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Sample records for cyclic enol ethers

  1. Cycloaddition of Arynes and Cyclic Enol Ethers as a Platform for Access to Stereochemically Defined 1,2-Disubstituted Benzocyclobutenes

    PubMed Central

    Yedulla, Vijayendar R.; Pradhan, Padmanava; Yang, Lijia; Lakshman, Mahesh K.

    2015-01-01

    Benzocyclobutenes (BCBs) are important entities in a multitude of areas, such as complex organic synthesis, materials and polymer chemistry, and electronics. Whereas reactions between arynes and ketene acetals have been well studied, reactions with cyclic enol ethers are unknown. A cis olefin geometry in cyclic enol ethers makes them well suited for formal [2 + 2] cycloaddition with arynes than for competing ene reactions, making them effective reactants. Reactions of 2,3-dihydrofuran, 2,3-dihydro-3H-pyran, 5-butyl-2,3-dihydrofuran, (S)-2-((benzyloxy)methyl)-2,3-dihydrofuran, and 1,4-dioxene with various arynes were successful. An advantage of the use of cyclic enol ethers is that despite the plausible intermediacy of zwitterionic intermediates, the products are limited to a cis ring junction. This can be exploited for potential access to stereochemically-defined 1,2-disubstituted BCBs. As a demonstration, ether ring cleavage with BBr3 provided trans-functionalized BCBs and displacement with azide then provided cis derivatives. DFT computations have been utilized to understand the structures of three arynes in relation to the cycloadditions and for a predictive evaluation of product ratios in two cases. A comparative evaluation of the HOMO energies of a related series of cyclic olefins has also been performed by DFT computations. PMID:27642260

  2. Oxidative acetoxylation of the silyl ethers of ketone enols

    SciTech Connect

    Brunovlenskaya, I.I.; Kusainova, K.M.; Kashin, A.K.

    1988-07-20

    The authors studied the reaction of (dicarboxyiodo)benzenes with the trimethylsilyl ethers of ketone enols having various structures. They also undertook a comparative investigation of the oxidation of these compounds with lead tetraacetate. The reaction of (diacetoxyiodo)benzene with the trimethylsilyl ethers of ketone enols takes place with retention of the (CH/sub 3/)/sub 3/Si group in two directions, i.e., substitution of the vinylic hydrogen or diacetoxylation of the double bond. The reaction can be used for the regioselective synthesis of /alpha/-acetoxy ketones, since the trimethylsilyl group is readily eliminated from the obtained products by the action of fluoride ion or boron trifluoride etherate with the formation of the corresponding substituted ketones.

  3. 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.

  4. Visible-Light-Promoted Oxidative [4 + 2] Cycloadditions of Aryl Silyl Enol Ethers.

    PubMed

    Yang, Bo; Lu, Zhan

    2016-08-19

    Visible-light-promoted oxidative [4 + 2] cycloadditions of ε,3-unsaturated silyl enol ethers have been developed to efficiently and diastereoselectively construct polycyclic skeletons under mild conditions. The diastereoselectivities were dependent on the stereoconfiguration of silyl enol ether, substitutions on the link, as well as electric properties of substitutions on aryl rings. The intermediates could be trapped by TEMPO, oxygen or methanol. Mechanistic studies indicated the reaction was initiated by one-electron oxidation of the silyl enol ether. PMID:27391768

  5. Rhodium-Catalyzed Dehydrogenative Silylation of Acetophenone Derivatives: Formation of Silyl Enol Ethers versus Silyl Ethers.

    PubMed

    Garcés, Karin; Lalrempuia, Ralte; Polo, Víctor; Fernández-Alvarez, Francisco J; García-Orduña, Pilar; Lahoz, Fernando J; Pérez-Torrente, Jesús J; Oro, Luis A

    2016-10-01

    A series of rhodium-NSiN complexes (NSiN=bis (pyridine-2-yloxy)methylsilyl fac-coordinated) is reported, including the solid-state structures of [Rh(H)(Cl)(NSiN)(PCy3 )] (Cy=cyclohexane) and [Rh(H)(CF3 SO3 )(NSiN)(coe)] (coe=cis-cyclooctene). The [Rh(H)(CF3 SO3 )(NSiN)(coe)]-catalyzed reaction of acetophenone with silanes performed in an open system was studied. Interestingly, in most of the cases the formation of the corresponding silyl enol ether as major reaction product was observed. However, when the catalytic reactions were performed in closed systems, formation of the corresponding silyl ether was favored. Moreover, theoretical calculations on the reaction of [Rh(H)(CF3 SO3 )(NSiN)(coe)] with HSiMe3 and acetophenone showed that formation of the silyl enol ether is kinetically favored, while the silyl ether is the thermodynamic product. The dehydrogenative silylation entails heterolytic cleavage of the Si-H bond by a metal-ligand cooperative mechanism as the rate-determining step. Silyl transfer from a coordinated trimethylsilyltriflate molecule to the acetophenone followed by proton transfer from the activated acetophenone to the hydride ligand results in the formation of H2 and the corresponding silyl enol ether.

  6. Rhodium-Catalyzed Dehydrogenative Silylation of Acetophenone Derivatives: Formation of Silyl Enol Ethers versus Silyl Ethers.

    PubMed

    Garcés, Karin; Lalrempuia, Ralte; Polo, Víctor; Fernández-Alvarez, Francisco J; García-Orduña, Pilar; Lahoz, Fernando J; Pérez-Torrente, Jesús J; Oro, Luis A

    2016-10-01

    A series of rhodium-NSiN complexes (NSiN=bis (pyridine-2-yloxy)methylsilyl fac-coordinated) is reported, including the solid-state structures of [Rh(H)(Cl)(NSiN)(PCy3 )] (Cy=cyclohexane) and [Rh(H)(CF3 SO3 )(NSiN)(coe)] (coe=cis-cyclooctene). The [Rh(H)(CF3 SO3 )(NSiN)(coe)]-catalyzed reaction of acetophenone with silanes performed in an open system was studied. Interestingly, in most of the cases the formation of the corresponding silyl enol ether as major reaction product was observed. However, when the catalytic reactions were performed in closed systems, formation of the corresponding silyl ether was favored. Moreover, theoretical calculations on the reaction of [Rh(H)(CF3 SO3 )(NSiN)(coe)] with HSiMe3 and acetophenone showed that formation of the silyl enol ether is kinetically favored, while the silyl ether is the thermodynamic product. The dehydrogenative silylation entails heterolytic cleavage of the Si-H bond by a metal-ligand cooperative mechanism as the rate-determining step. Silyl transfer from a coordinated trimethylsilyltriflate molecule to the acetophenone followed by proton transfer from the activated acetophenone to the hydride ligand results in the formation of H2 and the corresponding silyl enol ether. PMID:27553810

  7. Turning Spiroketals Inside Out: A Rearrangement Triggered by an Enol Ether Epoxidation

    PubMed Central

    Lorenc, Chris; Saurí, Josep; Moser, Arvin; Buevich, Alexei V; Williams, Antony J; Williamson, R Thomas; Martin, Gary E; Peczuh, Mark W

    2015-01-01

    Spiroketals organize small molecule structures into well-defined, three-dimensional configurations that make them good ligands of proteins. We recently discovered a tandem cycloisomerization–dimerization reaction of alkynyl hemiketals that delivered polycyclic, enol-ether-containing spiroketals. Here we describe rearrangements of those compounds, triggered by epoxidation of their enol ethers that completely remodel their structures, essentially turning them “inside out”. Due to the high level of substitution on the carbon skeletons of the substrates and products, characterization resorted to X-ray crystallography and advanced computation and NMR techniques to solve the structures of representative compounds. In particular, a new proton-detected ADEQUATE NMR experiment (1,1-HD-ADEQUATE) enabled the unequivocal assignment of the carbon skeleton of one of the new compounds. Solution of the structures of the representative compounds allowed for the assignment of product structures for the other compounds in two separate series. Both the rearrangement and the methods used for structural determination of the products are valuable tools for the preparation of characterization of new small molecule compounds. PMID:26491634

  8. 40 CFR 721.3440 - Haloalkyl substituted cyclic ethers.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Haloalkyl substituted cyclic ethers... Substances § 721.3440 Haloalkyl substituted cyclic ethers. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substances haloalkyl substituted cyclic ethers (PMN P-85-368 and...

  9. 40 CFR 721.3440 - Haloalkyl substituted cyclic ethers.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Haloalkyl substituted cyclic ethers... Substances § 721.3440 Haloalkyl substituted cyclic ethers. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substances haloalkyl substituted cyclic ethers (PMN P-85-368 and...

  10. Cyclic ethers adsorbed on Ru(001)

    NASA Astrophysics Data System (ADS)

    Walczak, M. M.; Thiel, P. A.

    1990-11-01

    The three cyclic ethers 1,3-dioxane. 1,4-dioxane and 1,3,5-trioxane all exhibit multiple desorption states from Ru(001) between 200 and 310 K, in addition to the multilayer and metastable states at lower temperature. Most distinctive are the two low-temperature α-states. which are similar in shape, position, and relative population for all three compounds. This suggests that these states are associated with configurations which are accessible to all three molecules. The data also indicate that there is some molecular decomposition to gaseous CO and H 2. 1,4-Dioxane yields the largest amounts of these decomposition products, suggesting that this molecule is most susceptible to surface-catalyzed decomposition. The desorption data for the three cyclic ethers are grossly similar to each other, and also to the straight-chain diethers which we have previously studied.

  11. Synthesis of α-trifluoromethyl ketones via the Cu-catalyzed trifluoromethylation of silyl enol ethers using an electrophilic trifluoromethylating agent.

    PubMed

    Li, Lun; Chen, Qing-Yun; Guo, Yong

    2014-06-01

    A method has been developed for the synthesis of α-trifluoromethyl ketones via the Cu-catalyzed trifluoromethylation of silyl enol ethers with an electrophilic trifluoromethylating agent, which produces a trifluoromethyl radical.

  12. Asymmetric Electrophilic α-Amination of Silyl Enol Ether Derivatives via the Nitrosocarbonyl Hetero-ene Reaction.

    PubMed

    Sandoval, David; Samoshin, Andrey V; Read de Alaniz, Javier

    2015-09-18

    The first example of a general asymmetric nitrosocarbonyl hetero-ene reaction is described. The procedure uses a copper-catalyzed aerobic oxidation of a commercially available chiral nitrosocarbonyl precursor (EleNOr) and is operationally simple. The transformation is both high yielding and highly diastereoselective for a range of silyl enol ether derivatives. A variety of synthetically useful postfunctionalization reactions are presented along with a mechanistic rationale that can be used as a predictive model for future asymmetric reactions with nitrosocarbonyl intermediates.

  13. Photoinduced Formation of Hybrid Aryl Pd-Radical Species Capable of 1,5-HAT: Selective Catalytic Oxidation of Silyl Ethers into Silyl Enol Ethers.

    PubMed

    Parasram, Marvin; Chuentragool, Padon; Sarkar, Dhruba; Gevorgyan, Vladimir

    2016-05-25

    A direct visible light-induced generation of a hybrid aryl Pd-radical species from aryl iodide and Pd(0) is reported to enable an unprecedented (for hybrid Pd-radical species) hydrogen atom-transfer event. This approach allowed for efficient desaturation of readily available silyl ethers into synthetically valuable silyl enols. Moreover, this oxidation reaction proceeds at room temperature without the aid of exogenous photosensitizers or oxidants. PMID:27149524

  14. Geminal bis(silane)-controlled regio- and stereoselective oxidative Heck reaction of enol ethers with terminal alkenes to give push-pull 1,3-dienes.

    PubMed

    Li, Linjie; Chu, Yang; Gao, Lu; Song, Zhenlei

    2015-11-01

    A geminal bis(silane)-controlled regio- and stereoselective oxidative Heck reaction of enol ethers with terminal alkenes has been developed. The reaction proceeds with α,β-coupling regioselectivity to give push-pull Z,E-1,3-dienes in good yields. The product showed valuable utility in Sakurai homoallylation with acetals to generate α-substituted-γ-keto esters with good anti-selectivity.

  15. The cyclic keto-enol insecticide spirotetramat inhibits insect and spider mite acetyl-CoA carboxylases by interfering with the carboxyltransferase partial reaction.

    PubMed

    Lümmen, Peter; Khajehali, Jahangir; Luther, Kai; Van Leeuwen, Thomas

    2014-12-01

    Acetyl-CoA carboxylase (ACC) catalyzes the committed and rate-limiting step in fatty acid biosynthesis. The two partial reactions, carboxylation of biotin followed by carboxyl transfer to the acceptor acetyl-CoA, are performed by two separate domains in animal ACCs. The cyclic keto-enol insecticides and acaricides have been proposed to inhibit insect ACCs. In this communication, we show that the enol derivative of the cylic keto-enol insecticide spirotetramat inhibited ACCs partially purified from the insect species Myzus persicae and Spodoptera frugiperda, as well as the spider mite (Tetranychus urticae) ACC which was expressed in insect cells using a recombinant baculovirus. Steady-state kinetic analysis revealed competitive inhibition with respect to the carboxyl acceptor, acetyl-CoA, indicating that spirotetramat-enol bound to the carboxyltransferase domain of ACC. Interestingly, inhibition with respect to the biotin carboxylase substrate ATP was uncompetitive. Amino acid residues in the carboxyltransferase domains of plant ACCs are important for binding of established herbicidal inhibitors. Mutating the spider mite ACC at the homologous positions, for example L1736 to either isoleucine or alanine, and A1739 to either valine or serine, did not affect the inhibition of the spider mite ACC by spirotetramat-enol. These results indicated different binding modes of the keto-enols and the herbicidal chemical families.

  16. Regioselective Oxo-Amination of Alkenes and Enol Ethers with N-Bromosuccinimide-Dimethyl Sulfoxide Combination: A Facile Synthesis of α-Amino-Ketones and Esters.

    PubMed

    Prasad, Pragati K; Reddi, Rambabu N; Sudalai, Arumugam

    2016-02-01

    An unprecedented conversion of alkenes and enol ethers to the corresponding α-imido carbonyl compounds with excellent regioselectivity and yields has been developed. This oxo-amination process employs readily available N-bromosuccinimide (NBS) and secondary amines as N-sources and dimethyl sulfoxide (DMSO) as the oxidant and also leads to the production of amino alcohols in a single step on reduction, thus broadening the scope of this operationally simple reaction. For the first time, the formation of reactive Me2S(+)-O-Br species generated by the interaction of NBS with DMSO has been proven.

  17. Oligomer formation during gas-phase ozonolysis of small alkenes and enol ethers: new evidence for the central role of the Criegee Intermediate as oligomer chain unit

    NASA Astrophysics Data System (ADS)

    Sadezky, A.; Winterhalter, R.; Kanawati, B.; Römpp, A.; Spengler, B.; Mellouki, A.; Le Bras, G.; Chaimbault, P.; Moortgat, G. K.

    2008-05-01

    An important fraction of secondary organic aerosol (SOA) formed by atmospheric oxidation of diverse volatile organic compounds (VOC) has recently been shown to consist of high-molecular weight oligomeric species. In our previous study (Sadezky et al., 2006), we reported the identification and characterization of oligomers as main constituents of SOA from gas-phase ozonolysis of small enol ethers. These oligomers contained repeated chain units of the same chemical composition as the main Criegee Intermediates (CI) formed during the ozonolysis reaction, which were CH2O2 (mass 46) for alkyl vinyl ethers (AVE) and C2H4O2 (mass 60) for ethyl propenyl ether (EPE). In the present work, we extend our previous study to another enol ether (ethyl butenyl ether EBE) and a variety of structurally related small alkenes (trans-3-hexene, trans-4-octene and 2,3-dimethyl-2-butene). Experiments have been carried out in a 570 l spherical glass reactor at atmospheric conditions in the absence of seed aerosol. SOA formation was measured by a scanning mobility particle sizer (SMPS). SOA filter samples were collected and chemically characterized off-line by ESI(+)/TOF MS and ESI(+)/TOF MS/MS, and elemental compositions were determined by ESI(+)/FTICR MS and ESI(+)/FTICR MS/MS. The results for all investigated unsaturated compounds are in excellent agreement with the observations of our previous study. Analysis of the collected SOA filter samples reveal the presence of oligomeric compounds in the mass range 200 to 800 u as major constituents. The repeated chain units of these oligomers are shown to systematically have the same chemical composition as the respective main Criegee Intermediate (CI) formed during ozonolysis of the unsaturated compounds, which is C3H6O2 (mass 74) for ethyl butenyl ether (EBE), trans-3-hexene, and 2,3-dimethyl-2-butene, and C4H8O2 (mass 88) for trans-4-octene. Analogous fragmentation pathways among the oligomers formed by gas-phase ozonolysis of the different

  18. Oligomer formation during gas-phase ozonolysis of small alkenes and enol ethers: new evidence for the central role of the Criegee Intermediate as oligomer chain unit

    NASA Astrophysics Data System (ADS)

    Sadezky, A.; Winterhalter, R.; Kanawati, B.; Römpp, A.; Spengler, B.; Mellouki, A.; Le Bras, G.; Chaimbault, P.; Moortgat, G. K.

    2007-10-01

    An important fraction of secondary organic aerosol (SOA) formed by atmospheric oxidation of diverse volatile organic compounds (VOC) has recently been shown to consist of high-molecular weight oligomeric species. In our previous study (Sadezky et al., 2006), we reported the identification and characterization of oligomers as main constituents of SOA from gas-phase ozonolysis of small enol ethers. These oligomers contained repeated chain units of the same chemical composition as the main Criegee Intermediates (CI) formed during the ozonolysis reaction, which were CH2O2 (mass 46) for alkyl vinyl ethers (AVE) and C2H4O2 (mass 60) for ethyl propenyl ether (EPE). In the present work, we extend our previous study (Sadezky et al., 2006) to another enol ether (ethyl butenyl ether EBE) and a variety of structurally related small alkenes (trans-3-hexene, trans-4-octene and 2,3-dimethyl-2-butene). Experiments have been carried out in a 570 l spherical glass reactor at atmospheric conditions in the absence of seed aerosol. SOA formation was measured by a scanning mobility particle sizer (SMPS). SOA filter samples were collected and chemically characterized off-line by ESI(+)/MS-TOF and ESI(+)/MS/MS-TOF, and elemental compositions were confirmed by ESI(+)/MS/MS-FTICR. The results for all investigated unsaturated compounds are in excellent agreement with the observations of our previous study (Sadezky et al., 2006). Analysis of the collected SOA filter samples reveal the presence of oligomeric compounds in the mass range 200 to 800 u as major constituents. The repeated chain units of these oligomers are shown to systematically have the same chemical composition as the respective main Criegee Intermediate (CI) formed during ozonolysis of the unsaturated compounds, which is C3H6O2 (mass 74) for ethyl butenyl ether (EBE), trans-3-hexene, and 2,3-dimethyl-2-butene, and C4H8O2 (mass 88) for trans-4-octene. Analogous fragmentation pathways among the oligomers formed by gas

  19. Copper-catalyzed oxidative C-O bond formation of 2-acyl phenols and 1,3-dicarbonyl compounds with ethers: direct access to phenol esters and enol esters.

    PubMed

    Park, Jihye; Han, Sang Hoon; Sharma, Satyasheel; Han, Sangil; Shin, Youngmi; Mishra, Neeraj Kumar; Kwak, Jong Hwan; Lee, Cheong Hoon; Lee, Jeongmi; Kim, In Su

    2014-05-16

    A copper-catalyzed oxidative coupling of 2-carbonyl-substituted phenols and 1,3-dicarbonyl compounds with a wide range of dibenzyl or dialkyl ethers is described. This protocol provides an efficient preparation of phenol esters and enol esters in good yields with high chemoselectivity. This method represents an alternative protocol for classical esterification reactions.

  20. A spiroketal-enol ether derivative from Tanacetum vulgare selectively inhibits HSV-1 and HSV-2 glycoprotein accumulation in Vero cells.

    PubMed

    Álvarez, Ángel L; Habtemariam, Solomon; Abdel Moneim, Ahmed E; Melón, Santiago; Dalton, Kevin P; Parra, Francisco

    2015-07-01

    The inhibitory effects of Tanacetum vulgare rhizome extracts on HSV-1 and HSV-2 in vitro replication were assessed. Unlike extracts obtained from the aerial parts, adsorption inhibition and virucidal activities seemed not to be relevant for the observed antiviral action of tansy rhizome extracts. Instead, the most significant effects were the inhibition of virus penetration and a novel mechanism consisting of the specific arrest of viral gene expression and consequently the decrease of viral protein accumulation within infected cells. Through a bioactivity-guided fractionation protocol we isolated and identified the spiroketal-enol ether derivative (E)-2-(2,4-hexadiynyliden)-1,6-dioxaspiro[4.5]dec-3-ene as the active compound responsible for this inhibitory effect.

  1. Alkyl substituted cyclic ethers in 2,300 M yr old Transvaal algal stromatolite

    NASA Technical Reports Server (NTRS)

    Zumberge, J. E.; Nagy, B.

    1975-01-01

    Two cyclic ethers have been identified for the first time from insoluble polymer-like kerogen in a Precambrian rock by ozonolysis, gas chromatography, and mass spectrometry. The ethers are 2-n-propyl-3-methyltetrahydrofuran and 2-n-propyltetrahydropyran. These compounds could prove to be the oldest indigenous biochemical fossils. The sample was obtained 750 m stratigraphically above the base of the Transvaal Sequence from an outcrop approximately 315 km north-east of Johannesburg, South Africa.

  2. Structures and Surface Properties of "Cyclic" Polyoxyethylene Alkyl Ethers: Unusual Behavior of Cyclic Surfactants in Water.

    PubMed

    Hirose, Yuki; Taira, Toshiaki; Sakai, Kenichi; Sakai, Hideki; Endo, Akira; Imura, Tomohiro

    2016-08-23

    The cyclization of amphiphiles has emerged as an attractive strategy for inducing remarkable properties in these materials without changing their chemical composition. In this study, we successfully synthesized three cyclic polyoxyethylene dodecyl ethers (c-POEC12's) with different ring sizes and explored the effects of their topology on their surface and self-assembly properties related to their function, comparing them with those of their linear counterparts (l-POEC12's). The surface activity of the c-POEC12's remained almost constant despite the change in their hydrophobic and hydrophilic balance (HLB) value, while that of the l-POEC12's decreased with an increase in the HLB value as general surfactants. In contrast to the normal micelles seen in the case of the l-POEC12's (3.4-9.7 nm), the cyclization of the POEC12's resulted in the formation of large spherical structures 72.8-256.8 nm in size. It also led to a dramatic decrease of 28 °C in the cloud point temperature. Furthermore, the cyclization of the POEC12's markedly suppressed the rate of protease hydrolysis caused by the surfactants. The initial rate of reduction of a detergent enzyme from Bacillus licheniformis was increased by more than 40% in the case of c-POE600C12 and c-POE1000C12, even though they exhibited surface activities almost equal to or higher than those of their linear counterparts. These results suggest that cyclization induces unusual aqueous behaviors in POEC12, making the surfactant milder with respect to detergent enzymes while ensuring it exhibits increased surface activity. PMID:27462805

  3. SmI(2)-induced reductive cyclizations for the synthesis of cyclic ethers and applications in natural product synthesis.

    PubMed

    Nakata, Tadashi

    2010-06-01

    This tutorial review covers SmI(2)-induced reductive cyclizations of beta-alkoxyacrylate, beta-alkoxyvinyl sulfone, and beta-alkoxyvinyl sulfoxide, as methods for efficient construction of cyclic ethers. These cyclizations were developed as tools to aid in the total synthesis of marine polycyclic ethers, whose complex, synthetically challenging structures and potent bioactivities have attracted the attention of numerous synthetic organic chemists. Applications of the methods to total syntheses of various natural products containing cyclic ether are also described.

  4. Optimisation of a 5-[3-phenyl-(2-cyclic-ether)-methyl-ether]-4-aminopyrrolopyrimidine series of IGF-1R inhibitors.

    PubMed

    Fairhurst, Robin A; Marsilje, Thomas H; Stutz, Stefan; Boos, Andreas; Niklaus, Michel; Chen, Bei; Jiang, Songchun; Lu, Wenshuo; Furet, Pascal; McCarthy, Clive; Stauffer, Frédéric; Guagnano, Vito; Vaupel, Andrea; Michellys, Pierre-Yves; Schnell, Christian; Jeay, Sébastien

    2016-04-15

    Taking the pyrrolopyrimidine derived IGF-1R inhibitor NVP-AEW541 as the starting point, the benzyl ether back-pocket binding moiety was replaced with a series of 2-cyclic ether methyl ethers leading to the identification of novel achiral [2.2.1]-bicyclic ether methyl ether containing analogues with improved IGF-1R activities and kinase selectivities. Further exploration of the series, including a fluorine scan of the 5-phenyl substituent, and optimisation of the sugar-pocket binding moiety identified compound 33 containing (S)-2-tetrahydrofuran methyl ether 6-fluorophenyl ether back-pocket, and cis-N-Ac-Pip sugar-pocket binding groups. Compound 33 showed improved selectivity and pharmacokinetics compared to NVP-AEW541, and produced comparable in vivo efficacy to linsitinib in inhibiting the growth of an IGF-1R dependent tumour xenograft model in the mouse.

  5. Resonance assisted hydrogen bonds in open-chain and cyclic structures of malonaldehyde enol: A theoretical study

    NASA Astrophysics Data System (ADS)

    Trujillo, Cristina; Sánchez-Sanz, Goar; Alkorta, Ibon; Elguero, José; Mó, Otilia; Yáñez, Manuel

    2013-09-01

    In 1989 Gilli, Bellucci, Ferretti and Bertolasi introduced the notion of Resonance Assisted Hydrogen Bonding (RAHB) one of the most fruitful concepts in structural chemistry. After reviewing our previous contributions to this topic, the present work analyzes theoretically this concept especially in non-cyclic structures. Geometries, electron densities and Laplacian at the bond critical points, cooperativity through many body interaction energies, deformation energies as well as NMR properties (chemical shifts and 2hJOO coupling constants) are used for the discussion.

  6. Metabolism and Cometabolism of Cyclic Ethers by a Filamentous Fungus, a Graphium sp.▿

    PubMed Central

    Skinner, Kristin; Cuiffetti, Lynda; Hyman, Michael

    2009-01-01

    The filamentous fungus Graphium sp. (ATCC 58400) grows on gaseous n-alkanes and diethyl ether. n-Alkane-grown mycelia of this strain also cometabolically oxidize the gasoline oxygenate methyl tert-butyl ether (MTBE). In this study, we characterized the ability of this fungus to metabolize and cometabolize a range of cyclic ethers, including tetrahydrofuran (THF) and 1,4-dioxane (14D). This strain grew on THF and other cyclic ethers, including tetrahydropyran and hexamethylene oxide. However, more vigorous growth was consistently observed on the lactones and terminal diols potentially derived from these ethers. Unlike the case in all previous studies of microbial THF oxidation, a metabolite, γ-butyrolactone, was observed during growth of this fungus on THF. Growth on THF was inhibited by the same n-alkenes and n-alkynes that inhibit growth of this fungus on n-alkanes, while growth on γ-butyrolactone or succinate was unaffected by these inhibitors. Propane and THF also behaved as mutually competitive substrates, and propane-grown mycelia immediately oxidized THF, without a lag phase. Mycelia grown on propane or THF exhibited comparable high levels of hemiacetal-oxidizing activity that generated methyl formate from mixtures of formaldehyde and methanol. Collectively, these observations suggest that THF and n-alkanes may initially be oxidized by the same monooxygenase and that further transformation of THF-derived metabolites involves the activity of one or more alcohol dehydrogenases. Both propane- and THF-grown mycelia also slowly cometabolically oxidized 14D, although unlike THF oxidation, this reaction was not sustainable. Specific rates of THF, 14D, and MTBE degradation were very similar in THF- and propane-grown mycelia. PMID:19581469

  7. 40 CFR 721.10381 - Cyclic carboxylic acid, polymer with dihydroxy dialkyl ether, hydroxy substituted alkane and...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Cyclic carboxylic acid, polymer with dihydroxy dialkyl ether, hydroxy substituted alkane and carboxylic acid anhydride, methacrylate terminated... Specific Chemical Substances § 721.10381 Cyclic carboxylic acid, polymer with dihydroxy dialkyl...

  8. 40 CFR 721.10381 - Cyclic carboxylic acid, polymer with dihydroxy dialkyl ether, hydroxy substituted alkane and...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Cyclic carboxylic acid, polymer with dihydroxy dialkyl ether, hydroxy substituted alkane and carboxylic acid anhydride, methacrylate terminated... Specific Chemical Substances § 721.10381 Cyclic carboxylic acid, polymer with dihydroxy dialkyl...

  9. 40 CFR 721.10381 - Cyclic carboxylic acid, polymer with dihydroxy dialkyl ether, hydroxy substituted alkane and...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Cyclic carboxylic acid, polymer with dihydroxy dialkyl ether, hydroxy substituted alkane and carboxylic acid anhydride, methacrylate terminated... Specific Chemical Substances § 721.10381 Cyclic carboxylic acid, polymer with dihydroxy dialkyl...

  10. Synthesis of five-membered cyclic ethers by reaction of 1,4-diols with dimethyl carbonate.

    PubMed

    Aricò, Fabio; Tundo, Pietro; Maranzana, Andrea; Tonachini, Glauco

    2012-08-01

    The reaction of 1,4-diols with dimethyl carbonate in the presence of a base led to selective and high-yielding syntheses of related five-membered cyclic ethers. This synthetic pathway has the potential for a wide range of applications. Distinctive cyclic ethers and industrially relevant compounds were synthesized in quantitative yield. The reaction mechanism for the cyclization was investigated. Notably, the chirality of the starting material was maintained. DFT calculations indicated that the formation of five-membered cyclic ethers was energetically the most favorable pathway. Typically, the selectivity exhibited by these systems could be rationalized on the basis of hard-soft acid-base theory. Such principles were applicable as far as computed energy barriers were concerned, but in practice cyclization reactions were shown to be entropically driven.

  11. Toward a formal synthesis of laureatin: unexpected rearrangements involving cyclic ether nucleophiles.

    PubMed

    Keshipeddy, Santosh; Martínez, Isamir; Castillo, Bernard F; Morton, Martha D; Howell, Amy R

    2012-09-21

    Laureatin, a metabolite of the red algae Laurencia nipponica, has shown potent activity as a mosquito larvicide. The two previously published syntheses of laureatin involved an initial preparation of the 8-membered cyclic ether, followed by formation of the oxetane ring. Our strategy was the reverse, i.e., to utilize an oxetane as the framework to construct the larger ring. During this work, attempted N-bromosuccinimide (NBS)-mediated cyclization of oxetane alcohol 17, prepared from readily accessible 2-methyleneoxetane 12, yielded epoxytetrahydrofuran 19 rather than the expected laureatin core. Further derivatization of 19 yielded trans fused bis-tetrahydrofuran 32. The synthesis of 19 and 32, as well as structural and stereochemical elucidation studies, are described.

