in some cases. Additionally, the γ,δ-unsaturated products can be further functionalized in a stereodivergent fashion with high selectivity and with preservation of stereochemical integrity at the Cα  position. PMID:26427612

  17. Synthesis of substituted quinolines via allylic amination and intramolecular Heck-coupling.

    PubMed

    Murru, Siva; McGough, Brandon; Srivastava, Radhey S

    2014-12-01

    A new catalytic approach for the synthesis of substituted quinolines via C-N and C-C bond formation using 2-haloaryl hydroxylamines and allylic C-H substrates is described. Fe-catalyzed allylic C-H amination followed by Pd-catalyzed intramolecular Heck-coupling and aerobic dehydrogenation deliver the valuable quinoline and naphthyridine heterocycles in good to excellent overall yields. In this process, Pd(OAc)2 plays a dual role in catalyzing Heck coupling as well as aerobic dehydrogenation of dihydroquinolines. PMID:25247637

  18. Asymmetric epoxidation of allylic alcohols catalyzed by vanadium-binaphthylbishydroxamic Acid complex.

    PubMed

    Noji, Masahiro; Kobayashi, Toshihiro; Uechi, Yuria; Kikuchi, Asami; Kondo, Hisako; Sugiyama, Shigeo; Ishii, Keitaro

    2015-03-20

    A vanadium-binaphthylbishydroxamic acid (BBHA) complex-catalyzed asymmetric epoxidation of allylic alcohols is described. The optically active binaphthyl-based ligands BBHA 2a and 2b were synthesized from (S)-1,1'-binaphthyl-2,2'-dicarboxylic acid and N-substituted-O-trimethylsilyl (TMS)-protected hydroxylamines via a one-pot, three-step procedure. The epoxidations of 2,3,3-trisubstituted allylic alcohols using the vanadium complex of 2a were easily performed in toluene with a TBHP water solution to afford (2R)-epoxy alcohols in good to excellent enantioselectivities.

  19. Chemoselective and stereoselective lithium carbenoid mediated cyclopropanation of acyclic allylic alcohols.

    PubMed

    Durán-Peña, M J; Flores-Giubi, M E; Botubol-Ares, J M; Harwood, L M; Collado, I G; Macías-Sánchez, A J; Hernández-Galán, R

    2016-03-01

    The reaction of geraniol with different lithium carbenoids generated from n-BuLi and the corresponding dihaloalkane has been evaluated. The reaction occurs in a chemo and stereoselective manner, which is consistent with a directing effect from the oxygen of the allylic moiety. Furthermore, a set of polyenes containing allylic hydroxyl or ether groups were chemoselectively and stereoselectively converted into the corresponding gem-dimethylcyclopropanes in one single step in moderate to good yields mediated by a lithium carbenoid generated in situ by the reaction of n-BuLi and 2,2-dibromopropane.

  20. Stereodivergent α-allylation of linear aldehydes with dual iridium and amine catalysis.

    PubMed

    Krautwald, Simon; Schafroth, Michael A; Sarlah, David; Carreira, Erick M

    2014-02-26

    We describe the fully stereodivergent, dual catalytic α-allylation of linear aldehydes. The reaction proceeds via direct iridium-catalyzed substitution of racemic allylic alcohols with enamines generated in situ. The use of an Ir(P,olefin) complex and a diarylsilyl prolinol ether as catalysts in the presence of dimethylhydrogen phosphate as the promoter proved to be crucial for achieving high enantio- and diastereoselectivity (>99% ee, up to >20:1 dr). The utility of the method is demonstrated in a concise enantioselective synthesis of the antidepressant (-)-paroxetine.

  1. Asymmetric catalysis with silicon-based cuprates: enantio- and regioselective allylic substitution of linear precursors.

    PubMed

    Hensel, Alexander; Oestreich, Martin

    2015-06-15

    An enantio- and regioselective allylic silylation of linear allylic phosphates that makes use of catalytically generated cuprate-type silicon nucleophiles is reported. The method relies on soft bis(triorganosilyl) zincs as silicon pronucleophiles that are prepared in situ from the corresponding hard lithium reagents by transmetalation with ZnCl2 . With a preformed chiral N-heterocyclic carbene-copper(I) complex as catalyst, exceedingly high enantiomeric excesses are achieved. The new method is superior to existing ones using a silicon-boron reagent as the source of the silicon nucleophile.

  2. Non-stabilized nucleophiles in Cu-catalysed dynamic kinetic asymmetric allylic alkylation

    NASA Astrophysics Data System (ADS)

    You, Hengzhi; Rideau, Emeline; Sidera, Mireia; Fletcher, Stephen P.

    2015-01-01

    The development of new reactions forming asymmetric carbon-carbon bonds has enabled chemists to synthesize a broad range of important carbon-containing molecules, including pharmaceutical agents, fragrances and polymers. Most strategies to obtain enantiomerically enriched molecules rely on either generating new stereogenic centres from prochiral substrates or resolving racemic mixtures of enantiomers. An alternative strategy--dynamic kinetic asymmetric transformation--involves the transformation of a racemic starting material into a single enantiomer product, with greater than 50 per cent maximum yield. The use of stabilized nucleophiles (pKa < 25, where Ka is the acid dissociation constant) in palladium-catalysed asymmetric allylic alkylation reactions has proved to be extremely versatile in these processes. Conversely, the use of non-stabilized nucleophiles in such reactions is difficult and remains a key challenge. Here we report a copper-catalysed dynamic kinetic asymmetric transformation using racemic substrates and alkyl nucleophiles. These nucleophiles have a pKa of >=50, more than 25 orders of magnitude more basic than the nucleophiles that are typically used in such transformations. Organometallic reagents are generated in situ from alkenes by hydrometallation and give highly enantioenriched products under mild reaction conditions. The method is used to synthesize natural products that possess activity against tuberculosis and leprosy, and an inhibitor of para-aminobenzoate biosynthesis. Mechanistic studies indicate that the reaction proceeds through a rapidly isomerizing intermediate. We anticipate that this approach will be a valuable complement to existing asymmetric catalytic methods.

  3. Allylic amination reactivity of Ni, Pd, and Pt heterobimetallic and monometallic complexes.

    PubMed

    Carlsen, Ryan W; Ess, Daniel H

    2016-06-14

    Transition metal heterobimetallic complexes with dative metal-metal interactions have the potential for novel fast reactivity. There are few studies that both compare the reactivity of different metal centers in heterobimetallic complexes and compare bimetallic reactivity to monometallic reactivity. Here we report density-functional calculations that show the reactivity of [Cl2Ti(N(t)BuPPh2)2M(II)(η(3)-methallyl)] heterobimetallic complexes for allylic amination follows M = Ni > Pd > Pt. This reactivity trend was not anticipated since the amine addition transition state involves M(II) to M(0) reduction and this could disadvantage Ni. Comparison of heterobimetallic complexes to the corresponding monometallic (CH2)2(N(t)BuPPh2)2M(II)(η(3)-methallyl) complexes reveals that this reactivity trend is due to the bimetallic interaction and that the bimetallic interaction significantly lowers the barrier height for amine addition by >10 kcal mol(-1). The impact of the early transition metal center on the amination addition barrier height depends on the late transition metal center. The lowest barrier heights for this reaction occur when late and early transition metal centers are from the same periodic table row. PMID:26893287

  4. Allyl Isothiocyanate Inhibits Actin-Dependent Intracellular Transport in Arabidopsis thaliana

    PubMed Central

    Sporsheim, Bjørnar; Øverby, Anders; Bones, Atle Magnar

    2015-01-01

    Volatile allyl isothiocyanate (AITC) derives from the biodegradation of the glucosinolate sinigrin and has been associated with growth inhibition in several plants, including the model plant Arabidopsis thaliana. However, the underlying cellular mechanisms of this feature remain scarcely investigated in plants. In this study, we present evidence of an AITC-induced inhibition of actin-dependent intracellular transport in A. thaliana. A transgenic line of A. thaliana expressing yellow fluorescent protein (YFP)-tagged actin filaments was used to show attenuation of actin filament movement by AITC. This appeared gradually in a time- and dose-dependent manner and resulted in actin filaments appearing close to static. Further, we employed four transgenic lines with YFP-fusion proteins labeling the Golgi apparatus, endoplasmic reticulum (ER), vacuoles and peroxisomes to demonstrate an AITC-induced inhibition of actin-dependent intracellular transport of or, in these structures, consistent with the decline in actin filament movement. Furthermore, the morphologies of actin filaments, ER and vacuoles appeared aberrant following AITC-exposure. However, AITC-treated seedlings of all transgenic lines tested displayed morphologies and intracellular movements similar to that of the corresponding untreated and control-treated plants, following overnight incubation in an AITC-absent environment, indicating that AITC-induced decline in actin-related movements is a reversible process. These findings provide novel insights into the cellular events in plant cells following exposure to AITC, which may further expose clues to the physiological significance of the glucosinolate-myrosinase system. PMID:26690132

  5. Effect of allyl isothiocyanate against Anisakis larvae during the anchovy marinating process.

    PubMed

    Giarratana, Filippo; Panebianco, Felice; Muscolino, Daniele; Beninati, Chiara; Ziino, Graziella; Giuffrida, Alessandro

    2015-04-01

    Allyl isothiocyanate (AITC), is a natural compound found in plants belonging to the family Cruciferae and has strong antimicrobial activity and a biocidal activity against plants parasites. Anisakidosis is a zoonotic disease caused by the ingestion of larval nematodes in raw, almost raw, and marinated and/or salted seafood dishes. The aim of this work was to evaluate the effect of AITC against Anisakis larvae and to study its potential use during the marinating process. The effects of AITC against Anisakis larvae were tested in three experiment: in vitro with three liquid media, in semisolid media with a homogenate of anchovy muscle, and in a simulation of two kinds of anchovy fillets marinating processes. For all tests, the concentrations of AITC were 0, 0.01, 0.05, and 0.1%. Significant activity of AITC against Anisakis larvae was observed in liquid media, whereas in the semisolid media, AITC was effective only at higher concentrations. In anchovy fillets, prior treatment in phosphate buffer solution (1.5% NaCl, pH 6.8) with 0.1% AITC and then marination under standard conditions resulted in a high level of larval inactivation. AITC is a good candidate for further investigation as a biocidal agent against Anisakis larvae during the industrial marinating process.

  6. Arsenic speciation in natural sulfidic geothermal waters

    NASA Astrophysics Data System (ADS)

    Keller, Nicole S.; Stefánsson, Andri; Sigfússon, Bergur

    2014-10-01

    The speciation of arsenic in natural sulfidic geothermal waters was studied using chemical analyses and thermodynamic aqueous speciation calculations. Samples were collected in three geothermal systems in Iceland, having contrasting H2S concentrations in the reservoir (high vs. low). The sampled waters contained 7-116 ppb As and <0.01-77.6 ppm H2S with pH of 8.56-9.60. The analytical setup used for the determination of arsenic species (Ion Chromatography-Hydride Generation Atomic Fluorescence Spectrometry, IC-HG-AFS) was field-deployed and the samples analyzed within ∼5 min of sampling in order to prevent changes upon storage, which were shown to be considerable regardless of the sample storage method used. Nine aqueous arsenic species were detected, among others arsenite (HnAsO3n-3), thioarsenite (HnAsS3n-3), arsenate (HnAsO4n-3), monothioarsenate (HnAsSO3n-3), dithioarsenate (HnAsS2O2n-3), trithioarsenate (HnAsS3O) and tetrathioarsenate (HnAsS4n-3). The results of the measured aqueous arsenic speciation in the natural geothermal waters and comparison with thermodynamic calculations reveal that the predominant factors determining the species distribution are sulfide concentration and pH. In alkaline waters with low sulfide concentrations the predominant species are AsIII oxyanions. This can be seen in samples from a liquid-only well, tapping water that is H2S-poor and free of oxygen. At intermediate sulfide concentration AsIII and AsV thio species become important and predominate at high sulfide concentration, as seen in two-phase well waters, which have high H2S concentrations in the reservoir. Upon oxidation, for instance due to mixing of the reservoir fluid with oxygenated water upon ascent to the surface, AsV oxyanions form, as well as AsV thio complexes if the sulfide concentration is intermediate to high. This oxidation process can be seen in samples from hot springs in the Geysir geothermal area. While the thermodynamic modeling allows for a first

  7. Sulfide capacity of high alumina blast furnace slags

    NASA Astrophysics Data System (ADS)

    Shankar, Amitabh; Görnerup, Märten; Seetharaman, S.; Lahiri, A. K.

    2006-12-01

    Sulfide capacities of high alumina blast furnace slags were experimentally determined using the gas-slag equilibration technique. Two different slag systems were considered for the current study, namely, CaO-SiO2-MgO-Al2O3 quaternary and CaO-SiO2-MgO-Al2O3-TiO2 quinary system. The liquid slag was equilibrated with the Ar-CO-CO2-SO2 gas mixture. Experiments were conducted in the temperature range of 1773 to 1873 K. The effects of temperature, basicity, and the MgO and TiO2 contents of slags on sulfide capacity were studied. As expected, sulfide capacity was found to increase with the increase in temperature and basicity. At the higher experimental temperature, titania decreases the sulfide capacity of slag. However, at the lower temperature, there was no significant effect of titania on the sulfide capacity of slag. Sulfide capacity increases with the increase in MgO content of slag if the MgO content is more than 5 pct.

  8. Mobility and bioavailability of trace metals in sulfidic coastal sediments.

    PubMed

    Sundelin, B; Eriksson, A K

    2001-04-01

    High concentrations of Hg, Cd, Pb, Cu, and Zn were found in the euxinic sediment of the inner archipelago of Stockholm. In the sulfide-rich sediment, they are precipitated as metal sulfides with low dissolving capacity and bioavailability. In two experiments, the significance of acid-volatile sulfide (AVS) and dissolved sulfides for mobility, bioavailability, and toxicity of metals were studied by oxygenation of intact sediment cores. Influence of bioturbating deposit-feeding amphipods, that is, Monoporeia affinis, was examined on studied sediment processes. Results showed a low mobility of most metals except Cd and Zn. Bioturbation did not enhance mobility. Cd and Zn, released from the sediment, were not bioaccumulated in amphipods. In contrast, the less mobile metals Hg and Pb were bioaccumulated. A low toxicity of contaminated sediments, in terms of mortality and embryonic malformations of amphipods, was recorded. Results indicate that Cd, Zn, and Cu are comparatively unavailable after oxygenation of the metal sulfides. Similar results were recorded in contaminated sediments differing in redox potential, AVS, dissolved sulfides, and organic contents, suggesting that other metal ligands, in addition to AVS, are important for metal bioavailability and toxicity in anoxic and suboxic environments. PMID:11345449

  9. Unlocking ylide reactivity in the metal-catalyzed allylic substitution reaction: stereospecific construction of primary allylic amines with aza-ylides.

    PubMed

    Evans, P Andrew; Clizbe, Elizabeth A

    2009-07-01

    The transition metal catalyzed allylic amination represents a powerful and versatile cross-coupling for the asymmetric construction of stereogenic C-N bonds that are present in secondary metabolites and medicinally important agents. We have developed a regio- and enantiospecific rhodium-catalyzed allylic amination reaction using the aza-ylide derived from 1-aminopyridinium iodide. This investigation demonstrates the importance of the ylide-stabilizing group for obtaining the desired nucleophilicity and the ability to utilize the aza-ylide as a commercially available ammonia equivalent, which serves to illustrate the synthetic potential of this nucleophile for the preparation of primary amines. Overall, this work provides an opportunity to investigate the utility of this new class of nucleophiles in related metal-catalyzed reactions.

  10. Photon correlation spectroscopic and spectrophotometric studies of the formation of cadmium sulfide nanoparticles in ammonia-thiourea solutions

    NASA Astrophysics Data System (ADS)

    Bulavchenko, A. I.; Kolodin, A. N.; Podlipskaya, T. Yu.; Demidova, M. G.; Maksimovskii, E. A.; Beizel', N. F.; Larionov, S. V.; Okotrub, A. V.

    2016-05-01

    Nucleation of CdS in an aqueous ammonia solution of thiourea and cadmium chloride was studied by photon correlation spectroscopy (PCS), static light scattering, and spectrophotometry. The hydrodynamic diameter of nanoparticles, light scattering intensity, and optical density of the solutions increased with temperature and synthesis time. The processes of formation, growth, and coagulation of nanoparticles can be transferred from solution to the filter surface by continuously filtering the reaction mixture through a 200-nm filter.