  12. Mass spectra of cyclic ethers formed in the low-temperature oxidation of a series of n-alkanes

    PubMed Central

    Herbinet, Olivier; Bax, Sarah; Glaude, Pierre-Alexandre; Carré, Vincent; Battin-Leclerc, Frédérique

    2013-01-01

    Cyclic ethers are important intermediate species formed during the low-temperature oxidation of hydrocarbons. Along with ketones and aldehydes, they could consequently represent a significant part of the heavy oxygenated pollutants observed in the exhaust gas of engines. Apart a few of them such as ethylene oxide and tetrahydrofuran, cyclic ethers have not been much studied and very few of them are available for calibration and identification. Electron impact mass spectra are available for very few of them, making their detection in the exhaust emissions of combustion processes very difficult. The main goal of this study was to complete the existing set of mass spectra for this class of molecules. Thus cyclic ethers have been analyzed in the exhaust gases of a jet-stirred reactor in which the low-temperature oxidation of a series of n-alkanes was taking place. Analyzes were performed by gas chromatography coupled to mass spectrometry and to MS/MS. The second goal of this study was to derive some rules for the fragmentation of cyclic ethers in electron impact mass spectrometry and allow the identification of these species when no mass spectrum is available. PMID:24092947

  13. Mass spectra of cyclic ethers formed in the low-temperature oxidation of a series of n-alkanes.

    PubMed

    Herbinet, Olivier; Bax, Sarah; Glaude, Pierre-Alexandre; Carré, Vincent; Battin-Leclerc, Frédérique

    2011-02-01

    Cyclic ethers are important intermediate species formed during the low-temperature oxidation of hydrocarbons. Along with ketones and aldehydes, they could consequently represent a significant part of the heavy oxygenated pollutants observed in the exhaust gas of engines. Apart a few of them such as ethylene oxide and tetrahydrofuran, cyclic ethers have not been much studied and very few of them are available for calibration and identification. Electron impact mass spectra are available for very few of them, making their detection in the exhaust emissions of combustion processes very difficult. The main goal of this study was to complete the existing set of mass spectra for this class of molecules. Thus cyclic ethers have been analyzed in the exhaust gases of a jet-stirred reactor in which the low-temperature oxidation of a series of n-alkanes was taking place. Analyzes were performed by gas chromatography coupled to mass spectrometry and to MS/MS. The second goal of this study was to derive some rules for the fragmentation of cyclic ethers in electron impact mass spectrometry and allow the identification of these species when no mass spectrum is available. PMID:24092947

  14. Selective Nickel- and Manganese-Catalyzed Decarboxylative Cross Coupling of Some α,β-Unsaturated Carboxylic Acids with Cyclic Ethers

    PubMed Central

    Zhang, Jia-Xiang; Wang, Yan-Jing; Zhang, Wei; Wang, Nai-Xing; Bai, Cui-Bing; Xing, Ya-Lan; Li, Yi-He; Wen, Jia-Long

    2014-01-01

    A nickel- and manganese-catalyzed decarboxylative cross coupling of α, β-unsaturated carboxylic acids with cyclic ethers such as tetrahydrofuran and 1, 4-dioxane was developed. Oxyalkylation was achieved when nickel acetate was used as catalyst, while manganese acetate promoted the reaction of alkenylation. PMID:25502282

  15. Ambient gold-catalyzed O-vinylation of cyclic 1,3-diketone: A vinyl ether synthesis

    PubMed Central

    Xi, Yumeng; Dong, Boliang

    2013-01-01

    Summary Gold-catalyzed O-vinylation of cyclic 1,3-diketones has been achieved for the first time, which provides direct access to various vinyl ethers. A catalytic amount of copper triflate was identified as the significant additive in promoting this transformation. Both aromatic and aliphatic alkynes are suitable substrates with good to excellent yields. PMID:24367417

  16. An ether-functionalised cyclic sulfonium based ionic liquid as an electrolyte for electrochemical double layer capacitors

    NASA Astrophysics Data System (ADS)

    Neale, Alex R.; Murphy, Sinead; Goodrich, Peter; Schütter, Christoph; Hardacre, Christopher; Passerini, Stefano; Balducci, Andrea; Jacquemin, Johan

    2016-09-01

    A novel cyclic sulfonium cation-based ionic liquid (IL) with an ether-group appendage and the bis{(trifluoromethyl)sulfonyl}imide anion was synthesised and developed for electrochemical double layer capacitor (EDLC) testing. The synthesis and chemical-physical characterisation of the ether-group containing IL is reported in parallel with a similarly sized alkyl-functionalised sulfonium IL. Results of the chemical-physical measurements demonstrate how important transport properties, i.e. viscosity and conductivity, can be promoted through the introduction of the ether-functionality without impeding thermal, chemical or electrochemical stability of the IL. Although the apparent transport properties are improved relative to the alkyl-functionalised analogue, the ether-functionalised sulfonium cation-based IL exhibits moderately high viscosity, and poorer conductivity, when compared to traditional EDLC electrolytes based on organic solvents (propylene carbonate and acetonitrile). Electrochemical testing of the ether-functionalised sulfonium IL was conducted using activated carbon composite electrodes to inspect the performance of the IL as a solvent-free electrolyte for EDLC application. Good cycling stability was achieved over the studied range and the performance was comparable to other solvent-free, IL-based EDLC systems. Nevertheless, limitations of the attainable performance are primarily the result of sluggish transport properties and a restricted operative voltage of the IL, thus highlighting key aspects of this field which require further attention.

  17. Effect of temperature and pressure on the volumetric properties of branched and cyclic ethers

    SciTech Connect

    Govender, U.P.; Letcher, T.M.; Garg, S.K.; Ahluwalia, J.C.

    1996-01-01

    The densities of liquid diisopropyl ether, 1,1-dimethylethyl methyl ether, 1,1-dimethylpropyl methyl ether, tetrahydrofuran, tetrahydropyran, and 1,4-dioxane have been determined from 288.15 to 328.15 K at pressures ranging from 0.1 to 8 MPa. The molar volumes (derived from densities) have been fitted to a polynomial as a function of temperature and pressure. Where available, the results have been compared to literature values.

  18. Diastereoselective Ring-Closing Metathesis as a Means to Construct Medium-Sized Cyclic Ethers: Application to the Synthesis of a Photoactivatable Gambierol Derivative.

    PubMed

    Onodera, Yu; Hirota, Kazuaki; Suga, Yuto; Konoki, Keiichi; Yotsu-Yamashita, Mari; Sasaki, Makoto; Fuwa, Haruhiko

    2016-09-16

    This paper describes a concise synthesis of six- to eight-membered α,α'-substituted cyclic ethers by exploiting diastereoselective ring-closing metathesis (RCM) of 1,4-pentadien-3-yl ether derivatives. The RCM precursors could be efficiently prepared via a vinylation of the corresponding α-acetoxy ether derivatives using divinylzinc. Diastereoselective RCM of 1,4-pentadien-3-yl ether derivatives afforded a series of six- to eight-membered α,α'-substituted cyclic ethers with moderate to good diastereoselectivity. The stereochemical consequence of the diastereoselective RCM appeared to be dependent on the structure of the ring being forged. The diastereoselectivity of six- and seven-membered cyclic ethers appeared to be largely under kinetic control irrespective of the catalyst reactivity, whereas that of an eight-membered cyclic ether could be controlled by the catalyst reactivity. Finally, the diastereoselective RCM chemistry was applied to the synthesis of a biotin-tagged photoactivatable derivative of gambierol. PMID:27529493

  19. Transferable potentials for phase equilibria-united atom description of five- and six-membered cyclic alkanes and ethers.

    PubMed

    Keasler, Samuel J; Charan, Sophia M; Wick, Collin D; Economou, Ioannis G; Siepmann, J Ilja

    2012-09-13

    While the transferable potentials for phase equilibria-united atom (TraPPE-UA) force field has generally been successful at providing parameters that are highly transferable between different molecules, the polarity and polarizability of a given functional group can be significantly perturbed in small cyclic structures, which limits the transferability of parameters obtained for linear molecules. This has motivated us to develop a version of the TraPPE-UA force field specifically for five- and six-membered cyclic alkanes and ethers. The Lennard-Jones parameters for the methylene group obtained from cyclic alkanes are transferred to the ethers for each ring size, and those for the oxygen atom are common to all compounds for a given ring size. However, the partial charges are molecule specific and parametrized using liquid-phase dielectric constants. This model yields accurate saturated liquid densities and vapor pressures, critical temperatures and densities, normal boiling points, heat capacities, and isothermal compressibilities for the following molecules: cyclopentane, tetrahydrofuran, 1,3-dioxolane, cyclohexane, oxane, 1,4-dioxane, 1,3-dioxane, and 1,3,5-trioxane. The azeotropic behavior and separation factor for the binary mixtures of 1,3-dioxolane/cyclohexane and ethanol/1,4-dioxane are qualitively reproduced. PMID:22900670

  20. Temperature-responsive in situ nanoparticle hydrogels based on hydrophilic pendant cyclic ether modified PEG-PCL-PEG.

    PubMed

    Feng, Zujian; Zhao, Junqiang; Li, Yin; Xu, Shuxin; Zhou, Junhui; Zhang, Jianhua; Deng, Liandong; Dong, Anjie

    2016-10-20

    Thermo-sensitive injectable hydrogels based on poly(ε-caprolactone)/poly(ethylene glycol) (PCL/PEG) block copolymers have attracted considerable attention for sustained drug release and tissue engineering applications. Previously, we have reported a thermo-sensitive hydrogel of P(CL-co-TOSUO)-PEG-P(CL-co-TOSUO) (PECT) triblock copolymers modified by hydrophilic cyclic ether pendant groups 1,4,8-trioxa-[4.6]spiro-9-undecanone (TOSUO). Unfortunately, the low gel modulus of PECT (only 50-70 Pa) may limit its applications. Herein, another kind of thermogelling triblock copolymer of a pendant cyclic ether-modified caprolactonic poloxamer analog, PEG-P(CL-co-TOSUO)-PEG (PECTE), was successfully prepared by control of the hydrophilicity/hydrophobicity balance and chemical compositions of the copolymers. PECTE powder could directly disperse in water to form a stable nanoparticle (NP) aqueous dispersion and underwent sol-gel-sol transition behavior at a higher concentration with the temperature increasing from ambient or lower temperatures. Significantly, the microstructure parameters (e.g., different chemical compositions of the hydrophobic block and topology) played a critical role in the phase transition behavior. Furthermore, comparison studies on PECTE and PEG-PCL-PEG (PECE) showed that the introduction of pendant cyclic ether groups into PCL blocks could avoid unexpected ahead-of-time gelling of the PECE aqueous solution. In addition, the rheological analysis of PECTE and PECT indicated that the storage modulus of the PECTE hydrogel could be 100 times greater than that of the PECT hydrogel under the same mole ratios of TOSUO/CL and lower molecular weight. Consequently, PECTE thermal hydrogel systems are believed to be promising as in situ gel-forming biomaterials for drug delivery and tissue engineering. PMID:27546028

  1. Asymmetric Catalysis with Ethylene. Synthesis of Functionalized Chiral Enolates

    PubMed Central

    Biswas, Souvagya; Page, Jordan P.; Dewese, Kendra R.; RajanBabu, T. V.

    2016-01-01

    Trialkylsilyl enol ethers are versatile intermediates often used as enolate surrogates for the synthesis of carbonyl compounds. Yet there are no reports of broadly applicable, catalytic methods for the synthesis of chiral silyl enol ethers carrying latent functionalities useful for synthetic operations beyond the many possible reactions of the silyl enol ether moiety itself. Here we report a general procedure for highly catalytic (substrate:catalyst ratio up to 1000:1) and enantioselective (92% to 98% major enantiomer) synthesis of such compounds bearing a vinyl group at a chiral carbon at the β-position. The reactions, run under ambient conditions, use trialkylsiloxy-1,3-dienes and ethylene (1 atmosphere) as precursors, and readily available (bis-phosphine)-cobalt(II) complexes as catalysts. The silyl enolates can be readily converted into novel enantiopure vinyl triflates, a class of highly versatile cross-coupling reagents, enabling the syntheses of other enantiomerically pure, stereo-defined trisubstituted alkene intermediates not easily accessible by current methods. Examples of Kumada, Stille and Suzuki coupling reactions are illustrated. PMID:26529467

  2. Enantioselective synthesis of hindered cyclic dialkyl ethers via catalytic oxa-Michael/Michael desymmetrization†

    PubMed Central

    Corbett, Michael T.; Johnson, Jeffrey S.

    2014-01-01

    An asymmetric oxa-Michael/Michael cascade reaction of p-quinols and α,β-unsaturated aldehydes provides access to hindered dialkyl ethers. A highly enantioselective oxa-Michael addition of a tertiary alcohol precedes an intramolecular cyclohexadienone desymmetrization, which allows for the concomitant formation of four contiguous stereocenters in a single step. The highly functionalized bicyclic frameworks are rapidly obtained from simple starting materials with good diastereoselection and serve as valuable precursors for further manipulation. PMID:24683449

  3. Activation of Marginally Reactive Boron Enolates by MeLi for the Formation of Enol Phosphates and Synthesis of the Δ(9)-THC Intermediate.

    PubMed

    Kawada, Hiroki; Ikoma, Atsushi; Ogawa, Narihito; Kobayashi, Yuichi

    2015-09-18

    The addition of MeLi to boron enolates produced by the 1,4-addition of Ar2Cu(CN)Li2 to BF3·OEt2-activated enones was followed by the reaction with ClP(O)(OEt)2 to afford the corresponding enol phosphates in moderate to good yields. The scope of this method was examined with sterically hindered or electronically biased enones and/or reagents. This activation of boron enolates was successfully applied to the synthesis of the methyl ether of Δ(9)-tetrahydrocannabinol.

  4. Fatigue data for polyether ether ketone (PEEK) under fully-reversed cyclic loading

    PubMed Central

    Shrestha, Rakish; Simsiriwong, Jutima; Shamsaei, Nima

    2016-01-01

    In this article, the data obtained from the uniaxial fully-reversed fatigue experiments conducted on polyether ether ketone (PEEK), a semi-crystalline thermoplastic, are presented. The tests were performed in either strain-controlled or load-controlled mode under various levels of loading. The data are categorized into four subsets according to the type of tests, including (1) strain-controlled fatigue tests with adjusted frequency to obtain the nominal temperature rise of the specimen surface, (2) strain-controlled fatigue tests with various frequencies, (3) load-controlled fatigue tests without step loadings, and (4) load-controlled fatigue tests with step loadings. Accompanied data for each test include the fatigue life, the maximum (peak) and minimum (valley) stress–strain responses for each cycle, and the hysteresis stress–strain responses for each collected cycle in a logarithmic increment. A brief description of the experimental method is also given. PMID:26937465

  5. Fatigue data for polyether ether ketone (PEEK) under fully-reversed cyclic loading.

    PubMed

    Shrestha, Rakish; Simsiriwong, Jutima; Shamsaei, Nima

    2016-03-01

    In this article, the data obtained from the uniaxial fully-reversed fatigue experiments conducted on polyether ether ketone (PEEK), a semi-crystalline thermoplastic, are presented. The tests were performed in either strain-controlled or load-controlled mode under various levels of loading. The data are categorized into four subsets according to the type of tests, including (1) strain-controlled fatigue tests with adjusted frequency to obtain the nominal temperature rise of the specimen surface, (2) strain-controlled fatigue tests with various frequencies, (3) load-controlled fatigue tests without step loadings, and (4) load-controlled fatigue tests with step loadings. Accompanied data for each test include the fatigue life, the maximum (peak) and minimum (valley) stress-strain responses for each cycle, and the hysteresis stress-strain responses for each collected cycle in a logarithmic increment. A brief description of the experimental method is also given. PMID:26937465

  6. Phase equilibrium of binary mixtures of cyclic ethers + chlorobutane isomers: experimental measurements and SAFT-VR modeling.

    PubMed

    Giner, Beatriz; Gascón, Ignacio; Artigas, Héctor; Lafuente, Carlos; Galindo, Amparo

    2007-08-16

    The phase equilibria (experimental and modeled) of eight binary mixtures each formed by a cyclic ether (1,3-dioxolane or 1,4-dioxane) and a chlorobutane isomer (1-chlorobutane, 2-chlorobutane, 1-chloro-2-methylpropane, or 2-chloro-2-methylpropane) are presented. New experimental vapor-liquid equilibrium data at isothermal conditions (298.15, 313.15, and 328.15 K) has been obtained, and the statistical associating fluid theory for potentials of variable range (SAFT-VR) is used to model the mixtures. The results are discussed in terms of both the molecular characteristics of the pure compounds and the unlike intermolecular interactions present in the mixtures. The SAFT-VR approach is first used together with standard combining rules without adjustable parameters in order to predict the phase behavior at isothermal conditions. Good agreement between experiment and the prediction is found with such a model. Mean absolute deviations for pressures lie between 1 and 3 kPa, while for vapor phase compositions are less than 0.03 in mole fraction. However, a better agreement, can be obtained by introducing one adjustable parameter kij, which modifies the strength of the dispersion interaction between unlike components in the mixtures. This parameter is adjusted so as to model the phase equilibrium of the whole family of mixtures studied here at isothermal and isobaric conditions. We find that a unique unlike parameter kij is valid for all the studied mixtures and it is not temperature or pressure dependent. This unique transferable parameter together with the SAFT-VR approach provide a description of the vapor-liquid equilibrium of the mixtures that is in excellent agreement with the experimental data. In this case, the absolute deviations are of the order of 0.001 in mole fraction for vapor-phase compositions and less than 1 kPa for pressure.

  7. Tunable reactivity of geminal bis(silyl) enol derivatives leading to selective exo-IEDDA or Sakurai allylation with a β,γ-unsaturated ketoester.

    PubMed

    Gan, Zubao; Chu, Zhiwen; Hu, Jia; Su, Zhishan; Hu, Changwei; Gao, Lu; Song, Zhenlei

    2016-08-01

    Two contrasting pathways in a SnCl4-catalyzed reaction of geminal bis(silyl) enol derivatives with β,γ-unsaturated ketoesters have been achieved by tuning the R group in the enol moiety. While the electron-donating Bn-substituted enol ether undergoes an exo-selective inverse-electron-demand Diels-Alder (IEDDA) reaction to give dihydropyran, the electron-withdrawing Ac-substituted enol ester reacts as an allylsilane to provide a Sakurai-allylated product with predominant syn-selectivity. PMID:27457733

  8. Short-range solvation patterns of pentachlorophenol, triethylamine, and their reaction products by cyclic ethers in cyclohexane

    NASA Astrophysics Data System (ADS)

    Van Camp, Sister Mary Josepha; Morris, Shawn; Mudge, Annmarie; Points, Richard; Knight, Jodi B.; Schullery, Stephen E.; Scott, Ronald M.

    1998-07-01

    The proton-transfer indicator reaction method is applied to the pentachlorophenol-triethylamine proton-transfer equilibrium KPT undergoing solvation by tetrahydropyran, 1,3-dioxane, and 1,4-dioxane in bulk cyclohexane. A predicted decrease in KPT occurs owing to hydrogen bonding solvation of the free phenol upon increasing ether concentration. However, the data unexpectedly suggest that hydrogen bonding solvation by the ethers to the proton of the proton-transfer adduct also occurs.

  9. Chiral Sulfinamide/Achiral Sulfonic Acid Co-Catalyzed Enantioselective Protonation of Enol Silanes

    PubMed Central

    Beck, Elizabeth M.; Hyde, Alan M.

    2011-01-01

    The application of chiral sulfinamides and achiral sulfonic acids as a co-catalyst system for enantioselective protonation reactions is described. Structurally simple, easily accessible sulfinamides were found to induce moderate-to-high ee's in the formation of 2-aryl-substituted cycloalkanones from the corresponding trimethylsilyl enol ethers. PMID:21786775

  10. Flexible Cyclic Ethers/Polyethers as Novel P2-Ligands for HIV-1 Protease Inhibitors: Design, Synthesis, Biological Evaluation, and Protein-Ligand X-Ray Studies

    SciTech Connect

    Ghosh, Arun; Gemma, Sandra; Baldridge, Abigal; Wang, Yuan-Fang; Kovalevsky, Andrey; Koh, Yashiro; Weber, Irene; Mitsuya, Hiroaki

    2008-12-05

    We report the design, synthesis, and biological evaluation of a series of novel HIV-1 protease inhibitors. The inhibitors incorporate stereochemically defined flexible cyclic ethers/polyethers as high affinity P2-ligands. Inhibitors containing small ring 1,3-dioxacycloalkanes have shown potent enzyme inhibitory and antiviral activity. Inhibitors 3d and 3h are the most active inhibitors. Inhibitor 3d maintains excellent potency against a variety of multi-PI-resistant clinical strains. Our structure-activity studies indicate that the ring size, stereochemistry, and position of oxygens are important for the observed activity. Optically active synthesis of 1,3-dioxepan-5-ol along with the syntheses of various cyclic ether and polyether ligands have been described. A protein-ligand X-ray crystal structure of 3d-bound HIV-1 protease was determined. The structure revealed that the P2-ligand makes extensive interactions including hydrogen bonding with the protease backbone in the S2-site. In addition, the P2-ligand in 3d forms a unique water-mediated interaction with the NH of Gly-48.

  11. Esterification of bio-oil from mallee (Eucalyptus loxophleba ssp. gratiae) leaves with a solid acid catalyst: Conversion of the cyclic ether and terpenoids into hydrocarbons.

    PubMed

    Hu, Xun; Gunawan, Richard; Mourant, Daniel; Wang, Yi; Lievens, Caroline; Chaiwat, Weerawut; Wu, Liping; Li, Chun-Zhu

    2012-11-01

    Bio-oil from pyrolysis of mallee (Eucalyptus loxophleba ssp. gratiae) leaves differs from that obtained with wood by its content of cyclic ethers, terpenoids and N-containing organic compounds. Upgrading of the leaf bio-oil in methanol with a solid acid catalyst was investigated and it was found that the N-containing organics in the bio-oil lead to deactivation of the catalyst in the initial stage of exposure and have to be removed via employing high catalyst loading to allow the occurrence of other acid-catalysed reactions. Eucalyptol, the main cyclic ether in the bio-oil, could be converted into the aromatic hydrocarbon, p-cymene, through a series of intermediates including α-terpineol, terpinolene, and α-terpinene. Various steps such as ring-opening, dehydration, isomerisation, and aromatization were involved in the conversion of eucalyptol. The terpenoids in bio-oil could also be converted into aromatic hydrocarbons that can serve as starting materials for the synthesis of fine chemicals, via the similar processes.

  12. Coupling Reaction of Enol Derivatives with Silyl Ketene Acetals Catalyzed by Gallium Trihalides.

    PubMed

    Nishimoto, Yoshihiro; Kita, Yuji; Ueda, Hiroki; Imaoka, Hiroto; Chiba, Kouji; Yasuda, Makoto; Baba, Akio

    2016-08-01

    A cross-coupling reaction between enol derivatives and silyl ketene acetals catalyzed by GaBr3 took place to give the corresponding α-alkenyl esters. GaBr3 showed the most effective catalytic ability, whereas other metal salts such as BF3 ⋅OEt2 , AlCl3 , PdCl2 , and lanthanide triflates were not effective. Various types of enol ethers and vinyl carboxylates as enol derivatives are amenable to this coupling. The scope of the reaction with silyl ketene acetals was also broad. We successfully observed an alkylgallium intermediate by using NMR spectroscopy, suggesting a mechanism involving anti-carbogallation among GaBr3 , an enol derivative, and a silyl ketene acetal, followed by syn-β-alkoxy elimination from the alkylgallium. Based on kinetic studies, the turnover-limiting step of the reaction using a vinyl ether and a vinyl carboxylate involved syn-β-alkoxy elimination and anti-carbogallation, respectively. Therefore, the leaving group had a significant effect on the progress of the reaction. Theoretical calculations analysis suggest that the moderate Lewis acidity of gallium would contribute to a flexible conformational change of the alkylgallium intermediate and to the cleavage of the carbon-oxygen bond in the β-alkoxy elimination process, which is the turnover-limiting step in the reaction between a vinyl ether and a silyl ketene acetal. PMID:27400389

  13. Coupling Reaction of Enol Derivatives with Silyl Ketene Acetals Catalyzed by Gallium Trihalides.

    PubMed

    Nishimoto, Yoshihiro; Kita, Yuji; Ueda, Hiroki; Imaoka, Hiroto; Chiba, Kouji; Yasuda, Makoto; Baba, Akio

    2016-08-01

    A cross-coupling reaction between enol derivatives and silyl ketene acetals catalyzed by GaBr3 took place to give the corresponding α-alkenyl esters. GaBr3 showed the most effective catalytic ability, whereas other metal salts such as BF3 ⋅OEt2 , AlCl3 , PdCl2 , and lanthanide triflates were not effective. Various types of enol ethers and vinyl carboxylates as enol derivatives are amenable to this coupling. The scope of the reaction with silyl ketene acetals was also broad. We successfully observed an alkylgallium intermediate by using NMR spectroscopy, suggesting a mechanism involving anti-carbogallation among GaBr3 , an enol derivative, and a silyl ketene acetal, followed by syn-β-alkoxy elimination from the alkylgallium. Based on kinetic studies, the turnover-limiting step of the reaction using a vinyl ether and a vinyl carboxylate involved syn-β-alkoxy elimination and anti-carbogallation, respectively. Therefore, the leaving group had a significant effect on the progress of the reaction. Theoretical calculations analysis suggest that the moderate Lewis acidity of gallium would contribute to a flexible conformational change of the alkylgallium intermediate and to the cleavage of the carbon-oxygen bond in the β-alkoxy elimination process, which is the turnover-limiting step in the reaction between a vinyl ether and a silyl ketene acetal.

  14. The evolution of the structural, vibrational and electronic properties of the cyclic ethers - on ring size. An ab initio study

    NASA Astrophysics Data System (ADS)

    Ford, Thomas A.

    2014-09-01

    The molecular structures, vibrational spectra and atomic charges of the alicyclic ethers containing from two to five carbon atoms have been determined by means of ab initio calculations, at the level of second order Møller-Plesset perturbation theory and using Dunning's augmented correlation-consistent polarized valence triple-zeta basis set. Two isomers of the oxetane, tetrahydrofuran and tetrahydropyran molecules have been identified and their relative energies determined. Structural properties, such as the COC bond angles and the CH bond lengths, are found to increase steadily with increasing ring size and with decreasing ionization energy. The mean CH2 stretching and bending wavenumbers exhibit the reverse behaviour, while the mean wavenumbers of the CH2 wagging and twisting modes follow the same trend as the structural features. The ring mode wavenumbers vary in a less regular way. The charges of the oxygen, α-carbon and axial and equatorial α- and β-hydrogen atoms also do not show systematic dependences on ring size or ionization energy. The trends in the values of these properties have been rationalized.

  15. Electronic effects on keto-enol tautomerism of p-substituted aryl-1,3-diketone malonates

    NASA Astrophysics Data System (ADS)

    Jiménez-Cruz, Federico; Ríos-Olivares, Hector; García-Gutiérrez, José Luis; Mar, Lubanski Fragoza

    2015-12-01

    Electronic effects on keto-enol tautomerism of 1-(p-substituted aryl)-1,3-diketone malonates 1-10 were determined and established by NMR-Hammett linear free energy relationships. In addition, tautomeric equilibrium constants were determined for the title compounds by 1H NMR in DMSO-d6, showing an increasing to diketo tautomer with the increasing in the temperature. In this context, the enol form becomes less stable with increasing temperature suggesting that the intramolecular hydrogen bonding of the cis enol-keto form are increasingly broken at higher temperatures. In general, the enolic form (rather than the keto) is the most stable conformation due to its six member cyclic structure fulfilled by an internal O-H … O hydrogen bond.

  16. Stereoselective Formation of Fully Substituted Ketone Enolates.

    PubMed

    Haimov, Elvira; Nairoukh, Zackaria; Shterenberg, Alexander; Berkovitz, Tiran; Jamison, Timothy F; Marek, Ilan

    2016-04-25

    The application of stereochemically defined acyclic fully substituted enolates of ketones to the enantioselective synthesis of quaternary carbon stereocenters would be highly valuable. Herein, we describe an approach leading to the formation of several new stereogenic centers through a combined metalation-addition of a carbonyl-carbamoyl transfer to reveal in situ stereodefined α,α-disubstituted enolates of ketone as a single stereoisomer. This approach could produce a series of aldol and Mannich products from enol carbamate with excellent diastereomeric ratios. PMID:27027778

  17. Stereoselective Formation of Fully Substituted Ketone Enolates.

    PubMed

    Haimov, Elvira; Nairoukh, Zackaria; Shterenberg, Alexander; Berkovitz, Tiran; Jamison, Timothy F; Marek, Ilan

    2016-04-25

    The application of stereochemically defined acyclic fully substituted enolates of ketones to the enantioselective synthesis of quaternary carbon stereocenters would be highly valuable. Herein, we describe an approach leading to the formation of several new stereogenic centers through a combined metalation-addition of a carbonyl-carbamoyl transfer to reveal in situ stereodefined α,α-disubstituted enolates of ketone as a single stereoisomer. This approach could produce a series of aldol and Mannich products from enol carbamate with excellent diastereomeric ratios.

  18. Calmodulin Regulates Human Ether à Go-Go 1 (hEAG1) Potassium Channels through Interactions of the Eag Domain with the Cyclic Nucleotide Binding Homology Domain*

    PubMed Central

    Lörinczi, Eva; Helliwell, Matthew; Finch, Alina; Stansfeld, Phillip J.; Davies, Noel W.; Mahaut-Smith, Martyn; Muskett, Frederick W.; Mitcheson, John S.

    2016-01-01

    The ether à go-go family of voltage-gated potassium channels is structurally distinct. The N terminus contains an eag domain (eagD) that contains a Per-Arnt-Sim (PAS) domain that is preceded by a conserved sequence of 25–27 amino acids known as the PAS-cap. The C terminus contains a region with homology to cyclic nucleotide binding domains (cNBHD), which is directly linked to the channel pore. The human EAG1 (hEAG1) channel is remarkably sensitive to inhibition by intracellular calcium (Ca2+i) through binding of Ca2+-calmodulin to three sites adjacent to the eagD and cNBHD. Here, we show that the eagD and cNBHD interact to modulate Ca2+-calmodulin as well as voltage-dependent gating. Sustained elevation of Ca2+i resulted in an initial profound inhibition of hEAG1 currents, which was followed by a phase when current amplitudes partially recovered, but activation gating was slowed and shifted to depolarized potentials. Deletion of either the eagD or cNBHD abolished the inhibition by Ca2+i. However, deletion of just the PAS-cap resulted in a >15-fold potentiation in response to elevated Ca2+i. Mutations of residues at the interface between the eagD and cNBHD have been linked to human cancer. Glu-600 on the cNBHD, when substituted with residues with a larger volume, resulted in hEAG1 currents that were profoundly potentiated by Ca2+i in a manner similar to the ΔPAS-cap mutant. These findings provide the first evidence that eagD and cNBHD interactions are regulating Ca2+-dependent gating and indicate that the binding of the PAS-cap with the cNBHD is required for the closure of the channels upon CaM binding. PMID:27325704

  19. Propenyl ether monomers for photopolymerization

    DOEpatents

    Crivello, James V.

    1996-01-01

    Propenyl ether monomers of formula V A(OCH.dbd.CHCH.sub.3).sub.n wherein n is an integer from one to six and A is selected from cyclic ethers, polyether and alkanes are disclosed. The monomers are readily polymerized in the presence of cationic photoinitiators, when exposed to actinic radiation, to form poly(propenyl ethers) that are useful for coatings, sealants, varnishes and adhesives. Compositions for preparing polymeric coatings comprising the compounds of formula V together with particular cationic photoinitiators are also disclosed, as are processes for making the monomers from allyl halides and readily available alcohols. The process involves rearranging the resulting allyl ethers to propenyl ethers.

  20. Propenyl ether monomers for photopolymerization

    DOEpatents

    Crivello, J.V.

    1996-10-22

    Propenyl ether monomers of formula A(OCH{double_bond}CHCH{sub 3}){sub n} wherein n is an integer from one to six and A is selected from cyclic ethers, polyether and alkanes are disclosed. The monomers are readily polymerized in the presence of cationic photoinitiators, when exposed to actinic radiation, to form poly(propenyl ethers) that are useful for coatings, sealants, varnishes and adhesives. Compositions for preparing polymeric coatings comprising the compounds of the above formula together with particular cationic photoinitiators are also disclosed, as are processes for making the monomers from allyl halides and readily available alcohols. The process involves rearranging the resulting allyl ethers to propenyl ethers.

  1. Lithium Hexamethyldisilazide-Mediated Enolizations: Influence of Triethylamine on E/Z Selectivities and Enolate Reactivities

    PubMed Central

    Godenschwager, Peter

    2010-01-01

    Lithium hexamethyldisilazide (LiHMDS) in triethylamine (Et3N)/toluene is shown to enolize acyclic ketones and esters rapidly and with high E/Z selectivity. Mechanistic studies reveal a dimer-based mechanism consistent with previous studies of LiHMDS/Et3N. E/Z equilibration occurs when <2.0 equiv of LiHMDS are used. Studies of the aldol condensation and Ireland-Claisen rearrangement of the resulting Et3N-solvated enolates show higher and often complementary diastereoselectivities when compared with analogous reactions in THF. The Et3N-solvated enolates also display a marked (20-fold) acceleration of the Ireland-Claisen rearrangement with evidence of autocatalysis. A possible importance of amine-solvated enolates is discussed. PMID:18557616

  2. Tandem Bond-Forming Reactions of 1-Alkynyl Ethers.

    PubMed

    Minehan, Thomas G

    2016-06-21

    Electron-rich alkynes, such as ynamines, ynamides, and ynol ethers, are functional groups that possess significant potential in organic chemistry for the formation of carbon-carbon bonds. While the synthetic utility of ynamides has recently been expanded considerably, 1-alkynyl ethers, which possess many of the reactivity features of ynamides, have traditionally been far less investigated because of concerns about their stability. Like ynamides, ynol ethers are relatively unhindered to approach by functional groups present in the same or different molecules because of their linear geometry, and they can potentially form up to four new bonds in a single transformation. Ynol ethers also possess unique reactivity features that make them complementary to ynamides. Research over the past decade has shown that ynol ethers formed in situ from stable precursors engage in a variety of useful carbon-carbon bond-forming processes. Upon formation at -78 °C, allyl alkynyl ethers undergo a rapid [3,3]-sigmatropic rearrangement to form allyl ketene intermediates, which may be trapped with alcohol or amine nucleophiles to form γ,δ-unsaturated carboxylic acid derivatives. The process is stereospecific, takes place in minutes at cryogenic temperatures, and affords products containing (quaternary) stereogenic carbon atoms. Trapping of the intermediate allyl ketene with carbonyl compounds, epoxides, or oxetanes instead leads to complex α-functionalized β-, γ-, or δ-lactones, respectively. [3,3]-Sigmatropic rearrangement of benzyl alkynyl ethers also takes place at temperatures ranging from -78 to 60 °C to afford substituted 2-indanones via intramolecular carbocyclization of the ketene intermediate. tert-Butyl alkynyl ethers containing pendant di- and trisubstituted alkenes and enol ethers are stable to chromatographic isolation and undergo a retro-ene/[2 + 2] cycloaddition reaction upon mild thermolysis (90 °C) to afford cis-fused cyclobutanones and donor

  3. Stereoelectronic requirements for optimal hydrogen-bond-catalyzed enolization.

    PubMed

    Pápai, Imre; Hamza, Andrea; Pihko, Petri M; Wierenga, Rik K

    2011-03-01

    Protein crystallographic analysis of the active sites of enolizing enzymes and structural analysis of hydrogen-bonded carbonyl compounds in small molecule crystal structures, complemented by quantum chemical calculations on related model enolization reactions, suggest a new stereoelectronic model that accounts for the observed out-of-plane orientation of hydrogen-bond donors (HBDs) in the oxyanion holes of enolizing enzymes. The computational results reveal that the lone-pair directionality of HBDs characteristic for hydrogen-bonded carbonyls is reduced upon enolization, and the enolate displays almost no directional preference for hydrogen bonding. Positioning the HBDs perpendicular to the carbonyl plane induces strain in the catalyst-substrate complex, which is released upon enolization, resulting in more favorable kinetics and thermodynamics than the in-plane arrangement of HBDs. PMID:21308811

  4. Oxidative Coupling of Enolates, Enol Silanes and Enamines: Methods and Natural Product Synthesis

    PubMed Central

    Guo, Fenghai; Clift, Michael D.

    2013-01-01

    The oxidative coupling of enolates, enol silanes, and enamines provides a direct method for the construction of useful 1,4-dicarbonyl synthons. Despite being first reported in 1935, with subsequent important advances beginning in the 1970’s, the development of this powerful reaction into a reliable methodology was somewhat limited. In recent years, there have been a number of reports from several research groups demonstrating advances in several neglected areas of oxidative coupling. This microreview summarizes these new advances in methodology and provides an overview of recent natural product syntheses that showcase the power of these transformations. PMID:23471479

  5. Spectral-structural effects of the keto-enol-enolate and phenol-phenolate equilibria of oxyluciferin.

    PubMed

    Naumov, Pance; Kochunnoonny, Manoj

    2010-08-25

    The effects of environmental polarity on the enolization of the keto form and the deprotonation of the enol, and the role of the neutral and ionized 6'-OH group in the fluorescence of the firefly emitter, oxyluciferin, were assessed through a detailed study of the structure and absorption and fluorescence spectra of its 6'-dehydroxylated analogue. It was found that the deprotonated 6'-O(-) group is a necessary, albeit insufficient, factor in accounting for the observed yellow-green and red emissions of oxyluciferin. Its negative charge is essential for effective excited-state charge transfer, which lowers the emission energy and broadens the emission spectrum. Deprotonation of the 6'-OH group changes its effect on the emission energy from blue- to red-shifting. Furthermore, the combination of these opposite effects and resonance stabilization of the phenolate-keto form causes switching of the order of maximum emission wavelengths of the three species involved in the keto-enol-enolate equilibrium from enol < keto < enolate in absence of 6'-OH to keto < enol < enolate with 6'-OH, to enol < enolate < keto with 6'-O(-). If only the keto-enol-enolate equilibrium is considered, solvents of medium polarity are the most effective in decreasing the excited-state energy. Polar or very polar environments also stimulate shift of the ground-state equilibrium toward the enol form. Under such circumstances, the enol group can be partly or completely deprotonated in the ground state or from the excited state: a polar environment facilitates the ionization, while a less polar environment requires the presence of a stronger base. In the absence of bases, the ground-state keto form exists only in solvents of very weak to medium polarity, but with stronger bases, it can also exist in a nonpolar or very weakly polar environment, usually together with the enolate anion. The phenol-enolate form of oxyluciferin, a species that could not be experimentally detected prior to this study, was

  6. Lactate Dehydrogenase Catalysis: Roles of Keto, Hydrated, and Enol Pyruvate

    ERIC Educational Resources Information Center

    Meany, J. E.

    2007-01-01

    Many carbonyl substrates of oxidoreductase enzymes undergo hydration and enolization so that these substrate systems are partitioned between keto, hydrated (gem-diol), and enol forms in aqueous solution. Some oxidoreductase enzymes are subject to inhibition by high concentrations of substrate. For such enzymes, two questions arise pertaining to…

  7. Room temperature rechargeable magnesium batteries with sulfur-containing composite cathodes prepared from elemental sulfur and bis(alkenyl) compound having a cyclic or linear ether unit

    NASA Astrophysics Data System (ADS)

    Itaoka, Kanae; Kim, In-Tae; Yamabuki, Kazuhiro; Yoshimoto, Nobuko; Tsutsumi, Hiromori

    2015-11-01

    Room temperature rechargeable magnesium (Mg) batteries are constructed from Mg as a negative material, sulfur (S)-containing composite prepared from elemental sulfur and the bis(alkenyl) compound having a crown ether unit (BUMB18C6) or linear ether unit (UOEE) as a positive material and the simple electrolyte (0.7 mol dm-3 Mg[N(SO2CF3)2]2-triglyme (G3) solution). The reaction between molten S and the bis(alkenyl) compound (BUMB18C6 or UOEE) provides the sulfur-containing composite, S-BUMB18C6 or S-UOEE. Both of the sulfur-containing composites are electrochemically active in the Mg salt-based electrolyte, acetonitrile- or G3- Mg[N(SO2CF3)2]2 electrolyte. The first discharge capacity of the test cells with the sulfur-containing composite is 460 Ah kg-1 (per the weight of sulfur in the composite) with the S-BUMB18C6 electrode and 495 Ah kg-1 with the S-UOEE electrode. According to the continuous charge-discharge cycle tests (at 10th cycle), the discharge capacity of the test cell with the S-BUMB18C6 electrode (68.1 Ah kg-1) is higher than that with the S-UOEE electrode (0.18 Ah kg-1). The crown ether units in the S-BUMB18C6 composite may create ion-conducting paths in the cathode, prevent rise in the internal resistance of the cathode, and provide better cycle performance of the test cells with the S-BUMB18C6 composite electrode than that with the S-UOEE electrode.

  8. Synthesis, optical and electrochemical properties of substituted 2-cinnamoyl-1, 3-indandione O-methyl ethers

    NASA Astrophysics Data System (ADS)

    Malina, Ilze; Kampars, Valdis; Turovska, Baiba

    2016-07-01

    Seven new 2-cinnamoyl-1,3-indandione (2CID) O-methyl ethers with different substituents (R = -H, -CH3, -OCH3, -N(C6H5)2, -N(CH2CH2CN)2, julolidyl, -N(CH3)2) in 4-position of the cinnamoyl moiety were synthesized. The methylation with dimethylsulfate occurred at the oxygen atom of the exocyclic enol group with high selectivity. The synthesized compounds were characterized by 1H, 13C NMR, IR, UV-Vis and luminescence spectroscopy, their electrochemical properties were investigated by cyclic voltammetry. The obtained results indicates that introducing an electron donating substituents in the 4-position of cinnamoyl moiety facilitates electrochemical oxidation, remarkably shifts absorption and emission bands to longer wavelengths, simultaneously increases extinction coefficient (ε). O-methyl ethers with strong electron donating groups (R = -N(C6H5)2, -N(CH2CH2CN)2, julolidyl, -N(CH3)2) in molecule are characterized by luminescence with maximum in range from 547 to 647 nm and absolute photoluminescence quantum yields from 0.02 to 0.32. Quantum yield (QY) of chromophore containing julolidyl fragment is solvent dependent. It was 0.32 in chloroform and decreased in other polar (ethanol, acetone) solvents.

  9. Isolation and structure determination of the unstable 13 2, 17 3-Cyclopheophorbide a enol from recent sediments

    NASA Astrophysics Data System (ADS)

    Ocampo, Rubén; Sachs, Julian P.; Repeta, Daniel J.

    1999-11-01

    We observed that the unstable 13 2, 17 3-cyclopheophorbide a enol is one of the most abundant pigments in recent sediments (Black Sea, Mediterranean Sea, Peru margin) and here we report its isolation and structure determination (high-performance liquid chromatography, ultraviolet-visible spectrometry, mass spectrometry, and nuclear magnetic resonance). This enol has been considered as the precusor of sedimentary chlorins and porphyrins bearing either a seven + five- or a seven-membered ring system. Analysis of sediment trap samples collected from the Peru Upwelling area revealed relatively high concentrations of 13 2, 17 3-cyclopheophorbide a enol in trap samples containing high concentrations of metabolically derived carotenoid transformation products. The abundance of 13 2, 17 3-cyclopheophorbide a enol in sediment trap samples and recent sediments suggests that formation of an exocyclic seven-membered ring is a major diagenetic pathway for chlorophylls. Biologically mediated transformations of chlorophylls can therefore yield products not included in the classical Triebs degradation scheme for cyclic tetrapyrroles.

  10. Identification of a 5-[3-phenyl-(2-cyclic-ether)-methylether]-4-aminopyrrolo[2,3-d]pyrimidine series of IGF-1R inhibitors.

    PubMed

    Stauffer, Frédéric; Cowan-Jacob, Sandra W; Scheufler, Clemens; Furet, Pascal

    2016-04-15

    We report structure-guided modifications of the benzyloxy substituent of the Insulin-like Growth Factor-1 Receptor (IGF-1R) inhibitor NVP-AEW541. This chemical group has been shown to confer selectivity against other protein kinases but at the expense of a metabolism liability. X-ray crystallography has revealed that the benzyloxy moiety interacts with a lysine cation of the IGF-1R kinase domain via its ether function and its aromatic π-system and is nicely embedded in an induced hydrophobic pocket. We show that 1,4-diethers displaying an adequate hydrophobic and constrained shape are advantageous benzyloxy replacements. A single digit nanomolar inhibitor (compound 20, IC50=8.9 nM) was identified following this approach.

  11. Keto-enol tautomerism in estrogen hormone. A theoretical study

    NASA Astrophysics Data System (ADS)

    Jameh-Bozorghi, Saeed; Shirani, Hossein; Ghaempanah, Aram; Ghapanvari, Hamed

    2015-01-01

    The HF/6-311+G** calculation was used to investigate Keto-Enol tautomerism of Estrogen Hormone. Molecular geometries of keto, enol and transition state of this reaction were optimized and NBO calculations were performed. These calculation results showed that activation energy (Ea) of Keto-Enol tautomerization of Estrogen is 118.65 Kcal mol-1. Energetic study at B3LYP/6-311+G** level of theory revealed that keto tautomer is more stable structure. NBO analysis results have a good agreements with optimized geometries and experimental data.

  12. [Asymmetric intramolecular conjugate addition of chiral enolates via non-equilibrium].

    PubMed

    Monguchi, Daiki

    2006-08-01

    Optically active alpha,alpha-disubstituted alpha-amino acids belong to an important class of unnatural amino acids. Since the synthesis of such amino acids involves the creation of a quaternary stereocenter, methods for their synthesis have been extensively studied. We have reported that N-t-butoxycarbonyl(Boc)-N-methoxymethyl(MOM)-amino acid derivatives undergo asymmetric alpha-alkylation in up to 93% ee. Original chiral information on an amino acid is preserved in axially chiral enolate intermediates, and thus asymmetric induction is achieved without the aid of external chiral sources (i.e., memory of chirality). Recently, we have reported a new protocol for the asymmetric cyclization of amino acid derivatives, which enables straightforward synthesis of cyclic amino acids with a tetrasubstituted carbon center from the usual alpha-amino acids in up to 98% ee. Here we report the asymmetric construction of highly substituted chiral nitrogen heterocycles via intramolecular conjugate addition of chiral enolates generated from N-Boc-N-alkylylamino acid derivatives. This method is applicable to the asymmetric construction of pyrrolidine, piperidine, tetrahydroisoquinoline, and indoline derivatives with contiguous quaternary and tertiary stereocenters.

  13. A new alternative to expandable pedicle screws: Expandable poly-ether-ether-ketone shell.

    PubMed

    Demir, Teyfik

    2015-05-01

    Screw pullout is a very common problem in the fixation of sacrum with pedicle screws. The principal cause of this problem is that the cyclic micro motions in the fixation of sacrum are higher than the other regions of the vertebrae that limit the osteo-integration between bone and screw. In addition to that, the bone quality is very poor at sacrum region. This study investigated a possible solution to the pullout problem without the expandable screws' handicaps. Newly designed poly-ether-ether-ketone expandable shell and classical pedicle screws were biomechanically compared. Torsion test, pullout tests, fatigue tests, flexion/extension moment test, axial gripping capacity tests and torsional gripping capacity tests were conducted in accordance with ASTM F543, F1798 and F1717. Standard polyurethane foam and calf vertebrae were used as embedding medium for pullout tests. Classical pedicle screw pullout load on polyurethane foam was 564.8 N compared to the failure load for calf vertebrae's 1264 N. Under the same test conditions, expandable poly-ether-ether-ketone shell system's pullout loads from polyurethane foam and calf vertebrae were 1196.3 and 1890 N, respectively. The pullout values for expandable poly-ether-ether-ketone shell were 33% and 53% higher than classical pedicle screw on polyurethane foam and calf vertebrae, respectively. The expandable poly-ether-ether-ketone shell exhibited endurance on its 90% of yield load. Contrary to poly-ether-ether-ketone shell, classical pedicle screw exhibited endurance on 70% of its yield load. Expandable poly-ether-ether-ketone shell exhibited much higher pullout performance than classical pedicle screw. Fatigue performance of expandable poly-ether-ether-ketone shell is also higher than classical pedicle screw due to damping the micro motion capacity of the poly-ether-ether-ketone. Expandable poly-ether-ether-ketone shell is a safe alternative to all other expandable pedicle screw systems on mechanical perspective.

  14. A new alternative to expandable pedicle screws: Expandable poly-ether-ether-ketone shell.

    PubMed

    Demir, Teyfik

    2015-05-01

    Screw pullout is a very common problem in the fixation of sacrum with pedicle screws. The principal cause of this problem is that the cyclic micro motions in the fixation of sacrum are higher than the other regions of the vertebrae that limit the osteo-integration between bone and screw. In addition to that, the bone quality is very poor at sacrum region. This study investigated a possible solution to the pullout problem without the expandable screws' handicaps. Newly designed poly-ether-ether-ketone expandable shell and classical pedicle screws were biomechanically compared. Torsion test, pullout tests, fatigue tests, flexion/extension moment test, axial gripping capacity tests and torsional gripping capacity tests were conducted in accordance with ASTM F543, F1798 and F1717. Standard polyurethane foam and calf vertebrae were used as embedding medium for pullout tests. Classical pedicle screw pullout load on polyurethane foam was 564.8 N compared to the failure load for calf vertebrae's 1264 N. Under the same test conditions, expandable poly-ether-ether-ketone shell system's pullout loads from polyurethane foam and calf vertebrae were 1196.3 and 1890 N, respectively. The pullout values for expandable poly-ether-ether-ketone shell were 33% and 53% higher than classical pedicle screw on polyurethane foam and calf vertebrae, respectively. The expandable poly-ether-ether-ketone shell exhibited endurance on its 90% of yield load. Contrary to poly-ether-ether-ketone shell, classical pedicle screw exhibited endurance on 70% of its yield load. Expandable poly-ether-ether-ketone shell exhibited much higher pullout performance than classical pedicle screw. Fatigue performance of expandable poly-ether-ether-ketone shell is also higher than classical pedicle screw due to damping the micro motion capacity of the poly-ether-ether-ketone. Expandable poly-ether-ether-ketone shell is a safe alternative to all other expandable pedicle screw systems on mechanical perspective

  15. Ether production

    SciTech Connect

    Harandi, M.N.; Owen, H.

    1991-05-14

    This patent describes a multistage process for etherifying a mixed C{sub 4} + olefinic hydrocarbon feedstock containing isoalkene. It comprises: contacting the olefinic feedstock and aliphatic alcohol in a first reaction stage under partial etherification conditions with a regenerable inorganic metal oxide acid solid catalyst to convert a major amount of the isoalkene to C{sub 5} + tertiary-alkyl ether; recovering a reactant effluent from the first stage containing ether product, unreacted alcohol and unreacted olefin including isoalkene; charging the first stage effluent to a second stage catalytic distillation column containing solid acid resin etherification catalyst in a plurality of fixed bed catalysis-distillation zones to complete substantially full etherification of isoalkene; recovering C{sub 5} + ether as a liquid from the catalytic distillation column; regenerating the first stage catalyst to remove feedstock impurity and coke and to acid activity; and continuing ether production with regenerated catalyst.

  16. Enantioselective synthesis of allenylenol silyl ethers via chiral lithium amide mediated reduction of ynenoyl silanes and their Diels-Alder reactions.

    PubMed

    Sasaki, Michiko; Kondo, Yasuhiro; Moto-ishi, Ta-ichi; Kawahata, Masatoshi; Yamaguchi, Kentaro; Takeda, Kei

    2015-03-01

    An enantioselective Meerwein-Ponndorf-Verley-type reduction of ynenoylsilanes by a chiral lithium amide followed by a Brook rearrangement and anti-mode protonation across conjugated 1,3-enynes provides allene derivatives bearing a 2-siloxyvinyl moiety in high enantioselectivity. The E/Z geometry of enol silyl ethers is controlled by the geometry of the starting enyne moiety. Thus, (E)- and (Z)-enol silyl ethers are obtained from (Z)- and (E)-ynenoylsilans, respectively. The 2-siloxyvinylallene products can participate in Diels-Alder reactions with reactive dienophiles such as PTAD, which can be achieved in a one-pot operation from ynenoylsilanes.

  17. Substituent Effects on Keto-Enol Equilibria Using NMR Spectroscopy

    ERIC Educational Resources Information Center

    Manbeck, Kimberly A.; Boaz, Nicholas C.; Bair, Nathaniel C.; Sanders, Allix M. S.; Marsh, Anderson L.

    2011-01-01

    In this extension to a classic physical chemistry experiment, students record the proton nuclear magnetic resonance spectra of the [beta]-diketones 2,4-pentanedione, 3-methyl-2,4-pentanedione, and 3-chloro-2,4-pentanedione to investigate the effect of substituents on keto-enol tautomerization equilibria. From the integrated intensities of keto and…

  18. First Isolation and Characterization of the Highly Coordinated Group 14 Enolates: Effects of the Coordination Controls on the Geometry and Tautomerization of Germyl Enolates.

    PubMed

    Konishi, Akihito; Minami, Yohei; Hosoi, Takahisa; Chiba, Kouji; Yasuda, Makoto

    2016-08-26

    The Group 14 enolates play an important part in many organic reactions. Herein, the reduction of an α-bromo ketone with germanium(II) salts cleanly afforded the corresponding germyl enolate as an isolatable species. This experimental reductive generation of a germyl enolate enabled us to characterize both C- and O-bound tautomers derived from an identical precursor and to unveil the tautomeric mechanisms, including the kinetic parameters and the relative stability of these tautomers, along with confirmation from DFT calculations. Moreover, the highly coordinated germyl enolates were isolated by a stabilization process induced by adding ligands. All products were characterized by NMR spectroscopy and X-ray crystallography. PMID:27377796

  19. Tetrabromodiphenyl ether

    Integrated Risk Information System (IRIS)

    Tetrabromodiphenyl ether ; CASRN 40088 - 47 - 9 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 Noncar

  20. Pentabromodiphenyl ether

    Integrated Risk Information System (IRIS)

    Pentabromodiphenyl ether ; CASRN 32534 - 81 - 9 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 Noncar

  1. Hexabromodiphenyl ether

    Integrated Risk Information System (IRIS)

    Hexabromodiphenyl ether ; CASRN 36483 - 60 - 0 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 Noncarc

  2. Ethyl ether

    Integrated Risk Information System (IRIS)

    Ethyl ether ; CASRN 60 - 29 - 7 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 Effect

  3. Octabromodiphenyl ether

    Integrated Risk Information System (IRIS)

    Octabromodiphenyl ether ; CASRN 32536 - 52 - 0 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 Noncarc

  4. Tribromodiphenyl ether

    Integrated Risk Information System (IRIS)

    Tribromodiphenyl ether ; CASRN 49690 - 94 - 0 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 Noncarci

  5. Nonabromodiphenyl ether

    Integrated Risk Information System (IRIS)

    Nonabromodiphenyl ether ; CASRN 63936 - 56 - 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 Noncarc

  6. Process for making propenyl ethers and photopolymerizable compositions containing them

    DOEpatents

    Crivello, James V.

    1996-01-01

    Propenyl ether monomers of formula V A(OCH.dbd.CHCH.sub.3).sub.n wherein n is an integer from one to six and A is selected from cyclic ethers, polyether and alkanes are disclosed. The monomers are readily polymerized in the presence of cationic photoinitiators, when exposed to actinic radiation, to form poly(propenyl ethers) that are useful for coatings, sealants, varnishes and adhesives. Compositions for preparing polymeric coatings comprising the compounds of formula V together with particular cationic photoinitiators are also disclosed, as are processes for making the monomers from allyl halides and readily available alcohols. The process involves rearranging the resulting allyl ethers to propenyl ethers.

  7. Process for making propenyl ethers and photopolymerizable compositions containing them

    DOEpatents

    Crivello, J.V.

    1996-01-23

    Propenyl ether monomers of formula A(OCH{double_bond}CHCH{sub 3}){sub n} (V) wherein n is an integer from one to six and A is selected from cyclic ethers, polyether, and alkanes are disclosed. The monomers are readily polymerized in the presence of cationic photoinitiators, when exposed to actinic radiation, to form poly(propenyl ethers) that are useful for coatings, sealants, varnishes and adhesives. Compositions for preparing polymeric coatings comprising the compounds of formula V together with particular cationic photoinitiators are also disclosed, as are processes for making the monomers from allyl halides and readily available alcohols. The process involves rearranging the resulting allyl ethers to propenyl ethers.

  8. Chemiexcitation induced proton transfer: enolate oxyluciferin as the firefly bioluminophore.

    PubMed

    Pinto da Silva, Luís; Esteves da Silva, Joaquim C G

    2015-02-12

    Firefly bioluminescence is a phenomenon that attracts attention from the research community because of complex challenges for fundamental investigation, as well as diverse opportunities for practical application. Here we have studied the potential deprotonation of firefly oxyluciferin by using a theoretical approach in an enzymatic-like microenvironment in chemiexcited proton transfer involving adenosine 5'-monophosphate. We have uncovered a reaction route that links the evidence that the light-emitter is an anionic molecule while it is chemiexcited in its neutral form. Moreover, the results indicated that the anionic bioluminophore is the enolate anion and not the ketonic one. Further calculations supported this identification of the light-emitter: the spectrum of resulting enolate anion covers the entire yellow-green/red bioluminescence range, which is in line with the experimental findings regarding firefly multicolor bioluminescence.

  9. Synthesis of l-muscone by asymmetric methylation via enol esters.

    PubMed

    Matsuda, Hiroyuki; Tanaka, Shigeru; Yamamoto, Kenichi; Ishida, Kenya

    2008-06-01

    An effective synthetic route of l-muscone (1) by asymmetric methylation, followed by enolate-trapping to generate enol esters as intermediates, was described. Interestingly, the enol esters can be used as substrates for enzymatic optical resolution to improve optical purity. Additionally, several excellent new chiral ligands were discovered for asymmetric methylation of (E)-cyclopentadec-2-enone to produce l-muscone with high optical purity.

  10. "Crown Ether" Synthesis: An Organic Laboratory Experiment.

    ERIC Educational Resources Information Center

    Field, Kurt W.; And Others

    1979-01-01

    This experiment is designed to acquaint the student with a macromolecular synthesis of a crown ether type compound. The starting materials are readily available and the product, a cyclic polyether, belongs to a class of compounds that has aroused the interest of chemist and biologist alike. (Author/BB)

  11. Iron-Catalyzed Stereoselective Cross-Coupling Reactions of Stereodefined Enol Carbamates with Grignard Reagents.

    PubMed

    Rivera, Ana Cristina Parra; Still, Raymond; Frantz, Doug E

    2016-06-01

    A practical and highly stereoselective iron-catalyzed cross-coupling reaction of stereodefined enol carbamates and Grignard reagents to yield tri- and tetrasubstituted acrylates is reported. A facile method for the stereoselective generation of these enol carbamates has also been developed. PMID:27088754

  12. Efficient methods for enol phosphate synthesis using carbon-centred magnesium bases.

    PubMed

    Kerr, William J; Lindsay, David M; Patel, Vipulkumar K; Rajamanickam, Muralikrishnan

    2015-10-28

    Efficient conversion of ketones into kinetic enol phosphates under mild and accessible conditions has been realised using the developed methods with di-tert-butylmagnesium and bismesitylmagnesium. Optimisation of the quench protocol resulted in high yields of enol phosphates from a range of cyclohexanones and aryl methyl ketones, with tolerance of a range of additional functional units.

  13. Dynamic chirality of (E)-5-cyclononen-1-one and its enolate.

    PubMed

    Tomooka, Katsuhiko; Ezawa, Takayuki; Inoue, Hiroko; Uehara, Kazuhiro; Igawa, Kazunobu

    2011-02-16

    It has been found that (E)-5-cyclononen-1-one (2a) exhibits marginal planar chirality owing to an insufficient topological constraint, whereas the enolates 3 derived from 2a show robust planar chirality. Enantioenriched enolates are easily prepared by enzymatic hydrolysis, and they show an ability to serve as chiral nucleophiles.

  14. Experimental evidence for chair-like transition states in aldol reactions of methyl ketone lithium enolates: stereoselective synthesis and utilization of a deuterium-labeled enolate as a probe of reaction stereochemistry.

    PubMed

    Liu, Christopher M; Smith, William J; Gustin, Darin J; Roush, William R

    2005-04-27

    Aldol reactions of methyl ketone lithium enolates proceed via chairlike Zimmerman-Traxler transition states with 7:1 to 50:1 preference over alternative, boatlike transition structures, as determined by studies involving the configurationally stable deuterium-labeled enol silane 18 as the lithium enolate precursor.

  15. Method of Continuous Variation: Characterization of Alkali Metal Enolates Using 1H and 19F NMR Spectroscopies

    PubMed Central

    2015-01-01

    The method of continuous variation in conjunction with 1H and 19F NMR spectroscopies was used to characterize lithium and sodium enolates solvated by N,N,N′,N′-tetramethylethyldiamine (TMEDA) and tetrahydrofuran (THF). A strategy developed using lithium enolates was then applied to the more challenging sodium enolates. A number of sodium enolates solvated by TMEDA or THF afford exclusively tetramers. Evidence suggests that TMEDA chelates sodium on cubic tetramers. PMID:24915602

  16. Stereochemistry and function of oxaloacetate keto-enol tautomerase

    SciTech Connect

    Creighton, D.J.; Johnson, J.D.; Lambert, M.R.

    1986-05-01

    Oxaloacetate keto-enol tautomerase, partially purified from porcine kidney, catalyzes the conversions of enol- to keto-oxaloacetate by a mechanism in which solvent protons end up equally distributed between the two prochiral positions at C3 of keto-oxaloacetate. This conclusion is based upon the observation that when enzyme catalyzed ketonization is conducted in /sup 3/H/sub 2/O in the presence of excess malate dehydrogenase and NADH, only 50% of the /sup 3/H in the isolated (2S)-(3-/sup 3/H)malate is labilized to solvent upon treatment with fumarase. Either the tautomerase operates on the basis of a highly unusual stereomechanistic principle or tautomerase activity is not an evolved property of the enzyme protein. As a result of an attempt to clarify the physiological importance of oxaloacetate tautomerase activity, keto-oxaloacetate was demonstrated to be directly transported across the inner membrane of rat liver mitochrondria, on the basis of the results of kinetic and isotope-trapping experiments.

  17. Palladium-Catalyzed α-Arylation of Zinc Enolates of Esters: Reaction Conditions and Substrate Scope

    PubMed Central

    Hama, Takuo; Ge, Shaozhong; Hartwig, John F.

    2013-01-01

    The intermolecular α-arylation of esters by palladium-catalyzed coupling of aryl bromides with zinc enolates of esters is reported. Reactions of three different types of zinc enolates have been developed. α-Arylation of esters occurs in high yields with isolated Reformatsky reagents, with Reformatsky reagents generated from α-bromo esters and activated zinc, and with zinc enolates generated by quenching lithium enolates of esters with zinc chloride. The use of zinc enolates, instead of alkali metal enolates, greatly expands the scope of the arylation of esters. The reactions occur at room temperature or at 70 °C with bromoarenes containing cyano, nitro, ester, keto, fluoro, enolizable hydrogen, hydroxyl or amino functionality and with bromopyridines. The scope of esters encompasses acyclic acetates, propionates, and isobutyrates, α-alkoxyesters, and lactones. The arylation of zinc enolates of esters was conducted with catalysts bearing the hindered pentaphenylferrocenyl di-tert-butylphosphine (Q-phos) or the highly reactive dimeric Pd(I) complex {[P(t-Bu)3]PdBr}2. PMID:23931445

  18. Catalytic asymmetric protonation of lithium enolates using amino acid derivatives as chiral proton sources.

    PubMed

    Mitsuhashi, Kaori; Ito, Rie; Arai, Takayoshi; Yanagisawa, Akira

    2006-04-13

    [reaction: see text] Asymmetric protonation of lithium enolates was examined using commercially available amino acid derivatives as chiral proton sources. Among the amino acid derivatives tested, Nbeta-l-aspartyl-l-phenylalanine methyl ester was found to cause significant asymmetric induction in the protonation of lithium enolates. The enantiomeric excess (up to 88% ee) of the products obtained in the presence of a catalytic amount of the chiral proton source was higher than those obtained in the stoichiometric reaction. PMID:16597150

  19. Catalytic asymmetric protonation of lithium enolates using amino acid derivatives as chiral proton sources.

    PubMed

    Mitsuhashi, Kaori; Ito, Rie; Arai, Takayoshi; Yanagisawa, Akira

    2006-04-13

    [reaction: see text] Asymmetric protonation of lithium enolates was examined using commercially available amino acid derivatives as chiral proton sources. Among the amino acid derivatives tested, Nbeta-l-aspartyl-l-phenylalanine methyl ester was found to cause significant asymmetric induction in the protonation of lithium enolates. The enantiomeric excess (up to 88% ee) of the products obtained in the presence of a catalytic amount of the chiral proton source was higher than those obtained in the stoichiometric reaction.

  20. Theoretical study of the nontraditional enol-based photoacidity of firefly oxyluciferin.

    PubMed

    Pinto da Silva, Luís; Esteves da Silva, Joaquim C G

    2015-02-01

    A theoretical analysis of the enol-based photoacidity of oxyluciferin in water is presented. The basis for this phenomenon is found to be the hydrogen-bonding network that involves the conjugated photobase of oxyluciferin. The hydrogen-bonding network involving the enolate thiazole moiety is stronger than that of the benzothiazole phenolate moiety. Therefore, enolate oxyluciferin should be stabilized versus the phenolate anion. This difference in strength is attributed to the fact that the thiazole moiety has more potential hydrogen-bond acceptors near the proton donor atom than the benzothiazole moiety. Moreover, the phenol-based excited-state proton transfer leads to a decrease in the hydrogen-bond acceptor potential of the thiazole atoms. The ground-state enol-based acidity of oxyluciferin is also studied. This phenomenon can be explained by stabilization of the enolate anion through strengthening of a bond between water and the nitrogen atom of the thiazole ring, in an enol-based proton-transfer-dependent way. PMID:25404255

  1. Theoretical study of the nontraditional enol-based photoacidity of firefly oxyluciferin.

    PubMed

    Pinto da Silva, Luís; Esteves da Silva, Joaquim C G

    2015-02-01

    A theoretical analysis of the enol-based photoacidity of oxyluciferin in water is presented. The basis for this phenomenon is found to be the hydrogen-bonding network that involves the conjugated photobase of oxyluciferin. The hydrogen-bonding network involving the enolate thiazole moiety is stronger than that of the benzothiazole phenolate moiety. Therefore, enolate oxyluciferin should be stabilized versus the phenolate anion. This difference in strength is attributed to the fact that the thiazole moiety has more potential hydrogen-bond acceptors near the proton donor atom than the benzothiazole moiety. Moreover, the phenol-based excited-state proton transfer leads to a decrease in the hydrogen-bond acceptor potential of the thiazole atoms. The ground-state enol-based acidity of oxyluciferin is also studied. This phenomenon can be explained by stabilization of the enolate anion through strengthening of a bond between water and the nitrogen atom of the thiazole ring, in an enol-based proton-transfer-dependent way.