  11. Influence of sulfide concentration on the corrosion behavior of titanium in a simulated oral environment.

    PubMed

    Harada, Rino; Takemoto, Shinji; Kinoshita, Hideaki; Yoshinari, Masao; Kawada, Eiji

    2016-05-01

    This study assessed the corrosion behavior of titanium in response to sulfide by determining the effects of sulfide concentration and pH over immersion period. Corrosion was evaluated through changes in color, glossiness, surface characterization, and titanium release. Sulfide solutions were prepared in 3 different concentrations with Na2S, each in pH unadjusted (sulfide-alkaline) and pH adjusted to 7.5 (sulfide-neutral). Titanium discoloration increased and glossiness decreased as sulfide concentration and immersion period increased in sulfide-alkaline solutions. Coral-like complexes were observed on the surface of these specimens, which became more pronounced as concentration increased. Small amounts of titanium release were detected in sulfide-alkaline solutions; however, this was not affected by immersion periods. Corrosion was indicated through considerable surface oxidation suggesting the formation of a thick oxide layer. No significant changes in color and glossiness, or titanium release were indicated for titanium specimens immersed in sulfide-neutral solutions indicating that pH had a significant effect on corrosion. Our findings suggest that a thick oxide layer on the titanium surface was formed in sulfide-alkaline solutions due to excessive oxidation.

  12. Influence of sulfide concentration on the corrosion behavior of titanium in a simulated oral environment.

    PubMed

    Harada, Rino; Takemoto, Shinji; Kinoshita, Hideaki; Yoshinari, Masao; Kawada, Eiji

    2016-05-01

    This study assessed the corrosion behavior of titanium in response to sulfide by determining the effects of sulfide concentration and pH over immersion period. Corrosion was evaluated through changes in color, glossiness, surface characterization, and titanium release. Sulfide solutions were prepared in 3 different concentrations with Na2S, each in pH unadjusted (sulfide-alkaline) and pH adjusted to 7.5 (sulfide-neutral). Titanium discoloration increased and glossiness decreased as sulfide concentration and immersion period increased in sulfide-alkaline solutions. Coral-like complexes were observed on the surface of these specimens, which became more pronounced as concentration increased. Small amounts of titanium release were detected in sulfide-alkaline solutions; however, this was not affected by immersion periods. Corrosion was indicated through considerable surface oxidation suggesting the formation of a thick oxide layer. No significant changes in color and glossiness, or titanium release were indicated for titanium specimens immersed in sulfide-neutral solutions indicating that pH had a significant effect on corrosion. Our findings suggest that a thick oxide layer on the titanium surface was formed in sulfide-alkaline solutions due to excessive oxidation. PMID:26952423

  13. Formation of Dimethyl Sulfide and Methanethiol in Anoxic Freshwater Sediments

    PubMed Central

    Lomans, B. P.; Smolders, A.; Intven, L. M.; Pol, A.; Op, De; Van Der Drift, C.

    1997-01-01

    Concentrations of volatile organic sulfur compounds (VOSC) were measured in water and sediment columns of ditches in a minerotrophic peatland in The Netherlands. VOSC, with methanethiol (4 to 40 nM) as the major compound, appeared to be mainly of sediment origin. Both VOSC and hydrogen sulfide concentrations decreased dramatically towards the water surface. High methanethiol and high dimethyl sulfide concentrations in the sediment and just above the sediment surface coincided with high concentrations of hydrogen sulfide (correlation factors, r = 0.91 and r = 0.81, respectively). Production and degradation of VOSC were studied in 32 sediment slurries collected from various freshwater systems in The Netherlands. Maximal endogenous methanethiol production rates of the sediments tested (up to 1.44 (mu)mol per liter of sediment slurry (middot) day(sup-1)) were determined after inhibition of methanogenic and sulfate-reducing populations in order to stop VOSC degradation. These experiments showed that the production and degradation of VOSC in sediments are well balanced. Statistical analysis revealed multiple relationships of methanethiol production rates with the combination of methane production rates (indicative of total anaerobic mineralization) and hydrogen sulfide concentrations (r = 0.90) or with the combination of methane production rates and the sulfate/iron ratios in the sediment (r = 0.82). These findings and the observed stimulation of methanethiol formation in sediment slurry incubations in which the hydrogen sulfide concentrations were artificially increased provided strong evidence that the anaerobic methylation of hydrogen sulfide is the main mechanism for VOSC formation in most freshwater systems. Methoxylated aromatic compounds are likely a major source of methyl groups for this methylation of hydrogen sulfide, since they are important degradation products of the abundant biopolymer lignin. Increased sulfate concentrations in several freshwater

  14. Solvent-Controlled, Tunable β-OAc and β-H Elimination in Rh(III)-Catalyzed Allyl Acetate and Aryl Amide Coupling via C-H Activation.

    PubMed

    Dai, Huimin; Yu, Chao; Wang, Zihao; Yan, Hong; Lu, Changsheng

    2016-07-15

    The Heck reaction between arenes and allyl acetate has led to cinnamyl derivatives and allyl products depending on the regioselectivity of β-elimination. The regioselectivity can be controlled by the solvent in the Rh(III)-catalyzed arene-allyl acetate coupling via C-H activation: (1) in THF, cinnamyl derivatives via β-H elimination were generated; (2) in MeOH, allyl products via β-OAc elimination were produced. Both routes have advantages such as excellent γ-selectivity toward allyl acetate, good to excellent yields, and broad substrate scope. PMID:27351917

  15. The development of a potassium-sulfide glass fiber cell and studies on impurities in alkali metal-sulfur cells

    NASA Technical Reports Server (NTRS)

    Tsang, F. Y.

    1977-01-01

    Potassium sulfur rechargeable cells, having as the electrolyte the thin walls of hollow glass fibers made from permeable glass, were developed. The cells had short lives, probably due to the construction materials and impurities in the potassium. The effect of the impurities in the analogous NA-S system was studied. Calcium, potassium, and NaOH/oxide impurities caused increased resistance or corrosion of the glass fibers. For long lived cell operation, the Na must contain less than 1 ppm Ca and less than a few ppm of hydroxide/oxide. Up to 150 ppm K can be tolerated. After purification of the Na anolyte, cell lifetimes in excess of 1000 deep charge-discharge cycles or over 8 months on continuous cycling at 10-30 percent depth of discharge were obtained.

  16. Study of caffeine as corrosion inhibitors of carbon steel in chloride solution containing hydrogen sulfide using electrochemical impedance spectroscopy (EIS)

    NASA Astrophysics Data System (ADS)

    Solehudin, Agus; Berman, Ega Taqwali; Nurdin, Isdiriayani

    2015-09-01

    The corrosion behaviour of steel surface in the absence and presence of caffeine in 3.5% NaCl solution containing dissolved H2S gas is studied using electrochemical impedance spectroscopy (EIS). The experimental results of carbon steel corrosion in 3.5% NaCl solution containing 500 mg/l H2S at different caffeine concentrations showed that corrosion rate of carbon steel decreases with increasing of caffeine concentrations from 0 to 0,1 mmol/l. Whereas, the corrosion rate increase with increasing of caffeine concentrations from 1 to 10 mmol/l. It is clear that no inhibition efficiency increases with increasing inhibitor concentration. The optimum value of inhibition efficiency was 90% at a caffeine concentration of 0.1 mmol/l. This suggests that caffeine's performance as a corrosion inhibitor is more effective at a concentration of 0.1 mmol/l.

  17. Sulfide oxidation in fluidized bed bioreactor using nylon support material.

    PubMed

    Midha, Varsha; Jha, M K; Dey, Apurba

    2012-01-01

    A continuous fluidized bed bioreactor (FBBR) with nylon support particles was used to treat synthetic sulfide wastewater at different hydraulic retention time of 25, 50 and 75 min and upflow velocity of 14, 17 and 20 m/hr. The effects of upflow velocity, hydraulic retention time and reactor operation time on sulfide oxidation rate were studied using statistical model. Mixed culture obtained from the activated sludge, taken from tannery effluent treatment plant, was used as a source for microorganisms. The diameter and density of the nylon particles were 2-3 mm and 1140 kg/m3, respectively. Experiments were carried out in the reactor at a temperature of (30 +/- 2) degrees C, at a fixed bed height of 16 cm after the formation of biofilm on the surface of support particles. Biofilm thickness reached (42 +/- 3) microm after 15 days from reactor start-up. The sulfide oxidation, sulfate and sulfur formation is examined at all hydraulic retention times and upflow velocities. The results indicated that almost 90%-92% sulfide oxidation was achieved at all hydraulic retention times. Statistical model could explain 94% of the variability and analysis of variance showed that upflow velocity and hydraulic retention time slightly affected the sulfide oxidation rate. The highest sulfide oxidation of 92% with 70% sulfur was obtained at hydraulic retention time of 75 min and upflow velocity of 14 m/hr.

  18. Hydrogen sulfide and traffic-related air pollutants in association with increased mortality: a case-crossover study in Reykjavik, Iceland

    PubMed Central

    Finnbjornsdottir, Ragnhildur Gudrun; Elvarsson, Bjarki Thor; Gislason, Thorarinn; Rafnsson, Vilhjalmur

    2015-01-01

    Objectives To study the association between daily mortality and short-term increases in air pollutants, both traffic-related and the geothermal source-specific hydrogen sulfide (H2S). Design Population-based, time stratified case-crossover. A lag time to 4 days was considered. Seasonal, gender and age stratification were calculated. Also, the best-fit lag when introducing H2S >7 µg/m3 was selected by the Akaike Information Criterion (AIC). Setting The population of the greater Reykjavik area (n=181 558) during 2003–2009. Participants Cases were defined as individuals living in the Reykjavik capital area, 18 years or older (N=138 657), who died due to all natural causes (ICD-10 codes A00-R99) other than injury, poisoning and certain other consequences of external causes, or cardiovascular disease (ICD-10 codes I00-I99) during the study period. Main outcome measure Percentage increases in risk of death (IR%) following an interquartile range increase in pollutants. Results The total number of deaths due to all natural causes was 7679 and due to cardiovascular diseases was 3033. The interquartile range increased concentrations of H2S (2.6 µg/m3) were associated with daily all natural cause mortality in the Reykjavik capital area. The IR% was statistically significant during the summer season (lag 1: IR%=5.05, 95% CI 0.61 to 9.68; lag 2: IR%=5.09, 95% CI 0.44 to 9.97), among males (lag 0: IR%=2.26, 95% CI 0.23 to 4.44), and among the elderly (lag 0: IR%=1.94, 95% CI 0.12 to 1.04; lag 1: IR%=1.99, 95% CI 0.21 to 1.04), when adjusted for traffic-related pollutants and meteorological variables. The traffic-related pollutants were generally not associated with statistical significant IR%s. Conclusions The results suggest that ambient H2S air pollution may increase mortality in Reykjavik, Iceland. To the best of our knowledge, ambient H2S exposure has not previously been associated with increased mortality in population-based studies and therefore the results

  19. Characterization of a newly isolated strain Pseudomonas sp. C27 for sulfide oxidation: Reaction kinetics and stoichiometry

    PubMed Central

    Xu, Xi-Jun; Chen, Chuan; Guo, Hong-liang; Wang, Ai-jie; Ren, Nan-qi; Lee, Duu-Jong

    2016-01-01

    Sulfide biooxidation by the novel sulfide-oxidizing bacteria Pseudomonas sp. C27, which could perform autotrophic and heterotrophic denitrification in mixotrophic medium, was studied in batch and continuous systems. Pseudomonas sp. C27 was able to oxidize sulfide at concentrations as high as 17.66 mM. Sulfide biooxidation occurred in two distinct stages, one resulting in the formation of sulfur with nitrate reduction to nitrite, followed by thiosulfate formation with nitrite reduction to N2. The composition of end-products was greatly impacted by the ratio of sulfide to nitrate initial concentrations. At a ratio of 0.23, thiosulfate represented 100% of the reaction products, while only 30% with a ratio of 1.17. In the continuous bioreactor, complete removal of sulfide was observed at sulfide concentration as high as 9.38 mM. Overall sulfide removal efficiency decreased continuously upon further increases in influent sulfide concentrations. Based on the experimental data kinetic parameter values were determined. The value of maximum specific growth rate, half saturation constant, decay coefficient, maintenance coefficient and yield were to be 0.11 h−1, 0.68 mM sulfide, 0.11 h−1, 0.21 mg sulfide/mg biomass h and 0.43 mg biomass/mg sulfide, respectively, which were close to or comparable with those reported in literature by other researches. PMID:26864216

  20. Study of copper sulfide counter electrode on the performances of CdS/CdSe/ZnS-sensitized hierarchical TiO2 spheres quantum dots solar cells

    NASA Astrophysics Data System (ADS)

    Buatong, Nattha; Tang, I.-Ming; Pon-On, Weeraphat

    2015-07-01

    The effects of using copper sulfide (CuS) counter electrodes on the performances of solar cells made with CdS/CdSe/ZnS quantum dots co-sensitized onto hierarchical TiO2 spheres (HTS) used as photoelectrode is reported. The HTS in the QDSSCs is composed of an assembly of numerous TiO2 spheres made by the solvolthermal method. The photoelectrical performance of HTS/CdS/CdSe/ZnS coupled to CuS counter electrode was compared to those coupled to Pt CE. The HTS/CdS/CdSe/ZnS coupled to the CuS CE showed the highest power conversion efficiency η (of 1.310 %.) which is significantly higher than those using a standard Pt CE (η = 0.374%) (3.50 fold). This higher efficiency is the results of the higher electrocatalytic activities when the copper sulfide CEs is used.

  1. Reactivity of Sulfide Mineral Surfaces

    SciTech Connect

    Rosso, Kevin M.; Vaughan, David J.

    2006-08-01

    In the preceding chapter, the fundamental nature of sulfide mineral surfaces has been discussed, and the understanding we have of the ways in which the surface differs from a simple truncation of the bulk crystal structure reviewed. This naturally leads on to considering our understanding of sulfide surface chemistry, in the sense of how sulfide surfaces interact and react, particularly with gases and liquids. As noted elsewhere in this volume, research on sulfide mineral surfaces and surface reactivity is a relatively recent concern of mineralogists and geochemists, partly prompted by the availability of new imaging and spectroscopic methods, powerful computers and new computer algorithms. There has been a significantly longer history of sulfide mineral surface research associated with technologists working with, or within, the mining industry. Here, electrochemical methods, sometimes combined with analytical and spectroscopic techniques, have been used to probe surface chemistry. The motivation for this work has been to gain a better understanding of the controls of leaching reactions used to dissolve out metals from ores, or to understand the chemistry of the froth flotation systems used in concentrating the valuable (usually sulfide) minerals prior to metal extraction. The need for improved metal extraction technologies is still a major motivation for research on sulfide surfaces, but in the last couple of decades, new concerns have become important drivers for such work. In particular, much greater awareness of the negative environmental impact of acid and toxic metal-bearing waters derived from breakdown of sulfide minerals at former mining operations has prompted research on oxidation reactions, and on sorption of metals at sulfide surfaces. At the interface between fundamental geochemistry and industrial chemistry, the role of sulfide substrates in catalysis, and in the self-assembly and functionalization of organic molecules, has become an area of

  2. H2S exposure elicits differential expression of candidate genes in fish adapted to sulfidic and non-sulfidic environments.

    PubMed

    Tobler, Michael; Henpita, Chathurika; Bassett, Brandon; Kelley, Joanna L; Shaw, Jennifer H

    2014-09-01

    Disentangling the effects of plasticity, genetic variation, and their interactions on organismal responses to environmental stressors is a key objective in ecological physiology. We quantified the expression of five candidate genes in response to hydrogen sulfide (H2S) exposure in fish (Poecilia mexicana, Poeciliidae) from a naturally sulfide-rich environment as well as an ancestral, non-sulfidic population to test for constitutive and environmentally dependent population differences in gene expression patterns. Common garden raised individuals that had never encountered environmental H2S during their lifetime were subjected to short or long term H2S exposure treatments or respective non-sulfidic controls. The expression of genes involved in responses to H2S toxicity (cytochrome c oxidase, vascular endothelial growth factor, and cytochrome P450-2J6), H2S detoxification (sulfide:quinone oxidoreductase), and endogenous H2S production (cystathionine γ lyase) was determined in both gill and liver tissues by real time PCR. The results indicated complex changes in expression patterns that--depending on the gene--not only differed between organs and populations, but also on the type of H2S exposure. Populations differences, both constitutive and H2S exposure dependent (i.e., plastic), in gene expression were particularly evident for sulfide:quinone oxidoreductase, vascular endothelial growth factor, and to a lesser degree for cytochrome P450-2J6. Our study uncovered putatively adaptive modifications in gene regulation that parallel previously documented adaptive changes in phenotypic traits.