  2. Cyclic Voltammetry.

    ERIC Educational Resources Information Center

    Evans, Dennis H.; And Others

    1983-01-01

    Cyclic voltammetry is a simple experiment that has become popular in chemical research because it can provide useful information about redox reactions in a form which is easily obtained and interpreted. Discusses principles of the method and illustrates its use in the study of four electrode reactions. (Author/JN)

  3. Poly(arylene ether)s containing pendent ethynyl groups

    NASA Technical Reports Server (NTRS)

    Hergenrother, Paul M. (Inventor); Jensen, Brian J. (Inventor)

    1996-01-01

    Poly(arylene ether)s containing pendent ethynyl and substituted ethynyl groups and poly(arylene ether) copolymers containing pendent ethynyl and substituted ethynyl groups are readily prepared from bisphenols containing ethynyl and substituted ethynyl groups. The resulting polymers are cured up to 350.degree. C. to provide crosslinked poly(arylene ether)s with good solvent resistance, high strength and modulus.

  4. Chemistry of enolates on organic-molybdenum complexes

    SciTech Connect

    Mallik, S.

    1992-01-01

    Asymmetric deprotonation of a prochiral ketone was studied using a variety of chiral secondary lithium amide bases. The lithium amide 2 furnished the monomethylated complex in 40% optical purity. Properties of the larger ketones (4 and 5) were studied to determine the relative effects of the steric bulk of the metal and the conformations of the molecules in determining their reactivities. For the complex 4, enolization and subsequent alkylation at C-4 was facile and the stereochemistry was controlled by the steric bulk of the Mo(CO)[sub 2]Cp moiety. However, for nucleophile additions to the carbonyl group at C-5, the conformation of the molecule was the major factor in directing the stereochemistry of the products. Alkylation at C-6 was achieved only under drastic conditions with consequent loss of stereoselectivity. For the ketone 5 and its derivatives, conformation played the deciding role for both alkylation and nucleophile addition reactions. The two ketones 4 and 5 were used to synthesize multiply functionalized cycloheptenes and cyclooctene with defined stereochemistry of the substituents.

  5. Keto-Enol Tautomeric Equilibrium of Acetylacetone Solution Confined in Extended Nanospaces.

    PubMed

    Tsukahara, Takehiko; Nagaoka, Kyosuke; Morikawa, Kyojiro; Mawatari, Kazuma; Kitamori, Takehiko

    2015-11-19

    We aim to clarify the effects of size confinement, solvent, and deuterium substitution on keto-enol tautomerization of acetylacetone (AcAc) in solutions confined in 10-100 nm spaces (i.e., extended nanospaces) using (1)H NMR spectroscopy. The keto-enol equilibrium constants of AcAc (K(EQ) = [keto]/[enol]) in various solvents confined in extended nanospaces of 200-3000 nm were examined using the area ratios of -CH3 peaks in keto to enol forms. The results showed that the keto form of AcAc in hydrogen-bonded solvents such as water and ethanol increased drastically with decreasing space sizes below about 500 nm, but the size confinement did not induce equilibrium shifts in aprotic solvents such as DMSO. The magnitudes of K(EQ) enhancement were well correlated with solvent proton donicity. It followed from the determination of thermodynamic parameters that the stabilization of intermolecular interactions between protons in water and carbonyl oxygen (C═O) in the keto form of AcAc were promoted by size-confinement, and that the keto form could be energetically and structurally favored in extended nanospaces vis-à-vis the bulk space. Furthermore, the measurements of deuterium dependence of the K(EQ) values verified that the nanoconfinement-induced shifts of keto-enol tautomerization of AcAc are attributable to high proton mobility via a proton hopping mechanism of the confined water.

  6. Keto-Enol Tautomeric Equilibrium of Acetylacetone Solution Confined in Extended Nanospaces.

    PubMed

    Tsukahara, Takehiko; Nagaoka, Kyosuke; Morikawa, Kyojiro; Mawatari, Kazuma; Kitamori, Takehiko

    2015-11-19

    We aim to clarify the effects of size confinement, solvent, and deuterium substitution on keto-enol tautomerization of acetylacetone (AcAc) in solutions confined in 10-100 nm spaces (i.e., extended nanospaces) using (1)H NMR spectroscopy. The keto-enol equilibrium constants of AcAc (K(EQ) = [keto]/[enol]) in various solvents confined in extended nanospaces of 200-3000 nm were examined using the area ratios of -CH3 peaks in keto to enol forms. The results showed that the keto form of AcAc in hydrogen-bonded solvents such as water and ethanol increased drastically with decreasing space sizes below about 500 nm, but the size confinement did not induce equilibrium shifts in aprotic solvents such as DMSO. The magnitudes of K(EQ) enhancement were well correlated with solvent proton donicity. It followed from the determination of thermodynamic parameters that the stabilization of intermolecular interactions between protons in water and carbonyl oxygen (C═O) in the keto form of AcAc were promoted by size-confinement, and that the keto form could be energetically and structurally favored in extended nanospaces vis-à-vis the bulk space. Furthermore, the measurements of deuterium dependence of the K(EQ) values verified that the nanoconfinement-induced shifts of keto-enol tautomerization of AcAc are attributable to high proton mobility via a proton hopping mechanism of the confined water. PMID:26503906

  7. Crown ethers in graphene

    SciTech Connect

    Guo, Junjie; Lee, Jaekwang; Contescu, Cristian I.; Gallego, Nidia C.; Pantelides, Sokrates T.; Pennycook, Stephen J.; Moyer, Bruce A.; Chisholm, Matthew F.

    2014-11-13

    Crown ethers, introduced by Pedersen1, are at their most basic level neutral rings constructed of oxygen atoms linked by two- or three-carbon chains. They have attracted special attention for their ability to selectively incorporate various atoms2 or molecules within the cavity formed by the ring3-6. This property has led to the use of crown ethers and their compounds in a wide range of chemical and biological applications7,8. However, crown ethers are typically highly flexible, frustrating efforts to rigidify them for many uses that demand higher binding affinity and selectivity9,10. In this Letter, we report atomic-resolution images of the same basic structures of the original crown ethers embedded in graphene. This arrangement constrains the crown ethers to be rigid and planar and thus uniquely suited for the many applications that crown ethers are known for. First-principles calculations show that the close similarity of the structures seen in graphene with those of crown ether molecules also extends to their selectivity towards specific metal cations depending on the ring size. Atoms (or molecules) incorporated within the crown ethers in graphene offer a simple environment that can be easily and systematically probed and modeled. Thus, we expect that this discovery will introduce a new wave of investigations and applications of chemically functionalized graphene.

  8. Crown ethers in graphene

    DOE PAGESBeta

    Guo, Junjie; Lee, Jaekwang; Contescu, Cristian I.; Gallego, Nidia C.; Pantelides, Sokrates T.; Pennycook, Stephen J.; Moyer, Bruce A.; Chisholm, Matthew F.

    2014-11-13

    Crown ethers, introduced by Pedersen1, are at their most basic level neutral rings constructed of oxygen atoms linked by two- or three-carbon chains. They have attracted special attention for their ability to selectively incorporate various atoms2 or molecules within the cavity formed by the ring3-6. This property has led to the use of crown ethers and their compounds in a wide range of chemical and biological applications7,8. However, crown ethers are typically highly flexible, frustrating efforts to rigidify them for many uses that demand higher binding affinity and selectivity9,10. In this Letter, we report atomic-resolution images of the same basicmore » structures of the original crown ethers embedded in graphene. This arrangement constrains the crown ethers to be rigid and planar and thus uniquely suited for the many applications that crown ethers are known for. First-principles calculations show that the close similarity of the structures seen in graphene with those of crown ether molecules also extends to their selectivity towards specific metal cations depending on the ring size. Atoms (or molecules) incorporated within the crown ethers in graphene offer a simple environment that can be easily and systematically probed and modeled. Thus, we expect that this discovery will introduce a new wave of investigations and applications of chemically functionalized graphene.« less

  9. 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

  10. Spectroscopic Evidence of Keto-enol Tautomerism in Deliquesced Malonic Acid Particles

    SciTech Connect

    Ghorai, Suman; Laskin, Alexander; Tivanski, Alexei V.

    2011-04-11

    Scanning Transmission X-ray Microscopy combined with Near Edge X-ray Absorption Fine Structure Spectroscopy (STXM/NEXAFS), and optical microscopy coupled with Fourier Transform Infrared Spectroscopy (micro-FTIR) have been applied to observe hygroscopic growth and chemical changes in malonic acid particles deposited on substrates. Extent of the hygroscopic growth of particles has been quantified in terms of the corresponding water-to-solute ratios (WSR) based on STXM/NEXAFS and micro-FTIR data sets. WSR values derived separately from two applied methods displayed a remarkable agreement with previous data reported in the literature. Comparison of NEXAFS and FTIR spectra acquired at different relative humidity (RH) shows efficient keto-enol tautomerization of malonic acid, with the enol form dominated at higher RH. The keto-enol equilibrium constants were calculated using relevant peak intensities in the carbon and oxygen K-edge NEXAFS spectra as a function of RH.

  11. Cyclic multiverses

    NASA Astrophysics Data System (ADS)

    Marosek, Konrad; Dąbrowski, Mariusz P.; Balcerzak, Adam

    2016-09-01

    Using the idea of regularization of singularities due to the variability of the fundamental constants in cosmology we study the cyclic universe models. We find two models of oscillating and non-singular mass density and pressure (`non-singular' bounce) regularized by varying gravitational constant G despite the scale factor evolution is oscillating and having sharp turning points (`singular' bounce). Both violating (big-bang) and non-violating (phantom) null energy condition models appear. Then, we extend this idea on to the multiverse containing cyclic individual universes with either growing or decreasing entropy though leaving the net entropy constant. In order to get an insight into the key idea, we consider the doubleverse with the same geometrical evolution of the two `parallel' universes with their physical evolution [physical coupling constants c(t) and G(t)] being different. An interesting point is that there is a possibility to exchange the universes at the point of maximum expansion - the fact which was already noticed in quantum cosmology. Similar scenario is also possible within the framework of Brans-Dicke theory where varying G(t) is replaced by the dynamical Brans-Dicke field φ(t) though these theories are slightly different.

  12. Metal ion complexation by ionizable crown ethers. Progress report, January 1, 1991--December 31, 1993

    SciTech Connect

    Bartsch, R.A.

    1993-07-01

    Cyclic and acyclic polyether compounds with pendent carboxylic acid, phosphonic acid monoethyl ester, sulfonic acid, phosphinic acid and hydroxamic acid groups have been synthesized. The proton-ionizable polyethers can come with and without lipophilic groups. Two types of lipophilic di-ionizable lariat ethers have been prepared. Conformations of proton-ionizable lariat ethers have been probed. Competitive alkali metal cation transport by syn-(decyl)dibenzo-16-crown-5-oxyacetic acid and lipophilic proton-ionizable dibenzo lariat ethers in polymer-supported liquid membranes was studied. Complexation of alkali metal cations with ionized lariat ethers was studied. Condensation polymerization of cyclic and acyclic dibenzo polyethers containing pendent mono-ionizable groups with formaldehyde produces novel ion exchange resins with both ion exchange sites for metal ion complexation and polyether binding sites for metal ion recognition. Resins prepared from lariat ether dibenzo phosphonic acid monoethyl esters show strong sorption of divalent heavy metal cations with selectivity for Pb{sup 2+}.

  13. Synthesis of oxacyclic scaffolds via dual ruthenium hydride/Brønsted acid-catalyzed isomerization/cyclization of allylic ethers.

    PubMed

    Ascic, Erhad; Ohm, Ragnhild G; Petersen, Rico; Hansen, Mette R; Hansen, Casper L; Madsen, Daniel; Tanner, David; Nielsen, Thomas E

    2014-03-17

    A ruthenium hydride/Brønsted acid-catalyzed tandem sequence is reported for the synthesis of 1,3,4,9-tetrahydropyrano[3,4-b]indoles (THPIs) and related oxacyclic scaffolds. The process was designed on the premise that readily available allylic ethers would undergo sequential isomerization, first to enol ethers (Ru catalysis), then to oxocarbenium ions (Brønsted acid catalysis) amenable to endo cyclization with tethered nucleophiles. This methodology provides not only an attractive alternative to the traditional oxa-Pictet-Spengler reaction for the synthesis of THPIs, but also convenient access to THPI congeners and other important oxacycles such as acetals. PMID:24616060

  14. Enol tautomers of Watson-Crick base pair models are metastable because of nuclear quantum effects.

    PubMed

    Pérez, Alejandro; Tuckerman, Mark E; Hjalmarson, Harold P; von Lilienfeld, O Anatole

    2010-08-25

    Intermolecular enol tautomers of Watson-Crick base pairs could emerge spontaneously via interbase double proton transfer. It has been hypothesized that their formation could be facilitated by thermal fluctuations and proton tunneling, and possibly be relevant to DNA damage. Theoretical and computational studies, assuming classical nuclei, have confirmed the dynamic stability of these rare tautomers. However, by accounting for nuclear quantum effects explicitly through Car-Parrinello path integral molecular dynamics calculations, we find the tautomeric enol form to be dynamically metastable, with lifetimes too insignificant to be implicated in DNA damage. PMID:20681591

  15. Michael Additions of Highly Basic Enolates to ortho-Quinone Methides

    PubMed Central

    Lewis, Robert S.; Garza, Christopher J.; Dang, Ann T.; Pedro, Te Kie A.; Chain, William J.

    2015-01-01

    A protocol by which ketone or ester enolates and ortho-quinone methides (o-QMs) are generated in situ in a single reaction flask from silylated precursors under the action of anhydrous fluoride is reported. The reaction partners are joined to give a variety of β-(2-hydroxyphenyl)-carbonyl compounds in 32–94% yield in a single laboratory operation. The intermediacy of o-QMs is supported by control experiments utilizing enolate precursors and conventional alkyl halides as competitive alkylating agents and the isolation of 1,5-dicarbonyl products resulting from conjugate additions that do not restore the aromatic system. PMID:25906358

  16. Influence of substituent on UV absorption and keto-enol tautomerism equilibrium of dibenzoylmethane derivatives.

    PubMed

    Zawadiak, Jan; Mrzyczek, Marek

    2012-10-01

    UV absorption spectra of dibenzoylmethane and its 23 derivatives with acetamide, tert-butyl, chloride, fluoride, hydroxyl, methyl, methoxy and nitro substituents in aromatic rings were collected. General influence of substituent on absorption maxima and absorption intensity was defined. Hyperchromic effects were observed for diketones with electron-donating groups in para postion. The keto-enol tautomerism equilibrium constant of obtained compounds was investigated with (1)H NMR spectroscopy. Significant changes of equilibrium were observed only for ortho substituted compounds. Results revealed dissimilarity of substituent effects on absorption and keto-enol tautomerism of aromatic β-diketones.

  17. Michael Additions of Highly Basic Enolates to ortho-Quinone Methides.

    PubMed

    Lewis, Robert S; Garza, Christopher J; Dang, Ann T; Pedro, Te Kie A; Chain, William J

    2015-05-01

    A protocol by which ketone or ester enolates and ortho-quinone methides (o-QMs) are generated in situ in a single reaction flask from silylated precursors under the action of anhydrous fluoride is reported. The reaction partners are joined to give a variety of β-(2-hydroxyphenyl)-carbonyl compounds in 32-94% yield in a single laboratory operation. The intermediacy of o-QMs is supported by control experiments utilizing enolate precursors and conventional alkyl halides as competitive alkylating agents and the isolation of 1,5-dicarbonyl products resulting from conjugate additions that do not restore the aromatic system.

  18. Catalytic oxidation of dimethyl ether

    DOEpatents

    Zelenay, Piotr; Wu, Gang; Johnston, Christina M.; Li, Qing

    2016-05-10

    A composition for oxidizing dimethyl ether includes an alloy supported on carbon, the alloy being of platinum, ruthenium, and palladium. A process for oxidizing dimethyl ether involves exposing dimethyl ether to a carbon-supported alloy of platinum, ruthenium, and palladium under conditions sufficient to electrochemically oxidize the dimethyl ether.

  19. Modulation of multifunctional N,O,P ligands for enantioselective copper-catalyzed conjugate addition of diethylzinc and trapping of the zinc enolate.

    PubMed

    Ye, Fei; Zheng, Zhan-Jiang; Deng, Wen-Hui; Zheng, Long-Sheng; Deng, Yuan; Xia, Chun-Gu; Xu, Li-Wen

    2013-09-01

    In this work, we have successfully synthesized a new family of chiral Schiff base–phosphine ligands derived from chiral binaphthol (BINOL) and chiral primary amine. The controllable synthesis of a novel hexadentate and tetradentate N,O,P ligand that contains both axial and sp3-central chirality from axial BINOL and sp3-central primary amine led to the establishment of an efficient multifunctional N,O,P ligand for copper-catalyzed conjugate addition of an organozinc reagent. In the asymmetric conjugate reaction of organozinc reagents to enones, the polymer-like bimetallic multinuclear Cu-Zn complex constructed in situ was found to be substrate-selective and a highly excellent catalyst for diethylzinc reagents in terms of enantioselectivity (up to >99 % ee). More importantly, the chirality matching between different chiral sources, C2-axial binaphthol and sp3-central chiral phosphine, was crucial to the enantioselective induction in this reaction. The experimental results indicated that our chiral ligand (R,S,S)-L1- and (R,S)-L4-based bimetallic complex catalyst system exhibited the highest catalytic performance to date in terms of enantioselectivity and conversion even in the presence of 0.005 mol % of catalyst (S/C = 20 000, turnover number (TON) = 17,600). We also studied the tandem silylation or acylation of enantiomerically enriched zinc enolates that formed in situ from copper-L4-complex-catalyzed conjugate addition, which resulted in the high-yield synthesis of chiral silyl enol ethers and enoacetates, respectively. Furthermore, the specialized structure of the present multifunctional N,O,P ligand L1 or L4, and the corresponding mechanistic study of the copper catalyst system were investigated by 31P NMR spectroscopy, circular dichroism (CD), and UV/Vis absorption. PMID:23983068

  20. Base triggered enhancement of first hyperpolarizability of a keto-enol tautomer.

    PubMed

    De, Soumi; Ray, Manisha; Pati, Anusooya Y; Das, Puspendu K

    2013-12-01

    This work describes the base triggered enhancement of first hyperpolarizability of a tautomeric organic molecule, namely, benzoylacetanilide (BA). We have used the hyper-Rayleigh scattering technique to measure the first hyperpolarizability (β) of BA which exists in the pure keto form in water and as a keto-enol tautomer in ethanol. Its anion exists in equilibrium with the keto and enol forms at pH 11 in aqueous solution. The β value of the anion form is 709 × 10(-30) esu, whereas that of the enol is 232 × 10(-30) esu and of the keto is 88 × 10(-30) esu. There is an enhancement of β by ~8 times for the anion and ~3 times for the enol compared to the keto form. All these are achieved by altering the equilibrium between the three forms of BA by simple means. MP2 calculations reproduce the experimental trend, but the computed β values are much lower than the measured values. DFT calculations with the standard B3LYP functional could not predict the right order in the β values. The difference between experimental and calculated values is, perhaps, due to the fact that electron correlation effects are important in computing optical nonlinearities of large organic molecules and MP2 and B3LYP calculations done here for different forms of BA could not account for such effects adequately.

  1. Keto-enol tautomerization of a peptide group with proton transfer through a water bridge

    NASA Astrophysics Data System (ADS)

    Isaev, A. N.

    2015-08-01

    Calculations were performed for structures of the keto and enol forms of dipeptide N-glycylglycine and its complexes with water molecules using the quantum-chemical B3LYP/6-31+G** method. The barrier for the reactions of the dipeptide's keto-enol tautomerization that proceed by the mechanism of intramolecular proton transfer and proton transfer through water molecules connecting the oxygen and nitrogen atoms of the (-CONH-) peptide group was calculated. It was found that the barrier of the keto-enol tautomerization reaction with proton transfer by an exchange mechanism through water molecules is decreased halved compared to direct intramolecular transfer. It was shown that addition of a second water molecule in the transfer chain leads to linearization of the H-bonds bridges and increases hydrogen bonding between the peptide group and water molecules, but has virtually no influence on the calculated value of the keto-enol tautomerization barrier of about 20 kcal/mol. The structures of the transition states of the reaction indicate that the transfer of protons along the H-bonds chain is in both cases concerted but asynchronous. The order of the protons translocations along the water bridge is explained on the basis of NBO analysis of the relative strength of H-bonds in the transfer chain when the proton involved in the strongest H-bond is transferred first.

  2. On the origin of the stereoselectivity in the alkylation of oxazolopiperidone enolates.

    PubMed

    Soteras, Ignacio; Lozano, Oscar; Gómez-Esqué, Arantxa; Escolano, Carmen; Orozco, Modesto; Amat, Mercedes; Bosch, Joan; Luque, F Javier

    2006-05-24

    The origin of the diastereoselective alkylation of enolates of oxazolopiperidones is studied by means of theoretical calculations and experimental assays. For the unsubstituted oxazolopiperidone, the alkylation with methyl chloride is predicted to afford mainly the exo product, a finding further corroborated from the analysis of the experimental outcome obtained in the reaction of the racemic oxazolopiperidone. However, such a preference can be drastically altered by the presence of substituents attached to the fused ring. In particular, when the angular carbon adopts an R configuration in a phenylglycinol-derived oxazolopiperidone, the presence of a phenyl ring at position 3 forces the pseudo-planarity of the bicyclic lactam, and the diastereoselectivity is dictated by the internal torsional strain induced in the enolate. However, when the angular carbon adopts an S configuration, the preference for the exo alkylation stems from the intermolecular steric hindrance between the enolate and the alkylating reagent. Interestingly, the intramolecular hydrogen bond formed between the phenyl ring and the carbonyl oxygen in the enolate largely reduces the difference in stability of the two TSs compared to the unsubstituted oxazolopiperidone. PMID:16704257

  3. An NMR Study of Isotope Effect on Keto-Enol Tautomerization: A Physical Organic Chemistry Experiment

    ERIC Educational Resources Information Center

    Atkinson, D.; Chechik, V.

    2004-01-01

    Isotope substitution often affects the rate of an organic reaction and can be used to reveal the underlying mechanism. A series of experiments that use (super 1)H NMR to determine primary and secondary isotope effects, activation parameters, and the regioselectivity of butanone enolization are described.

  4. Cobalt-catalyzed hydrogenation of esters to alcohols: unexpected reactivity trend indicates ester enolate intermediacy.

    PubMed

    Srimani, Dipankar; Mukherjee, Arup; Goldberg, Alexander F G; Leitus, Gregory; Diskin-Posner, Yael; Shimon, Linda J W; Ben David, Yehoshoa; Milstein, David

    2015-10-12

    The atom-efficient and environmentally benign catalytic hydrogenation of carboxylic acid esters to alcohols has been accomplished in recent years mainly with precious-metal-based catalysts, with few exceptions. Presented here is the first cobalt-catalyzed hydrogenation of esters to the corresponding alcohols. Unexpectedly, the evidence indicates the unprecedented involvement of ester enolate intermediates.

  5. Enantioselective Annulations for Dihydroquinolones by in Situ Generation of Azolium Enolates

    PubMed Central

    2015-01-01

    A convergent, catalytic asymmetric formal [4 + 2] annulation for the synthesis of dihydroquinolones has been developed. Carboxylic acids can be employed as precursors to NHC enolates through an in situ activation strategy. Simultaneous generation of a reactive aza-o-quinone methide under the basic conditions employed for NHC generation leads to a dual activation approach. PMID:25017004

  6. Kinetic and Mechanistic Studies of the Deuterium Exchange in Classical Keto-Enol Tautomeric Equilibrium Reactions

    ERIC Educational Resources Information Center

    Nichols, Michael A.; Waner, Mark J.

    2010-01-01

    An extension of the classic keto-enol tautomerization of beta-dicarbonyl compounds into a kinetic analysis of deuterium exchange is presented. It is shown that acetylacetone and ethyl acetoacetate undergo nearly complete deuterium exchange of the alpha-methylene carbon when dissolved in methanol-d[subscript 4]. The extent of deuteration may be…

  7. Linear-cyclic polymer structural transformation and its reversible control using a rational rotaxane strategy.

    PubMed

    Ogawa, Takahiro; Usuki, Naoya; Nakazono, Kazuko; Koyama, Yasuhito; Takata, Toshikazu

    2015-04-01

    Linear-cyclic polymer structural transformation and its reversibility are demonstrated by a simple but rational strategy using the structural characteristics of crown ether-based rotaxanes. The structure of a polymer containing a [1]rotaxane unit at one end was controlled by conventional protection-deprotection reactions, giving rise to a reversible linear-cyclic polymer structural transformation. PMID:25531061

  8. Linear-cyclic polymer structural transformation and its reversible control using a rational rotaxane strategy.

    PubMed

    Ogawa, Takahiro; Usuki, Naoya; Nakazono, Kazuko; Koyama, Yasuhito; Takata, Toshikazu

    2015-04-01

    Linear-cyclic polymer structural transformation and its reversibility are demonstrated by a simple but rational strategy using the structural characteristics of crown ether-based rotaxanes. The structure of a polymer containing a [1]rotaxane unit at one end was controlled by conventional protection-deprotection reactions, giving rise to a reversible linear-cyclic polymer structural transformation.

  9. 40 CFR 721.3440 - Haloalkyl substituted cyclic ethers.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... does not apply when a MSDS was not required under § 721.72(c). The provisions of § 721.72(g) requiring placement of specific information on a label and MSDS do not apply when a label and MSDS are not required... provided with information on the location and availability of MSDSs does not apply when a MSDS was...

  10. 40 CFR 721.3440 - Haloalkyl substituted cyclic ethers.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... does not apply when a MSDS was not required under § 721.72(c). The provisions of § 721.72(g) requiring placement of specific information on a label and MSDS do not apply when a label and MSDS are not required... provided with information on the location and availability of MSDSs does not apply when a MSDS was...

  11. Taming the carboxyl group for directed carbometalation: observations on the use of anions, dianions and ester enolates.

    PubMed

    Desrat, Sandy; Gray, Philip J; Penny, Matthew R; Motherwell, William B

    2014-07-14

    Carboxylate anions, dianions and ester enolates provide simultaneous protection and activation for directed carbometalation reactions. Advantage can be taken of the bis-carbanionic character of the intermediate for further controlled C-C bond forming reactions.

  12. Taming the carboxyl group for directed carbometalation: observations on the use of anions, dianions and ester enolates.

    PubMed

    Desrat, Sandy; Gray, Philip J; Penny, Matthew R; Motherwell, William B

    2014-07-14

    Carboxylate anions, dianions and ester enolates provide simultaneous protection and activation for directed carbometalation reactions. Advantage can be taken of the bis-carbanionic character of the intermediate for further controlled C-C bond forming reactions. PMID:24961599

  13. 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.

  14. Chloromethyl methyl ether (CMME)

    Integrated Risk Information System (IRIS)

    Chloromethyl methyl ether ( CMME ) ; CASRN 107 - 30 - 2 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 fo

  15. Triethylene glycol monoethyl ether

    Integrated Risk Information System (IRIS)

    Triethylene glycol monoethyl ether ; CASRN 112 - 50 - 5 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 fo

  16. Triethylene glycol monobutyl ether

    Integrated Risk Information System (IRIS)

    Triethylene glycol monobutyl ether ; CASRN 143 - 22 - 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 fo

  17. p-Bromodiphenyl ether

    Integrated Risk Information System (IRIS)

    p - Bromodiphenyl ether ; CASRN 101 - 55 - 3 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 Noncarcin

  18. Propylene glycol monoethyl ether

    Integrated Risk Information System (IRIS)

    Propylene glycol monoethyl ether ; CASRN 52125 - 53 - 8 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 fo

  19. Acid-Base Pairs in Lewis Acidic Zeolites Promote Direct Aldol Reactions by Soft Enolization.

    PubMed

    Lewis, Jennifer D; Van de Vyver, Stijn; Román-Leshkov, Yuriy

    2015-08-17

    Hf-, Sn-, and Zr-Beta zeolites catalyze the cross-aldol condensation of aromatic aldehydes with acetone under mild reaction conditions with near quantitative yields. NMR studies with isotopically labeled molecules confirm that acid-base pairs in the Si-O-M framework ensemble promote soft enolization through α-proton abstraction. The Lewis acidic zeolites maintain activity in the presence of water and, unlike traditional base catalysts, in acidic solutions.

  20. Degradation of various alkyl ethers by alkyl ether-degrading Actinobacteria isolated from activated sludge of a mixed wastewater treatment.

    PubMed

    Kim, Yong-Hak; Cha, Chang-Jun; Engesser, Karl-Heinrich; Kim, Sang-Jong

    2008-11-01

    Various substrate specificity groups of alkyl ether (AE)-degrading Actinobacteria coexisted in activated sewage sludge of a mixed wastewater treatment. There were substrate niche overlaps including diethyl ether between linear AE- and cyclic AE-degrading strains and phenetole between monoalkoxybenzene- and linear AE-degrading strains. Representatives of each group showed different substrate specificities and degradation pathways for the preferred substrates. Determining the rates of initial reactions and the initial metabolite(s) from whole cell biotransformation helped us to get information about the degradation pathways. Rhodococcus sp. strain DEE5311 and Rhodococcus rhodochrous strain 117 both were able to degrade anisole and phenetole through aromatic 2-monooxygenation to form 2-alkoxyphenols. In contrast, diethyl ether-oxidizing strain DEE5311 capable of degrading a broad range of linear AE, dibenzyl ether and monoalkoxybenzenes initially transformed anisole and phenetole to phenol via direct O-dealkylation. Compared to this, cyclic AE-degrading Rhodococcus sp. strain THF100 preferred tetrahydrofuran (265 ± 35 nmol min(-1)mg(-1) protein) to diethyl ether (<30), but it cannot oxidize bulkier AE than diethyl ether. Otherwise, 1,4-diethoxybenzene-degrading Rhodococcus sp. strain DEOB100 and Gordonia sp. strain DEOB200 transformed 1,3-/1,4-dialkoxybenzenes to 3-/4-alkoxyphenols by similar manners in the order of rates (nmol min(-1) mg(-1) protein): 1,4-diethoxybenzene (11.1 vs. 3.9)>1,4-dimethoxybenzene (1.6 vs. 2.6)>1,3-dimethoxybenzene (0.6 vs. 0.6). This study suggests that the AE-degrading Actinobacteria can orchestrate various substrate specificity responses to the degradation of various categories of AE pollutants in activated sludge communities.

  1. Efficient Synthesis of Cyclic Block Copolymers by Rotaxane Protocol by Linear/Cyclic Topology Transformation.

    PubMed

    Valentina, Stephanie; Ogawa, Takahiro; Nakazono, Kazuko; Aoki, Daisuke; Takata, Toshikazu

    2016-06-20

    High-yielding synthesis of cyclic block copolymer (CBC) using the rotaxane protocol by linear-cyclic polymer topology transformation was first demonstrated. Initial complexation of OH-terminated sec-ammonium salt and a crown ether was followed by the successive living ring-opening polymerizations of two lactones to a linear block copolymer having a rotaxane structure by the final capping of the propagation end. CBC was obtained in a high yield by an exploitation of the mechanical linkage through the translational movement of the rotaxane component to transform polymer structure from linear to cyclic. Furthermore, the change of the polymer topology was translated into a macroscopic change in crystallinity of the block copolymer. PMID:27037975

  2. Efficient Synthesis of Cyclic Block Copolymers by Rotaxane Protocol by Linear/Cyclic Topology Transformation.

    PubMed

    Valentina, Stephanie; Ogawa, Takahiro; Nakazono, Kazuko; Aoki, Daisuke; Takata, Toshikazu

    2016-06-20

    High-yielding synthesis of cyclic block copolymer (CBC) using the rotaxane protocol by linear-cyclic polymer topology transformation was first demonstrated. Initial complexation of OH-terminated sec-ammonium salt and a crown ether was followed by the successive living ring-opening polymerizations of two lactones to a linear block copolymer having a rotaxane structure by the final capping of the propagation end. CBC was obtained in a high yield by an exploitation of the mechanical linkage through the translational movement of the rotaxane component to transform polymer structure from linear to cyclic. Furthermore, the change of the polymer topology was translated into a macroscopic change in crystallinity of the block copolymer.

  3. Ether and hydrocarbon production

    SciTech Connect

    Harandi, M.N.; Owen, H.

    1991-03-19

    This patent describes a continuous process for converting lower aliphatic alkanol and olefinic hydrocarbon to alkyl tertiary-alkyl ethers and C{sub 5} + gasoline boiling range hydrocarbons. It comprises contacting alkanol and a light olefinic hydrocarbon stream rich in isobutylene and other C{sub 4} isomeric hydrocarbons under iso-olefin etherification conditions in an etherification reaction zone containing acid etherification catalyst; separating etherification effluent to recover a light stream comprising unreacted alkanol and light olefinic hydrocarbon and a liquid product stream containing alkyl tertiary-butyl ether; and contacting the light stream with acidic, medium pore metallosilicate catalyst under alkanol and hydrocarbon conversion conditions whereby C{sub 5} + gasoline boiling range hydrocarbons are produced.

  4. Reaction Pathways and Energetics of Etheric C–O Bond Cleavage Catalyzed by Lanthanide Triflates

    SciTech Connect

    Assary, Rajeev S.; Atesin, Abdurrahman C.; Li, Zhi; Curtiss, Larry A.; Marks, Tobin J.

    2013-09-06

    Efficient and selective cleavage of etheric C-O bonds is crucial for converting biomass into platform chemicals and liquid transportation fuels. In this contribution, computational methods at the DFT B3LYP level of theory are employed to understand the efficacy of lanthanide triflate catalysts (Ln(OTf)3, Ln = La, Ce, Sm, Gd, Yb, and Lu) in cleaving etheric C-O bonds. In agreement with experiment, the calculations indicate that the reaction pathway for C-O cleavage occurs via a C-H → O-H proton transfer in concert with weakening of the C-O bond of the coordinated ether substrate to ultimately yield a coordinated alkenol. The activation energy for this process falls as the lanthanide ionic radius decreases, reflecting enhanced metal ion electrophilicity. Details of the reaction mechanism for Yb(OTf)3-catalyzed ring opening are explored in depth, and for 1-methyl-d3-butyl phenyl ether, the computed primary kinetic isotope effect of 2.4 is in excellent agreement with experiment (2.7), confirming that etheric ring-opening pathway involves proton transfer from the methyl group alpha to the etheric oxygen atom, which is activated by the electrophilic lanthanide ion. Calculations of the catalytic pathway using eight different ether substrates indicate that the more rapid cleavage of acyclic versus cyclic ethers is largely due to entropic effects, with the former C-O bond scission processes increasing the degrees of freedom/particles as the transition state is approached.

  5. VO2+ complexation by bioligands showing keto-enol tautomerism: a potentiometric, spectroscopic, and computational study.

    PubMed

    Sanna, Daniele; Varnágy, Katalin; Timári, Sarolta; Micera, Giovanni; Garribba, Eugenio

    2011-10-17

    The interaction of VO(2+) ion with ligands of biological interest that are present in important metabolic pathways--2-oxopropanoic acid (pyruvic acid, pyrH), 3-hydroxy-2-oxopropanoic acid (3-hydroxypyruvic acid, hydpyrH), oxobutanedioic acid (oxalacetic acid, oxalH(2)), (S)-hydroxybutanedioic acid (l-malic acid, malH(2)), and 2,3-dihydroxy-(E)-butanedioic acid (dihydroxyfumaric acid, dhfH(2))--was described. Their complexing capability was compared with that of similar ligands: 3-hydroxy-2-butanone (hydbut) and 3,4-dihydroxy-3-cyclobutene-1,2-dione (squaric acid, squarH(2)). All of these ligands (except l-malic acid) exhibit keto-enol tautomerism, and the presence of a metal ion can influence such an equilibrium. The different systems were studied with electron paramagnetic resonance (EPR) and UV-vis spectroscopies and with pH potentiometry. Density functional theory (DFT) methods provide valuable information on the relative energy of the enol and keto forms of the ligands both in the gas phase and in aqueous solution, on the geometry of the complexes, and on EPR and electronic absorption parameters. The results show that most of the ligands behave like α-hydroxycarboxylates, forming mono- and bis-chelated species with (COO(-), O(-)) coordination, demonstrating that the metal ion is able to stabilize the enolate form of some ligands. With dihydroxyfumaric acid, the formation of a non-oxidovanadium(IV) complex, because of rearrangement of dihydroxyfumaric to dihydroxymaleic acid (dhmH(2)), can be observed. With 3-hydroxy-2-butanone and 3,4-dihydroxy-3-cyclobutene-1,2-dione, complexation of VO(2+) does not take place and the reason for this behavior is explained by chemical considerations and computational calculations. PMID:21902189

  6. Enolate-Forming Phloretin Pharmacophores: Hepatoprotection in an Experimental Model of Drug-Induced Toxicity.

    PubMed

    Geohagen, Brian C; Vydyanathan, Amaresh; Kosharskyy, Boleslav; Shaparin, Naum; Gavin, Terrence; LoPachin, Richard M

    2016-06-01

    Drug-induced toxicity is often mediated by electrophilic metabolites, such as bioactivation of acetaminophen (APAP) to N-acetyl-p-benzoquinone imine (NAPQI). We have shown that APAP hepatotoxicity can be prevented by 2-acetylcyclopentanone (2-ACP). This 1,3-dicarbonyl compound ionizes to form an enolate nucleophile that scavenges NAPQI and other electrophilic intermediates. In this study, we expanded our investigation of enolate-forming compounds to include analyses of the phloretin pharmacophores, 2',4',6'-trihydroxyacetophenone (THA) and phloroglucinol (PG). Studies in a mouse model of APAP overdose showed that THA provided hepatoprotection when given either by intraperitoneal injection or oral administration, whereas PG was hepatoprotective only when given intraperitoneally. Corroborative research characterized the molecular pharmacology (efficacy, potency) of 2-ACP, THA, and PG in APAP-exposed isolated mouse hepatocytes. For comparative purposes, N-acetylcysteine (NAC) cytoprotection was also evaluated. Measurements of multiple cell parameters (e.g., cell viability, mitochondrial membrane depolarization) indicated that THA and, to a lesser extent, PG provided concentration-dependent protection against APAP toxicity, which exceeded that of 2-ACP or NAC. The enolate-forming compounds and NAC truncated ongoing APAP exposure and thereby returned intoxicated hepatocytes toward normal viability. The superior ability of THA to protect is related to multifaceted modes of action that include metal ion chelation, free radical trapping, and scavenging of NAPQI and other soft electrophiles involved in oxidative stress. The rank order of potency for the tested cytoprotectants was consistent with that determined in a parallel mouse model. These data suggest that THA or a derivative might be useful in treating drug-induced toxicities and other conditions that involve electrophile-mediated pathogenesis. PMID:27029584

  7. Poly(arylene ether)s That Resist Atomic Oxygen

    NASA Technical Reports Server (NTRS)

    Connell, John W.; Hergenrother, Paul; Smith, Joseph G., Jr.

    1994-01-01

    Novel poly(arylene ether)s containing phosphine oxide (PAEPO's) made via aromatic nucleophilic displacement reactions of activated aromatic dihalides (or, in some cases, activated aromatic dinitro compounds) with new bisphenol monomers containing phosphine oxide. Exhibited favorable combination of physical and mechanical properties and resistance to monatomic oxygen in oxygen plasma environment. Useful as adhesives, coatings, films, membranes, moldings, and composite matrices.

  8. Highly Regio- and Enantioselective Formal [3 + 2]-Annulation of Indoles with Electrophilic Enol Carbene Intermediates.

    PubMed

    Jing, Changcheng; Cheng, Qing-Qing; Deng, Yongming; Arman, Hadi; Doyle, Michael P

    2016-09-16

    Chiral cyclopentane-fused indolines are synthesized with high regio- and enantiocontrol by formal [3 + 2]-annulation reactions of indoles and electrophilic enol carbenes. High enantioselectivity and exclusive regiocontrol occurred with enoldiazoacetamides using a less sterically encumbered prolinate-ligated dirhodium(II) catalyst in reactions with N-substituted indoles without substituents at the 2- or 3-positions via a selective vinylogous addition process. In this transformation, donor-acceptor cyclopropenes generated from enoldiazoacetamides serve as the carbene precursors to form metal carbene intermediates. PMID:27589203

  9. The hydrolysis of geminal ethers: a kinetic appraisal of orthoesters and ketals

    PubMed Central

    Repetto, Sonia L; Butts, Craig P; Lam, Joseph K W; Ratcliffe, Norman M

    2016-01-01

    Summary A novel approach to protecting jet fuel against the effects of water contamination is predicated upon the coupling of the rapid hydrolysis reactions of lipophilic cyclic geminal ethers, with the concomitant production of a hydrophilic acyclic hydroxyester with de-icing properties (Fuel Dehydrating Icing Inhibitors - FDII). To this end, a kinetic appraisal of the hydrolysis reactions of representative geminal ethers was undertaken using a convenient surrogate for the fuel–water interface (D2O/CD3CN 1:4). We present here a library of acyclic and five/six-membered cyclic geminal ethers arranged according to their hydroxonium catalytic coefficients for hydrolysis, providing for the first time a framework for the development of FDII. A combination of 1H NMR, labelling and computational studies was used to assess the effects that may govern the observed relative rates of hydrolyses. PMID:27559399

  10. The hydrolysis of geminal ethers: a kinetic appraisal of orthoesters and ketals.

    PubMed

    Repetto, Sonia L; Costello, James F; Butts, Craig P; Lam, Joseph K W; Ratcliffe, Norman M

    2016-01-01

    A novel approach to protecting jet fuel against the effects of water contamination is predicated upon the coupling of the rapid hydrolysis reactions of lipophilic cyclic geminal ethers, with the concomitant production of a hydrophilic acyclic hydroxyester with de-icing properties (Fuel Dehydrating Icing Inhibitors - FDII). To this end, a kinetic appraisal of the hydrolysis reactions of representative geminal ethers was undertaken using a convenient surrogate for the fuel-water interface (D2O/CD3CN 1:4). We present here a library of acyclic and five/six-membered cyclic geminal ethers arranged according to their hydroxonium catalytic coefficients for hydrolysis, providing for the first time a framework for the development of FDII. A combination of (1)H NMR, labelling and computational studies was used to assess the effects that may govern the observed relative rates of hydrolyses. PMID:27559399

  11. Cyclic phosphonium ionic liquids

    PubMed Central

    Mukhlall, Joshua A; Romeo, Alicia R; Gohdo, Masao; Ramati, Sharon; Berman, Marc; Suarez, Sophia N

    2014-01-01

    Summary Ionic liquids (ILs) incorporating cyclic phosphonium cations are a novel category of materials. We report here on the synthesis and characterization of four new cyclic phosphonium bis(trifluoromethylsulfonyl)amide ILs with aliphatic and aromatic pendant groups. In addition to the syntheses of these novel materials, we report on a comparison of their properties with their ammonium congeners. These exemplars are slightly less conductive and have slightly smaller self-diffusion coefficients than their cyclic ammonium congeners. PMID:24605146

  12. Solvent effect in keto-enol tautomerism for a polymerizable β-ketonitrile monomer. Spectroscopy and theoretical study

    NASA Astrophysics Data System (ADS)

    Giussi, Juan M.; Gastaca, Belén; Lavecchia, Martín J.; Schiavoni, Mercedes; Susana Cortizo, M.; Allegretti, Patricia E.

    2015-02-01

    The beta-ketonitrile 2-methyl-5-phenyl-3-oxo-4-pentenenitrile, a polymerizable monomer, exists in two important tautomeric forms, keto and enol isomers. This compound has been studied as monomer in polymerization reactions and the resulting polymers have been applied in fields of nanotechnology. Currently, these are being studied in nanomedicine. To understand the tautomeric equilibrium, we have studied this compound in solution by NMR spectrometry. Correlation with DFT calculations has been carried out in order to understand the system behavior. The results found in this work, both by experiments and calculations, show that the enol content increases with solvent polarity.

  13. Keto-enol tautomerization and intermolecular proton transfer in photoionized cyclopentanone dimer in the gas phase

    SciTech Connect

    Ghosh, Arup K.; Chatterjee, Piyali; Chakraborty, Tapas

    2014-07-28

    Time-of-flight mass spectra of cyclopentanone and its clusters cooled in a supersonic jet expansion have been measured following 4-, 3-, and 2-photon ionizations by the 2nd, 3rd, and 4th harmonic wavelengths, respectively, of a Q-switched Nd:YAG laser. The mass spectra reveal signatures of energetically favored keto to enol tautomerization of the molecular ion leading to intermolecular proton transfer, and this observation is found sharply dependent on the ionization wavelengths used. Electronic structure calculation predicts that in spite of the energetic preference, keto-enol conversion barrier of isolated molecular ion is high. However, the barrier is significantly reduced in a CH⋯O hydrogen-bonded dimer of the molecule. The transition states associated with tautomeric conversion of both cyclopentanone monomer and dimer cations have been identified by means of intrinsic reaction co-ordinate calculation. In a supersonic jet expansion, although a weakly bound dimer is readily generated, the corresponding cation and also the protonated counterpart are observed only for ionization by 532 nm. For other two ionization wavelengths, these species do not register in the mass spectra, where the competing reaction channels via α-cleavage of the ring become dominant. In contrast to the report of a recent study, we notice that the intact molecular ion largely survives fragmentations when ionized from the 2-photon resonant 3p Rydberg state as intermediate using nanosecond laser pulses, and the corresponding resonant 3-photon ionization spectrum has been recorded probing the intact molecular ion.

  14. Are Math Grades Cyclical?

    ERIC Educational Resources Information Center

    Adams, Gerald J.; Dial, Micah

    1998-01-01

    The cyclical nature of mathematics grades was studied for a cohort of elementary school students from a large metropolitan school district in Texas over six years (average cohort size of 8495). The study used an autoregressive integrated moving average (ARIMA) model. Results indicate that grades do exhibit a significant cyclical pattern. (SLD)

  15. Affordable Cyclic Voltammetry

    ERIC Educational Resources Information Center

    Stewart, Greg; Kuntzleman, Thomas S.; Amend, John R.; Collins, Michael J.

    2009-01-01

    Cyclic voltammetry is an important component of the undergraduate chemical curriculum. Unfortunately, undergraduate students rarely have the opportunity to conduct experiments in cyclic voltammetry owing to the high cost of potentiostats, which are required to control these experiments. By using MicroLab data acquisition interfaces in conjunction…

  16. Quercetin 3,7-dimethyl ether: a vasorelaxant flavonoid isolated from Croton schiedeanus Schlecht.

    PubMed

    Guerrero, M F; Puebla, P; Carrón, R; Martín, M L; San Román, L

    2002-10-01

    The vasorelaxant profile of quercetin 3,7-dimethyl ether, a flavonoid isolated from Croton schiedeanus Schlecht (Euphorbiaceae), was assessed in aortic rings isolated from Wistar rats. To gain insight into its structure-activity relationship, we compared this substance with quercetin 3,4',7-trimethyl ether (ayanin), another flavonoid isolated from this plant, quercetin 3,3',4',7-tetramethyl ether, a flavonoid synthesized by us, and quercetin. In addition we examined the interaction of quercetin 3,7-dimethyl ether with the nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) pathway. According to their pEC50 values (concentration producing a 50% inhibition of the maximal contractile response) to phenylephrine-induced precontraction in rat isolated aorta, the potency order was quercetin 3,7-dimethyl ether > quercetin > quercetin 3,4',7-trimethyl ether > quercetin 3,3',4',7-tetramethyl ether (4.70+/-0.18; 3.96+/-0.07; 3.64+/-0.02; 3.11+/-0.16). The relaxant effect of quercetin 3,7-dimethyl ether was significantly decreased by the removal of endothelium as well as by methylene blue, an inhibitor of guanylyl cyclase, and by N(G)-nitro-L-arginine methyl ester hydrochloride (L-NAME), an NO-synthase inhibitor. Therefore, quercetin 3,7-dimethyl ether has a NO/cGMP pathway-related profile, with increased vasorelaxant activity due to hydroxylation at positions 3 and 4 of the B ring. In addition, methylation at positions 3 and 7 with respect to quercetin of the C and A rings, respectively, seems to further enhance the vasorelaxant activity of quercetin 3,7-dimethyl ether.

  17. Polyarylene Ethers with Improved Properties

    NASA Technical Reports Server (NTRS)

    Hergenrother, P. M. (Inventor); Jensen, B. J. (Inventor); Havens, S. J. (Inventor)

    1986-01-01

    This invention relates to novel polyarylene ethers which possess the combination of high strength, toughness, and high use temperature with ease of extrusion and formation into complex objects. These polyarylene ethers are suitable for use in adhesives, coatings, films, membranes, and composite matrices. The polyarylene ethers of this invention are the polycondensation products from the reaction of either 1,3-bis (4-chloro or fluorobenzoyl) benzene with any one of the following bisphenolic compounds: bis (3-hydroxyphenyl) methane; bis (4-hydroxyphenyl) methane; 1,1-dimethyl-bis (4-hydroxyphenyl)methane, or 9,9-bis (4-hydroxyphenyl) fluorene. Random and block copolymers are also comprehended.

  18. Biodegradation of gasoline ether oxygenates.

    PubMed

    Hyman, Michael

    2013-06-01

    Ether oxygenates such as methyl tertiary butyl ether (MTBE) are added to gasoline to improve fuel combustion and decrease exhaust emissions. Ether oxygenates and their tertiary alcohol metabolites are now an important group of groundwater pollutants. This review highlights recent advances in our understanding of the microorganisms, enzymes and pathways involved in both the aerobic and anaerobic biodegradation of these compounds. This review also aims to illustrate how these microbiological and biochemical studies have guided, and have helped refine, molecular and stable isotope-based analytical approaches that are increasingly being used to detect and quantify biodegradation of these compounds in contaminated environments.

  19. Decarboxylative Csp(3)-Csp(3) coupling for benzylation of unstable ketone enolates: synthesis of p-(acylethyl)phenols.

    PubMed

    Wang, Sasa; Chen, Xinzheng; Ao, Qiaoqiao; Wang, Huifei; Zhai, Hongbin

    2016-08-01

    A new decarboxylative Csp(3)-Csp(3) coupling approach for the benzylation of ketone enolates has been developed. A variety of raspberry ketone derivatives were conveniently synthesized in good to excellent yields under mild conditions. A crossover reaction shed light on the mechanism of this tandem reaction. PMID:27378390

  20. The deglaciation in Picos de Europa (area of Enol Glacier) based on geomorphological and sedimentological studies

    NASA Astrophysics Data System (ADS)

    Ruiz-Fernández, Jesus; Oliva, Marc; García, Cristina

    2013-04-01

    The chronology for the deglaciation in the Cantabrian Range is still poorly understood. Several papers have proposed a maximum advance well before the LGM (Jiménez and Farias, 2002; Moreno et al. 2010; Serrano et al. 2012). The Western massif of Picos de Europa held a ice field of 50 km2. In this communication we present two cores collected in two glacial depressions in the frontal area of Enol Glacier that allow reconstructing the environment since the deglaciation of the massif. The first core (5.6 m long) was collected in the kame terrace of Belbin. This terrace was dammed by a lateral moraine corresponding to the phase of maximum expansion of Enol Glacier. Three clear layers are observed: the basal 2.5 m consists of grey clay with small gravel limestones; the second is 2 m thick and is composed of grey clays; the upper 1.1 m shows several paleosoils with abundant organic matter and charcoals. The based was dated at 14,810 ± 70 yr BP. This age represents a minimum age for the maximum expansion of Enol Glacier. The second core was collected in the glaciokarst depression of Vega del Bricial, located within a moraine complex corresponding to LGM. The core is 8 m long and looks very homogeneous. It consists of a succession of organic layers and slope deposits. Two radiocarbon dates were performed on the sediments at 8 and 2.8 m depth, resulting in 9,690 ± 260 and 3,420 ± 95 yr BP, respectively. Based on sedimentological and geomorphological evidences, we propose a chronology for the environmental changes occurred in this massif since the last glacial period. References Jiménez, M. and Farias, P., 2002. New radiometric and geomorphologic evidences of a Last Glacial Maximum older than 18 ka in SW European mountains: the example of Redes Natural Park (Cantabrian Mountains, NW Spain). Geodinamica Acta, 15, 93-101. Moreno, A., Valero, B. L., Jiménez, M., Domínguez, M. J., Mata, M. P., Navas, A., González, P., Stoll, H., Farias, P., Morellón, M., Corella, J. P

  1. Genetics Home Reference: cyclic neutropenia

    MedlinePlus

    ... Understand Genetics Home Health Conditions cyclic neutropenia cyclic neutropenia Enable Javascript to view the expand/collapse boxes. Download PDF Open All Close All Description Cyclic neutropenia is a disorder that causes frequent infections and ...

  2. Experimental and theoretical study of enol-keto prototropic tautomerism and photophysics of azomethine-BODIPY dyads.

    PubMed

    Pan, Zhong-Hua; Zhou, Jing-Wei; Luo, Geng-Geng

    2014-08-14

    In this study we report about two novel azomethine–BODIPY dyads 1 and 2. The two dyads have been, respectively, synthesized by covalent tethering of tautomeric ortho-hydroxy aromatic azomethine moieties including N-salicylideneaniline (SA) and N-naphthlideneaniline (NA) to a BODIPY fluorophore. Both of the two dyads 1 and 2 show enol-imine (OH) structures dominating in the crystalline state. Dyad 1 in the enol state is the most stable form at room temperature in most media, while enol–keto prototropic tautomerism of the NA moiety in solution is preserved in dyad 2, which can be reversibly converted between enol and keto forms in the environment's polarity. Visible illumination of dyad 2 in the enol state excites selectively the BODIPY fragment and then deactivates radiatively by emitting green light in the form of fluorescence, while the emission intensity of 2 in the keto state is quenched on the basis of the proton-coupled photoinduced electron transfer (PCPET) mechanism. This allows large fluorescence modulation between the two states of dyad 2 and generates a novel tautomerisable fluorescent switch. Theoretical calculations including calculated energies, potential energy surfaces (PESs) and intrinsic reaction coordinate (IRC) analysis further support that the single proton transfer reaction from an enol form to a transition state (TS) and from the TS to a keto form for 2 is easier to occur than that for 1, which accounts for the fluorescence quenching of 2 in methanol. The agreement of the experimental results and theoretical calculations clearly suggests that fluorescent and tautomeric components can be paired within the same molecular skeleton and the proton tautomerization of the latter can be designed to regulate the emission of the former. In addition, preliminary experiments revealed that 1 can be potentially used as a simple on/off fluorescent chemosensor which exhibited higher selectivity for Cu(2+) over other common cations.

  3. Chemoselective Deprotection of Triethylsilyl Ethers

    PubMed Central

    Chandra, Tilak; Broderick, William E.; Broderick, Joan B.

    2009-01-01

    An efficient and selective method was developed for the deprotection of triethylsilyl (TES) ethers using formic acid in methanol (5–10%) or in methylene chloride 2–5%) with excellent yields. TES ethers are selectively deprotected to the corresponding alcohols in high yields using formic acid in methanol under mild reaction conditions. Other hydroxyl protecting groups like t-butyldimethylsilyl (TBDMS) remain unaffected. PMID:20183570

  4. Imide/arylene ether copolymers

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J. (Inventor); Hergenrother, Paul M. (Inventor); Bass, Robert G. (Inventor)

    1992-01-01

    Imide/arylene ether block copolymers are prepared by reacting anhydride terminated poly(amic acids) with amine terminated poly(arylene ethers) in polar aprotic solvents and by chemically or thermally cyclodehydrating the resulting intermediate poly(amic acids). The resulting block copolymers have one glass transition temperature or two, depending upon the particular structure and/or the compatibility of the block units. Most of these block copolymers form tough, solvent resistant films with high tensile properties.

  5. Rearrangements of Cycloalkenyl Aryl Ethers.

    PubMed

    Törincsi, Mercedesz; Nagy, Melinda; Bihari, Tamás; Stirling, András; Kolonits, Pál; Novak, Lajos

    2016-01-01

    Rearrangement reactions of cycloalkenyl phenol and naphthyl ethers and the acid-catalyzed cyclization of the resulting product were investigated. Claisen rearrangement afforded 2-substituted phenol and naphthol derivatives. Combined Claisen and Cope rearrangement resulted in the formation of 4-substituted phenol and naphthol derivatives. In the case of cycloocthylphenyl ether the consecutive Claisen and Cope rearrangements were followed by an alkyl migration. The mechanism of this novel rearrangement reaction is also discussed. PMID:27104504

  6. Solid-State and Solution Structures of Glycinimine-Derived Lithium Enolates.

    PubMed

    Jin, Kyoung Joo; Collum, David B

    2015-11-18

    A combination of crystallographic, spectroscopic, and computational studies was applied to study the structures of lithium enolates derived from glycinimines of benzophenone and (+)-camphor. The solvents examined included toluene and toluene containing various concentrations of tetrahydrofuran, N,N,N',N'-tetramethylethylenediamine (TMEDA), (R,R)-N,N,N',N'-tetramethylcyclohexanediamine [(R,R)-TMCDA], and (S,S)-N,N,N',N'-tetramethylcyclohexanediamine [(S,S)-TMCDA]. Crystal structures show chelated monomers, symmetric disolvated dimers, S4-symmetric tetramers, and both S6- and D3d-symmetric hexamers. (6)Li NMR spectroscopic studies in conjunction with the method of continuous variations show how these species distribute in solution. Density functional theory computations offer insights into experimentally elusive details. PMID:26554898

  7. Crystal structure of the enol form of mesotrione: a benzoyl-cyclo-hexa-nedione herbicide.

    PubMed

    Kang, Gihaeng; Kim, Jineun; Park, Hyunjin; Kim, Tae Ho

    2015-08-01

    The title compound [systematic name: 3-hy-droxy-2-(4-methyl-sulfonyl-2-nitro-benzo-yl)cyclo-hex-2-enone], C14H13NO7S, is the enol form of a benzoyl-cyclo-hexa-nedione herbicide. As a result of this tautomerization, there is intra-molecular O-H⋯O hydrogen bond enclosing an S(6) ring motif. The cyclo-hexene ring has an envelope conformation, with the central CH2 C atom as the flap. Its mean plane is inclined to the benzene ring by 87.46 (8)°. In the crystal, mol-ecules are linked by a series of C-H⋯O hydrogen bonds, forming a three-dimensional framework. PMID:26396790

  8. Keto-enol tautomerization and intermolecular proton transfer in photoionized cyclopentanone dimer in the gas phase

    NASA Astrophysics Data System (ADS)

    Ghosh, Arup K.; Chatterjee, Piyali; Chakraborty, Tapas

    2014-07-01

    Time-of-flight mass spectra of cyclopentanone and its clusters cooled in a supersonic jet expansion have been measured following 4-, 3-, and 2-photon ionizations by the 2nd, 3rd, and 4th harmonic wavelengths, respectively, of a Q-switched Nd:YAG laser. The mass spectra reveal signatures of energetically favored keto to enol tautomerization of the molecular ion leading to intermolecular proton transfer, and this observation is found sharply dependent on the ionization wavelengths used. Electronic structure calculation predicts that in spite of the energetic preference, keto-enol conversion barrier of isolated molecular ion is high. However, the barrier is significantly reduced in a CH⋯O hydrogen-bonded dimer of the molecule. The transition states associated with tautomeric conversion of both cyclopentanone monomer and dimer cations have been identified by means of intrinsic reaction co-ordinate calculation. In a supersonic jet expansion, although a weakly bound dimer is readily generated, the corresponding cation and also the protonated counterpart are observed only for ionization by 532 nm. For other two ionization wavelengths, these species do not register in the mass spectra, where the competing reaction channels via α-cleavage of the ring become dominant. In contrast to the report of a recent study, we notice that the intact molecular ion largely survives fragmentations when ionized from the 2-photon resonant 3p Rydberg state as intermediate using nanosecond laser pulses, and the corresponding resonant 3-photon ionization spectrum has been recorded probing the intact molecular ion.

  9. Cyclic control stick

    DOEpatents

    Whitaker, Charles N.; Zimmermann, Richard E.

    1989-01-01

    A cyclic control stick of the type used in helicopters for reducing the safety hazards associated with such a mechanism in the event of a crewman being thrown violently into contact with the cyclic control stick resulting from a crash or the like. The cyclic control stick is configured to break away upon the exertion of an impact force which exceeds a predetermined value and/or is exerted for more than a momentary time duration. The cyclic control stick is also configured to be adjustable so as to locate the grip thereof as far away from the crewman as possible for safety reasons without comprising the comfort of the crewman or the use of the control stick, and a crushable pad is provided on the top of the grip for impact energy absorbing purposes.

  10. Cyclic steps on ice

    NASA Astrophysics Data System (ADS)

    Yokokawa, M.; Izumi, N.; Naito, K.; Parker, G.; Yamada, T.; Greve, R.

    2016-05-01

    Boundary waves often form at the interface between ice and fluid flowing adjacent to it, such as ripples under river ice covers, and steps on the bed of supraglacial meltwater channels. They may also be formed by wind, such as the megadunes on the Antarctic ice sheet. Spiral troughs on the polar ice caps of Mars have been interpreted to be cyclic steps formed by katabatic wind blowing over ice. Cyclic steps are relatives of upstream-migrating antidunes. Cyclic step formation on ice is not only a mechanical but also a thermodynamic process. There have been very few studies on the formation of either cyclic steps or upstream-migrating antidunes on ice. In this study, we performed flume experiments to reproduce cyclic steps on ice by flowing water, and found that trains of steps form when the Froude number is larger than unity. The features of those steps allow them to be identified as ice-bed analogs of cyclic steps in alluvial and bedrock rivers. We performed a linear stability analysis and obtained a physical explanation of the formation of upstream-migrating antidunes, i.e., precursors of cyclic steps. We compared the results of experiments with the predictions of the analysis and found the observed steps fall in the range where the analysis predicts interfacial instability. We also found that short antidune-like undulations formed as a precursor to the appearance of well-defined steps. This fact suggests that such antidune-like undulations correspond to the instability predicted by the analysis and are precursors of cyclic steps.

  11. Space, Time, Ether, and Kant

    NASA Astrophysics Data System (ADS)

    Wong, Wing-Chun Godwin

    This dissertation focused on Kant's conception of physical matter in the Opus postumum. In this work, Kant postulates the existence of an ether which fills the whole of space and time with its moving forces. Kant's arguments for the existence of an ether in the so-called Ubergang have been acutely criticized by commentators. Guyer, for instance, thinks that Kant pushes the technique of transcendental deduction too far in trying to deduce the empirical ether. In defense of Kant, I held that it is not the actual existence of the empirical ether, but the concept of the ether as a space-time filler that is subject to a transcendental deduction. I suggested that Kant is doing three things in the Ubergang: First, he deduces the pure concept of a space-time filler as a conceptual hybrid of the transcendental object and permanent substance to replace the category of substance in the Critique. Then he tries to prove the existence of such a space-time filler as a reworking of the First Analogy. Finally, he takes into consideration the empirical determinations of the ether by adding the concept of moving forces to the space -time filler. In reconstructing Kant's proofs, I pointed out that Kant is absolutely committed to the impossibility of action-at-a-distance. If we add this new principle of no-action-at-a-distance to the Third Analogy, the existence of a space-time filler follows. I argued with textual evidence that Kant's conception of ether satisfies the basic structure of a field: (1) the ether is a material continuum; (2) a physical quantity is definable on each point in the continuum; and (3) the ether provides a medium to support the continuous transmission of action. The thrust of Kant's conception of ether is to provide a holistic ontology for the transition to physics, which can best be understood from a field-theoretical point of view. This is the main thesis I attempted to establish in this dissertation.

  12. Cyclic polymers from alkynes

    NASA Astrophysics Data System (ADS)

    Roland, Christopher D.; Li, Hong; Abboud, Khalil A.; Wagener, Kenneth B.; Veige, Adam S.