  3. Photocatalytic synthesis of allylic trifluoromethyl substituted styrene derivatives in batch and flow.

    PubMed

    Kreis, Lukas M; Krautwald, Simon; Pfeiffer, Nicole; Martin, Rainer E; Carreira, Erick M

    2013-04-01

    A cobalt-catalyzed photochemical synthesis of allylic trifluoromethanes from styrene derivatives using 2,2,2-trifluoroethyl iodide is described. The method complements existing approaches, providing an alternative bond construction strategy to access these compounds. The process may be conducted in continuous mode in a novel photochemical flow reactor, resulting in a notable productivity increase. PMID:23517196

  4. Oxidative allylic rearrangement of cycloalkenols: Formal total synthesis of enantiomerically pure trisporic acid B

    PubMed Central

    Dubberke, Silke; Abbas, Muhammad

    2011-01-01

    Summary Enantiomerically highly enriched unsaturated β-ketoesters bearing a quaternary stereocenter can be utilized as building blocks for the synthesis of natural occurring terpenes, i. a., trisporic acid and its derivatives. An advanced building block has been synthesized in a short reaction sequence, which involves an oxidative allylic rearrangement initiated by pyridinium dichromate (PDC) as the key step. PMID:21512603

  5. Catalytic enantioselective synthesis of naturally occurring butenolides via hetero-allylic alkylation and ring closing metathesis.

    PubMed

    Mao, Bin; Geurts, Koen; Fañanás-Mastral, Martín; van Zijl, Anthoni W; Fletcher, Stephen P; Minnaard, Adriaan J; Feringa, Ben L

    2011-03-01

    An efficient catalytic asymmetric synthesis of chiral γ-butenolides was developed based on the hetero-allylic asymmetric alkylation (h-AAA) in combination with ring closing metathesis (RCM). The synthetic potential of the h-AAA-RCM protocol was illustrated with the facile synthesis of (-)-whiskey lactone, (-)-cognac lactone, (-)-nephrosteranic acid, and (-)-roccellaric acid.

  6. Direct and Highly Regioselective and Enantioselective Allylation of β-Diketones

    PubMed Central

    Chalifoux, Wesley A.; Reznik, Samuel K.; Leighton, James L.

    2012-01-01

    The enantioselective allylation of ketones represents both a problem of fundamental importance in asymmetric reaction design and one of only a very small number of available methods to access valuable tertiary carbinols. Despite the vast amount of attention from chemists that this problem has elicited,1-8 however, success has generally been limited to just a few simple ketone types thus limiting the utility of these methods. A method for the selective allylation of functionally complex ketones would be expected to increase the utility of ketone allylation methods in the chemical synthesis of important targets. Here we describe the operationally simple, direct, regioselective, and enantioselective allylation of β-diketones. The strong tendency of β-diketones to act as nucleophilic species was overcome by the co-optation of their enol form to provide the necessary Brønsted acid activation. This unprecedented reaction thus not only significantly expands the pool of enantiomerically enriched and functionally complex tertiary carbinols that may be easily accessed, but also overturns more than a century of received wisdom regarding the reactivity of β-diketones. PMID:22763452

  7. Ping-pong polymerization by allylation and hydroformylation for alternating vinyl alcohol-vinyl monomer copolymers.

    PubMed

    Ito, Shingo; Noguchi, Masaki; Nozaki, Kyoko

    2012-11-01

    Inspired by the enzymatic ping-pong mechanism, we designed a novel "ping-pong polymerization", which employs allylation and hydroformylation in an iterative and alternating manner. Thus, alternating and regioregular vinyl alcohol-vinyl monomer copolymers possessing multiple hydroxy groups in a periodical manner were successfully synthesized.

  8. The Defense Metabolite, Allyl Glucosinolate, Modulates Arabidopsis thaliana Biomass Dependent upon the Endogenous Glucosinolate Pathway

    PubMed Central

    Francisco, Marta; Joseph, Bindu; Caligagan, Hart; Li, Baohua; Corwin, Jason A.; Lin, Catherine; Kerwin, Rachel; Burow, Meike; Kliebenstein, Daniel J.

    2016-01-01

    Glucosinolates (GSLs) play an important role in plants as direct mediators of biotic and abiotic stress responses. Recent work is beginning to show that the GSLs can also inducing complex defense and growth networks. However, the physiological significance of these GSL-induced responses and the molecular mechanisms by which GSLs are sensed and/or modulate these responses are not understood. To identify these potential mechanisms within the plant and how they may relate to the endogenous GSLs, we tested the regulatory effect of exogenous allyl GSL application on growth and defense metabolism across sample of Arabidopsis thaliana accessions. We found that application of exogenous allyl GSL had the ability to initiate changes in plant biomass and accumulation of defense metabolites that genetically varied across accessions. This growth effect was related to the allyl GSL side-chain structure. Utilizing this natural variation and mutants in genes within the GSL pathway we could show that the link between allyl GSL and altered growth responses are dependent upon the function of known genes controlling the aliphatic GSL pathway. PMID:27313596

  9. Diastereoselective zinco-cyclopropanation of chiral allylic alcohols with gem-dizinc carbenoids.

    PubMed

    Fournier, Jean-François; Mathieu, Simon; Charette, André B

    2005-09-28

    The highly diastereoselective zinco-cyclopropanation of chiral allylic alcohols using gem-dizinc carbenoids is described. The reaction produces three contiguous stereogenic centers, and the resulting chiral cyclopropylzinc derivatives can be trapped with electrophiles with retention of configuration. Simple functional group manipulations lead to the efficient synthesis of orthogonally protected 1,2,3-substituted cyclopropane derivatives. PMID:16173730

  10. Total synthesis of (±)-leuconolam: intramolecular allylic silane addition to a maleimide carbonyl group

    PubMed Central

    Izgu, Enver Cagri

    2014-01-01

    A concise total synthesis of the plant alkaloid (±)-leuconolam (1) has been achieved. A regio- and diastereoselective Lewis-acid mediated allylative cyclization was used to establish, simultaneously, two adjacent tetrasubstituted carbon centers. Furthermore, an essential arene cross-coupling to a hindered haloalkene was enabled by the use of a novel 2-anilinostannane. PMID:25419448

  11. Oxidative rearrangement of cyclic tertiary allylic alcohols with IBX in DMSO.

    PubMed

    Shibuya, Masatoshi; Ito, Shinichiro; Takahashi, Michiyasu; Iwabuchi, Yoshiharu

    2004-11-11

    A practical and environmentally friendly method for oxidative rearrangement of five- and six-membered cyclic tertiary allylic alcohols to beta-disubstituted alpha,beta-unsaturated ketones by the IBX/DMSO reagent system is described. Several conventional protecting groups (e.g., Ac, MOM, and TBDPS) are compatible under the reaction conditions prescribed.

  12. GALLIUM-MEDIATED ALLYLATION OF CARBONYL COMPOUNDS IN WATER. (R828129)

    EPA Science Inventory

    Ga-mediated allylation of aldehydes or ketones in distilled or tap water generated the corresponding homoallyl alcohols in high yields without the assistance of either acidic media or sonication.


    Grap...

  13. α-Regioselective Barbier Reaction of Carbonyl Compounds and Allyl Halides Mediated by Praseodymium.

    PubMed

    Wu, San; Li, Ying; Zhang, Songlin

    2016-09-01

    The first utility of praseodymium as a mediating metal in the Barbier reaction of carbonyl compounds with allyl halides was reported in this paper. In contrast to the traditional metal-mediated or catalyzed Barbier reactions, exclusive α-adducts were obtained in this one-pot reaction with a broad scope of substrates and feasible reaction conditions.

  14. The Defense Metabolite, Allyl Glucosinolate, Modulates Arabidopsis thaliana Biomass Dependent upon the Endogenous Glucosinolate Pathway.

    PubMed

    Francisco, Marta; Joseph, Bindu; Caligagan, Hart; Li, Baohua; Corwin, Jason A; Lin, Catherine; Kerwin, Rachel; Burow, Meike; Kliebenstein, Daniel J

    2016-01-01

    Glucosinolates (GSLs) play an important role in plants as direct mediators of biotic and abiotic stress responses. Recent work is beginning to show that the GSLs can also inducing complex defense and growth networks. However, the physiological significance of these GSL-induced responses and the molecular mechanisms by which GSLs are sensed and/or modulate these responses are not understood. To identify these potential mechanisms within the plant and how they may relate to the endogenous GSLs, we tested the regulatory effect of exogenous allyl GSL application on growth and defense metabolism across sample of Arabidopsis thaliana accessions. We found that application of exogenous allyl GSL had the ability to initiate changes in plant biomass and accumulation of defense metabolites that genetically varied across accessions. This growth effect was related to the allyl GSL side-chain structure. Utilizing this natural variation and mutants in genes within the GSL pathway we could show that the link between allyl GSL and altered growth responses are dependent upon the function of known genes controlling the aliphatic GSL pathway. PMID:27313596

  15. [N-allyl-Dmt1]-endomorphins are micro-opioid receptor antagonists lacking inverse agonist properties.

    PubMed

    Marczak, Ewa D; Jinsmaa, Yunden; Li, Tingyou; Bryant, Sharon D; Tsuda, Yuko; Okada, Yoshio; Lazarus, Lawrence H

    2007-10-01

    [N-allyl-Dmt1]-endomorphin-1 and -2 ([N-allyl-Dmt1]-EM-1 and -2) are new selective micro-opioid receptor antagonists obtained by N-alkylation with an allyl group on the amino terminus of 2',6'-dimethyl-L-tyrosine (Dmt) derivatives. To further characterize properties of these compounds, their intrinsic activities were assessed by functional guanosine 5'-O-(3-[35S]thiotriphosphate) binding assays and forskolin-stimulated cyclic AMP accumulation in cell membranes obtained from vehicle, morphine, and ethanol-treated SK-N-SH cells and brain membranes isolated from naive and morphine-dependent mice; their mode of action was compared with naloxone or naltrexone, which both are standard nonspecific opioid-receptor antagonists. [N-allyl-Dmt1]-EM-1 and -2 were neutral antagonists under all of the experimental conditions examined, in contrast to naloxone and naltrexone, which behave as neutral antagonists only in membranes from vehicle-treated cells and mice but act as inverse agonists in membranes from morphine- and ethanol-treated cells as well as morphine-treated mice. Both endomorphin analogs inhibited the naloxone- and naltrexone-elicited withdrawal syndromes from acute morphine dependence in mice. This suggests their potential therapeutic application in the treatment of drug addiction and alcohol abuse without the adverse effects observed with inverse agonist alkaloid-derived compounds that produce severe withdrawal symptoms.

  16. Method of preparing water purification membranes. [polymerization of allyl amine as thin films in plasma discharge

    NASA Technical Reports Server (NTRS)

    Hollahan, J. R.; Wydeven, T. J., Jr. (Inventor)

    1974-01-01

    Allyl amine and chemically related compounds are polymerized as thin films in the presence of a plasma discharge. The monomer compound can be polymerized by itself or in the presence of an additive gas to promote polymerization and act as a carrier. The polymerized films thus produced show outstanding advantages when used as reverse osmosis membranes.

  17. Catalytic enantioselective synthesis of naturally occurring butenolides via hetero-allylic alkylation and ring closing metathesis.

    PubMed

    Mao, Bin; Geurts, Koen; Fañanás-Mastral, Martín; van Zijl, Anthoni W; Fletcher, Stephen P; Minnaard, Adriaan J; Feringa, Ben L

    2011-03-01

    An efficient catalytic asymmetric synthesis of chiral γ-butenolides was developed based on the hetero-allylic asymmetric alkylation (h-AAA) in combination with ring closing metathesis (RCM). The synthetic potential of the h-AAA-RCM protocol was illustrated with the facile synthesis of (-)-whiskey lactone, (-)-cognac lactone, (-)-nephrosteranic acid, and (-)-roccellaric acid. PMID:21268603

  18. Silylene-Mediated Ring Contraction of Homoallylic Ethers to Form Allylic Silanes

    PubMed Central

    Bourque, Laura E.; Haile, Pamela A.; Woerpel, K. A.

    2009-01-01

    (—)-Isopulegol derivatives undergo a ring contraction under silylene-mediated conditions to provide cyclopentane products. Silylene transfer to other homoallylic ethers did not provide the ring contraction products. Allylic silane products were elaborated to determine the stereochemical course of the ring contraction reaction. A mechanism for the transformation is proposed. PMID:19681592

  19. Silylene-mediated ring contraction of homoallylic ethers to form allylic silanes.

    PubMed

    Bourque, Laura E; Haile, Pamela A; Woerpel, K A

    2009-09-18

    (-)-Isopulegol derivatives undergo a ring contraction under silylene-mediated conditions to provide cyclopentane products. Silylene transfer to other homoallylic ethers did not provide the ring contraction products. Allylic silane products were elaborated to determine the stereochemical course of the ring contraction reaction. A mechanism for the transformation is proposed. PMID:19681592

  20. Zirconium-allyl complexes as resting states in zirconocene-catalyzed α-olefin polymerization.

    PubMed

    Panchenko, Valentina N; Babushkin, Dmitrii E; Brintzinger, Hans H

    2015-01-01

    UV-vis spectroscopic data indicate that zirconocene cations with Zr-bound allylic chain ends are generally formed during olefin polymerization with zirconocene catalysts. The rates and extent of their formation and of their re-conversion to the initial pre-catalyst cations depend on the types of zirconocene complexes and activators used.

  1. α-Regioselective Barbier Reaction of Carbonyl Compounds and Allyl Halides Mediated by Praseodymium.

    PubMed

    Wu, San; Li, Ying; Zhang, Songlin

    2016-09-01

    The first utility of praseodymium as a mediating metal in the Barbier reaction of carbonyl compounds with allyl halides was reported in this paper. In contrast to the traditional metal-mediated or catalyzed Barbier reactions, exclusive α-adducts were obtained in this one-pot reaction with a broad scope of substrates and feasible reaction conditions. PMID:27490708

  2. Sulfidation of a Novel Iron Sorbent Supported on Lignite Chars during Hot Coal Gas Desulfurization

    NASA Astrophysics Data System (ADS)

    Yin, Fengkui; Yu, Jianglong; Gupta, Sushil; Wang, Shaoyan; Wang, Dongmei; Yang, Li; Tahmasebi, Arash

    The sulfidation behavior of novel iron oxide sorbents supported using activated-chars during desulfurization of hot coal gases has been studied. The sulfidation of the char-supported sorbents was investigated using a fixed-bed quartz reactor in the temperature range of 673K to 873K. The product gases were analyzed using a GC equipped with a TCD and a FPD detector. The sorbent samples before and after sulfidation were examined using SEM and XRD.

  3. Synthesis of novel triterpene and N-allylated/N-alkylated niacin hybrids as α-glucosidase inhibitors.

    PubMed

    Narender, Tadigoppula; Madhur, Gaurav; Jaiswal, Natasha; Agrawal, Manali; Maurya, Chandan K; Rahuja, Neha; Srivastava, Arvind K; Tamrakar, Akhilesh K

    2013-05-01

    Diabetes mellitus is a metabolic disorder characterized by chronic hyperglycemia. α-Glucosidase (EC 3.2.1.20) inhibitors interfere with enzymatic action to slow down the liberation of d-glucose from oligosaccharides and disaccharides, resulting in delayed glucose absorption and decreased postprandial plasma glucose levels. In continuation of our drug discovery program on antidiabetic agents, we synthesized novel N-allylated/N-alkylated niacin and α-amyrin (4-9) and lupeol (12-16) hybrids and tested for their α-glucosidase inhibiting activity. Compounds 4-9 showed better activity profile than the marketed α-glucosidase inhibitor i.e. acarbose. Compound 4 possess the highest inhibitory action with IC50 of 5 μM. Kinetic and CD studies revealed that 4 inhibited the α-glucosidase in a noncompetitive manner and caused conformational changes in secondary structure of the enzyme protein.