    2016-08-01

    Cyclic polymers have dramatically different physical properties compared with those of their equivalent linear counterparts. However, the exploration of cyclic polymers is limited because of the inherent challenges associated with their synthesis. Conjugated linear polyacetylenes are important materials for electrical conductivity, paramagnetic susceptibility, optical nonlinearity, photoconductivity, gas permeability, liquid crystallinity and chain helicity. However, their cyclic analogues are unknown, and therefore the ability to examine how a cyclic topology influences their properties is currently not possible. We have solved this challenge and now report a tungsten catalyst supported by a tetraanionic pincer ligand that can rapidly polymerize alkynes to form conjugated macrocycles in high yield. The catalyst works by tethering the ends of the polymer to the metal centre to overcome the inherent entropic penalty of cyclization. Gel-permeation chromatography, dynamic and static light scattering, viscometry and chemical tests are all consistent with theoretical predictions and provide unambiguous confirmation of a cyclic topology. Access to a wide variety of new cyclic polymers is now possible by simply choosing the appropriate alkyne monomer.

  13. Cyclic polymers from alkynes.

    PubMed

    Roland, Christopher D; Li, Hong; Abboud, Khalil A; Wagener, Kenneth B; Veige, Adam S

    2016-08-01

    Cyclic polymers have dramatically different physical properties compared with those of their equivalent linear counterparts. However, the exploration of cyclic polymers is limited because of the inherent challenges associated with their synthesis. Conjugated linear polyacetylenes are important materials for electrical conductivity, paramagnetic susceptibility, optical nonlinearity, photoconductivity, gas permeability, liquid crystallinity and chain helicity. However, their cyclic analogues are unknown, and therefore the ability to examine how a cyclic topology influences their properties is currently not possible. We have solved this challenge and now report a tungsten catalyst supported by a tetraanionic pincer ligand that can rapidly polymerize alkynes to form conjugated macrocycles in high yield. The catalyst works by tethering the ends of the polymer to the metal centre to overcome the inherent entropic penalty of cyclization. Gel-permeation chromatography, dynamic and static light scattering, viscometry and chemical tests are all consistent with theoretical predictions and provide unambiguous confirmation of a cyclic topology. Access to a wide variety of new cyclic polymers is now possible by simply choosing the appropriate alkyne monomer. PMID:27442285

  14. Sulfonimide-containing poly(arylene ether)s and poly(arylene ether sulfone)s, methods for producing the same, and uses thereof

    DOEpatents

    Hofmann, Michael A.

    2006-11-14

    The present invention is directed to sulfonimide-containing polymers, specifically sulfonimide-containing poly(arylene ether)s and sulfonimide-containing poly(arylene ether sulfone)s, and processes for making the sulfonimide-containing poly(arylene ether)s and sulfonimide-containing poly(arylene ether sulfone)s, for use conductive membranes and fuel cells.

  15. Enolate Stabilization by Anion-π Interactions: Deuterium Exchange in Malonate Dilactones on π-Acidic Surfaces.

    PubMed

    Miros, François N; Zhao, Yingjie; Sargsyan, Gevorg; Pupier, Marion; Besnard, Céline; Beuchat, César; Mareda, Jiri; Sakai, Naomi; Matile, Stefan

    2016-02-18

    Of central importance in chemistry and biology, enolate chemistry is an attractive topic to elaborate on possible contributions of anion-π interactions to catalysis. To demonstrate the existence of such contributions, experimental evidence for the stabilization of not only anions but also anionic intermediates and transition states on π-acidic aromatic surfaces is decisive. To tackle this challenge for enolate chemistry with maximal precision and minimal uncertainty, malonate dilactones are covalently positioned on the π-acidic surface of naphthalenediimides (NDIs). Their presence is directly visible in the upfield shifts of the α-protons in the (1) H NMR spectra. The reactivity of these protons on π-acidic surfaces is measured by hydrogen-deuterium (H-D) exchange for 11 different examples, excluding controls. The velocity of H-D exchange increases with π acidity (NDI core substituents: SO2 R>SOR>H>OR>OR/NR2 >SR>NR2 ). The H-D exchange kinetics vary with the structure of the enolate (malonates>methylmalonates, dilactones>dithiolactones). Moreover, they depend on the distance to the π surface (bridge length: 11-13 atoms). Most importantly, H-D exchange depends strongly on the chirality of the π surface (chiral sulfoxides as core substituents; the crystal structure of the enantiopure (R,R,P)-macrocycle is reported). For maximal π acidity, transition-state stabilizations up to -18.8 kJ mol(-1) are obtained for H-D exchange. The Brønsted acidity of the enols increases strongly with π acidity of the aromatic surface, the lowest measured pKa =10.9 calculates to a ΔpKa =-5.5. Corresponding to the deprotonation of arginine residues in neutral water, considered as "impossible" in biology, the found enolate-π interactions are very important. The strong dependence of enolate stabilization on the unprecedented seven-component π-acidity gradient over almost 1 eV demonstrates quantitatively that such important anion-π activities can be expected only from

  16. Ether resistance in Drosophila melanogaster.

    PubMed

    Deery, B J; Parsons, P A

    1972-01-01

    Strains set up from single inseminated females of D. melanogaster from the wild differ in their resistance to the anaesthetics, ether and chloroform. The main differences between four selected extreme strains could be explained by additive genes, which in the case of ether resistance were located to regions of chromosomes 2 and 3. The lack of correspondence between ether and chloroform resistance between strains indicates that although the type of genetic architecture controlling the traits is similar, the actual genes differ, which is reasonable in view of their differing chemical structures. Quite high heritabilities were found for resistance to ether based on five inbred strains. No significant associations between resistance to ether and body weight, developmental rate or longevity were found.It is clear that resistance to both anaesthetics would be amenable to more detailed genetic analyses. It is pointed out that the general conclusions reached from such studies will have implications with respect to the effect of chemicals such as insecticides, not naturally present in nature.

  17. Direct carbon-carbon bond formation via reductive soft enolization: a syn-selective Mannich addition of α-iodo thioesters.

    PubMed

    Truong, Ngoc; Sauer, Scott J; Seraphin-Hatcher, Cyndie; Coltart, Don M

    2016-08-16

    The β-amino carboxylic acid moiety is a key feature of numerous important biologically active compounds. We describe a syn-selective direct Mannich addition reaction that uses α-iodo thioesters and sulfonyl imines and produces β-amino thioesters. Enolate formation is achieved by reductive soft enolization. The products of the reaction provide straightforward access to biologically important β-lactams through a variety of known reactions. PMID:27492274

  18. Anion-π Catalysis of Enolate Chemistry: Rigidified Leonard Turns as a General Motif to Run Reactions on Aromatic Surfaces.

    PubMed

    Cotelle, Yoann; Benz, Sebastian; Avestro, Alyssa-Jennifer; Ward, Thomas R; Sakai, Naomi; Matile, Stefan

    2016-03-18

    To integrate anion-π, cation-π, and ion pair-π interactions in catalysis, the fundamental challenge is to run reactions reliably on aromatic surfaces. Addressing a specific question concerning enolate addition to nitroolefins, this study elaborates on Leonard turns to tackle this problem in a general manner. Increasingly refined turns are constructed to position malonate half thioesters as close as possible on π-acidic surfaces. The resulting preorganization of reactive intermediates is shown to support the disfavored addition to enolate acceptors to an absolutely unexpected extent. This decisive impact on anion-π catalysis increases with the rigidity of the turns. The new, rigidified Leonard turns are most effective with weak anion-π interactions, whereas stronger interactions do not require such ideal substrate positioning to operate well. The stunning simplicity of the motif and its surprisingly strong relevance for function should render the introduced approach generally useful.

  19. Random cyclic matrices.

    PubMed

    Jain, Sudhir R; Srivastava, Shashi C L

    2008-09-01

    We present a Gaussian ensemble of random cyclic matrices on the real field and study their spectral fluctuations. These cyclic matrices are shown to be pseudosymmetric with respect to generalized parity. We calculate the joint probability distribution function of eigenvalues and the spacing distributions analytically and numerically. For small spacings, the level spacing distribution exhibits either a Gaussian or a linear form. Furthermore, for the general case of two arbitrary complex eigenvalues, leaving out the spacings among real eigenvalues, and, among complex conjugate pairs, we find that the spacing distribution agrees completely with the Wigner distribution for a Poisson process on a plane. The cyclic matrices occur in a wide variety of physical situations, including disordered linear atomic chains and the Ising model in two dimensions. These exact results are also relevant to two-dimensional statistical mechanics and nu -parametrized quantum chromodynamics. PMID:18851127

  20. Ethereal embodiment of cancer patients.

    PubMed

    van der Riet, P

    1999-10-01

    Ethereal embodiment is the attending and focusing on the body through discourses such as meditation, visualisation and massage, and the experiencing a new sense of the embodied being as balanced, connected, centred and of being made whole. This paper continues a previous article titled 'Massaged embodiment of cancer patients'. Data from my doctoral studies are analysed utilising crucial concepts of poststructuralism such as subjectivity, discourse, power and history to examine ethereal embodiment. This paper will address the advantages of visualisation and discusses the link between spirituality, embodiment, and memory.

  1. Grignard Reactions in "Wet" Ether

    NASA Astrophysics Data System (ADS)

    Smith, David H.

    1999-10-01

    A small laboratory ultrasonic bath can be used to initiate the Grignard reaction of alkyl or aryl bromides in regular laboratory-quality, undried, diethyl ether and in simple undried test tubes. The reaction typically starts within 30 to 45 seconds and is self-sustaining. Yields and products are the same as obtained with carefully dried ether and equipment. We normally run this reaction at the 1.5-gram scale, but the procedure can be scaled up to at least 10 g of the bromide.

  2. Synthesis of 11C labelled methyl esters: transesterification of enol esters versus BF 3 catalysed esterification—a comparative study

    NASA Astrophysics Data System (ADS)

    Ackermann, Uwe; Blanc, Paul; Falzon, Cheryl L.; Issa, William; White, Jonathan; Tochon-Danguy, Henri J.; Sachinidis, John I.; Scott, Andrew M.

    2006-01-01

    C-11 labelled methyl esters have been synthesized via the transesterification of enol esters in the presence of C-11 methanol and 1,3 dichlorodibutylstannoxane as catalyst. This method leaves functional groups intact and allows access to a wider variety of C-11 labelled methyl esters compared to the BF 3 catalysed ester formation, which uses carboxylic acids and C-11 methanol as starting materials.

  3. Flow in cyclic cosmology

    SciTech Connect

    Kinney, William H.; Dizgah, Azadeh Moradinezhad

    2010-10-15

    In this paper, we use a known duality between expanding and contracting cosmologies to construct a dual of the inflationary flow hierarchy applicable to contracting cosmologies such as ekpyrotic and cyclic models. We show that the inflationary flow equations are invariant under the duality and therefore apply equally well to inflation or to cyclic cosmology. We construct a self-consistent small-parameter approximation dual to the slow-roll approximation in inflation, and calculate the power spectrum of perturbations in this limit. We also recover the matter-dominated contracting solution of Wands, and the recently proposed adiabatic ekpyrosis solution.

  4. Cyclic membrane separation process

    DOEpatents

    Nemser, Stuart M.

    2005-05-03

    A cyclic process for controlling environmental emissions of volatile organic compounds (VOC) from vapor recovery in storage and dispensing operations of liquids maintains a vacuum in the storage tank ullage. In the first part of a two-part cyclic process ullage vapor is discharged through a vapor recovery system in which VOC are stripped from vented gas with a selectively gas permeable membrane. In the second part, the membrane is inoperative while gas pressure rises in the ullage. In one aspect of this invention, a vacuum is drawn in the membrane separation unit thus reducing overall VOC emissions.

  5. Realistic Cyclic Magnetic Universe

    NASA Astrophysics Data System (ADS)

    Medeiros, L. G.

    2012-09-01

    This work presents a complete cyclic cosmological scenario based on nonlinear magnetic field. It is constructed from a model composed of five fluids, namely baryonic matter, dark matter, radiation, neutrinos and a cosmological magnetic field. The first four fluids are treated in the standard way and the fifth fluid, the magnetic field, is described by a nonlinear electrodynamics. The free parameters are fitted by observational data (SNIa, CMB, extragalactic magnetic fields, etc.) and by simple theoretical considerations. As a result arises a cyclic cosmological model that preserves the main successes of the standard Big Bang model and solves some other problems such as the initial singularity, the present acceleration and the Big Rip.

  6. Artificial photosynthesis of. beta. -ketocarboxylic acids from carbon dioxide and ketones via enolate complexes of aluminum porphyrin

    SciTech Connect

    Hirai, Yasuhiro; Aida, Takuzo; Inoue, Shohei )

    1989-04-12

    Photochemical fixation of carbon dioxide is of much interest in connection with biological photosynthesis by green plants as well as from the viewpoint of carbon resource utilization. One of the important steps in the assimilation of carbon dioxide is the carboxylation of a carbonyl compound into ketocarboxylic acid, where the reaction proceeds via an enolate species as reactive intermediate. For example, in four carbon (C{sub 4}) pathway and Crassulacean acid metabolism (CAM) processes, pyruvate is converted with the aid of ATP into phosphoenolpyruvate, which is subsequently carboxylated to give oxaloacetate by the action of pyruvate carboxylase. In relation to this interesting biological process, some artificial systems have been exploited for the synthesis of {beta}-ketocarboxylic acid derivatives from carbon dioxide and ketones using nucleophiles such as metal carbonates, thiazolates, phenolates, alkoxides, and strong organic as well as inorganic basis, which promote the enolization of ketones in the intermediate step. We wish to report here a novel, visible light-induced fixation of carbon dioxide with the enolate complex of aluminum porphyrin, giving {beta}-ketocarboxylic acid under mild conditions.

  7. 21 CFR 868.5420 - Ether hook.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Ether hook. 868.5420 Section 868.5420 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5420 Ether hook. (a) Identification. An ether hook is a...

  8. 21 CFR 868.5420 - Ether hook.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Ether hook. 868.5420 Section 868.5420 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5420 Ether hook. (a) Identification. An ether hook is a...

  9. 21 CFR 868.5420 - Ether hook.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Ether hook. 868.5420 Section 868.5420 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5420 Ether hook. (a) Identification. An ether hook is a...

  10. 21 CFR 868.5420 - Ether hook.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Ether hook. 868.5420 Section 868.5420 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5420 Ether hook. (a) Identification. An ether hook is a...

  11. 21 CFR 868.5420 - Ether hook.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Ether hook. 868.5420 Section 868.5420 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5420 Ether hook. (a) Identification. An ether hook is a...

  12. 40 CFR 721.3364 - Aliphatic ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Aliphatic ether. 721.3364 Section 721... Aliphatic ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an aliphatic ether (PMN P-93-1381) is subject to reporting under...

  13. 40 CFR 721.3374 - Alkylenediolalkyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Alkylenediolalkyl ether. 721.3374... Substances § 721.3374 Alkylenediolalkyl ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as an alkylenediolalkyl ether (PMN P-93-362) is subject...

  14. 40 CFR 721.3374 - Alkylenediolalkyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alkylenediolalkyl ether. 721.3374... Substances § 721.3374 Alkylenediolalkyl ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as an alkylenediolalkyl ether (PMN P-93-362) is subject...

  15. 40 CFR 721.3437 - Dialkyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Dialkyl ether. 721.3437 Section 721... Dialkyl ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as dialkyl ether (PMN P-93-1308) is subject to reporting under this...

  16. 40 CFR 721.3380 - Anilino ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Anilino ether. 721.3380 Section 721... Anilino ether. (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified generically as anilino ether (P-83-910) is subject to reporting under this section...

  17. 40 CFR 721.3364 - Aliphatic ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Aliphatic ether. 721.3364 Section 721... Aliphatic ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an aliphatic ether (PMN P-93-1381) is subject to reporting under...

  18. 40 CFR 721.3380 - Anilino ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Anilino ether. 721.3380 Section 721... Anilino ether. (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified generically as anilino ether (P-83-910) is subject to reporting under this section...

  19. 40 CFR 721.3437 - Dialkyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Dialkyl ether. 721.3437 Section 721... Dialkyl ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as dialkyl ether (PMN P-93-1308) is subject to reporting under this...

  20. Cyclic Voltammetry Experiment.

    ERIC Educational Resources Information Center

    Van Benschoten, James J.; And Others

    1983-01-01

    Describes a three-part experiment designed to introduce cyclic voltammetry to graduate/undergraduate students. Part 1 demonstrates formal reduction potential, redox electron transfer, diffusion coefficient, and electrochemical reversibility. Part 2 investigates electrochemical behavior of acetaminophen. Part 3 examines such experimental variables…

  1. Radioimmunoassay for cyclic nucleotides

    SciTech Connect

    Chiang, C.S.

    1984-02-21

    An improved radioimmunoassay for the determination of cyclic nucleotides in body fluids which comprises adding a source of divalent cation prior to assay minimizes the effects of both endogenous calcium ion and EDTA used as an anticoagulant in blood plasma samples.

  2. Bis(chloroethyl)ether (BCEE)

    Integrated Risk Information System (IRIS)

    Bis ( chloroethyl ) ether ( BCEE ) ; CASRN 111 - 44 - 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 fo

  3. p,p\\'-Dibromodiphenyl ether

    Integrated Risk Information System (IRIS)

    p , p ' - Dibromodiphenyl ether ; CASRN 2050 - 47 - 7 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

  4. Bis(chloromethyl)ether (BCME)

    Integrated Risk Information System (IRIS)

    Bis ( chloromethyl ) ether ( BCME ) ; CASRN 542 - 88 - 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 f

  5. Propylene glycol monomethyl ether (PGME)

    Integrated Risk Information System (IRIS)

    Propylene glycol monomethyl ether ( PGME ) ; CASRN 107 - 98 - 2 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 Assess

  6. Lacinilene C 7-methyl ether

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Lacinilene C 7-methyl ether is an antimicrobial compound produced by the cotton plant in response to attack by pathogens. For the first time, we now report the crystal structure of this compound. This may prove useful in studies on the interaction of the compound with pathogenic fungal cells....

  7. Desoxyhemigossypol-6-methyl-ether

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Desoxyhemigossypol-6-methyl ether is an antimicrobial compound produced by the cotton plant in response to attack by pathogens. For the first time, we now report the crystal structure of this compound. This may prove useful in studies on the interaction of the compound with pathogenic fungal cells...

  8. Synthesis of (E,E)-Germacrane Sesquiterpene Alcohols via Enolate-Assisted 1,4-Fragmentation.

    PubMed

    Minnaard, Adriaan J.; Wijnberg, Joannes B. P. A.; de Groot, Aede

    1997-10-17

    An efficient method has been developed for the synthesis of (E,E)-germacrane sesquiterpene alcohols. The key step in these syntheses involves the enolate-assisted 1,4-fragmentation of properly functionalized perhydro-1-naphthalenecarboxaldehydes with 1 equiv of sodium tert-amylate as base, to give the corresponding (E,E)-germacrane aldehydes. These aldehydes are not very stable, and in situ reduction of the aldehyde function with Red-Al is required to obtain high yields of the desired germacrane alcohols. This procedure has led to the successful synthesis of 15-hydroxygermacrene B (4) and 15-hydroxyhedycaryol (35) from the mesylates 6 and 33, respectively. When KHMDS is used instead of sodium tert-amylate in the fragmentation reaction of 6, isomerization of the initially formed C(4)-C(5) E double bond cannot be avoided and results, after in situ reduction with Red-Al, in the formation of the (E,Z)-germacrane alcohol 24. The 15-hydroxy-(E,E)-germacranes are excellent starting materials for the selective synthesis of the corresponding 4,5-epoxides, which in turn can perfectly well be used in studies on the biomimetic formation of guaiane sesquiterpenes.

  9. Mechanistic Study of the Asymmetric Carbonyl-Ene Reaction between Alkyl Enol Ethers and Isatin Catalyzed by the N,N'-Dioxide-Mg(OTf)2 Complex.

    PubMed

    Wang, Junming; Su, Zhishan; Yang, Na; Hu, Changwei

    2016-08-01

    The mechanism and origin of the stereoselectivity of the asymmetric carbonyl-ene reaction between N-methyl-protected isatin and 2-methyloxypropene catalyzed by the N,N'-dioxide-Mg(OTf)2 complex were investigated by DFT and ONIOM methods. The background reaction occurred via a two-stage, one-step mechanism with a high activation barrier of 30.4 kcal mol(-1) at the B3LYP-D3(BJ)/6-311G**(SMD, CH2Cl2)//B3LYP/6-31G*(SMD, CH2Cl2) level at 303 K. Good linear correlations between the global nucleophilicity index (N) and the activation energy barrier (ΔG(⧧)) were found. The chiral N,N'-Mg(II) complex catalyst could enhance the electrophilicity of the isatin substrate by forming hexacoordinate Mg(II) reactive species. The substituent at the ortho positions of aniline combined with the aliphatic ring of the backbone in the chiral N,N'-dioxide ligand played an important role in the construction of a favorable "pocket-like" chiral environment (chiral pocket) around the Mg(II) center, directing the preferential orientation of the incoming substrate. An unfavorable steric arrangement in the re-face attack pathway translated into a more destabilizing activation strain of the ene substrate, enhancing enantiodifferentiation of two competing pathways for the desired R product. This work also suggested a new phosphine ligand (N-L1) for the formation of the Mg(II) complex catalyst for the asymmetric carbonyl-ene reaction. The chiral environment and Lewis acidity of the Mg(II) complex could be fine-tuned by introduction of P-donor units into the ligand for highly efficient asymmetric catalysis. PMID:27400326

  10. Engineering cyclic peptide toxins.

    PubMed

    Clark, Richard J; Craik, David J

    2012-01-01

    Peptide-based toxins have attracted much attention in recent years for their exciting potential applications in drug design and development. This interest has arisen because toxins are highly potent and selectively target a range of physiologically important receptors. However, peptides suffer from a number of disadvantages, including poor in vivo stability and poor bioavailability. A number of naturally occurring cyclic peptides have been discovered in plants, animals, and bacteria that have exceptional stability and potentially ameliorate these disadvantages. The lessons learned from studies of the structures, stabilities, and biological activities of these cyclic peptides can be applied to the reengineering of toxins that are not naturally cyclic but are amenable to cyclization. In this chapter, we describe solid-phase chemical synthetic methods for the reengineering of peptide toxins to improve their suitability as therapeutic, diagnostic, or imaging agents. The focus is on small disulfide-rich peptides from the venoms of cone snails and scorpions, but the technology is potentially widely applicable to a number of other peptide-based toxins. PMID:22230565

  11. Excited state enol-keto tautomerization in salicylic acid: A supersonic free jet study

    NASA Astrophysics Data System (ADS)

    Bisht, Prem B.; Petek, Hrvoje; Yoshihara, Keitaro; Nagashima, Umpei

    1995-10-01

    Excited state enol-keto isomerization in salicylic acid (SA) monomer and dimer has been studied in a supersonic free jet expansion. Two carboxylic group rotamers of SA with significantly different photophysical properties are found in the expansion. Rotamer I, the major form of SA in the expansion, has an intramolecular hydrogen bond and can undergo excited state tautomerization reaction. Its S1 origin is at 335.34 nm. Single vibronic level emission spectra are dominated by progressions in OH stretching (3230 cm-1), and in-plane bending of the carboxylic group (240 cm-1). The spectra appear to consist of two components, normal (UV) and tautomer (BLUE) emissions, even at the origin. The intensity of the BLUE relative to the UV emission depends on the vibronic state, rather than the excess vibrational energy between the origin and 1100 cm-1. The fluorescence decay time profiles for both the emission components of rotamer I are identical within ˜1 ns experimental time resolution. A nonradiative decay process with an activation energy of ˜1100 cm-1 is deduced from an abrupt decrease in fluorescence lifetimes above this energy. The rotamer II cannot undergo excited state tautomerization. Its electronic origin is at 311.52 nm and emits only UV fluorescence. Upon increasing the concentration of the SA sample, a new spectrum is observed. Due to a nonlinear concentration dependence of the intensity and the propensity of SA to form dimers in solution, it is assigned to the SA dimer. This spectrum shows possible evidence of double proton transfer in the S1 state.

  12. Inhibition of E. coli P-enolpyruvate carboxylase by P-enol-3-bromopyruvate

    SciTech Connect

    Asem, K.; Smith, T.E.

    1986-05-01

    The generality of the mechanism based inhibition of P-enolpyruvate carboxylases (PEPCase) by P-enol-3-bromopyruvate (BrPEP) was tested by measuring its effects on the allosterically regulated enzyme from E. coli. In the presence of 1mM Mn/sup 2 +/, BrPEP appears to be a competitive inhibitor (K/sub i/ = 0.0087mM) of PEPCase. Incubation of 0.005mM PEPCase with 0.5mM (or 1.0mM)BrPEP along with H/sup 14/CO/sub 3//sup -/ and Mn/sup 2 +/, yielded, upon reduction with NaBH/sub 4/, a protein containing radioactivity in an amount approximately proportional to that expected from the loss of catalytic activity. At both a 25- and a 50-fold excess (0.5mM and 1.0mM, respectively) of BrPEP to PEPCase subunits, first order loss of activity occurred with k values of 5.24 x 10/sup -3/ min/sup -1/ and 1.03 x 10/sup -2/ min/sup -1/, respectively. At the lower concentration of BrPEP the inactivation process appeared to be reversible after 40 min with no further inhibition occurring even up to two hours of incubation. At the higher concentration of BrPEP, the rate of inhibition slowed dramatically after 50 min and appeared insignificant over the next hour. These data suggest that BrPEP irreversibly inactivates the E. coli PEP carboxylase, but that there may be considerable dissociation of the product, Br-oxaloacetate, before irreversible binding occurs, and that the reduced rate of inactivation may be due to depletion of BrPEP.

  13. Theoretical and vibrational spectroscopic approach to keto-enol tautomerism in methyl-2-(4-methoxybenzoyl)-3-(4-methoxyphenyl)-3-oxopropanoylcarbamate

    NASA Astrophysics Data System (ADS)

    Arı, Hatice; Özpozan, Talat; Büyükmumcu, Zeki; Kabacalı, Yiğit; Saçmaci, Mustafa

    2016-10-01

    A carbamate compound having tricarbonyl groups, methyl-2-(4-methoxybenzoyl)-3-(4-methoxyphenyl)-3-oxopropanoylcarbamate (BPOC) was investigated from theoretical and vibrational spectroscopic point of view employing quantum chemical methods. Hybrid Density Functionals (B3LYP, X3LYP and B3PW91) with 6-311 G(d,p) basis set were used for the calculations. Rotational barrier and conformational analyses were performed to find the most stable conformers of keto and enol forms of the molecule. Three transition states for keto-enol tautomerism in gas phase were determined. The results of the calculations show that enol-1 form of BPOC is more stable than keto and enol-2 forms. Hydrogen bonding investigation including Natural bond orbital analysis (NBO) for all the tautomeric structures was employed to compare intra-molecular interactions. The energies of HOMO and LUMO molecular orbitals for all tautomeric forms of BPOC were predicted. Normal Coordinate Analysis (NCA) was carried out for the enol-1 to assign vibrational bands of IR and Raman spectra. The scaling factors were calculated as 0.9721, 0.9697 and 0.9685 for B3LYP, X3LYP and B3PW91 methods, respectively. The correlation graphs of experimental versus calculated vibrational wavenumbers were plotted and X3LYP method gave better frequency agreement than the others.

  14. Wholly Aromatic Ether-imides. Potential Materials for n-Type Semiconductors

    NASA Technical Reports Server (NTRS)

    Dingemans, Theo J.; St.Clair, Terry L.; Samulski, Edward T.; Bushnell, Dennis M. (Technical Monitor)

    2002-01-01

    We report on the synthesis and characterization of a novel series low-molar-mass ether-imide rod-shaped model compounds. All ether-imides were obtained by terminating the appropriate rigid core dianhydride, i.e. pyromellitic dianhydride (PMDA), 1,4,5,8-naphthalenetetracarboxylic dianhydride (NDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), and 3,3,4,4'-oxydiphthalic dianhydride (ODPA) with three flexible aryl-ether tails of different chain length. The mono-functional aryl-ether amines, i.e. 4-(3-phenoxy-phenoxy)-phenylamine (2) and 4-(3-phenoxy-3-phenoxy-phenoxy)-phenylamine (4), were synthesized using standard fluoro-displacement and Ullmann condensation techniques. The corresponding ether-imide model compounds were obtained in high yields using a one-step solution imidization procedure. Increasing the number of meta-substituted aryl-ether units reduces the melt transition temperatures and at the same time it increases the solubility of the model compounds. Most model compounds are crystalline solids and form isotropic melts upon heating. 2,7-Bis-(-4-phenoxy-phenyl)-benzo[Imn][3,8]phenanthroline1,3,6,8-tetraone (NDA-n0), however, displays a smectic A (SA) when cooled from the isotropic phase, followed by what appears to be either a highly ordered smectic phase or a, columnar phase. This is the first example, known to date, in which a mesophase is detected in a wholly aromatic ether-imide compound. For all compounds we present spectroscopic data and X-ray diffraction data. Cyclic voltammetry was used to determine the redox behavior and pertinent energy levels of the model compounds.

  15. Measuring exposures to glycol ethers.

    PubMed Central

    Clapp, D E; Zaebst, D D; Herrick, R F

    1984-01-01

    In 1981, NIOSH began investigating the potential reproductive health effects resulting from exposures to a class of organic solvents known generically as glycol ethers (GE). This research was begun as a result of the NIOSH criteria document development program which revealed little data available on the health effects of glycol ether exposure. Toxicologic research was begun by NIOSH and other researchers which suggested substantial reproductive effects in animals. These animal data motivated a study of human exposures in the occupational setting. In 1981 and 1982 NIOSH conducted several walk-through surveys which included preliminary measurements of exposures in a variety of industries including painting trades, coal mining, production blending and distribution facilities, aircraft fueling, and communications equipment repair facilities. The human exposure data from these surveys is summarized in this paper with most results well below 1 parts per million (ppm) and only a few values approaching 10 ppm. Blood samples were collected at one site resulting in GE concentrations below the limit of detection. Exposures to airborne glycol ethers, in the industries investigated during the collection of this data, revealed several problems in reliably sampling GE at low concentrations. It became apparent, from the data and observations of work practices, that air monitoring alone provided an inadequate index of GE exposure. Further field studies of exposure to GE are anticipated, pending location of additional groups of exposed workers and development of more reliable methods for characterizing exposure, especially biological monitoring. PMID:6499824

  16. Structure and vibrational assignment of the enol form of 1,1,1-trifluoro-2,4-pentanedione.

    PubMed

    Zahedi-Tabrizi, Mansoureh; Tayyari, Fariba; Moosavi-Tekyeh, Zainab; Jalali, Alireza; Tayyari, Sayyed Faramarz

    2006-10-01

    Molecular structure of 1,1,1-trifluoro-pentane-2,4-dione, known as trifluoro-acetylacetone (TFAA), has been investigated by means of Density Functional Theory (DFT) calculations and the results were compared with those of acetylacetone (AA) and hexafluoro-acetylacetone (HFAA). The harmonic vibrational frequencies of both stable cis-enol forms were calculated at B3LYP level of theory using 6-31G** and 6-311++G** basis sets. We also calculated the anharmonic frequencies at B3LYP/6-31G** level of theory for both stable cis-enol isomers. The calculated frequencies, Raman and IR intensities, and depolarization ratios were compared with the experimental results. The energy difference between the two stable cis-enol forms, calculated at B3LYP/6-311++G**, is only 5.89 kJ/mol. The observed vibrational frequencies and Raman and IR intensities are in excellent agreement with the corresponding values calculated for the most stable conformation, 2TFAA. According to the theoretical calculations, the hydrogen bond strength for the most stable conformer is 57 kJ/mol, about 9.5kJ/mol less than that of AA and about 14.5 kJ/mol more than that of HFAA. These hydrogen bond strengths are consistent with the frequency shifts for OH/OD stretching and OH/OD out-of-plane bending modes upon substitution of CH(3) groups with CF(3) groups. By comparing the vibrational spectra of both theoretical and experimental data, it was concluded that 2TFAA is the dominant isomer. PMID:16500140

  17. Structure and vibrational assignment of the enol form of 1,1,1-trifluoro-2,4-pentanedione

    NASA Astrophysics Data System (ADS)

    Zahedi-Tabrizi, Mansoureh; Tayyari, Fariba; Moosavi-Tekyeh, Zainab; Jalali, Alireza; Tayyari, Sayyed Faramarz

    2006-10-01

    Molecular structure of 1,1,1-trifluoro-pentane-2,4-dione, known as trifluoro-acetylacetone (TFAA), has been investigated by means of Density Functional Theory (DFT) calculations and the results were compared with those of acetylacetone (AA) and hexafluoro-acetylacetone (HFAA). The harmonic vibrational frequencies of both stable cis-enol forms were calculated at B3LYP level of theory using 6-31G** and 6-311++G** basis sets. We also calculated the anharmonic frequencies at B3LYP/6-31G** level of theory for both stable cis-enol isomers. The calculated frequencies, Raman and IR intensities, and depolarization ratios were compared with the experimental results. The energy difference between the two stable cis-enol forms, calculated at B3LYP/6-311++G**, is only 5.89 kJ/mol. The observed vibrational frequencies and Raman and IR intensities are in excellent agreement with the corresponding values calculated for the most stable conformation, 2TFAA. According to the theoretical calculations, the hydrogen bond strength for the most stable conformer is 57 kJ/mol, about 9.5 kJ/mol less than that of AA and about 14.5 kJ/mol more than that of HFAA. These hydrogen bond strengths are consistent with the frequency shifts for OH/OD stretching and OH/OD out-of-plane bending modes upon substitution of CH 3 groups with CF 3 groups. By comparing the vibrational spectra of both theoretical and experimental data, it was concluded that 2TFAA is the dominant isomer.