  4. Modeling of hydrogen sulfide oxidation in concrete corrosion products from sewer pipes.

    PubMed

    Jensen, Henriette Stokbro; Nielsen, Asbjørn Haaning; Hvitved-Jacobsen, Thorkild; Vollertsen, Jes

    2009-04-01

    Abiotic and biotic oxidation of hydrogen sulfide related to concrete corrosion was studied in corrosion products originating from a sewer manhole. The concrete corrosion products were suspended in an acidic solution, mimicking the conditions in the pore water of corroded concrete. The removal of hydrogen sulfide and dissolved oxygen was measured in parallel in the suspension, upon which the suspension was sterilized and the measurement repeated. The results revealed the biotic oxidation to be fast compared with the abiotic oxidation. The stoichiometry of the hydrogen sulfide oxidation was evaluated using the ratio between oxygen and hydrogen sulfide uptake. The ratio for the biotic oxidation pointed in the direction of elemental sulfur being formed as an intermediate in the oxidation of hydrogen sulfide to sulfuric acid. The experimental results were applied to suggest a hypothesis and a mathematical model describing the hydrogen sulfide oxidation pathway in a matrix of corroded concrete. PMID:19445325

  5. Modeling of hydrogen sulfide oxidation in concrete corrosion products from sewer pipes.

    PubMed

    Jensen, Henriette Stokbro; Nielsen, Asbjørn Haaning; Hvitved-Jacobsen, Thorkild; Vollertsen, Jes

    2009-04-01

    Abiotic and biotic oxidation of hydrogen sulfide related to concrete corrosion was studied in corrosion products originating from a sewer manhole. The concrete corrosion products were suspended in an acidic solution, mimicking the conditions in the pore water of corroded concrete. The removal of hydrogen sulfide and dissolved oxygen was measured in parallel in the suspension, upon which the suspension was sterilized and the measurement repeated. The results revealed the biotic oxidation to be fast compared with the abiotic oxidation. The stoichiometry of the hydrogen sulfide oxidation was evaluated using the ratio between oxygen and hydrogen sulfide uptake. The ratio for the biotic oxidation pointed in the direction of elemental sulfur being formed as an intermediate in the oxidation of hydrogen sulfide to sulfuric acid. The experimental results were applied to suggest a hypothesis and a mathematical model describing the hydrogen sulfide oxidation pathway in a matrix of corroded concrete.

  6. Influence of sulfide concentration on the corrosion behavior of pure copper in synthetic seawater

    NASA Astrophysics Data System (ADS)

    Taniguchi, Naoki; Kawasaki, Manabu

    2008-09-01

    Corrosion rate and stress corrosion cracking (SCC) behavior of pure copper under anaerobic conditions were studied by immersion tests and slow strain rate tests (SSRT) in synthetic seawater containing Na 2S. The corrosion rate was increased with sulfide concentration both in simple saline solution and in bentnite-sand mixture. The results of SSRT showed that copper was susceptible to intergranular attack; selective dissolution at lower sulfide concentration (less than 0.005 M) and SCC at higher sulfide concentration (0.01 M). It was expected that if the sulfide concentration in groundwater is less than 0.001 M, pure copper is possible to exhibit superior corrosion resistance under anaerobic condition evident by very low corrosion rates and immunity to SCC. In such a low sulfide environment, copper overpack has the potential to achieve super-long lifetimes exceeding several tens of thousands years according to long-term simulations of corrosion based on diffusion of sulfide in buffer material.

  7. Sulfate and organic carbon removal by microbial fuel cell with sulfate-reducing bacteria and sulfide-oxidising bacteria anodic biofilm.

    PubMed

    Lee, Duu-Jong; Liu, Xiang; Weng, Hsiang-Ling

    2014-03-01

    Biological sulfur removal can be achieved by reducing sulfate to sulfide with sulfate-reducing bacteria (SRB) and then oxidising sulfide to elemental sulfur (S(0)) with sulfide oxidising bacteria (SOB) for recovery. In sulfate-carbon wastewaters lacking electron acceptor for sulfide, excess sulfide will be produced and accumulated in the reactor. This study applied the microbial fuel cell (MFC) cultivated with the SRB+SOB anodic biofilm for treating the sulfate+organic carbon wastewaters. Excess sulfate ions were efficiently converted to sulfide by SRB cells in the biofilm, while the formed sulfide was diffused to the neighboring SOB cells to be irreversibly converted to S(0) with produced electrons being transferred to the anode. The cell-cell sulfide transport principally determined the electron flux of the MFC. Short diffusional distance of sulfide ions between cells significantly reduced the polarization resistances, hence enhancing performance of the MFC.

  8. Hydrogen Sulfide as a Gasotransmitter

    PubMed Central

    Gadalla, Moataz M.; Snyder, Solomon H.

    2010-01-01

    Nitric oxide (NO) and carbon monoxide (CO) are well established as messenger molecules throughout the body, gasotransmitters, based on striking alterations in mice lacking the appropriate biosynthetic enzymes. Hydrogen sulfide (H2S) is even more chemically reactive, but till recently there was little definitive evidence for its physiologic formation. Cystathionine β-synthase (CBS, EC 4.2.1.22), and Cystathionine γ-lyase (CSE; EC 4.4.1.1), also known as cytathionase, can generate H2S from cyst(e)ine. Very recent studies with mice lacking these enzymes have established that CSE is responsible for H2S formation in the periphery, while in the brain CBS is the biosynthetic enzyme. Endothelial-derived relaxing factor (EDRF) activity is reduced 80% in the mesenteric artery of mice with deletion of CSE, establishing H2S as a major physiologic EDRF. H2S appears to signal predominantly by S-sulfhydrating cysteines in its target proteins, analogous to S-nitrosylation by NO. Whereas S-nitrosylation typically inhibits enzymes, S-sulfhydration activates them. S-nitrosylation basally affects 1–2% of its target proteins, while 10–25% of H2S target proteins are S-sulfhydrated. In summary, H2S appears to be a physiologic gasotransmitter of comparable importance to NO and CO. PMID:20067586

  9. Temporary silicon connection strategies in intramolecular allylation of aldehydes with allylsilanes.

    PubMed

    Beignet, Julien; Jervis, Peter J; Cox, Liam R

    2008-07-18

    Three gamma-(amino)silyl-substituted allylsilanes 14a-c have been prepared in three steps from the corresponding dialkyldichlorosilane. The aminosilyl group has been used to link this allylsilane nucleophile to a series of beta-hydroxy aldehydes through a silyl ether temporary connection. The size of the alkyl substituents at the silyl ether tether governs the outcome of the reaction on exposure to acid. Thus, treatment of aldehyde (E)-9aa, which contains a dimethylsilyl ether connection between the aldehyde and allylsilane, with a range of Lewis and Brønsted acid activators provides an (E)-diene product. The mechanism of formation of this undesired product is discussed. Systems containing a sterically more bulky diethylsilyl ether connection react differently: thus in the presence of TMSOTf and a Brønsted acid scavenger, intramolecular allylation proceeds smoothly to provide two out of the possible four diastereoisomeric oxasilacycles, 23 (major) and 21 (minor). A diene product again accounts for the remaining mass balance in the reaction. This side product can be completely suppressed by using a sterically even more bulky diisopropylsilyl ether connection in the cyclization precursor, although this is now at the expense of a slight erosion in the 1,3-stereoinduction in the allylation products. The sense of 1,3-stereoinduction observed in these intramolecular allylations has been rationalized by using an electrostatic argument, which can also explain the stereochemical outcome of a number of related reactions. Levels of 1,4-stereoinduction in the intramolecular allylation are more modest but can be significantly improved in some cases by using a tethered (Z)-allylsilane in place of its (E)-stereoisomer. Oxidation of the major diastereoisomeric allylation product 23 under Tamao-Kumada conditions provides an entry into stereodefined 1,2-anti-2,4-syn triols 28.

  10. The direct arylation of allylic sp(3) C-H bonds via organic and photoredox catalysis.

    PubMed

    Cuthbertson, James D; MacMillan, David W C

    2015-03-01

    The direct functionalization of unactivated sp(3) C-H bonds is still one of the most challenging problems facing synthetic organic chemists. The appeal of such transformations derives from their capacity to facilitate the construction of complex organic molecules via the coupling of simple and otherwise inert building blocks, without introducing extraneous functional groups. Despite notable recent efforts, the establishment of general and mild strategies for the engagement of sp(3) C-H bonds in C-C bond forming reactions has proved difficult. Within this context, the discovery of chemical transformations that are able to directly functionalize allylic methyl, methylene and methine carbons in a catalytic manner is a priority. Although protocols for direct oxidation and amination of allylic C-H bonds (that is, C-H bonds where an adjacent carbon is involved in a C = C bond) have become widely established, the engagement of allylic substrates in C-C bond forming reactions has thus far required the use of pre-functionalized coupling partners. In particular, the direct arylation of non-functionalized allylic systems would enable access to a series of known pharmacophores (molecular features responsible for a drug's action), though a general solution to this long-standing challenge remains elusive. Here we report the use of both photoredox and organic catalysis to accomplish a mild, broadly effective direct allylic C-H arylation. This C-C bond forming reaction readily accommodates a broad range of alkene and electron-deficient arene reactants, and has been used in the direct arylation of benzylic C-H bonds. PMID:25739630

  11. The direct arylation of allylic sp(3) C-H bonds via organic and photoredox catalysis.

    PubMed

    Cuthbertson, James D; MacMillan, David W C

    2015-03-01

    The direct functionalization of unactivated sp(3) C-H bonds is still one of the most challenging problems facing synthetic organic chemists. The appeal of such transformations derives from their capacity to facilitate the construction of complex organic molecules via the coupling of simple and otherwise inert building blocks, without introducing extraneous functional groups. Despite notable recent efforts, the establishment of general and mild strategies for the engagement of sp(3) C-H bonds in C-C bond forming reactions has proved difficult. Within this context, the discovery of chemical transformations that are able to directly functionalize allylic methyl, methylene and methine carbons in a catalytic manner is a priority. Although protocols for direct oxidation and amination of allylic C-H bonds (that is, C-H bonds where an adjacent carbon is involved in a C = C bond) have become widely established, the engagement of allylic substrates in C-C bond forming reactions has thus far required the use of pre-functionalized coupling partners. In particular, the direct arylation of non-functionalized allylic systems would enable access to a series of known pharmacophores (molecular features responsible for a drug's action), though a general solution to this long-standing challenge remains elusive. Here we report the use of both photoredox and organic catalysis to accomplish a mild, broadly effective direct allylic C-H arylation. This C-C bond forming reaction readily accommodates a broad range of alkene and electron-deficient arene reactants, and has been used in the direct arylation of benzylic C-H bonds.

  12. The direct arylation of allylic sp3 C-H bonds via organic and photoredox catalysis

    NASA Astrophysics Data System (ADS)

    Cuthbertson, James D.; MacMillan, David W. C.

    2015-03-01

    The direct functionalization of unactivated sp3 C-H bonds is still one of the most challenging problems facing synthetic organic chemists. The appeal of such transformations derives from their capacity to facilitate the construction of complex organic molecules via the coupling of simple and otherwise inert building blocks, without introducing extraneous functional groups. Despite notable recent efforts, the establishment of general and mild strategies for the engagement of sp3 C-H bonds in C-C bond forming reactions has proved difficult. Within this context, the discovery of chemical transformations that are able to directly functionalize allylic methyl, methylene and methine carbons in a catalytic manner is a priority. Although protocols for direct oxidation and amination of allylic C-H bonds (that is, C-H bonds where an adjacent carbon is involved in a C = C bond) have become widely established, the engagement of allylic substrates in C-C bond forming reactions has thus far required the use of pre-functionalized coupling partners. In particular, the direct arylation of non-functionalized allylic systems would enable access to a series of known pharmacophores (molecular features responsible for a drug's action), though a general solution to this long-standing challenge remains elusive. Here we report the use of both photoredox and organic catalysis to accomplish a mild, broadly effective direct allylic C-H arylation. This C-C bond forming reaction readily accommodates a broad range of alkene and electron-deficient arene reactants, and has been used in the direct arylation of benzylic C-H bonds.

  13. Synthesis, Characterization, and Some Properties of Cp*W(NO)(H)(η(3)-allyl) Complexes.

    PubMed

    Baillie, Rhett A; Holmes, Aaron S; Lefèvre, Guillaume P; Patrick, Brian O; Shree, Monica V; Wakeham, Russell J; Legzdins, Peter; Rosenfeld, Devon C

    2015-06-15

    Sequential treatment at low temperatures of Cp*W(NO)Cl2 in THF with 1 equiv of a binary magnesium allyl reagent, followed by an excess of LiBH4, affords three new Cp*W(NO)(H)(η(3)-allyl) complexes, namely, Cp*W(NO)(H)(η(3)-CH2CHCMe2) (1), Cp*W(NO)(H)(η(3)-CH2CHCHPh) (2), and Cp*W(NO)(H)(η(3)-CH2CHCHMe) (3). Complexes 1-3 are isolable as air-stable, analytically pure yellow solids in good to moderate yields by chromatography or fractional crystallization. In solutions, complex 1 exists as two coordination isomers in an 83:17 ratio differing with respect to the endo/exo orientation of the allyl ligand. In contrast, complexes 2 and 3 each exist as four coordination isomers, all differing by the orientation of their allyl ligands which can have either an endo or an exo orientation with the phenyl or methyl groups being either proximal or distal to the nitrosyl ligand. A DFT computational analysis using the major isomer of Cp*W(NO)(H)(η(3)-CH2CHCHMe) (3a) as the model complex has revealed that its lowest-energy thermal-decomposition pathway involves the intramolecular isomerization of 3a to the 16e η(2)-alkene complex, Cp*W(NO)(η(2)-CH2═CHCH2Me). Such η(2)-alkene complexes are isolable as their 18e PMe3 adducts when compounds 1-3 are thermolyzed in neat PMe3, the other organometallic products formed during these thermolyses being Cp*W(NO)(PMe3)2 (5) and, occasionally, Cp*W(NO)(H)(η(1)-allyl)(PMe3). All new complexes have been characterized by conventional spectroscopic and analytical methods, and the solid-state molecular structures of most of them have been established by single-crystal X-ray crystallographic analyses.

  14. N-allyl epiderpride: An extremely potent SPECT radioligand for the dopamine D2 receptor

    SciTech Connect

    Kessler, R.M.; Mason, N.S.; Ansari, M.S.

    1994-05-01

    We have previously reported that epidepride is a potent (K{sub D} 24pM) and specific SPECT radioligand for the dopamine D2 receptor which can be used to study striatal and extrastriatal dopamine D2 receptors in man. We have synthesized and evaluated the N-allyl analogue of epiderpride (APID) as a potential SPECT radioligand for the dopamine D2 receptor. In comparison to epidepride it is even more potent at the dopamine D2 receptor, the K{sub D} for APID being 11 frontal cortical homogenate. The lipophilicity, evaluated using the log kw pH 7.5, was 2.9 versus 2.05 for epidepride. Competitive binding studies using rat striatal, hippocampal and frontal cortical homogenates showed high affinity for only dopamine D2 like cerebellar ratio of 275:1 at 320 minutes post injection-similar to that seen with epidepride, but with nearly four times higher brain uptake. Of interest was the off-rate from the dopamine D2 receptor; it was 0.0046 min{sup -1} in vitro at 25{degrees}C-corresponding to an t 1/2 of 150 minutes. Studies in rhesus monkeys show an in vivo off rate (following 2.5 mg/kg raclopride IV) of about 0.0082 min{sup -1} seen that with epidepride. SPECT studies in rhesus monkeys reveal APID is a promising SPECT radioligand that appears to be similar to epidepride, but with higher brain uptake due to its more optimal lipophilicity for entry into brain.

  15. The Wacker oxidation of allyl alcohol along cyclic-intermediate routes: An ab initio molecular dynamics investigation

    NASA Astrophysics Data System (ADS)

    Imandi, Venkataramana; Nair, Nisanth N.

    2016-09-01

    The absence of isotope scrambling observed by Henry and coworkers in the Wacker oxidation of deuterated allylic alcohol was used by them as support for the inner-sphere mechanism hydroxypalladation mechanism. One of the assumptions used to interpret their experimental data was that allyl alcohol oxidation takes place through non-cyclic intermediate routes as in the case of ethene. Here we verify this assumption through ab initio metadynamics simulations of the Wacker oxidation of allyl alcohol in explicit solvent. Importance of our results in interpreting the isotope scrambling experiments is discussed.

  16. A Reaction Involving Oxygen and Metal Sulfides.

    ERIC Educational Resources Information Center

    Hill, William D. Jr.

    1986-01-01

    Describes a procedure for oxygen generation by thermal decomposition of potassium chlorate in presence of manganese dioxide, reacted with various sulfides. Provides a table of sample product yields for various sulfides. (JM)

  17. Extreme enrichment of Se, Te, PGE and Au in Cu sulfide microdroplets: evidence from LA-ICP-MS analysis of sulfides in the Skaergaard Intrusion, east Greenland

    NASA Astrophysics Data System (ADS)

    Holwell, David A.; Keays, Reid R.; McDonald, Iain; Williams, Megan R.

    2015-12-01

    The Platinova Reef, in the Skaergaard Intrusion, east Greenland, is an example of a magmatic Cu-PGE-Au sulfide deposit formed in the latter stages of magmatic differentiation. As is characteristic with such deposits, it contains a low volume of sulfide, displays peak metal offsets and is Cu rich but Ni poor. However, even for such deposits, the Platinova Reef contains extremely low volumes of sulfide and the highest Pd and Au tenor sulfides of any magmatic ore deposit. Here, we present the first LA-ICP-MS analyses of sulfide microdroplets from the Platinova Reef, which show that they have the highest Se concentrations (up to 1200 ppm) and lowest S/Se ratios (190-700) of any known magmatic sulfide deposit and have significant Te enrichment. In addition, where sulfide volume increases, there is a change from high Pd-tenor microdroplets trapped in situ to larger, low tenor sulfides. The transition between these two sulfide regimes is marked by sharp peaks in Au, and then Te concentration, followed by a wider peak in Se, which gradually decreases with height. Mineralogical evidence implies that there is no significant post-magmatic hydrothermal S loss and that the metal profiles are essentially a function of magmatic processes. We propose that to generate these extreme precious and semimetal contents, the sulfides must have formed from an anomalously metal-rich package of magma, possibly formed via the dissolution of a previously PGE-enriched sulfide. Other processes such as kinetic diffusion may have also occurred alongside this to produce the ultra-high tenors. The characteristic metal offset pattern observed is largely controlled by partitioning effects, producing offset peaks in the order Pt+Pd>Au>Te>Se>Cu that are entirely consistent with published D values. This study confirms that extreme enrichment in sulfide droplets can occur in closed-system layered intrusions in situ, but this will characteristically form ore deposits that are so low in sulfide that they do

  18. Nickel sulfide hollow whisker formation

    SciTech Connect

    Holcomb, G.R.; Cramer, S.D.

    1997-02-01

    Hollow, high-aspect-ratio nickel sulfide whiskers were formed during aqueous corrosion experiments at 250 C by the US Department of Energy. The whiskers grew radially from Teflon thread at the waterline in acidic sodium sulfate solutions containing chloride additions. The hollow morphology is consistent with that reported for the mineral millerite found in nature in hematite cavities. The data suggest that iron and chloride impurities are necessary for the observed whisker structure. Hollow nickel sulfide whiskers were observed only in high-temperature corrosion experiments conducted on stainless steels; they were not observed in similar experiments on nickel-base alloys.

  19. Does 1-Allyl-3-methylimidazolium chloride Act as a Biocompatible Solvent for Stem Bromelain?

    PubMed

    Jha, Indrani; Bisht, Meena; Venkatesu, Pannuru

    2016-06-30

    The broader scope of ILs in chemical sciences particularly in pharmaceutical, bioanalytical and many more applications is increasing day by day. Hitherto, a very less amount of research is available in the depiction of conformational stability, activity, and thermal stability of enzymes in the presence of ILs. In the present study, the perturbation in the structure, stability, and activity of stem bromelain (BM) has been observed in the presence of 1-allyl-3-methylimidazolium chloride ([Amim][Cl]) using various techniques. This is the first report in which the influence of [Amim][Cl] has been studied on the enzyme BM. Fluorescence spectroscopy has been utilized to map out the changes in the environment around tryptophan (Trp) residues of BM and also to discuss the variations in the thermal stability of BM as an outcome of its interaction with the IL at different concentrations. Further, the work delineates the denaturing effect of high concentration of IL on enzyme structure and activity. It dictates the fact that low concentrations (0.01-0.10 M) of [Amim][Cl] are only changing the structural arrangement of the protein without having harsh consequences on its activity and stability. However, high concentrations of IL proved to be totally devastating for both activity and stability of BM. The observed decrease in the stability of BM at high concentration may be due to the combined effect of cation and anion interactions with the protein residues. The present work is successful in dictating the probable mechanism of interaction between BM and [Amim][Cl]. These results can prove to be fruitful in the studies of enzymes in aqueous IL systems since the used IL is thermally stable and nonvolatile in nature thereby providing a pathway of alteration in the activity of enzymes in potentially green systems.

  20. Anaerobic versus aerobic degradation of dimethyl sulfide and methanethiol in anoxic freshwater sediments

    SciTech Connect

    Lomans, B.P.; Op den Camp, H.J.M.; Pol, A.; Vogels, G.D.

    1999-02-01

    Degradation of dimethyl sulfide and methanethiol in slurries prepared from sediments of minerotrophic peatland ditches were studied under various conditions. Maximal aerobic dimethyl sulfide-degrading capacities, measured in bottles shaken under an air atmosphere, were 10-fold higher than the maximal anaerobic degrading capacities determined from bottles shaken under N{sub 2} or H{sub 2} atmosphere. Incubations under experimental conditions which mimic the in situ conditions, however, revealed that aerobic degradation of dimethyl sulfide and methanethiol in freshwater sediments is low due to oxygen limitation. Inhibition studies with bromoethanesulfonic acid and sodium tungstate demonstrated that the degradation of dimethyl sulfide and methanethiol in these incubations originated mainly from methanogenic activity. Prolonged incubation under a H{sub 2} atmosphere resulted in lower dimethyl sulfide degradation rates. Kinetic analysis of the data resulted in apparent K{sub m} values (6 to 8 {micro}M) for aerobic dimethyl sulfide degradation which are comparable to those reported for Thiobacillus spp., Hyphomicrobium spp., and other methylotrophs. Apparent K{sub m} values determined for anaerobic degradation of dimethyl sulfide were of the same order of magnitude. The low apparent K{sub m} values obtained explain the low dimethyl sulfide and methanethiol concentrations in freshwater sediments that they reported previously. The observations point to methanogenesis as the major mechanism of dimethyl sulfide and methanethiol consumption in freshwater sediments.

  1. Spontaneous electrochemical treatment for sulfur recovery by a sulfide oxidation/vanadium(V) reduction galvanic cell.

    PubMed

    Kijjanapanich, Pimluck; Kijjanapanich, Pairoje; Annachhatre, Ajit P; Esposito, Giovanni; Lens, Piet N L

    2015-02-01

    Sulfide is the product of the biological sulfate reduction process which gives toxicity and odor problems. Wastewaters or bioreactor effluents containing sulfide can cause severe environmental impacts. Electrochemical treatment can be an alternative approach for sulfide removal and sulfur recovery from such sulfide rich solutions. This study aims to develop a spontaneous electrochemical sulfide oxidation/vanadium(V) reduction cell with a graphite electrode system to recover sulfide as elemental sulfur. The effects of the internal and external resistance on the sulfide removal efficiency and electrical current produced were investigated at different pH. A high surface area of the graphite electrode is required in order to have as less internal resistance as possible. In this study, graphite powder was added (contact area >633 cm(2)) in order to reduce the internal resistance. A sulfide removal efficiency up to 91% and electrical charge of more than 400 C were achieved when using five graphite rods supplemented with graphite powder as the electrode at an external resistance of 30 Ω and a sulfide concentration of 250 mg L(-1).

  2. Sulfur speciation and sulfide oxidation in the water column of the Black Sea

    NASA Astrophysics Data System (ADS)

    Luther, George W., III; Church, Thomas M.; Powell, David

    We have applied sulfur speciation techniques to understand the chemistry and cycling of sulfur in Black Sea waters. The only reduced dissolved inorganic sulfur species detected (above the low minimum detection limits of the voltammetric methods employed) in the water column was hydrogen sulfide. The maximum concentration of sulfide (423 μM) is similar to previous reports. Using a cathodic stripping square wave voltammetry (CSSWV) method for nanomolar levels of sulfide, we determined the precise boundary between the "free" hydrogen sulfide (sulfidic) zone and the upper (oxic/suboxic) water column at the two stations studied. This boundary has apparently moved up by about 50 m in the past 20 years. Our results help demonstrate three chemically distinct zones of water in the central basin of the Black Sea: (1) the oxic [0-65 m], (2) the anoxic/nonsulfidic [65-100 m] and (3) the sulfidic [>100 m]. Sulfide bound to metals ("complexed" sulfide) is observed in both the oxic and anoxic/nonsulfidic zones of the water column. This supports previous studies on metal sulfide forms. From the electrochemical data, it is possible to estimate the strength of the complexation of sulfide to metals (log K = 10 to 11). Thiosulfate and sulfite were below our minimum detectable limit (MDL) of 50 nM using CSSWV. Elemental sulfur (MDL 5 nM) was detected below the onset of the hydrogen sulfide zone (90-100 m) with a maximum of 30-60 nM near 120 m. The sulfur speciation results for the Black Sea are lower by one order of magnitude or more than other marine systems such as the Cariaco Trench and salt marshes. New HPLC techniques were applied to detect thiols at submicromolar levels. The presence of thiols (2-mercaptoethylamine, 2-mercaptoethanol, N-acetylcysteine and glutathione) is correlated with the remineralization of organic matter at the oxic and anoxic/nonsulfidic interface. Water samples collected from the upper 50 m of the sulfidic zone showed significant sulfide oxidation on

  3. 30 CFR 250.604 - Hydrogen sulfide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 2 2010-07-01 2010-07-01 false Hydrogen sulfide. 250.604 Section 250.604... OPERATIONS IN THE OUTER CONTINENTAL SHELF Oil and Gas Well-Workover Operations § 250.604 Hydrogen sulfide. When a well-workover operation is conducted in zones known to contain hydrogen sulfide (H2S) or...

  4. 30 CFR 250.504 - Hydrogen sulfide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 2 2010-07-01 2010-07-01 false Hydrogen sulfide. 250.504 Section 250.504... OPERATIONS IN THE OUTER CONTINENTAL SHELF Oil and Gas Well-Completion Operations § 250.504 Hydrogen sulfide. When a well-completion operation is conducted in zones known to contain hydrogen sulfide (H2S) or...

  5. 30 CFR 250.808 - Hydrogen sulfide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 2 2010-07-01 2010-07-01 false Hydrogen sulfide. 250.808 Section 250.808... OPERATIONS IN THE OUTER CONTINENTAL SHELF Oil and Gas Production Safety Systems § 250.808 Hydrogen sulfide. Production operations in zones known to contain hydrogen sulfide (H2S) or in zones where the presence of...

  6. 30 CFR 250.808 - Hydrogen sulfide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 2 2012-07-01 2012-07-01 false Hydrogen sulfide. 250.808 Section 250.808 Mineral Resources BUREAU OF SAFETY AND ENVIRONMENTAL ENFORCEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE OIL... § 250.808 Hydrogen sulfide. Production operations in zones known to contain hydrogen sulfide (H2S) or...

  7. 30 CFR 250.604 - Hydrogen sulfide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 2 2011-07-01 2011-07-01 false Hydrogen sulfide. 250.604 Section 250.604...-Workover Operations § 250.604 Hydrogen sulfide. When a well-workover operation is conducted in zones known to contain hydrogen sulfide (H2S) or in zones where the presence of H2S is unknown (as defined...

  8. 30 CFR 250.504 - Hydrogen sulfide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 2 2011-07-01 2011-07-01 false Hydrogen sulfide. 250.504 Section 250.504...-Completion Operations § 250.504 Hydrogen sulfide. When a well-completion operation is conducted in zones known to contain hydrogen sulfide (H2S) or in zones where the presence of H2S is unknown (as defined...

  9. 30 CFR 250.808 - Hydrogen sulfide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 2 2014-07-01 2014-07-01 false Hydrogen sulfide. 250.808 Section 250.808 Mineral Resources BUREAU OF SAFETY AND ENVIRONMENTAL ENFORCEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE OIL... § 250.808 Hydrogen sulfide. Production operations in zones known to contain hydrogen sulfide (H2S) or...

  10. 30 CFR 250.808 - Hydrogen sulfide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 2 2013-07-01 2013-07-01 false Hydrogen sulfide. 250.808 Section 250.808 Mineral Resources BUREAU OF SAFETY AND ENVIRONMENTAL ENFORCEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE OIL... § 250.808 Hydrogen sulfide. Production operations in zones known to contain hydrogen sulfide (H2S) or...

  11. The effects of varying humidity on copper sulfide film formation.

    SciTech Connect

    Mayer, Thomas Michael; Missert, Nancy A.; Barbour, John Charles; Sullivan, John Patrick; Copeland, Robert Guild; Campin, Michael J.

    2004-02-01

    Detailed experiments involving extensive high resolution transmission electron microscopy (TEM) revealed significant microstructural differences between Cu sulfides formed at low and high relative humidity (RH). It was known from prior experiments that the sulfide grows linearly with time at low RH up to a sulfide thickness approaching or exceeding one micron, while the sulfide initially grows linearly with time at high RH then becomes sub-linear at a sulfide thickness less than about 0.2 microns, with the sulfidation rate eventually approaching zero. TEM measurements of the Cu2S morphology revealed that the Cu2S formed at low RH has large sized grains (75 to greater than 150 nm) that are columnar in structure with sharp, abrupt grain boundaries. In contrast, the Cu2S formed at high RH has small equiaxed grains of 20 to 50 nm in size. Importantly, the small grains formed at high RH have highly disordered grain boundaries with a high concentration of nano-voids. Two-dimensional diffusion modeling was performed to determine whether the existence of localized source terms at the Cu/Cu2S interface could be responsible for the suppression of Cu sulfidation at long times at high RH. The models indicated that the existence of static localized source terms would not predict the complete suppression of growth that was observed. Instead, the models suggest that the diffusion of Cu through Cu2S becomes restricted during Cu2S formation at high RH. The leading speculation is that the extensive voiding that exists at grain boundaries in this material greatly reduces the flux of Cu between grains, leading to a reduction in the rate of sulfide film formation. These experiments provide an approach for adding microstructural information to Cu sulfidation rate computer models. In addition to the microstructural studies, new micro-patterned test structures were developed in this LDRD to offer insight into the point defect structure of Cu2S and to permit measurement of surface reaction

  12. Phototrophic sulfide oxidation: environmental insights and a method for kinetic analysis

    PubMed Central

    Hanson, Thomas E.; Luther, George W.; Findlay, Alyssa J.; MacDonald, Daniel J.; Hess, Daniel

    2013-01-01

    Previously, we presented data that indicated microbial sulfide oxidation would out-compete strictly chemical, abiotic sulfide oxidation reactions under nearly all conditions relevant to extant ecosystems (Luther et al., 2011). In particular, we showed how anaerobic microbial sulfide oxidation rates were several orders of magnitude higher than even metal catalyzed aerobic sulfide oxidation processes. The fact that biotic anaerobic sulfide oxidation is kinetically superior to abiotic reactions implies that nearly all anaerobic and sulfidic environments should host microbial populations that oxidize sulfide at appreciable rates. This was likely an important biogeochemical process during long stretches of euxinia in the oceans suggested by the geologic record. In particular, phototrophic sulfide oxidation allows the utilization of carbon dioxide as the electron acceptor suggesting that this process should be particularly widespread rather than relying on the presence of other chemical oxidants. Using the Chesapeake Bay as an example, we argue that phototrophic sulfide oxidation may be more important in many environments than is currently appreciated. Finally, we present methodological considerations to assist other groups that wish to study this process. PMID:24391629

  13. Cu-Ni-PGE fertility of the Yoko-Dovyren layered massif (northern Transbaikalia, Russia): thermodynamic modeling of sulfide compositions in low mineralized dunite based on quantitative sulfide mineralogy

    NASA Astrophysics Data System (ADS)

    Ariskin, Alexey A.; Kislov, Evgeny V.; Danyushevsky, Leonid V.; Nikolaev, Georgy S.; Fiorentini, Marco L.; Gilbert, Sarah; Goemann, Karsten; Malyshev, Alexey

    2016-06-01

    The geology and major types of sulfide mineralization in the Yoko-Dovyren layered massif (northern Transbaikalia, Russia) are presented. This study focuses on the structure, mineralogy, and geochemistry of poorly mineralized plagiodunite and dunite in the lower part of the intrusion. Assuming these rocks contain key information on the timing of sulfide immiscibility in the original cumulate pile, we apply a novel approach which combines estimates of the average sulfide compositions in each particular rock with thermodynamic modeling of the geochemistry of the original sulfide liquid. To approach the goal, an updated sulfide version of the COMAGMAT-5 model was used. Results of simulations of sulfide immiscibility in initially S-undersaturated olivine cumulates demonstrate a strong effect of the decreasing fraction of the silicate melt, due to crystallization of silicate and oxide minerals, on the composition of the intercumulus sulfide liquid. Comparison of the observed and modeled sulfide compositions indicates that the proposed modeling reproduces well the average concentrations of Cu, Cd, Ag, and Pd in natural sulfides. This suggests the sulfide control on the distribution of these elements in the rocks. Conversely, data for Pt and Au suggest that a significant portion of these elements could present in a native form, thus depleting the intercumulus sulfide melt at an early stage of crystallization.

  14. One-Pot Conversion of N-Allyl-α-cyano Esters to α-Allyl-α-cyano Lactams through a Hydrolysis/Ketene Formation/Cyclization/Claisen Rearrangement Sequence.