  18. 13²,17³-Cyclopheophorbide b enol as a catabolite of chlorophyll b in phycophagy by protists.

    PubMed

    Kashiyama, Yuichiro; Yokoyama, Akiko; Shiratori, Takashi; Inouye, Isao; Kinoshita, Yusuke; Mizoguchi, Tadashi; Tamiaki, Hitoshi

    2013-08-19

    Both 13(2),17(3)-cyclopheophorbide a and b enols were produced along with ingestion of green microalgae containing chlorophylls a and b by a centrohelid protist (phycophagy). The results suggest that chlorophyll b as well as chlorophyll a were directly degraded to colored yet non-phototoxic catabolites in the protistan phycophagic process. Such a simple process by the predators makes a contrast to the much sophisticated chlorophyll degradation process of land plants and some algae, where phototoxicity of chlorophylls was cancelled through the multiple enzymatic steps resulting in colorless and non-phototoxic catabolites.

  19. Polyphenylene ethers with imide linking groups

    NASA Technical Reports Server (NTRS)

    St.clair, T. L.; Burks, H. D. (Inventor)

    1984-01-01

    Novel polyphenylene ethers with imide linking units are disclosed. These polymers incorporate the solvent and thermal resistance of polyimides and the processability of polyphenylene ethers. Improved physical properties over those of the prior art are obtained by incorporating meta linked ethers and/or polyphenylene oxides into the polymer backbone. A novel process for making polymers of this type is also disclosed. The process is unique in that the expected need of high process temperatures and/or special atmospheres are eliminated.

  20. Aza crown ether compounds as anion receptors

    DOEpatents

    Lee, H.S.; Yang, X.O.; McBreen, J.

    1998-08-04

    A family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the new family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of LI{sup +} ion in alkali metal batteries. 3 figs.

  1. Aza crown ether compounds as anion receptors

    DOEpatents

    Lee, Hung Sui; Yang, Xiao-Oing; McBreen, James

    1998-08-04

    A family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the new family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of LI.sup.+ ion in alkali metal batteries.

  2. A ring closing metathesis strategy for carbapyranosides of xylose and arabinose.

    PubMed

    Mattis, Clayton E; Mootoo, David R

    2016-04-29

    The synthesis of β-carba-xylo and arabino pyranosides of cholestanol is described. The synthetic strategy, which is analogous to the Postema approach to C-glycosides, centers on the ring closing metathesis of an enol ether-alkene precursor to give a cyclic enol ether that is elaborated to a carba-pyranoside via hydroboration-oxidation on the olefin. The method, which is attractive for its modularity and stereoselectivity, may find wider applications to carba-hexopyranosides and other complex cycloalkyl ether frameworks.

  3. A ring closing metathesis strategy for carbapyranosides of xylose and arabinose.

    PubMed

    Mattis, Clayton E; Mootoo, David R

    2016-06-24

    The synthesis of β-carba-xylo and arabino pyranosides of cholestanol is described. The synthetic strategy, which is analogous to the Postema approach to C-glycosides, centers on the ring closing metathesis of an enol ether-alkene precursor to give a cyclic enol ether that is elaborated to a carba-pyranoside via hydroboration-oxidation on the olefin. The method, which is attractive for its modularity and stereoselectivity, may find wider applications to carba-hexopyranosides and other complex cycloalkyl ether frameworks.

  4. A ring closing metathesis strategy for carbapyranosides of xylose and arabinose.

    PubMed

    Mattis, Clayton E; Mootoo, David R

    2016-04-29

    The synthesis of β-carba-xylo and arabino pyranosides of cholestanol is described. The synthetic strategy, which is analogous to the Postema approach to C-glycosides, centers on the ring closing metathesis of an enol ether-alkene precursor to give a cyclic enol ether that is elaborated to a carba-pyranoside via hydroboration-oxidation on the olefin. The method, which is attractive for its modularity and stereoselectivity, may find wider applications to carba-hexopyranosides and other complex cycloalkyl ether frameworks. PMID:27035910

  5. A ring closing metathesis strategy for carbapyranosides of xylose and arabinose.

    PubMed

    Mattis, Clayton E; Mootoo, David R

    2016-06-24

    The synthesis of β-carba-xylo and arabino pyranosides of cholestanol is described. The synthetic strategy, which is analogous to the Postema approach to C-glycosides, centers on the ring closing metathesis of an enol ether-alkene precursor to give a cyclic enol ether that is elaborated to a carba-pyranoside via hydroboration-oxidation on the olefin. The method, which is attractive for its modularity and stereoselectivity, may find wider applications to carba-hexopyranosides and other complex cycloalkyl ether frameworks. PMID:27236269

  6. A Metallacycle Fragmentation Strategy for Vinyl Transfer from Enol Carboxylates to Secondary Alcohol C-H Bonds via Osmium- or Ruthenium-Catalyzed Transfer Hydrogenation.

    PubMed

    Park, Boyoung Y; Luong, Tom; Sato, Hiroki; Krische, Michael J

    2015-06-24

    A strategy for catalytic vinyl transfer from enol carboxylates to activated secondary alcohol C-H bonds is described. Using XPhos-modified ruthenium(0) or osmium(0) complexes, enol carboxylate-carbonyl oxidative coupling forms transient β-acyloxy-oxametallacycles, which eliminate carboxylate to deliver allylic ruthenium(II) or osmium(II) alkoxides. Reduction of the metal(II) salt via hydrogen transfer from the secondary alcohol reactant releases the product of carbinol C-H vinylation and regenerates ketone and zero-valent catalyst.

  7. Flow-Induced Crystallization of Poly(ether ether ketone)

    NASA Astrophysics Data System (ADS)

    Nazari, Behzad; Rhoades, Alicyn; Colby, Ralph

    The effects of an interval of shear above the melting temperature Tm on subsequent isothermal crystallization below Tm is reported for the premier engineering thermoplastic, poly(ether ether ketone) (PEEK). The effect of shear on the crystallization rate of PEEK is investigated by means of rheological techniques and differential scanning calorimetry (DSC) under a protocol of imposing shear in a rotational cone and plate rheometer and monitoring crystallization after quenching. The rate of crystallization at 320 °C was not affected by shear for shear rates <7 s-1 at 350 °C, whereas intervals of adequate shear at higher shear rates prior to the quench to 320 °C accelerated crystallization significantly. As the duration of the interval of shear above 7 s-1 is increased, the crystallization time decreases but at each shear rate eventually saturates once the applied specific work exceeds ~120 MPa. The annealing of the flow-induced precursors was also investigated. The nuclei were fairly persistent at temperatures close to 350 °C, however very unstable at temperatures above 375 °C. This suggests that the nanostructures formed under shear might be akin to crystalline lamellae of greater thickness, compared to quiescently crystallized lamellae.

  8. Vibrational Study Of Poly(Ether Ether Ketone).

    NASA Astrophysics Data System (ADS)

    Dosiere, M.

    1989-12-01

    The medium infrared region (4000-400cm-1) has been widely used to study crystallinity because differences could be observed in the vibrational spectrum of several polymers which could be related to crystallinity as determined by X-ray diffraction, differential scanning calorimetry and density measurements. However, as crystallinity is concerned with packing of chains and interactions between neighboor chains, the absorption bands arising from such vibrations appear therefore at wavenumbers below 400 cm -1. Poly-(oxy-1,4-phenyleneoxy-1,4-phenylenecarbonyl-1,4-phenylene) or poly(aryl ether ether ketone) (PEEK),commercially introduced by ICI1, has been attracting increasing interest. It is a semicrystalline polymer with an unusual combination of properties such as high chemical resistance, excellent thermal stability as good mechanical properties. Taking into account of its high temperature high strength characteristics and melt processability, PEEK is generating interest for applications such as reinforced composites, coatings, electrical connectors, impeller housings... Fourier transform infrared spectroscopy is a quick and powerful tool to investigate orientation and/or crystallinity in polymeric materials.

  9. Gold-catalyzed annulations of 2-alkynyl benzaldehydes with vinyl ethers: synthesis of dihydronaphthalene, isochromene, and bicyclo[2.2.2]octane derivatives.

    PubMed

    Malhotra, Deepika; Liu, Le-Ping; Mashuta, Mark S; Hammond, G B

    2013-03-18

    With the suitable selection of a gold catalyst as well as the appropriate control of the reaction conditions, various new gold-catalyzed cyclizations of 2-alkynyl benzaldehyde with acyclic or cyclic vinyl ethers have been developed. Acetal-tethered dihydronaphthalene and isochromenes were obtained from the reactions of 2-alkynyl benzaldehydes with acyclic vinyl ethers under mild conditions. And, more interestingly, the gold-catalyzed reactions of 2-alkynyl benzaldehyde with a cyclic vinyl ether afforded the bicyclo[2.2.2]octane derivative involving two molecules of cyclic vinyl ethers. These products contain interesting substructures that have been found in many biologically active molecules and natural products. In addition, a gold-catalyzed homo-dimerization of 2-phenylethynyl benzaldehyde 1a was observed when the reaction was carried out in the absence of vinyl ether, affording a set of separable diastereomeric products. Plausible mechanisms for these transformations are discussed; a gold-containing benzopyrylium was regarded as the crucial intermediate by which a number of these new transformations took place. PMID:23362089

  10. Gold-catalyzed annulations of 2-alkynyl benzaldehydes with vinyl ethers: synthesis of dihydronaphthalene, isochromene, and bicyclo[2.2.2]octane derivatives.

    PubMed

    Malhotra, Deepika; Liu, Le-Ping; Mashuta, Mark S; Hammond, G B

    2013-03-18

    With the suitable selection of a gold catalyst as well as the appropriate control of the reaction conditions, various new gold-catalyzed cyclizations of 2-alkynyl benzaldehyde with acyclic or cyclic vinyl ethers have been developed. Acetal-tethered dihydronaphthalene and isochromenes were obtained from the reactions of 2-alkynyl benzaldehydes with acyclic vinyl ethers under mild conditions. And, more interestingly, the gold-catalyzed reactions of 2-alkynyl benzaldehyde with a cyclic vinyl ether afforded the bicyclo[2.2.2]octane derivative involving two molecules of cyclic vinyl ethers. These products contain interesting substructures that have been found in many biologically active molecules and natural products. In addition, a gold-catalyzed homo-dimerization of 2-phenylethynyl benzaldehyde 1a was observed when the reaction was carried out in the absence of vinyl ether, affording a set of separable diastereomeric products. Plausible mechanisms for these transformations are discussed; a gold-containing benzopyrylium was regarded as the crucial intermediate by which a number of these new transformations took place.

  11. Purification of aqueous cellulose ethers

    SciTech Connect

    Bartscherer, K.A.; de Pablo, J.J.; Bonnin, M.C.; Prausnitz, J.M.

    1990-07-01

    Manufacture of cellulose ethers usually involves high amounts of salt by-products. For application of the product, salt must be removed. In this work, we have studied the injection of high-pressure CO{sub 2} into an aqueous polymer-salt solution; we find that upon addition of isopropanol in addition to CO{sub 2}, the solution separates into two phases. One phase is rich in polymer and water, and the other phase contains mostly isopropanol, water and CO{sub 2}. The salt distributes between the two phases, thereby offering interesting possibilities for development of a new purification process for water-soluble polymers. This work presents experimental phase-equilibrium data for hydroxyethyl cellulose and sodium carboxymethyl cellulose with sodium acetate and potassium sulfate, respectively, in the region 40{degree}C and 30 to 80 bar. Based on these data, we suggest a process for the manufacture and purification of water-soluble cellulose ethers. 15 refs., 14 figs., 9 tabs.

  12. 27 CFR 21.108 - Ethyl ether.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2012-04-01 2012-04-01 false Ethyl ether. 21.108 Section 21.108 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY LIQUORS FORMULAS FOR DENATURED ALCOHOL AND RUM Specifications for Denaturants § 21.108 Ethyl ether. (a) Odor. Characteristic odor....

  13. 27 CFR 21.108 - Ethyl ether.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2014-04-01 2014-04-01 false Ethyl ether. 21.108 Section 21.108 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY ALCOHOL FORMULAS FOR DENATURED ALCOHOL AND RUM Specifications for Denaturants § 21.108 Ethyl ether. (a) Odor. Characteristic odor....

  14. 27 CFR 21.108 - Ethyl ether.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2013-04-01 2013-04-01 false Ethyl ether. 21.108 Section 21.108 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY ALCOHOL FORMULAS FOR DENATURED ALCOHOL AND RUM Specifications for Denaturants § 21.108 Ethyl ether. (a) Odor. Characteristic odor....

  15. 27 CFR 21.108 - Ethyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Ethyl ether. 21.108 Section 21.108 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT....108 Ethyl ether. (a) Odor. Characteristic odor. (b) Specific gravity at 15.56 °/15.56 °C. Not...

  16. 27 CFR 21.108 - Ethyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Ethyl ether. 21.108 Section 21.108 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT....108 Ethyl ether. (a) Odor. Characteristic odor. (b) Specific gravity at 15.56 °/15.56 °C. Not...

  17. An expedient synthesis of linden ether.

    PubMed

    Serra, Stefano; Cominetti, Alessandra A

    2014-03-01

    We here describe a comprehensive study on the preparation of the intensive flavor 3,9-epoxy-p-mentha-1,4(8)-diene (1). Key steps of the presented synthesis are the selective addition of MeLi to the keto-ester 7, the regioselective cyclization of the obtained triol to give the ethers 4 and 8 and the selective dehydration of ether 4 through the use of POCI3 and pyridine. It is worth noting that the presented synthesis represents the first expedient and reliable entry to ether 1. Being present in linden honey, 1 is also known as linden ether and it has been regarded as a potential marker for the authentication of the linden honey origin. Therefore, ether 1 can be used as a useful reference standard for the analysis of the natural flavors, as we demonstrated by means of its identification in a sample ofunifloral linden honey.

  18. Role of added chloride ions in alteration of reaction pathway in the oxidation of cyclic ketones by dichloroisocyanuric acid—A kinetic study

    NASA Astrophysics Data System (ADS)

    Lakshman Kumar, Y.; Venkata Nadh, R.; Radhakrishnamurti, P. S.

    2015-03-01

    Effect of added chloride ions on kinetics and pathway of reaction between cyclic ketones (five to eight membered rings) and dichloroisocyanuric acid (DCICA) was studied in aqueous acetic acid—perchloric acid medium. Formation of aliphatic dicarboxylic acids as the end products demonstrates the ring cleavage oxidation. Positive effect of acid and negative effect of dielectric constant on the reaction rate reveals a interaction between positive ion (oxidant in the form of H2OCl+) and dipolar substrate molecule. Zero and first orders by oxidant in absence and presence of added chloride ions illustrates the participation of substrate as enolic form of ketone and protonated ketone, respectively, in the rate determining steps. The observed order of reactivity of cyclic ketones (cyclohexanone > cyclooctanone > cyclopentanone > cycloheptanone) was explained on the bases of ring strain, change of hybridization and conformational considerations. The envisaged plausible mechanism based on order of reactants in presence and absence of added chloride ions was substantiated by the order of Arrhenius parameters.

  19. Lewis Acid Catalyzed Regiospecific Cross-Dehydrative Coupling Reaction of 2-Furylcarbinols with β-Keto Amides or 4-Hydroxycoumarins: A Route to Furyl Enols.

    PubMed

    Miao, Maozhong; Luo, Yi; Li, Hongli; Xu, Xin; Chen, Zhengkai; Xu, Jianfeng; Ren, Hongjun

    2016-06-17

    Lewis acid catalyzed directly dehydrative carbon-carbon bond formation reaction of 2-furylcarbinols with β-keto amides provides a straightforward method for regioselective synthesis of (Z)-furyl enols. Moreover, this Lewis acid catalyzed cross-coupling reaction can be extended to an interesting heterocyclic version featuring a functionalized 3-furyl-4-hydroxycoumarin synthesis. PMID:27224045

  20. Generation, Isolation, and Characterization of a Stable Enol from Grignard Addition to a Bis-Ester: A Microscale Experiment for the Undergraduate Organic Chemistry Laboratory

    ERIC Educational Resources Information Center

    Nicaise, Olivier J. C.; Ostrom, Kyle F.; Dalke, Brent J.

    2005-01-01

    An experiment is described that introduces students to the concept of temperature-dependent stability of the tetrahedral intermediate in an acyl-transfer reaction. The process involves the determination of the structure of an alpha-ketoester and its corresponding remarkably stable enol ester to suggest a mechanism for the formation of the products.

  1. Physiological, numerical and molecular characterization of alkyl ether-utilizing rhodococci.

    PubMed

    Kim, Yong-Hak; Engesser, Karl-Heinrich; Kim, Sang-Jong

    2007-06-01

    Twenty-seven Gram-positive strains were characterized physiologically and numerically and classified them into four groups according to their specific activities for utilization of linear alkyl ethers (AEs), cyclic AEs, monoalkoxybenzenes and 1,4-diethoxybenzene. The comparative analysis of the 16S ribosomal RNA gene and 16S-23S intergenic spacer region showed that they belonged to the genera Rhodococcus and Gordonia. Alkyl ether-utilizing rhodococci appeared to involve various and diverse cytochromes P450 of the families CYP116 (25 positive strains from 27), CYP153 (5/27), CYP249 (1/27) and a new family P450RR1 (27/27). The presence of P450RR1 was strongly related to the specific activity for utilization of 2-methoxyphenol and 2-ethoxyphenol. In addition, 26 of 27 strains contained multiple alkB genes coding for probable non-haem iron containing alkane monooxygenases and hydroxylases. Similar DNA fragments coding for a tetrahydrofuran monooxygenase A subunit (ThmA) were found in all cyclic AE-utilizing strains and nearly identical DNA fragments coding for likely orthologues of a propane monooxygenase A subunit (PrmA) in all linear AE-utilizing strains. The substrate availability in the degradation of aryl AEs, cyclic AEs and linear AEs agreed with the molecular probing of the respective genes encoding cytochrome P450RR1, ThmA and PrmA.

  2. Cutaneous metabolism of glycol ethers.

    PubMed

    Lockley, David J; Howes, Douglas; Williams, Faith M

    2005-03-01

    The toxicity of glycol ethers is associated with their oxidation to the corresponding aldehyde and alkoxyacetic acid by cytosolic alcohol dehydrogenase (ADH; EC 1.1.1.1.) and aldehyde dehydrogenase (ALDH; 1.2.1.3). Dermal exposure to these compounds can result in localised or systemic toxicity including skin sensitisation and irritancy, reproductive, developmental and haemotological effects. It has previously been shown that skin has the capacity for local metabolism of applied chemicals. Therefore, there is a requirement to consider metabolism during dermal absorption of these compounds in risk assessment for humans. Cytosolic fractions were prepared from rat liver, and whole and dermatomed skin by differential centrifugation. Rat skin cytosolic fractions were also prepared following multiple dermal exposure to dexamethasone, ethanol or 2-butoxyethanol (2-BE). The rate of ethanol, 2-ethoxyethanol (2-EE), ethylene glycol, 2-phenoxyethanol (2-PE) and 2-BE conversion to alkoxyacetic acid by ADH/ALDH in these fractions was continuously monitored by UV spectrophotometry via the conversion of NAD+ to NADH at 340 nm. Rates of ADH oxidation by rat liver cytosol were greatest for ethanol followed by 2-EE >ethylene glycol >2-PE >2-BE. However, the order of metabolism changed to 2-BE >2-PE >ethylene glycol >2-EE >ethanol using whole and dermatomed rat skin cytosolic fractions, with approximately twice the specific activity in dermatomed skin cytosol relative to whole rat skin. This suggests that ADH and ALDH are localised in the epidermis that constitutes more of the protein in dermatomed skin than whole skin cytosol. Inhibition of ADH oxidation in rat liver cytosol by pyrazole was greatest for ethanol followed by 2-EE >ethylene glycol >2-PE >2-BE, but it only inhibited ethanol metabolism by 40% in skin cytosol. Disulfiram completely inhibited alcohol and glycol ether metabolism in the liver and skin cytosolic fractions. Although ADH1, ADH2 and ADH3 are expressed at the

  3. Formation and stability of enolates of acetamide and acetate anion: an Eigen plot for proton transfer at alpha-carbonyl carbon.

    PubMed

    Richard, John P; Williams, Glenn; O'Donoghue, AnnMarie C; Amyes, Tina L

    2002-03-27

    Second-order rate constants were determined in D(2)O for deprotonation of acetamide, N,N-dimethylacetamide, and acetate anion by deuterioxide ion and for deprotonation of acetamide by quinuclidine. The values of k(B) = 4.8 x 10(-8) M(-1) s(-1) for deprotonation of acetamide by quinuclidine (pK(BH) = 11.5) and k(BH) = 2-5 x 10(9) M(-1) s(-1) for the encounter-limited reverse protonation of the enolate by protonated quinuclidine give pK(a)(C) = 28.4 for ionization of acetamide as a carbon acid. The limiting value of k(HOH) = 1 x 10(11) s(-1) for protonation of the enolate of acetate anion by solvent water and k(HO) = 3.5 x 10(-9) M(-1) s(-1) for deprotonation of acetate anion by HO(-) give pK(a)(C) approximately 33.5 for acetate anion. The change in the rate-limiting step from chemical proton transfer to solvent reorganization results in a downward break in the slope of the plot of log k(HO) against carbon acid pK(a) for deprotonation of a wide range of neutral alpha-carbonyl carbon acids by hydroxide ion, from -0.40 to -1.0. Good estimates are reported for the stabilization of the carbonyl group relative to the enol tautomer by electron donation from alpha-SEt, alpha-OMe, alpha-NH(2), and alpha-O(-) substituents. The alpha-NH(2) and alpha-OMe groups show similar stabilizing interactions with the carbonyl group, while the interaction of alpha-O(-) is only 3.4 kcal/mol more stabilizing than for alpha-OH. We propose that destabilization of the enolate intermediates of enzymatic reactions results in an increasing recruitment of metal ions by the enzyme to provide electrophilic catalysis of enolate formation.

  4. Molecular recognition of arginine by supramolecular complexation with calixarene crown ether based on surface plasmon resonance.

    PubMed

    Chen, Hongxia; Gu, Limin; Yin, Yongmei; Koh, Kwangnak; Lee, Jaebeom

    2011-01-01

    Arginine plays an important role in cell division and the functioning of the immune system. We describe a novel method by which arginine can be identified using an artificial monolayer based on surface plasmon resonance (SPR). The affinity of arginine binding its recognition molecular was compared to that of lysine. In fabrication of an arginine sensing interface, a calix[4]crown ether monolayer was anchored onto a gold surface and then characterized by Fourier Transform infrared reflection absorption spectroscopy, atomic force microscopy, and cyclic voltammetry. The interaction between arginine and its host compound was investigated by SPR. The calix[4]crown ether was found to assemble as a monolayer on the gold surface. Recognition of calix[4]crown monolayer was assessed by the selective binding of arginine. Modification of the SPR chip with the calix[4]crown monolayer provides a reliable and simple experimental platform for investigation of arginine under aqueous conditions.

  5. A study of the direct dimethyl ether fuel cell using alkaline anolyte

    NASA Astrophysics Data System (ADS)

    Xu, Kan; Lao, Shao Jiang; Qin, Hai Ying; Liu, Bin Hong; Li, Zhou Peng

    The electrooxidation behavior of dimethyl ether (DME) dissolved in acidic, neutral or alkaline anolyte has been studied. The cyclic voltammetry measurements reveal that DME in alkaline anolyte demonstrates higher electrooxidation reactivity than that in acidic or neutral anolyte. With increasing the NaOH concentration in the anolyte, the electrooxidation reactivity of DME can be further improved. Direct dimethyl ether fuel cells (DDFCs) are assembled by using Nafion membrane as the electrolyte, Pt/C as the cathode catalyst, and Pt-Ru/C as the anode catalyst. It is found that the use of alkaline anolyte can significantly improve the performance of DDFCs. A maximum power density of 60 mW cm -2 has been achieved when operating the DDFC at 80 °C under ambient pressure.

  6. Cyclic AMP in prokaryotes.

    PubMed Central

    Botsford, J L; Harman, J G

    1992-01-01

    Cyclic AMP (cAMP) is found in a variety of prokaryotes including both eubacteria and archaebacteria. cAMP plays a role in regulating gene expression, not only for the classic inducible catabolic operons, but also for other categories. In the enteric coliforms, the effects of cAMP on gene expression are mediated through its interaction with and allosteric modification of a cAMP-binding protein (CRP). The CRP-cAMP complex subsequently binds specific DNA sequences and either activates or inhibits transcription depending upon the positioning of the complex relative to the promoter. Enteric coliforms have provided a model to explore the mechanisms involved in controlling adenylate cyclase activity, in regulating adenylate cyclase synthesis, and in performing detailed examinations of CRP-cAMP complex-regulated gene expression. This review summarizes recent work focused on elucidating the molecular mechanisms of CRP-cAMP complex-mediated processes. For other bacteria, less detail is known. cAMP has been implicated in regulating antibiotic production, phototrophic growth, and pathogenesis. A role for cAMP has been suggested in nitrogen fixation. Often the only data that support cAMP involvement in these processes includes cAMP measurement, detection of the enzymes involved in cAMP metabolism, or observed effects of high concentrations of the nucleotide on cell growth. PMID:1315922

  7. Cyclic Vomiting Syndrome

    PubMed Central

    2009-01-01

    Initially described in children, cyclic vomiting syndrome (CVS) is an idiopathic disorder that affects patients of all ages and is characterized by recurrent episodes of vomiting separated by symptom-free intervals or baseline health. Frequent misdiagnoses and delays in diagnosis often lead to years of recurrent vomiting. Similarities in the clinical features and symptoms of children and adults with CVS are often linked to migraines. Association with mitochondrial disorders and neuroendocrine dysfunction have been described in the pediatric CVS literature, whereas migraines, anxiety, and panic are common in adults with CVS. Various psychological, infectious, and physical stressors commonly precipitate episodes of CVS. Treatment is mostly empiric, with few controlled therapeutic studies conducted thus far. Associations with migraines have aided in developing pharmacologic treatment strategies for prophylaxis as well as abortive therapy during episodes, including the use of trip-tans. Most children outgrow CVS with time, though some children transition to migraine headaches or continue to have CVS as adults. Improved recognition of CVS in adults, along with the emergence of data in the use of anticonvulsants and antiemetics, may help further delineate pathophysiologic connections and therapeutic options for this debilitating disorder.

  8. On Cyclically Symmetrical Spacetimes

    NASA Astrophysics Data System (ADS)

    Barnes, A.

    2001-07-01

    In a recent paper Carot et al. considered the definition of cylindrical symmetry as a specialisation of the case of axial symmetry. One of their propositions states that if there is a second Killing vector, which together with the one generating the axial symmetry, forms the basis of a two-dimensional Lie algebra, then the two Killing vectors must commute, thus generating an Abelian group. In this paper a similar result, valid under considerably weaker assumptions, is derived: any two-dimensional Lie transformation group which contains a one-dimensional subgroup whose orbits are circles, must be Abelian. The method used to prove this result is extended to apply to three-dimensional Lie transformation groups. It is shown that the existence of a one-dimensional subgroup with closed orbits restricts the Bianchi type of the associated Lie algebra to be I, II, III, VIIq = 0, VIII or IX. Some results on n-dimensional Lie groups are also derived and applied to show there are severe restrictions on the structure of the allowed four-dimensional Lie transformation groups compatible with cyclic symmetry.

  9. Ada and cyclic runtime scheduling

    NASA Technical Reports Server (NTRS)

    Hood, Philip E.

    1986-01-01

    An important issue that must be faced while introducing Ada into the real time world is efficient and prodictable runtime behavior. One of the most effective methods employed during the traditional design of a real time system is the cyclic executive. The role cyclic scheduling might play in an Ada application in terms of currently available implementations and in terms of implementations that might be developed especially to support real time system development is examined. The cyclic executive solves many of the problems faced by real time designers, resulting in a system for which it is relatively easy to achieve approporiate timing behavior. Unfortunately a cyclic executive carries with it a very high maintenance penalty over the lifetime of the software that is schedules. Additionally, these cyclic systems tend to be quite fragil when any aspect of the system changes. The findings are presented of an ongoing SofTech investigation into Ada methods for real time system development. The topics covered include a description of the costs involved in using cyclic schedulers, the sources of these costs, and measures for future systems to avoid these costs without giving up the runtime performance of a cyclic system.

  10. Algebraic curves of maximal cyclicity

    NASA Astrophysics Data System (ADS)

    Caubergh, Magdalena; Dumortier, Freddy

    2006-01-01

    The paper deals with analytic families of planar vector fields, studying methods to detect the cyclicity of a non-isolated closed orbit, i.e. the maximum number of limit cycles that can locally bifurcate from it. It is known that this multi-parameter problem can be reduced to a single-parameter one, in the sense that there exist analytic curves in parameter space along which the maximal cyclicity can be attained. In that case one speaks about a maximal cyclicity curve (mcc) in case only the number is considered and of a maximal multiplicity curve (mmc) in case the multiplicity is also taken into account. In view of obtaining efficient algorithms for detecting the cyclicity, we investigate whether such mcc or mmc can be algebraic or even linear depending on certain general properties of the families or of their associated Bautin ideal. In any case by well chosen examples we show that prudence is appropriate.

  11. Improved Li/TiS2 cell cycling in ether-based electrolytes with synergistic additives

    NASA Technical Reports Server (NTRS)

    Dominey, L. A.; Goldman, J. L.; Koch, V. R.; Shen, D.; Subbarao, S.; Huang, C.-K.; Halpert, G.; Deligiannis, F.

    1991-01-01

    Based on an extensive series of normalized full cell Li/TiS2 cycling studies, open-circuit storage tests, microcalorimetry and AC impedance studies, and chemical precedent, we propose an integrated chemical model consistent with experimental observations concerning the behavior of numerous LiAsF6/cyclic ether electrolytes. The particularly striking potency of certain additives such as 2-methylfuran and the hydroxide action resides in their ability to intercept several different adverse catalytic processes concurrently in the bulk electrolyte as well as the Li anode and TiS2 cathode.

  12. Nonsurgical treatment of cyclic esotropia.

    PubMed

    Voide, Nathalie; Presset, Claudine; Klainguti, Georges; Kaeser, Pierre-François

    2015-04-01

    Cyclic esotropia is characterized by a 24-hour period of straight eye position followed by 24 hours of large-angle esotropia. Possible mechanisms include notably progressive loss of compensation of a latent strabismus. The classic treatment is surgical correction of the angle measured on the days with manifest deviation. We report the first case of cyclic esotropia successfully treated by prismatic correction of the latent strabismus present on "straight" days. PMID:25828819

  13. Conformation-Specific Electronic and Vibrational Spectroscopy of DIBENZO-15-CROWN-5 Ether in a Supersonic Jet.

    NASA Astrophysics Data System (ADS)

    Buchanan, Evan G.; Rodrigo, Chirantha P.; James, William H. James, III; Newby, Josh J.; Zwier, Timothy S.