    PubMed

    Shen, Mei-Hua; Han, Mei; Xu, Hua-Dong

    2016-03-01

    An intramolecular ketene aza-Claisen rearrangement is developed for the first time to enable the stereoselective synthesis of α-ally-α-cyano-lactams from N-allyl amino esters. This reaction also exhibits outstanding chemoselectivity when an unsymmetrical bis-N-allyl group is present in the starting molecule. The usefulness of this method is demonstrated by a short synthesis of optically active bicyclolactam from l-proline. PMID:26872217

  15. Selenium content of sulfide ores related to ophiolites of Greece.

    PubMed

    Economou-Eliopoulos, M; Eliopoulos, D G

    1998-01-01

    Several deposits of sulfide mineralization have been described in the ophiolites of Greece. Based on their mineralogical and chemical composition and the host rocks, two types can be distinguished: (1) the Fe-Cu-Ni-Co type consisting of pyrrhotite, chalcopyrite, Co-pentlandite, pyrite, magnetite + arsenides, +/- chromite, hosted in serpentinites, gabbros or diabases, which have variable geochemical characteristics, and (2) sulfide mineralization of the Cyprus type containing variable proportions of pyrite, chalcopyrite, bornite, and sphalerite. The spatial association with shear zones and fault systems, which is a common feature in both types of mineralization, provided the necessary permeability for the circulation of the responsible mineralized hydrothermal fluids. The selenium (Se) content in representative samples of both types of mineralization from the ophiolites of Pindos (Kondro, Perivoli, and Neropriona), Othrys (Eretria and A. Theodoroi), Veria (Trilofon), and Argolis (Ermioni) shows a wide variation. The highest values of Se (130 to 1900 ppm) were found in massive Fe-Cu sulfide ores from Kondro, in particular the Cu-rich portions (average 1300 ppm Se). The average values of Se for the Othrys sulfides are low (< 40 ppm Se). The Se content in a diabase breccia pipe (50 x 200 m) with disseminated pyrite mineralization (Neropriona) ranges from < 1 to 35 ppm Se. The highest values were noted in strongly altered samples that also exhibited a significant enrichment in platinum (1 ppm Pt). Sulfide mineralization (irregular to lens-like masses and stringers) associated with magnetite, hosted in gabbros exposed in the Perivoli area (Tsouma hill), shows a content ranging from 40 to 350 ppm Se. The distribution of Se in the studied type of the sulfide mineralization may be of genetic significance, indicating that the Se level, which often is much higher than in typical magmatic sulfides related to mafic-ultramafic rocks (average 90-100 ppm Se), may positively affect

  16. Selenium content of sulfide ores related to ophiolites of Greece.

    PubMed

    Economou-Eliopoulos, M; Eliopoulos, D G

    1998-01-01

    Several deposits of sulfide mineralization have been described in the ophiolites of Greece. Based on their mineralogical and chemical composition and the host rocks, two types can be distinguished: (1) the Fe-Cu-Ni-Co type consisting of pyrrhotite, chalcopyrite, Co-pentlandite, pyrite, magnetite + arsenides, +/- chromite, hosted in serpentinites, gabbros or diabases, which have variable geochemical characteristics, and (2) sulfide mineralization of the Cyprus type containing variable proportions of pyrite, chalcopyrite, bornite, and sphalerite. The spatial association with shear zones and fault systems, which is a common feature in both types of mineralization, provided the necessary permeability for the circulation of the responsible mineralized hydrothermal fluids. The selenium (Se) content in representative samples of both types of mineralization from the ophiolites of Pindos (Kondro, Perivoli, and Neropriona), Othrys (Eretria and A. Theodoroi), Veria (Trilofon), and Argolis (Ermioni) shows a wide variation. The highest values of Se (130 to 1900 ppm) were found in massive Fe-Cu sulfide ores from Kondro, in particular the Cu-rich portions (average 1300 ppm Se). The average values of Se for the Othrys sulfides are low (< 40 ppm Se). The Se content in a diabase breccia pipe (50 x 200 m) with disseminated pyrite mineralization (Neropriona) ranges from < 1 to 35 ppm Se. The highest values were noted in strongly altered samples that also exhibited a significant enrichment in platinum (1 ppm Pt). Sulfide mineralization (irregular to lens-like masses and stringers) associated with magnetite, hosted in gabbros exposed in the Perivoli area (Tsouma hill), shows a content ranging from 40 to 350 ppm Se. The distribution of Se in the studied type of the sulfide mineralization may be of genetic significance, indicating that the Se level, which often is much higher than in typical magmatic sulfides related to mafic-ultramafic rocks (average 90-100 ppm Se), may positively affect

  17. Synthesis of Substituted Benzenes via Bi(OTf)3-Mediated Intramolecular Carbonyl Allylation of α-Prenyl or α-Geranyl β-Arylketosulfones.

    PubMed

    Chang, Meng-Yang; Cheng, Yu-Chieh; Lu, Yi-Ju

    2015-06-19

    Intramolecular carbonyl allylation of α-prenyl or α-geranyl β-arylketosulfones 5 in the presence of molecule sieves (MS) affords substituted benzenes 6-7 in moderate to good yields. The facile transformation proceeds by a synthetic sequence starting with the α-prenylation or α-geranylation of 1 and the Bi(OTf)3-mediated annulation of 5 followed by a sequential desulfonative aromatization or then an intramolecular Friedel-Crafts alkylation. A plausible mechanism has been studied and proposed. PMID:26068123

  18. Biogenic production of dimethyl sulfide: Krill grazing

    SciTech Connect

    Daly, K.L.; DiTullio, G.R. )

    1993-01-01

    Dimethyl sulfide (DMS), a dominant sulfur compound in sea water, is a possible precursor for cloud condensation nuclei in the atmosphere and may influence global climate. The primary source of DMS is phytoplankton, but the mechanisms remain uncertain, and concentrations of DMS in the ocean vary spatially and temporally. Laboratory studies suggest zooplankton grazing may be an important process leading to the formation of DMS in the ocean. This paper describes ocean studies which examine the suggestion that grazing by krill may be a significant source for DMS production in the antarctic coastal region. 11 refs., 2 figs.

  19. Enhanced durability and reactivity for zinc ferrite desulfurization sorbent. Volume 2, Single particle kinetic studies of sulfidation and regeneration reactions of candidate zinc ferrite sorbents

    SciTech Connect

    Silaban, A.; Harrison, D.P.

    1989-05-02

    AMAX Research & Development Center (AMAX R&D) has been investigating methods for enhancing the reactivity and durability of the zinc ferrite desulfurization sorbent. Zinc ferrite sorbents are intended for use in desulfurization of hot coal gas in integrated gasification combined cycle (IGCC) or molten carbonate fuel cell (MCFC) applications. For the present program, the reactivity of the sorbent may be defined as its sulfur sorption capacity at the breakthrough point and at saturation in a bench-scale, fixed-bed reactor. Durability may be defined as the ability of the sorbent to maintain important physical characteristics such as size, strength, and specific surface area during 10 cycles of sulfidation and oxidation.

  20. Platinum metals magmatic sulfide ores.

    PubMed

    Naldrett, A J; Duke, J M

    1980-06-27

    Platinum-group elements (PGE) are mined predominantly from deposits that have formed by the segregation of molten iron-nickel-copper sulfides from silicate magmas. The absolute concentrations of PGE in sulfides from different deposits vary over a range of five orders of magnitude, whereas those of other chalcophile elements vary by factors of only 2 to 100. However, the relative proportions of the different PGE in a given deposit are systematically related to the nature of the parent magma. The absolute and relative concentrations of PGE in magmatic sulfides are explained in terms of the degree of partial melting of mantle peridotite required to produce the parent magma and the processes of batch equilibration and fractional segregation of sulfides. The Republic of South Africa and the U.S.S.R. together possess more than 97 percent of the world PGE reserves, but significant undeveloped resources occur in North America. The Stillwater complex in Montana is perhaps the most important example. PMID:17796685

  1. p-Chlorophenyl methyl sulfide

    Integrated Risk Information System (IRIS)

    p - Chlorophenyl methyl sulfide ; CASRN 123 - 09 - 1 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for N

  2. Transition metal sulfide loaded catalyst

    DOEpatents

    Maroni, V.A.; Iton, L.E.; Pasterczyk, J.W.; Winterer, M.; Krause, T.R.

    1994-04-26

    A zeolite-based catalyst is described for activation and conversion of methane. A zeolite support includes a transition metal (Mo, Cr or W) sulfide disposed within the micropores of the zeolite. The catalyst allows activation and conversion of methane to C[sub 2]+ hydrocarbons in a reducing atmosphere, thereby avoiding formation of oxides of carbon.

  3. Transition metal sulfide loaded catalyst

    DOEpatents

    Maroni, Victor A.; Iton, Lennox E.; Pasterczyk, James W.; Winterer, Markus; Krause, Theodore R.

    1994-01-01

    A zeolite based catalyst for activation and conversion of methane. A zeolite support includes a transition metal (Mo, Cr or W) sulfide disposed within the micropores of the zeolite. The catalyst allows activation and conversion of methane to C.sub.2 + hydrocarbons in a reducing atmosphere, thereby avoiding formation of oxides of carbon.

  4. Inhibition of bladder cancer cell proliferation by allyl isothiocyanate (mustard essential oil).

    PubMed

    Sávio, André Luiz Ventura; da Silva, Glenda Nicioli; Salvadori, Daisy Maria Fávero

    2015-01-01

    Natural compounds hold great promise for combating antibiotic resistance, the failure to control some diseases, the emergence of new diseases and the toxicity of some contemporary medical products. Allyl isothiocyanate (AITC), which is abundant in cruciferous vegetables and mustard seeds and is commonly referred to as mustard essential oil, exhibits promising antineoplastic activity against bladder cancer, although its mechanism of action is not fully understood. Therefore, the aim of this study was to investigate the effects of AITC activity on bladder cancer cell lines carrying a wild type (wt; RT4) or mutated (T24) TP53 gene. Morphological changes, cell cycle kinetics and CDK1, SMAD4, BAX, BCL2, ANLN and S100P gene expression were evaluated. In both cell lines, treatment with AITC inhibited cell proliferation (at 62.5, 72.5, 82.5 and 92.5μM AITC) and induced morphological changes, including scattered and elongated cells and cellular debris. Gene expression profiles revealed increased S100P and BAX and decreased BCL2 expression in RT4 cells following AITC treatment. T24 cells displayed increased BCL2, BAX and ANLN and decreased S100P expression. No changes in SMAD4 and CDK1 expression were observed in either cell line. In conclusion, AITC inhibits cell proliferation independent of TP53 status. However, the mechanism of action of AITC differed in the two cell lines; in RT4 cells, it mainly acted via the classical BAX/BCL2 pathway, while in T24 cells, AITC modulated the activities of ANLN (related to cytokinesis) and S100P. These data confirm the role of AITC as a potential antiproliferative compound that modulates gene expression according to the tumor cell TP53 genotype. PMID:25771977

  5. [Characterization of surface properties of 1-allyl-3-methylimidazolium chloride ionic liquid by inverse gas chromatography].

    PubMed

    Chen, Yali; Wang, Qiang; Deng, Lishuang; Zhang, Zhengfang; Tang, Jun

    2013-02-01

    The determination of the dispersive component of surface free energies (gamma(s)d) at different temperatures and Lewis acid-base parameters of 1-allyl-3-methylimidazolium chloride ionic liquid ([AMIM]Cl) were investigated by means of inverse gas chromatography (IGC). Four n-alkanes, including n-hexane (C6), n-heptane (C7), n-octane (C8) and n-nonane (C9), were chosen as the apolar probes to characterize the dispersive component of the surface free energies at 343.15, 353.15, 363.15 and 373.15 K, respectively; and dichloromethane (DCM), trichloromethane (TCM), tetrahydrofuran (THF), ethyl acetate (EtAc), acetone (Acet) as the polar probes to estimate the Lewis acid-base parameters to judge the interactions between [AMIM] Cl and the solvents. The IGC characterizations encompassed the adsorption thermodynamic parameters to acid-base surface interactions, including the standard enthalpy (deltaHa(s)) and the free energy change of adsorption (deltaGa(s)) at different temperatures. The results showed that the Lewis acid parameter Ka of [AMIM] Cl was 0.34, and the base parameter Kb was 1.68, which indicated it was Lewis amphoteric with predominantly basic character. Furthermore, the free energy of adsorption deltaGa(s) was also figured out. It was found that the gamma(s)d of the [AMIM] Cl were 52.26, 50.82, 46.08 and 42.05 mJ/m2 at 343.15, 353.15, 363.15 and 373.15 K, respectively. The results are of great importance to the study of the surface properties and the application of ionic liquid.

  6. Inhibition of bladder cancer cell proliferation by allyl isothiocyanate (mustard essential oil).

    PubMed

    Sávio, André Luiz Ventura; da Silva, Glenda Nicioli; Salvadori, Daisy Maria Fávero

    2015-01-01

    Natural compounds hold great promise for combating antibiotic resistance, the failure to control some diseases, the emergence of new diseases and the toxicity of some contemporary medical products. Allyl isothiocyanate (AITC), which is abundant in cruciferous vegetables and mustard seeds and is commonly referred to as mustard essential oil, exhibits promising antineoplastic activity against bladder cancer, although its mechanism of action is not fully understood. Therefore, the aim of this study was to investigate the effects of AITC activity on bladder cancer cell lines carrying a wild type (wt; RT4) or mutated (T24) TP53 gene. Morphological changes, cell cycle kinetics and CDK1, SMAD4, BAX, BCL2, ANLN and S100P gene expression were evaluated. In both cell lines, treatment with AITC inhibited cell proliferation (at 62.5, 72.5, 82.5 and 92.5μM AITC) and induced morphological changes, including scattered and elongated cells and cellular debris. Gene expression profiles revealed increased S100P and BAX and decreased BCL2 expression in RT4 cells following AITC treatment. T24 cells displayed increased BCL2, BAX and ANLN and decreased S100P expression. No changes in SMAD4 and CDK1 expression were observed in either cell line. In conclusion, AITC inhibits cell proliferation independent of TP53 status. However, the mechanism of action of AITC differed in the two cell lines; in RT4 cells, it mainly acted via the classical BAX/BCL2 pathway, while in T24 cells, AITC modulated the activities of ANLN (related to cytokinesis) and S100P. These data confirm the role of AITC as a potential antiproliferative compound that modulates gene expression according to the tumor cell TP53 genotype.

  7. Stereoselective coordination: a six-membered P,N-chelate tailored for asymmetric allylic alkylation.

    PubMed

    Császár, Z; Farkas, G; Bényei, A; Lendvay, G; Tóth, I; Bakos, J

    2015-10-01

    Six-membered chelate complexes [Pd(1a-b)Cl2], (2a-b) and [Pd(1a-b)(η(3)-PhCHCHCHPh)]BF4, (3a-b) of P,N-type ligands 1a, ((2S,4S)-2-diphenyl-phosphino-4-isopropylamino-pentane) and 1b, ((2S,4S)-2-diphenyl-phosphino-4-methylamino-pentane) have been prepared. The Pd-complexes have been characterized in solution by 1D and 2D NMR spectroscopy. The observed structures were confirmed by DFT calculations and in the case of 2a also by X-ray crystallography. Unexpectedly, the coordination of the all-carbon-backbone aminophosphine 1a resulted in not only a stereospecific locking of the donor nitrogen atom into one of the two possible configurations but also the conformation of the six-membered chelate rings containing three alkyl substituents was forced into the same single chair structure showing the axially placed isopropyl group on the coordinated N-atom. The stereodiscriminative complexation of 1a led to the formation of a palladium catalyst with a conformationally rigid chelate having a configurationally fixed nitrogen and electronically different coordination sites due to the presence of P and N donors. The stereochemically fixed catalyst provided excellent ee's (up to 96%) and activities in asymmetric allylic alkylation reactions. In contrast, the chelate rings formed by 1b exist in two different chair conformations, both containing axial methyl groups, but with the opposite configurations of the coordinated N-atom. Pd-complexes of 1b provided low enantioselectivities in similar alkylations, therefore emphasizing the importance of the stereoselective coordination of N-atoms in analogous P-N chelates. The factors determining the coordination of the ligands were also studied with respect to the chelate ring conformation and the nitrogen configuration.

  8. Preparation, catalysis, and characterization of highly dispersed molybdenum sulfide catalysts supported on a NaY zeolite

    SciTech Connect

    Okamoto, Yasuaki; Katsuyama, Hiromoto

    1996-06-01

    The structure and dispersion of the molybdenum sulfides supported on a NaY zeolite were studied using XAFS techniques. It was found that molybdenum sulfide species prepared by sulfiding vapor deposited Mo(CO){sub 6} or by sulfiding molybdenum oxide dimer species encaged in the zeolite are highly dispersed and thermally stabilized against sintering or restructuring. These molybdenum species are formed via molybdenum sulfide dimer species as an intermediate. On the other hand, with the molybdenum sulfide catalysts prepared by an impregnation method, the sulfidation of molybdenum oxides was incomplete. The molybdenum oxide species are suggested to be mainly located in the zeolite cavities after calcination, forming isolated molybdenum oxides in tetrahedral configurations. The molybdenum sulfide species prepared from Mo(CO){sub 6} showed much higher catalytic activities for thiophene hydrodesulfurization and butadiene hydrogenation than the molybdenum sulfides prepared by the impregnation, in conformity with a higher dispersion and higher fraction of the molybdenum sulfide species. It is demonstrated that in combination with metal carbonyl techniques, zeolite supports are very suitable for the preparation of highly dispersed molybdenum sulfides at a high Mo loading.

  9. Effect of sulfiding on an unsupported hydrotreating catalyst

    SciTech Connect

    Ho, T.C. )

    1991-09-01

    It is well known that sulfiding plays a very important role in determining the performance of commercial hydroprocessing catalysts. Recently, Ho and Reyes described the sulfiding behavior of an unsupported catalyst derived from tris(ethylenediamine) cobalt molybdate, or Co(NH{sub 2}CH{sub 2}CH{sub 2}NH{sub 2}){sub 3}MoO{sub 4}. This water soluble metallate upon sulfiding shows very high volumetric activities for both hydrodesulfurization (HDS) and hydrodenitrogenation (HDN). A major finding in Ho and Reyes study is that gas (H{sub 2}S/H{sub 2}) sulfiding of this bulk catalyst is accompanied by significant hot spotting, much more so than sulfiding of commercial catalysts. They developed a mathematical model for predicting the speed and magnitude of the traveling thermal wave. At the conditions used by Ho and Reyes, the model calculated that the catalysts could be some 20 C hotter than the gas, and the H{sub 2}S level could drop from 10% at the reactor inlet to as low as 0.5% at the outlet. This study was carried out to get some idea on the extent to which the activity of the bulk catalyst is affected by presulfiding conditions. The comparative experiments were done under somewhat exaggerated conditions.

  10. Regioselectivity in the reaction of tantalum-unsymmetrical acetylene complexes with carbonyl compounds. Stereoselective preparation of 1-alkenyl sulfides, [alpha],[beta]-unsaturated esters, and amides

    SciTech Connect

    Kataoka, Yasutaka; Miyai, Jiro; Tezuka, Makoto; Takai, Kazuhiko; Utimoto, Kiitiro )

    1992-12-04

    Tantalum-alkyne complexes, derived by treatment of aklynes with low-valent tantalum (TaCl[sub 5] and zinc), react in situ with carbonyl compounds to give (E)-allylic alcohols stereoselectively. When unsymmetrical acetylenes are employed in the reaction, two regioisomeric allylic alcohols are produced. The regioselectivity of the reaction depends on the steric and electronic effects of the substituents on the acetylenes. For example, treatment of tantalum-allkyne complexes derived from methyl alkynyl sulfides with carbonyl compounds yields (E)-3-hydroxy-1-propenyl methyl sulfides in a regioselective manner. Tantalum-alkyne complexes derived from acetylenic esters react with carbonyl compounds regioselectively at the [alpha]-position of the esters to give Z-isomers of trisubstituted [alpha],[beta]-unsaturated esters. In contract, tantalum-alkyne complexes derived from acetylenic amides react with carbonyl compounds predominantly at the [beta]-position of the amides. The regioselectivity of the reaction between acytylenic amides and aldehydes, however, cannot be explained solely in terms of the steric and electronic effects of the substituents. Strong coordination of the amide group to the tantalum center could also be responsible for the observed selectivity, which is opposite to that observed with tantalum-acetylenic ester complexes. 18 refs., 1 tab.

  11. Diastereo- and enantioselective iridium-catalyzed allylation of cyclic ketone enolates: synergetic effect of ligands and barium enolates.

    PubMed

    Chen, Wenyong; Chen, Ming; Hartwig, John F

    2014-11-12

    We report asymmetric allylic alkylation of barium enolates of cyclic ketones catalyzed by a metallacyclic iridium complex containing a phosphoramidite ligand derived from (R)-1-(2-naphthyl)ethylamine. The reaction products contain adjacent quaternary and tertiary stereocenters. This process demonstrates that unstabilized cyclic ketone enolates can undergo diastereo- and enantioselective Ir-catalyzed allylic substitution reactions with the proper choice of enolate countercation. The products of these reactions can be conveniently transformed to various useful polycarbocyclic structures.

  12. Highly regio- and enantioselective synthesis of N-substituted 2-pyridones: iridium-catalyzed intermolecular asymmetric allylic amination.

    PubMed

    Zhang, Xiao; Yang, Ze-Peng; Huang, Lin; You, Shu-Li

    2015-02-01

    The first iridium-catalyzed intermolecular asymmetric allylic amination reaction with 2-hydroxypyridines has been developed, thus providing a highly efficient synthesis of enantioenriched N-substituted 2-pyridone derivatives from readily available starting materials. This protocol features a good tolerance of functional groups in both the allylic carbonates and 2-hydroxypyridines, thereby delivering multifunctionalized heterocyclic products with up to 98% yield and 99% ee. PMID:25504907

  13. Chemoenzymatic one-pot synthesis in an aqueous medium: combination of metal-catalysed allylic alcohol isomerisation-asymmetric bioamination.

    PubMed

    Ríos-Lombardía, Nicolás; Vidal, Cristian; Cocina, María; Morís, Francisco; García-Álvarez, Joaquín; González-Sabín, Javier

    2015-07-11

    The ruthenium-catalysed isomerisation of allylic alcohols was coupled, for the first time, with asymmetric bioamination in a one-pot process in an aqueous medium. In the cases involving prochiral ketones, the ω-TA exhibited excellent enantioselectivity, identical to that observed in the single step. As a result, amines were obtained from allylic alcohols with high overall yields and excellent enantiomeric excesses.

  14. Generation of CF3-containing epoxides and aziridines by visible-light-driven trifluoromethylation of allylic alcohols and amines.

    PubMed

    Kim, Eunjin; Choi, Sungkyu; Kim, Heejeong; Cho, Eun Jin

    2013-05-10

    Radical reactions! Efficient methods for the generation of CF3-containing epoxides and aziridines have been developed (see scheme). A variety of allylic alcohols and allylic amines were transformed into the corresponding epoxides and aziridines by using [Ru(bpy)3]Cl2 (bpy = 2,2'-bipyridine), CF3 I, and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) (or N,N,N',N'-tetramethylethylenediamine, TMEDA) under visible-light irradiation.

  15. Regio- and Stereospecific 1,3-Allyl Group Transfer Triggered by a Copper-Catalyzed Borylation/ortho-Cyanation Cascade.

    PubMed

    Yang, Yang

    2016-01-01

    A copper-catalyzed borylation/ortho-cyanation/allyl group transfer cascade was developed. Initiated by an unconventional copper-catalyzed electrophilic dearomatization, this process features regio- and stereospecific 1,3-transposition of the allyl fragment enabled by an aromatization-driven Cope rearrangement. This method provides an effective means for the construction of adjacent tertiary and quaternary stereocenters with excellent diastereocontrol. PMID:26509757

  16. Iridium-Catalyzed Allylic Amination Route to α-Aminoboronates: Illustration of the Decisive Role of Boron Substituents

    PubMed Central

    Touchet, Sabrina; Molander, Gary A.; Carboni, Bertrand; Bouillon, Alexandre

    2012-01-01

    The development of a new route to α-aminoboronates using an iridium-catalyzed allylic amination on boronated substrates is described. Unlike the boronate group, the trifluoroborato substituent was found to govern the regioselectivity exclusively in favor of branched products. The transformation of an allylic substitution product into an α-aminoboronic ester in an efficient way validated the implementation of this approach. PMID:22350584

  17. From a Sequential to a Concurrent Reaction in Aqueous Medium: Ruthenium-Catalyzed Allylic Alcohol Isomerization and Asymmetric Bioreduction.

    PubMed

    Ríos-Lombardía, Nicolás; Vidal, Cristian; Liardo, Elisa; Morís, Francisco; García-Álvarez, Joaquín; González-Sabín, Javier

    2016-07-18

    The ruthenium-catalyzed redox isomerization of allylic alcohols was successfully coupled with the enantioselective enzymatic ketone reduction (mediated by KREDs) in a concurrent process in aqueous medium. The overall transformation, formally the asymmetric reduction of allylic alcohols, took place with excellent conversions and enantioselectivities, under mild reaction conditions, employing commercially and readily available catalytic systems, and without external coenzymes or cofactors. Optimization resulted in a multistep approach and a genuine cascade reaction where the metal catalyst and biocatalyst coexist from the beginning.

  18. Sonication effect on the reaction of 4-bromo-1-methylbenzene with sodium sulfide in liquid-liquid multi-site phase-transfer catalysis condition - kinetic study.

    PubMed

    Abimannan, Pachaiyappan; Selvaraj, Varathan; Rajendran, Venugopal

    2015-03-01

    The synthesis of di-p-tolylsulfane from the reaction of 4-bromo-1-methylbenzene (BMB) with sodium sulfide was carried out using a multi-site phase-transfer catalyst (MPTC) viz., 1,4-dihexyl-1,4-diazoniabicyclo[2.2.2]octanium dibromide and ultrasonic irradiation in a liquid-liquid reaction condition. The overall reaction rate is greatly enhanced when catalyzed by multi-site phase-transfer catalyst (MPTC) combined with sonication (40 kHz, 300 W) in a batch reactor than catalyzed by MPTC without sonication. Effects on the reaction due to various operating conditions, such as agitation speed, different ultrasound frequencies, different phase-transfer catalysts, different organic solvents, the amount of MPTC, temperature, amount of sodium sulfide, effect of sodium hydroxide, volume of n-hexane and the concentration of 4-bromo-1-methylbenzene. The reaction obeys a pseudo first-order rate law and a suitable mechanism was proposed based on the experimental observation.

  19. Hydrogen Sulfide Inhibits Amyloid Formation

    PubMed Central

    2015-01-01

    Amyloid fibrils are large aggregates of misfolded proteins, which are often associated with various neurodegenerative diseases such as Alzheimer’s, Parkinson’s, Huntington’s, and vascular dementia. The amount of hydrogen sulfide (H2S) is known to be significantly reduced in the brain tissue of people diagnosed with Alzheimer’s disease relative to that of healthy individuals. These findings prompted us to investigate the effects of H2S on the formation of amyloids in vitro using a model fibrillogenic protein hen egg white lysozyme (HEWL). HEWL forms typical β-sheet rich fibrils during the course of 70 min at low pH and high temperatures. The addition of H2S completely inhibits the formation of β-sheet and amyloid fibrils, as revealed by deep UV resonance Raman (DUVRR) spectroscopy and ThT fluorescence. Nonresonance Raman spectroscopy shows that disulfide bonds undergo significant rearrangements in the presence of H2S. Raman bands corresponding to disulfide (RSSR) vibrational modes in the 550–500 cm–1 spectral range decrease in intensity and are accompanied by the appearance of a new 490 cm–1 band assigned to the trisulfide group (RSSSR) based on the comparison with model compounds. The formation of RSSSR was proven further using a reaction with TCEP reduction agent and LC-MS analysis of the products. Intrinsic tryptophan fluorescence study shows a strong denaturation of HEWL containing trisulfide bonds. The presented evidence indicates that H2S causes the formation of trisulfide bridges, which destabilizes HEWL structure, preventing protein fibrillation. As a result, small spherical aggregates of unordered protein form, which exhibit no cytotoxicity by contrast with HEWL fibrils. PMID:25545790

  20. Atomic layer deposition of aluminum sulfide thin films using trimethylaluminum and hydrogen sulfide

    SciTech Connect

    Sinha, Soumyadeep; Sarkar, Shaibal K.; Mahuli, Neha

    2015-01-15

    Sequential exposures of trimethylaluminum and hydrogen sulfide are used to deposit aluminum sulfide thin films by atomic layer deposition (ALD) in the temperature ranging from 100 to 200 °C. Growth rate of 1.3 Å per ALD cycle is achieved by in-situ quartz crystal microbalance measurements. It is found that the growth rate per ALD cycle is highly dependent on the purging time between the two precursors. Increased purge time results in higher growth rate. Surface limited chemistry during each ALD half cycle is studied by in-situ Fourier transformed infrared vibration spectroscopy. Time of flight secondary ion-mass spectroscopy measurement is used to confirm elemental composition of the deposited films.

  1. Nickel sulfide formation at low temperature: initial precipitates, solubility and transformation products

    EPA Science Inventory

    The formation of nickel sulfides has been examined experimentally over the temperature range from 25 to 60°C. At all conditions studied, hexagonal (α-NiS) was the initial precipitate from solution containing Ni2+ and dissolved sulfide. The formation of millerite (β- NiS, rhombo...

  2. Spectral properties of zinc sulfide sols stabilized by high-molecular polyvinylpyrrolidone

    NASA Astrophysics Data System (ADS)

    Evstrop'ev, S. K.; Gatchin, Yu. A.; Evstrop'ev, K. S.; Dukel'skii, K. V.; Kislyakov, I. M.

    2015-12-01

    Spectral properties of zinc sulfide sols stabilized by high-molecular polyvinylpyrrolidone have been studied. It is shown that the absorption spectra of colloidal solutions in the UV spectral range are determined by the quantum-confinement effect, exhibiting a dependence of the absorption edge on the size of zinc sulfide nanocrystals.

  3. Accessing Both Retention and Inversion Pathways in Stereospecific, Nickel-Catalyzed Miyaura Borylations of Allylic Pivalates.

    PubMed

    Zhou, Qi; Srinivas, Harathi D; Zhang, Songnan; Watson, Mary P

    2016-09-14

    We have developed a stereospecific, nickel-catalyzed Miyaura borylation of allylic pivalates, which delivers highly enantioenriched α-stereogenic γ-aryl allylboronates with good yields and regioselectivities. Our complementary sets of conditions enable access to either enantiomer of allylboronate product from a single enantiomer of readily prepared allylic pivalate substrate. Excellent functional group tolerance, yields, regioselectivities, and stereochemical fidelities are observed. The stereochemical switch from stereoretention to stereoinversion largely depends upon solvent and can be explained by competitive pathways for the oxidative addition step. Our mechanistic investigations support a stereoretentive pathway stemming from a directed oxidative addition and a stereoinvertive pathway that is dominant when MeCN blocks coordination of the directing group by binding the nickel catalyst. PMID:27589327

  4. Rheology and viscosity scaling of gelatin/1-allyl-3-methylimidazolium chloride solution

    NASA Astrophysics Data System (ADS)

    Qiao, Congde; Li, Tianduo; Zhang, Ling; Yang, Xiaodeng; Xu, Jing

    2014-05-01

    Gelatin/1-allyl-3-methylimidazolium chloride solutions are prepared by using the ionic liquid 1-allyl-3-methylimidazolium chloride as solvent. The rheological properties of the gelatin solutions have been investigated by steady shear and oscillatory shear measurements. In the steady shear measurements, the gelatin solutions with high concentration show a shear-thinning flow behavior at high shear rates, while another shear thinning region can be found in the dilute gelatin solutions at low shear rates. The overlap concentration of gelatin in [amim]Cl is 1.0 wt% and the entanglement concentration is a factor of 4 larger (4.0 wt%). The high intrinsic viscosity (295 mL/g) indicates that the gelatin chains dispersed freely in the ionic liquid and no aggregation phenomenon occurs in dilute gelatin solution. The frequency dependences of modulus changed obviously with an increase in gelatin concentration. The empirical time-temperature superposition principle holds true at the experimental temperatures.

  5. Iridium-Catalyzed Allylation of Chiral β-Stereogenic Alcohols: Bypassing Discrete Formation of Epimerizable Aldehydes

    PubMed Central

    Schmitt, Daniel C.; Dechert-Schmitt, Anne-Marie R.; Krische, Michael J.

    2012-01-01

    The cyclometallated π-allyliridium 3,4-dinitro-C,O-benzoate complex modified by (R)- or (S)-Cl,MeO-BIPHEP promotes the transfer hydrogenative coupling of allyl acetate to β-stereogenic alcohols with good to excellent levels of catalyst-directed diastereoselectivity to furnish homoallylic alcohols. Remote electronic effects of the C,O-benzoate of the catalyst play a critical role in suppressing epimerization of the transient α-stereogenic aldehyde. PMID:23231774

  6. Additive-free decarboxylative coupling of cinnamic acid derivatives in water: synthesis of allyl amines.

    PubMed

    Park, Kyungho; Lee, Sunwoo

    2015-03-01

    The first example of an additive-free decarboxylative coupling of cinnamic acid derivatives with formaldehyde and amines to afford the corresponding allyl amines is reported. This reaction is highly environmentally friendly because it was conducted in H2O and without any additives, releasing only CO2 and H2O as byproducts. This reaction showed a broad substrate scope including cyclic and acyclic amines and high functional group tolerance. Moreover, phenyl dienoic acid participated in this type of decarboxylative coupling reaction.

  7. Highly diastereoselective palladium-catalyzed indium-mediated allylation of chiral hydrazones.

    PubMed

    Balasubramanian, Narayanaganesh; Mandal, Tanmay; Cook, Gregory R

    2015-01-16

    The general and efficient palladium-catalyzed indium-mediated allylation of chiral hydrazones was accomplished with excellent yield (72-92%) and diastereoselectivity (up to 99:1). The development of this reaction and the substrate scope are described. The conversion was found to be proportional to the phosphine concentration, which provided insight into the mechanism and competing pathways of the redox transmetalation process.

  8. Synthesis of alkenyl boronates from allyl-substituted aromatics using an olefin cross-metathesis protocol.

    PubMed

    Hemelaere, Rémy; Carreaux, François; Carboni, Bertrand

    2013-07-01

    An efficient synthesis of 3-aryl-1-propenyl boronates from pinacol vinyl boronic ester and allyl-substituted aromatics by cross metathesis is reported. Although the allylbenzene derivatives are prone to isomerization reaction under metathesis conditions, we found that some ruthenium catalysts are effective for this methodology. This strategy thus provides an interesting alternative approach to alkyne hydroboration, leading to the preparation of unknown compounds. Moreover, the boron substituent can be replaced by various functional groups in good yields.

  9. Separate recovery of copper and zinc from acid mine drainage using biogenic sulfide.

    PubMed

    Sahinkaya, Erkan; Gungor, Murat; Bayrakdar, Alper; Yucesoy, Zeynep; Uyanik, Sinan

    2009-11-15

    Precipitation of metals from acid mine drainage (AMD) using sulfide gives the possibility of selective recovery due to different solubility product of each metal. Using sulfate reducing bacteria to produce sulfide for that purpose is advantageous due to in situ and on-demand sulfide production. In this study, separate precipitation of Cu and Zn was studied using sulfide produced in anaerobic baffled reactor (ABR). ABR fed with ethanol (1340 mg/L chemical oxygen demand (COD)) and sulfate (2000 mg/L) gave a stable performance with 65% sulfate reduction, 85% COD removal and around 320 mg/L sulfide production. Cu was separately precipitated at low pH (pH<2) using sulfide transported from ABR effluent via N(2) gas. Cu precipitation was complete within 45-60 min and Zn did not precipitate during Cu removal. The Cu precipitation rate increased with initial Cu concentration. After selective Cu precipitation, Zn recovery was studied using ABR effluent containing sulfide and alkalinity. Depending on initial sulfide/Zn ratio, removal efficiency varied between 84 and 98%. The low pH of Zn bearing AMD was also increased to neutral values using alkalinity produced by sulfate reducing bacteria in ABR. The mode of particle size distribution of ZnS and CuS precipitates was around 17 and 46 microm, respectively.

  10. Multi-dimensional modeling of atmospheric copper-sulfidation corrosion on non-planar substrates.

    SciTech Connect

    Chen, Ken Shuang

    2004-11-01

    This report documents the author's efforts in the deterministic modeling of copper-sulfidation corrosion on non-planar substrates such as diodes and electrical connectors. A new framework based on Goma was developed for multi-dimensional modeling of atmospheric copper-sulfidation corrosion on non-planar substrates. In this framework, the moving sulfidation front is explicitly tracked by treating the finite-element mesh as a pseudo solid with an arbitrary Lagrangian-Eulerian formulation and repeatedly performing re-meshing using CUBIT and re-mapping using MAPVAR. Three one-dimensional studies were performed for verifying the framework in asymptotic regimes. Limited model validation was also carried out by comparing computed copper-sulfide thickness with experimental data. The framework was first demonstrated in modeling one-dimensional copper sulfidation with charge separation. It was found that both the thickness of the space-charge layers and the electrical potential at the sulfidation surface decrease rapidly as the Cu{sub 2}S layer thickens initially but eventually reach equilibrium values as Cu{sub 2}S layer becomes sufficiently thick; it was also found that electroneutrality is a reasonable approximation and that the electro-migration flux may be estimated by using the equilibrium potential difference between the sulfidation and annihilation surfaces when the Cu{sub 2}S layer is sufficiently thick. The framework was then employed to model copper sulfidation in the solid-state-diffusion controlled regime (i.e. stage II sulfidation) on a prototypical diode until a continuous Cu{sub 2}S film was formed on the diode surface. The framework was also applied to model copper sulfidation on an intermittent electrical contact between a gold-plated copper pin and gold-plated copper pad; the presence of Cu{sub 2}S was found to raise the effective electrical resistance drastically. Lastly, future research needs in modeling atmospheric copper sulfidation are discussed.

  11. Rhodium-catalysed asymmetric allylic arylation of racemic halides with arylboronic acids

    NASA Astrophysics Data System (ADS)

    Sidera, Mireia; Fletcher, Stephen P.

    2015-11-01

    Csp2-Csp2 cross-coupling reactions between arylboronic acid and aryl halides are widely used in both academia and industry and are strategically important in the development of new agrochemicals and pharmaceuticals. Csp2-Csp3 cross-coupling reactions have been developed, but enantioselective variations are rare and simply retaining the stereochemistry is a problem. Here we report a highly enantioselective Csp2-Csp3 bond-forming method that couples arylboronic acids to racemic allyl chlorides. Both enantiomers of a cyclic chloride are converted into a single enantiomer of product via a dynamic kinetic asymmetric transformation. This Rh-catalysed method uses readily available and inexpensive building blocks and is mild and broadly applicable. For electron-deficient, electron-rich or ortho-substituted boronic acids better results are obtained with racemic allyl bromides. Oxygen substitution in the allyl halide is tolerated and the products can be functionalized to provide diverse building blocks. The approach fills a significant gap in the methods for catalytic asymmetric synthesis.

  12. Sulfidation of Silver Nanoparticles: Natural antidote to their toxicity

    PubMed Central

    Levard, Clément; Hotze, Ernest M.; Colman, Benjamin P.; Truong, Lisa; Yang, X. Y.; Bone, Audrey; Brown, Gordon E.; Tanguay, Robert L.; Di Giulio, Richard T.; Bernhardt, Emily S.; Meyer, Joel N.; Wiesner, Mark R.; Lowry, Gregory V.

    2014-01-01

    Nanomaterials are highly dynamic in biological and environmental media. A critical need for advancing environmental health and safety research for nanomaterials is to identify commonly occurring physical and chemical transformations affecting nanomaterial properties and toxicity. Silver nanoparticles, one of the most ecotoxic and well-studied nanomaterials, readily sulfidize in the environment. Here, we show that very low degrees of sulfidation (0.019 S/Ag mass ratio) universally and significantly decreases the toxicity of silver nanoparticles to four diverse types of aquatic and terrestrial eukaryotic organisms. Toxicity reduction is primarily associated with a decrease in Ag+ availability after sulfidation due to the lower solubility of Ag2S relative to elemental Ag (Ag(0)). We also show that chloride in exposure media determines silver nanoparticle toxicity by controlling the speciation of Ag. These results highlight the need to consider environmental transformation of NPs in assessing their toxicity to accurately portray their potential environmental risks. PMID:24180218

  13. Growth kinetics of hydrogen sulfide oxidizing bacteria in corroded concrete from sewers.

    PubMed

    Jensen, Henriette Stokbro; Lens, Piet N L; Nielsen, Jeppe L; Bester, Kai; Nielsen, Asbjørn Haaning; Hvitved-Jacobsen, Thorkild; Vollertsen, Jes

    2011-05-30

    Hydrogen sulfide oxidation by microbes present on concrete surfaces of sewer pipes is a key process in sewer corrosion. The growth of aerobic sulfur oxidizing bacteria from corroded concrete surfaces was studied in a batch reactor. Samples of corrosion products, containing sulfur oxidizing bacteria, were suspended in aqueous solution at pH similar to that of corroded concrete. Hydrogen sulfide was supplied to the reactor to provide the source of reduced sulfur. The removal of hydrogen sulfide and oxygen was monitored. The utilization rates of both hydrogen sulfide and oxygen suggested exponential bacterial growth with median growth rates of 1.25 d(-1) and 1.33 d(-1) as determined from the utilization rates of hydrogen sulfide and oxygen, respectively. Elemental sulfur was found to be the immediate product of the hydrogen sulfide oxidation. When exponential growth had been achieved, the addition of hydrogen sulfide was terminated leading to elemental sulfur oxidation. The ratio of consumed sulfur to consumed oxygen suggested that sulfuric acid was the ultimate oxidation product. To the knowledge of the authors, this is the first study to determine the growth rate of bacteria involved in concrete corrosion with hydrogen sulfide as source of reduced sulfur. PMID:21440988

  14. Growth kinetics of hydrogen sulfide oxidizing bacteria in corroded concrete from sewers.

    PubMed

    Jensen, Henriette Stokbro; Lens, Piet N L; Nielsen, Jeppe L; Bester, Kai; Nielsen, Asbjørn Haaning; Hvitved-Jacobsen, Thorkild; Vollertsen, Jes

    2011-05-30

    Hydrogen sulfide oxidation by microbes present on concrete surfaces of sewer pipes is a key process in sewer corrosion. The growth of aerobic sulfur oxidizing bacteria from corroded concrete surfaces was studied in a batch reactor. Samples of corrosion products, containing sulfur oxidizing bacteria, were suspended in aqueous solution at pH similar to that of corroded concrete. Hydrogen sulfide was supplied to the reactor to provide the source of reduced sulfur. The removal of hydrogen sulfide and oxygen was monitored. The utilization rates of both hydrogen sulfide and oxygen suggested exponential bacterial growth with median growth rates of 1.25 d(-1) and 1.33 d(-1) as determined from the utilization rates of hydrogen sulfide and oxygen, respectively. Elemental sulfur was found to be the immediate product of the hydrogen sulfide oxidation. When exponential growth had been achieved, the addition of hydrogen sulfide was terminated leading to elemental sulfur oxidation. The ratio of consumed sulfur to consumed oxygen suggested that sulfuric acid was the ultimate oxidation product. To the knowledge of the authors, this is the first study to determine the growth rate of bacteria involved in concrete corrosion with hydrogen sulfide as source of reduced sulfur.

  15. What do we really know about the role of microorganisms in iron sulfide mineral formation?

    NASA Astrophysics Data System (ADS)

    Picard, Aude; Gartman, Amy; Girguis, Peter

    2016-06-01

    Iron sulfide mineralization in low-temperature systems is a result of biotic and abiotic processes, though the delineation between these two modes of formation is not always straightforward. Here we review the role of microorganisms in the precipitation of extracellular iron sulfide minerals. We summarize the evidence that links sulfur-metabolizing microorganisms and sulfide minerals in nature and we present a critical overview of laboratory-based studies of the nucleation and growth of iron sulfide minerals in microbial cultures. We discuss whether biologically derived minerals are distinguishable from abiotic minerals, possessing attributes that are uniquely diagnostic of biomineralization. These inquiries have revealed the need for additional thorough, mechanistic and high-resolution studies to understand microbially mediated formation of a variety of sulfide minerals across a range of natural environments.

  16. Selenium sulfide in tinea versicolor: blood and urine levels.

    PubMed

    Sánchez, J L; Torres, V M

    1984-08-01

    The safety of topical selenium sulfide lotion in man has been demonstrated previously. Twenty male patients with a diagnosis of tinea versicolor were randomly assigned to two parallel groups who applied selenium sulfide lotion or the vehicle to the entire skin surface, excluding mucous membranes, for 10 minutes once daily for 7 consecutive days. Blood and urine selenium levels were determined before and after treatment and showed no significant differences between the active drug and vehicle groups on any study day. It would appear that no significant absorption of selenium took place as a result of this treatment regimen.

  17. Application of Borehole SIP Technique to Sulfide Mineral Exploration

    NASA Astrophysics Data System (ADS)

    Kim, Changryol; Park, Mi Kyung; Park, Samgyu; Sung, Nak Hoon; Shin, Seung Wook

    2016-04-01

    In the study, SIP (Spectral Induced Polarization) well logging probe system was developed to rapidly locate the metal ore bodies with sulfide minerals in the boreholes. The newly developed SIP logging probe employed the non-polarizable electrodes, consisting of zinc chloride (ZnCl2), sodium chloride (NaCl), gypsum (CaSO4·2H2O), and water (H2O), instead of existing copper electrodes, leading to eliminating the EM coupling effect in the IP surveys as much as possible. In addition, the SIP logging system is designed to make measurements down to maximum 500 meters in depth in the boreholes. The SIP well logging was conducted to examine the applicability of the SIP probe system to the boreholes at the ore mine in Jecheon area, Korea. The boreholes used in the SIP logging are known to have penetrated the metal ore bodies with sulfide minerals from the drilling investigations. The ore mine of the study area is the scarn deposits surrounded by the limestone or lime-silicate rocks in Ordovician period. The results of the SIP well logging have shown that the borehole segments with limestone or lime-silicate rocks yielded the insignificant SIP responses while the borehole segments with sulfide minerals (e.g. pyrite) provided the significant phase shifts of the SIP responses. The borehole segments penetrating the metal ore body, so-called cupola, have shown very high response of the phase shift, due to the high contents of the sulfide mineral pyrite. The phase shifts of the SIP response could be used to estimate the grade of the ore bodies since the higher contents of the sulfide minerals, the higher magnitudes of the phase shifts in the SIP responses. It is, therefore, believed that the borehole SIP technique can be applied to investigate the metal ore bodies with sulfide minerals, and that could be used to estimate the ore grades as a supplementary tool in the future.

  18. Sulfide smelting using Ausmelt technology

    NASA Astrophysics Data System (ADS)

    Mounsey, Edward N.; Robilliard, Ken R.

    1994-08-01

    Over the past decade, Ausmelt has been developing the top submerged lancing process for the smelting of sulfidic ores to recover such metals as copper, lead, silver, tin, antimony, and nickel as well as for separation of minor elements such as arsenic, antimony, and bismuth. Development has taken place in Ausmelt's pilot plant in Dandenong, near Melbourne, Australia. A number of projects have proceeded to commercial-scale operation. This paper reviews developments at both the pilot and commercial scales.

  19. Properties of pure and sulfided NiMoO{sub 4} and CoMoO{sub 4} catalysts: TPR, XANES and time-resolved XRD studies

    SciTech Connect

    Chaturvedi, S.; Rodriguez, J.A.; Hanson, J.C.; Albornoz, A.; Brito, J.L.

    1998-12-31

    X-ray absorption near-edge spectroscopy (XANES) was used to characterize the structural and electronic properties of a series of cobalt- and nickel-molybdate catalysts (AMoO{sub 4}.nH{sub 2}O, {alpha}-AMoO{sub 4}, {beta}-AMoO{sub 4}; A=Co or Ni). The results of XANES indicate that the Co and Ni atoms are in octahedral sites in all these compounds, while the coordination of Mo varies from octahedral in the {alpha}-phases to tetrahedral in the {beta}-phases and hydrate. Time-resolved x-ray diffraction shows a direct transformation of the hydrates into the {beta}-AMoO{sub 4} compounds (following a kinetics of first order) at temperatures between 200 and 350{degrees}C. This is facilitated by the similarities that the AMoO{sub 4}.nH{sub 2}O and H{sub 2} at temperatures between 400 and 600{degrees}C, forming gaseous water oxides in which the oxidation state of Co and Ni remains +2 while that of Mo is reduced to +5 or +4. After exposing {alpha}-NiMoO{sub 4} and {beta}-NiMoO{sub 4} to H{sub 2}S, both metals get sulfided and a NiMoS{sub x} phase is formed. For the {beta} phase of NiMoO{sub 4} the sulfidation of Mo is more extensive than for the {alpha} phase, making the former a better precursor for catalysts of hydrodesulfurization reactions.

  20. Investigation of the possibility of intermediate formation of allyl alcohol in the process of oxidative acetoxylation of propylene on a palladium-copper zeolite catalyst

    SciTech Connect

    Minachev, K.M.; Chizhov, O.S.; Kadentsev, V.I.; Kharlamov, V.V.; Nefedov, O.M.; Rodin, A.N.

    1985-12-10

    The formation of allyl acetate in reactions of oxidative acetoxylation of propylene by labeled acetic acid and esterification of labeled acetic acid by allyl alcohol on a Pd, Cu-zeolite catalyst occur with complete conservation of the labeled oxygen of the original labeled acetic acid in the reaction product. The authors propose a reaction scheme for the oxidative acetoxylation of propylene, providing for the formation of allyl alcohol as an intermediate compound, present in a chemisorbed state in the form of a complex with a Pd atom. The gas-phase oxidative acetoxylation of propylene is an industrial method of producing allyl acetate.