    2009-06-01

    Crown ethers are oxygen containing cyclic structures noted for their ability to preferentially bind substrates such as ions and water. Despite the high symmetry inherent to the chemical structure, crown ethers are remarkably flexible, adapting their conformation to the substrate to which they are bound. As such, it is valuable to study the conformational preferences of the isolated crown ethers in the absence of any substrate. Here, we present the electronic and infrared spectroscopy of jet-cooled, isolated dibenzo-15-crown-5 ether (DB15C). By incorporating two phenyl rings into the crown, we are afforded the opportunity to explore the ultraviolet spectroscopy of both groups and the coupling between them. One-color resonant two-photon ionization, laser induced fluorescence, UV-UV holeburning, and resonant ion-dip infrared spectroscopies are used to provide conformation-specific electronic and infrared spectra of the three conformers. Additionally, single vibronic level dispersed fluorescence spectra provide evidence for the existence of close lying S_2 states in the two major conformers, located about 527 cm^{-1} above their S_1 counterparts. Based on a comparison with benzo-15-crown-5 ether, we surmise that the local conformation of the ethoxy groups about the two phenyl rings are different. Electronic energy transfer appears to be slow between these phenyl rings on the timescale of the excited state fluorescence. Finally, DFT and MP2 calculations will be presented as a basis for tentative structural assignments and provide insight into the excitonic coupling of the two chromophores.

  14. Phenylethynl-terminated poly(arylene ethers)

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J. (Inventor); Bryant, Robert G. (Inventor); Hergenrother, Paul M. (Inventor)

    1993-01-01

    Phenylethynyl-terminated poly(arylene ethers) are prepared in a wide range of molecular weights by adjusting monomer ratio and adding an appropriate amount of 4-fluoro- 4'-phenylethynyl benzophenone during polymer synthesis. The resulting phenylethynyl-terminated poly(arylene ethers) react and crosslink upon curing for one hour at 350 C to provide materials with improved solvent resistance, higher modulus, and better high temperature properties than the linear, uncrosslinked polymers.

  15. A DFT study on the NHC catalysed Michael addition of enols to α,β-unsaturated acyl-azoliums. A base catalysed C-C bond-formation step.

    PubMed

    Domingo, Luis R; Sáez, José A; Arnó, Manuel

    2014-02-14

    The NHC catalysed nucleophilic additions of enols to α,β-unsaturated acyl-azolium intermediates have been investigated using DFT methods at the MPWB1K/6-31G** computational level. In the direct and the conjugate additions, formation of a hydrogen bond (HB) with the carboxyl oxygen is not sufficient to favour the C-C bond formation as a consequence of the low nucleophilic character of enols. Interestingly, when enols form a HB with the chloride counterion, the activation energies associated with the conjugate addition decrease as a consequence of the increased nucleophilic character of enols and the increased electrophilic character of the 'acyl-azolium + Cl' ion pair. Analysis of the DFT reactivity indices allows establishing a base catalysed C-C bond-formation step promoted by the chloride counterion. PMID:24343422

  16. A DFT study on the NHC catalysed Michael addition of enols to α,β-unsaturated acyl-azoliums. A base catalysed C-C bond-formation step.

    PubMed

    Domingo, Luis R; Sáez, José A; Arnó, Manuel

    2014-02-14

    The NHC catalysed nucleophilic additions of enols to α,β-unsaturated acyl-azolium intermediates have been investigated using DFT methods at the MPWB1K/6-31G** computational level. In the direct and the conjugate additions, formation of a hydrogen bond (HB) with the carboxyl oxygen is not sufficient to favour the C-C bond formation as a consequence of the low nucleophilic character of enols. Interestingly, when enols form a HB with the chloride counterion, the activation energies associated with the conjugate addition decrease as a consequence of the increased nucleophilic character of enols and the increased electrophilic character of the 'acyl-azolium + Cl' ion pair. Analysis of the DFT reactivity indices allows establishing a base catalysed C-C bond-formation step promoted by the chloride counterion.

  17. Catalytic Rearrangement of 2-Alkoxy Diallyl Alcohols: Access to Polysubstituted Cyclopentenones.

    PubMed

    Lempenauer, Luisa; Duñach, Elisabet; Lemière, Gilles

    2016-03-18

    A catalytic rearrangement of diallyl alcohols comprising a cyclic enol ether has been developed using very mild conditions. Bismuth(III) triflate was found to be a very active catalyst for the ring rearrangement of a range of tertiary allylic alcohols to efficiently afford polysubstituted cyclopentenones with a high degree of diastereoselectivity. PMID:26927227

  18. Synthesis of analogues of Eunicea gamma-cembranolides containing cyclic ethers via saponification.

    PubMed

    Rodríguez, A D; Piña, I C; Acosta, A L; Ramírez, C; Soto, J J

    2001-02-01

    A method for the synthesis of derivatives of the lead structures euniolide (1), 12,13-bisepieupalmerin (2), and eupalmerin acetate (3) containing tetrahydrofuran and tetrahydropyran ring systems was developed on the basis of alkali-induced intramolecular oxacyclizations. Representatives of the new analogues were submitted to the in vitro antitumor cell-line-screening program of the National Cancer Institute (NCI). While it was shown that a variety of structural modifications are possible, these transformations led typically to nontoxic synthetic cembranoids.

  19. The Direct α-Arylation of Ethers via the Merger of Photoredox Mediated C–H Functionalization and the Minisci Reaction**

    PubMed Central

    Jin, Jian

    2015-01-01

    The direct α-arylation of cyclic and acyclic ethers with heteroarenes has been accomplished via the design of a new photoredox mediated C–H functionalization pathway. Transiently generated α-oxyalkyl radicals, produced from a variety of widely available ethers via hydrogen atom transfer (HAT), were found to couple with a range of electron-deficient heteroarenes in a Minisci-type mechanism. This mild, visible light-driven protocol allows direct access to medicinal pharmacophores of broad utility using feedstock substrates and a commercial photocatalyst. PMID:25470570

  20. Conformations and Barriers to Methyl Group Internal Rotation in Two Asymmetric Ethers: Propyl Methyl Ether and Butyl Methyl Ether

    NASA Astrophysics Data System (ADS)

    Long, B. E.; Dechirico, F.; Cooke, S. A.

    2012-06-01

    The conformational preferences of the O-C-C-C unit are important in many biological systems with the unit generally preferring a gauche configuration compared to an anti configuration. Butyl methyl ether and propyl methyl ether provide very simple systems for this phenomenom to manifest. Pure rotational spectra of the title molecules have been recorded using chirped pulse Fourier transform microwave spectroscopy (CP-FTMW). In the case of butyl methyl ether, only one conformer has been observed. This conformer has torsional angles of COCC = 180°, OCCC = 62° and CCCC = 180° (anti-gauche-anti) and rotational constants of A = 10259.4591(33) MHz, B = 1445.6470(13) MHz, and C = 1356.2944(14) MHz. The rotational spectrum was doubled and has been analyzed to produce an effective barrier to methyl group internal rotation of 780(35) cm-1. A prior rotational spectroscopic study on propyl methyl ether had focused only on the high energy anti-anti conformer. We have analyzed spectra from the lowest energy anti-gauche conformer and the spectroscopic constants will be presented. A summary of the differences in conformational energies and methyl group internal rotation barriers for the class of aliphatic asymmetric ethers will be presented. K. N. Houk, J. E. Eksterowicz, Y.-D. Wu, C. D. Fuglesang, D. B. Mitchell. J. Am. Chem. Soc. 115 (4170), 1993. Hiroshi Kato, Jun Nakagawa, Michiro Hayashi. J. Mol. Spectrosc. 80 (272), 1980.

  1. Synthesis of Novel β-Keto-Enol Derivatives Tethered Pyrazole, Pyridine and Furan as New Potential Antifungal and Anti-Breast Cancer Agents.

    PubMed

    Radi, Smaail; Tighadouini, Said; Feron, Olivier; Riant, Olivier; Bouakka, Mohammed; Benabbes, Redouane; Mabkhot, Yahia N

    2015-11-10

    Recently, a new generation of highly promising inhibitors bearing β-keto-enol functionality has emerged. Reported herein is the first synthesis and use of novel designed drugs based on the β-keto-enol group embedded with heterocyclic moieties such as pyrazole, pyridine, and furan, prepared in a one-step procedure by mixed Claisen condensation. All the newly synthesized compounds were characterized by FT-IR, ¹H-NMR, (13)C-NMR, ESI/LC-MS, elemental analysis, and evaluated for their in vitro antiproliferative activity against breast cancer (MDA-MB241) human cell lines and fungal strains (Fusarium oxysporum f.sp albedinis FAO). Three of the synthesized compounds showed potent activity against fungal strains with IC50 values in the range of 0.055-0.092 µM. The results revealed that these compounds showed better IC50 values while compared with positive controls.

  2. Protonation at the aromatic ring of samarium benzophenone dianion species. Isolation and structural characterization of a samarium(III) enolate complex

    SciTech Connect

    Hou, Z.; Yoshimura, Takashi; Wakatsuki, Yasuo )

    1994-11-30

    The reduction of aromatic compounds into their dihydro derivatives by dissolving metal/alcohol systems (the Birch reduction) is a useful methodology in organic synthesis. Of particular importance is the reduction of aromatic carbonyl compounds such as aromatic acids, esters, amides, and monoaryl ketones, which usually generates in situ useful metal enolate intermediates that upon further reaction with electrophiles yield a variety of cyclohexadiene derivatives. One of the possible processes to generate these metal enolate intermediates is thought to be the monoprotonation of dianionic species at the para position of the aromatic rings. On the other hand, the reduction of diaryl ketones by alkali metals in liquid ammonia or by lanthanide metals in THF/HMPA or DME has been well known to afford the corresponding ketone dianions. The first X-ray structure of metal ketone dianion complexes, [Yb([mu]-[eta][sup 1],[eta][sup 2]-OCPh[sub 2]) (HMPA)[sub 2

  3. Dissociative Photoionization of Diethyl Ether.

    PubMed

    Voronova, Krisztina; Mozaffari Easter, Chrissa M; Covert, Kyle J; Bodi, Andras; Hemberger, Patrick; Sztáray, Bálint

    2015-10-29

    The dissociative photoionization of internal energy selected diethyl ether ions was investigated by imaging photoelectron photoion coincidence spectroscopy. In a large, 5 eV energy range Et2O(+) cations decay by two parallel and three sequential dissociative photoionization channels, which can be modeled well using statistical theory. The 0 K appearance energies of the CH3CHOCH2CH3(+) (H-loss, m/z = 73) and CH3CH2O═CH2(+) (methyl-loss, m/z = 59) fragment ions were determined to be 10.419 ± 0.015 and 10.484 ± 0.008 eV, respectively. The reemergence of the hydrogen-loss ion above 11 eV is attributed to transition-state (TS) switching, in which the second, outer TS is rate-determining at high internal energies. At 11.81 ± 0.05 eV, a secondary fragment of the CH3CHOCH2CH3(+) (m/z = 73) ion, protonated acetaldehyde, CH3CH═OH(+) (m/z = 45) appears. On the basis of the known thermochemical onset of this fragment, a reverse barrier of 325 meV was found. Two more sequential dissociation reactions were examined, namely, ethylene and formaldehyde losses from the methyl-loss daughter ion. The 0 K appearance energies of 11.85 ± 0.07 and 12.20 ± 0.08 eV, respectively, indicate no reverse barrier in these processes. The statistical model of the dissociative photoionization can also be used to predict the fractional ion abundances in threshold photoionization at large temperatures, which could be of use in, for example, combustion diagnostics. PMID:26444101

  4. Substrate polarization in enzyme catalysis: QM/MM analysis of the effect of oxaloacetate polarization on acetyl-CoA enolization in citrate synthase.

    PubMed

    van der Kamp, Marc W; Perruccio, Francesca; Mulholland, Adrian J

    2007-11-15

    Citrate synthase is an archetypal carbon-carbon bond forming enzyme. It promotes the conversion of oxaloacetate (OAA) to citrate by catalyzing the deprotonation (enolization) of acetyl-CoA, followed by nucleophilic attack of the enolate form of this substrate on OAA to form a citryl-CoA intermediate and subsequent hydrolysis. OAA is strongly bound to the active site and its alpha-carbonyl group is polarized. This polarization has been demonstrated spectroscopically, [(Kurz et al., Biochemistry 1985;24:452-457; Kurz and Drysdale, Biochemistry 1987;26:2623-2627)] and has been suggested to be an important catalytic strategy. Substrate polarization is believed to be important in many enzymes. The first step, formation of the acetyl-CoA enolate intermediate, is thought to be rate-limiting in the mesophilic (pig/chicken) enzyme. We have examined the effects of substrate polarization on this key step using quantum mechanical/molecular mechanical (QM/MM) methods. Free energy profiles have been calculated by AM1/CHARMM27 umbrella sampling molecular dynamics (MD) simulations, together with potential energy profiles. To study the influence of OAA polarization, profiles were calculated with different polarization of the OAA alpha-carbonyl group. The results indicate that OAA polarization influences catalysis only marginally but has a larger effect on intermediate stabilization. Different levels of treatment of OAA are compared (MM or QM), and its polarization in the protein and in water analyzed at the B3LYP/6-31+G(d)/CHARMM27 level. Analysis of stabilization by individual residues shows that the enzyme mainly stabilizes the enolate intermediate (not the transition state) through electrostatic (including hydrogen bond) interactions: these contribute much more than polarization of OAA. PMID:17623847

  5. Substrate polarization in enzyme catalysis: QM/MM analysis of the effect of oxaloacetate polarization on acetyl-CoA enolization in citrate synthase.

    PubMed

    van der Kamp, Marc W; Perruccio, Francesca; Mulholland, Adrian J

    2007-11-15

    Citrate synthase is an archetypal carbon-carbon bond forming enzyme. It promotes the conversion of oxaloacetate (OAA) to citrate by catalyzing the deprotonation (enolization) of acetyl-CoA, followed by nucleophilic attack of the enolate form of this substrate on OAA to form a citryl-CoA intermediate and subsequent hydrolysis. OAA is strongly bound to the active site and its alpha-carbonyl group is polarized. This polarization has been demonstrated spectroscopically, [(Kurz et al., Biochemistry 1985;24:452-457; Kurz and Drysdale, Biochemistry 1987;26:2623-2627)] and has been suggested to be an important catalytic strategy. Substrate polarization is believed to be important in many enzymes. The first step, formation of the acetyl-CoA enolate intermediate, is thought to be rate-limiting in the mesophilic (pig/chicken) enzyme. We have examined the effects of substrate polarization on this key step using quantum mechanical/molecular mechanical (QM/MM) methods. Free energy profiles have been calculated by AM1/CHARMM27 umbrella sampling molecular dynamics (MD) simulations, together with potential energy profiles. To study the influence of OAA polarization, profiles were calculated with different polarization of the OAA alpha-carbonyl group. The results indicate that OAA polarization influences catalysis only marginally but has a larger effect on intermediate stabilization. Different levels of treatment of OAA are compared (MM or QM), and its polarization in the protein and in water analyzed at the B3LYP/6-31+G(d)/CHARMM27 level. Analysis of stabilization by individual residues shows that the enzyme mainly stabilizes the enolate intermediate (not the transition state) through electrostatic (including hydrogen bond) interactions: these contribute much more than polarization of OAA.

  6. Why Do Enolate Anions Favor O-Alkylation over C-Alkylation in the Gas Phase? The Roles of Resonance and Inductive Effects in the Gas-Phase SN2 Reaction between the Acetaldehyde Enolate Anion and Methyl Fluoride.

    PubMed

    Seitz, Christian G; Zhang, Huaiyu; Mo, Yirong; Karty, Joel M

    2016-05-01

    Contributions by resonance and inductive effects toward the net activation barrier were determined computationally for the gas-phase SN2 reaction between the acetaldehyde enolate anion and methyl fluoride, for both O-methylation and C-methylation, in order to understand why this reaction favors O-methylation. With the use of the vinylogue extrapolation methodology, resonance effects were determined to contribute toward increasing the size of the barrier by about 9.5 kcal/mol for O-methylation and by about 21.2 kcal/mol for C-methylation. Inductive effects were determined to contribute toward increasing the size of the barrier by about 1.7 kcal/mol for O-methylation and 4.2 kcal/mol for C-methylation. Employing our block-localized wave function methodology, we determined the contributions by resonance to be 12.8 kcal/mol for O-methylation and 22.3 kcal/mol for C-methylation. Thus, whereas inductive effects have significant contributions, resonance is the dominant factor that leads to O-methylation being favored. More specifically, resonance serves to increase the size the barrier for C-methylation significantly more than it does for O-methylation. PMID:27011344

  7. Nuclear Magnetic Resonance (NMR), Infrared (IR) and Mass Spectrometry (MS) study of keto-enol tautomerism of isobenzofuran-1(3H)-one derivatives

    NASA Astrophysics Data System (ADS)

    Pires, Diego Arantes Teixeira; Pereira, Wagner Luiz; Teixeira, Róbson Ricardo; Figueroa-Villar, José Daniel; Nascimento, Claudia Jorge do

    2016-06-01

    The keto-enol tautomerism of 3-(2-hydroxy-4,4-dimethyl-6-oxo-cyclohexen-1-yl)isobenzofuran-1(3H-one (1), 3-(2-hydroxy-6-oxocyclohex-1-enyl)isobenzofuran-1(3H)-one (2), 3-(2-hydroxy-4-methyl-6-oxocyclohex-1-enyl)isobenzofuran-1(3H)-one (3), 3-(2-hydroxy-5-oxocyclopent-1-enyl)isobenzofuran-1(3H)-one (4) and 2-(3-oxo-1,3-dihydroisobenzofuran-1-yl)-1H-indene-1,3(2H)-dione (5) were investigated. We noticed that for compounds 1 to 4 only the enol form is observed in solid, in solution or in the gas phase. Their tautomeric equilibria are not affected by the solvent, temperature or physical state. Compound 5 was observed in its keto form in solution (NMR) and solid state (IR). The enol species of 5 was also observed upon Mass Spectrometry analysis. These findings were supported by NMR, IR, MS/MS and molecular modeling analyses.

  8. Production of liquid hydrocarbon and ether mixtures

    SciTech Connect

    Harandi, M.N.; Owen, H.

    1989-05-16

    An integrated process is described for the production of ether-rich liquid fuels, comprising: (a) etherifying a mixture of excess lower alkyl alcohol and aliphatic hydrocarbon feedstock rich in C/sub 4/+isoalkenes in the presence of acid etherification catalyst whereby lower alkyl tertiary alkyl ethers are produced; (b) separating etherification effluent from step(a) to provide a gasoline stream rich in C/sub 5/+ ethers and a stream comprising unreacted alcohol and alkenes; (c) contacting the unreacted alcohol and alkenes with an acidic metallosilicate zeolite conversion catalyst under olefinic and oxygenates conversion conditions at a temperature of at least 200/sup 0/C (392/sup 0/F) whereby a conversion effluent stream rich in C/sub 4/+ isoalkenes is produced; (d) recycling at least a portion of the conversion effluent stream to step (a) for etherification.

  9. Statistical analysis of fragmentation patterns of electron ionization mass spectra of enolized-trimethylsilylated anabolic androgenic steroids

    NASA Astrophysics Data System (ADS)

    Fragkaki, A. G.; Angelis, Y. S.; Tsantili-Kakoulidou, A.; Koupparis, M.; Georgakopoulos, C.

    2009-08-01

    Anabolic androgenic steroids (AAS) are included in the List of prohibited substances of the World Anti-Doping Agency (WADA) as substances abused to enhance athletic performance. Gas chromatography coupled to mass spectrometry (GC-MS) plays an important role in doping control analyses identifying AAS as their enolized-trimethylsilyl (TMS)-derivatives using the electron ionization (EI) mode. This paper explores the suitability of complementary GC-MS mass spectra and statistical analysis (principal component analysis, PCA and partial least squares-discriminant analysis, PLS-DA) to differentiate AAS as a function of their structural and conformational features expressed by their fragment ions. The results obtained showed that the application of PCA yielded a classification among the AAS molecules which became more apparent after applying PLS-DA to the dataset. The application of PLS-DA yielded a clear separation among the AAS molecules which were, thus, classified as: 1-ene-3-keto, 3-hydroxyl with saturated A-ring, 1-ene-3-hydroxyl, 4-ene-3-keto, 1,4-diene-3-keto and 3-keto with saturated A-ring anabolic steroids. The study of this paper also presents structurally diagnostic fragment ions and dissociation routes providing evidence for the presence of unknown AAS or chemically modified molecules known as designer steroids.

  10. Kinetic study of UV peroxidation of bis(2-chloroethyl) ether in aqueous solution

    SciTech Connect

    Li, K.Y.; Liu, C.C.; Ni, Q.; Colapret, J.A.; Liu, Z.F.; Huang, F.Y.C.

    1995-06-01

    The groundwater aquifer underneath a chemical manufacturing plant in Southeast Texas has been contaminated by the leachate from its landfill. Based on computer simulations, the current air flow rate used in the air-stripping unit is about 10 times higher than the calculated flow rate if bis(2-chloroethyl) ether (DCEE) is excluded. This excessive air flow rate has caused maintenance problems and a higher energy consumption. It was proposed to treat the contaminated groundwater by air stripping to remove the volatile compounds and by UV/H{sub 2}O{sub 2} oxidation to destruct the low-volatility compounds such as DCEE. Experimental data from the UV peroxidation of DCEE in aqueous solution indicated the rate equation is 0.163[DCEE]{sup 0.61}[H{sub 2}O{sub 2}]{sup 0.54}. Important intermediates identified are 2-chloroethyl acetate, an enolic tautomer of 2-chloroethyl acetate, 2-chloroethoxyethene, 2-chloroethanol, acetaldehyde, ethylene oxide, and chloroethene. All the intermediates could be reduced to undetectable levels after 30 min of irradiation when DCEE/H{sub 2}O{sub 2} initial ratio of 1/10 was used. A reaction mechanism with complex pathways through both the attack of hydroxy free radical and the direct photolysis on DCEE was proposed. Intermediate identification and the rate equation suggested that the pathways in which DCEE is attacked by hydroxy free radicals are predominant. The rate equation derived from this mechanism predicted the peroxidation of DCEE is half-order with respect to both DCEE and H{sub 2}O{sub 2} concentrations.

  11. Buffering in cyclic gene networks

    NASA Astrophysics Data System (ADS)

    Glyzin, S. D.; Kolesov, A. Yu.; Rozov, N. Kh.

    2016-06-01

    We consider cyclic chains of unidirectionally coupled delay differential-difference equations that are mathematical models of artificial oscillating gene networks. We establish that the buffering phenomenon is realized in these system for an appropriate choice of the parameters: any given finite number of stable periodic motions of a special type, the so-called traveling waves, coexist.

  12. Cyclical magnetic field flow fractionation

    NASA Astrophysics Data System (ADS)

    Tasci, T. O.; Johnson, W. P.; Gale, B. K.

    2012-04-01

    In this study, a new magnetic field flow fractionation (FFF) system was designed and modeled by using finite element simulations. Other than current magnetic FFF systems, which use static magnetic fields, our system uses cyclical magnetic fields. Results of the simulations show that our cyclical magnetic FFF system can be used effectively for the separation of magnetic nanoparticles. Cyclical magnetic FFF system is composed of a microfluidic channel (length = 5 cm, height = 30 μm) and 2 coils. Square wave currents of 1 Hz (with 90 deg of phase difference) were applied to the coils. By using Comsol Multiphysics 3.5a, magnetic field profile and corresponding magnetic force exerted on the magnetite nanoparticles were calculated. The magnetic force data were exported from Comsol to Matlab. In Matlab, a parabolic flow profile with maximum flow speed of 0.4 mL/h was defined. Particle trajectories were obtained by the calculation of the particle speeds resulted from both magnetic and hydrodynamic forces. Particle trajectories of the particles with sizes ranging from 10 to 50 nm were simulated and elution times of the particles were calculated. Results show that there is a significant difference between the elution times of the particles so that baseline separation of the particles can be obtained. In this work, it is shown that by the application of cyclical magnetic fields, the separation of magnetic nanoparticles can be done efficiently.

  13. Color visualization of cyclic magnitudes

    NASA Astrophysics Data System (ADS)

    Restrepo, Alfredo; Estupiñán, Viviana

    2014-02-01

    We exploit the perceptual, circular ordering of the hues in a technique for the visualization of cyclic variables. The hue is thus meaningfully used for the indication of variables such as the azimuth and the units of the measurement of time. The cyclic (or circular) variables may be both of the continuous type or the discrete type; among the first there is azimuth and among the last you find the musical notes and the days of the week. A correspondence between the values of a cyclic variable and the chromatic hues, where the natural circular ordering of the variable is respected, is called a color code for the variable. We base such a choice of hues on an assignment of of the unique hues red, yellow, green and blue, or one of the 8 even permutations of this ordered list, to 4 cardinal values of the cyclic variable, suitably ordered; color codes based on only 3 cardinal points are also possible. Color codes, being intuitive, are easy to remember. A possible low accuracy when reading instruments that use this technique is compensated by fast, ludic and intuitive readings; also, the use of a referential frame makes readings precise. An achromatic version of the technique, that can be used by dichromatic people, is proposed.

  14. Crystalline imide/arylene ether copolymers

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J. (Inventor); Hergenrother, Paul M. (Inventor); Bass, Robert G. (Inventor)

    1995-01-01

    Crystalline imide/arylene ether block copolymers are prepared by reacting anhydride terminated poly(amic acids) with amine terminated poly)arylene ethers) in polar aprotic solvents and chemically or thermally cyclodehydrating the resulting intermediate poly(amic acids). The block copolymers of the invention have one glass transition temperature or two, depending on the particular structure and/or the compatibility of the block units. Most of these crystalline block copolymers for tough, solvent resistant films with high tensile properties. While all of the copolymers produced by the present invention are crystalline, testing reveals that copolymers with longer imide blocks or higher imide content have increased crystallinity.

  15. 37. BUILDING NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, NORTHWEST ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    37. BUILDING NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, NORTHWEST CORNER OF BUILDING. BUILDING NO. 521 (ETHER VAULT) IN BACKGROUND LEFT. - Picatinny Arsenal, 500 Area, Powder Factory & Power House, State Route 15 near I-80, Dover, Morris County, NJ

  16. 41. LOOKING WEST AT BUILDING NO. 519, ETHER AND ALCOHOL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    41. LOOKING WEST AT BUILDING NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, (LEFT) AND BUILDING NO. 521, ETHER VAULT, (RIGHT) IN FOREGROUND - Picatinny Arsenal, 500 Area, Powder Factory & Power House, State Route 15 near I-80, Dover, Morris County, NJ

  17. Vinyl ethers containing an epoxy group. XVI. Reaction of glycidol vinyloxyethyl ether with acetals

    SciTech Connect

    Nedolya, N.A.; Khil'ko, M.Ya.; Trofimov, B.A.; Sigalov, M.V.

    1988-10-10

    In order to obtain branched acetals with epoxide groups (prospective monomers and intermediates) the authors investigated the reaction of acetaldehyde diethyl and di(1,1,3-trihydrotetrafluoropropyl) acetals with glycidol vinyloxyethyl ether. The addition of acetals to vinyl epoxy ethers was realized, and the first representative of compounds of this type, i.e., 9-glycidyloxy-6-ethoxy-4-methyl-3,7-dioxanonane, was obtained. It was also impossible to add a fluoroacetal to butyl vinyl ether (0.08-1.00 wt. % of catalyst CF/sub 3/COOH, BF/sub 3//times/ OEt/sub 2/, 20-80/degree/C, 0.5-3 h).

  18. Synthesis of cyclic disulfide-rich peptides.

    PubMed

    Akcan, Muharrem; Craik, David J

    2013-01-01

    In this chapter we describe two SPPS approaches for producing cyclic disulfide-rich peptides in our laboratory, including cyclotides from plants, cyclic conotoxins from cone snail venoms, chlorotoxin from scorpion venom, and the sunflower trypsin inhibitor peptide, SFTI-1.

  19. Sequencing Cyclic Peptides by Multistage Mass Spectrometry

    PubMed Central

    Mohimani, Hosein; Yang, Yu-Liang; Liu, Wei-Ting; Hsieh, Pei-Wen; Dorrestein, Pieter C.; Pevzner, Pavel A.

    2012-01-01

    Some of the most effective antibiotics (e.g., Vancomycin and Daptomycin) are cyclic peptides produced by non-ribosomal biosynthetic pathways. While hundreds of biomedically important cyclic peptides have been sequenced, the computational techniques for sequencing cyclic peptides are still in their infancy. Previous methods for sequencing peptide antibiotics and other cyclic peptides are based on Nuclear Magnetic Resonance spectroscopy, and require large amount (miligrams) of purified materials that, for most compounds, are not possible to obtain. Recently, development of mass spectrometry based methods has provided some hope for accurate sequencing of cyclic peptides using picograms of materials. In this paper we develop a method for sequencing of cyclic peptides by multistage mass spectrometry, and show its advantages over single stage mass spectrometry. The method is tested on known and new cyclic peptides from Bacillus brevis, Dianthus superbus and Streptomyces griseus, as well as a new family of cyclic peptides produced by marine bacteria. PMID:21751357

  20. 40 CFR 721.10669 - Tertiary amine alkyl ether (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Tertiary amine alkyl ether (generic... Specific Chemical Substances § 721.10669 Tertiary amine alkyl ether (generic). (a) Chemical substance and... alkyl ether (PMN P-13-78) is subject to reporting under this section for the significant new...

  1. 40 CFR 721.10385 - Phenoxy alkyl ether (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Phenoxy alkyl ether (generic). 721... Substances § 721.10385 Phenoxy alkyl ether (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as phenoxy alkyl ether (PMN...

  2. 40 CFR 721.10385 - Phenoxy alkyl ether (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Phenoxy alkyl ether (generic). 721... Substances § 721.10385 Phenoxy alkyl ether (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as phenoxy alkyl ether (PMN...

  3. 40 CFR 721.10385 - Phenoxy alkyl ether (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Phenoxy alkyl ether (generic). 721... Substances § 721.10385 Phenoxy alkyl ether (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as phenoxy alkyl ether (PMN...

  4. 40 CFR 721.10453 - Polyglycerin alkyl ether (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Polyglycerin alkyl ether (generic... Specific Chemical Substances § 721.10453 Polyglycerin alkyl ether (generic). (a) Chemical substance and... alkyl ether (PMN P-02-796) is subject to reporting under this section for the significant new...

  5. 40 CFR 721.10453 - Polyglycerin alkyl ether (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Polyglycerin alkyl ether (generic... Specific Chemical Substances § 721.10453 Polyglycerin alkyl ether (generic). (a) Chemical substance and... alkyl ether (PMN P-02-796) is subject to reporting under this section for the significant new...

  6. 40 CFR 721.10669 - Tertiary amine alkyl ether (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Tertiary amine alkyl ether (generic... Specific Chemical Substances § 721.10669 Tertiary amine alkyl ether (generic). (a) Chemical substance and... alkyl ether (PMN P-13-78) is subject to reporting under this section for the significant new...

  7. 21 CFR 520.1846 - Polyoxyethylene (23) lauryl ether blocks.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... Polyoxyethylene (23) lauryl ether blocks. (a) Specifications. Each molasses-based block contains 2.2 percent polyoxyethylene (23) lauryl ether. (b) Sponsor. See No. 067949 in § 510.600(c) of this chapter. (c) Conditions of... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Polyoxyethylene (23) lauryl ether blocks....

  8. 21 CFR 520.1846 - Polyoxyethylene (23) lauryl ether blocks.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... Polyoxyethylene (23) lauryl ether blocks. (a) Specifications. Each molasses-based block contains 2.2 percent polyoxyethylene (23) lauryl ether. (b) Sponsor. See No. 067949 in § 510.600(c) of this chapter. (c) Conditions of... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Polyoxyethylene (23) lauryl ether blocks....

  9. 21 CFR 520.1846 - Polyoxyethylene (23) lauryl ether blocks.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... Polyoxyethylene (23) lauryl ether blocks. (a) Specifications. Each molasses-based block contains 2.2 percent polyoxyethylene (23) lauryl ether. (b) Sponsor. See No. 067949 in § 510.600(c) of this chapter. (c) Conditions of... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Polyoxyethylene (23) lauryl ether blocks....

  10. 21 CFR 520.1846 - Polyoxyethylene (23) lauryl ether blocks.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... Polyoxyethylene (23) lauryl ether blocks. (a) Specifications. Each molasses-based block contains 2.2 percent polyoxyethylene (23) lauryl ether. (b) Sponsor. See No. 067949 in § 510.600(c) of this chapter. (c) Conditions of... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Polyoxyethylene (23) lauryl ether blocks....

  11. 21 CFR 520.1846 - Polyoxyethylene (23) lauryl ether blocks.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... Polyoxyethylene (23) lauryl ether blocks. (a) Specifications. Each molasses-based block contains 2.2 percent polyoxyethylene (23) lauryl ether. (b) Sponsor. See No. 067949 in § 510.600(c) of this chapter. (c) Conditions of... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Polyoxyethylene (23) lauryl ether blocks....

  12. 39. BUILDING NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, LOOKING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    39. BUILDING NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, LOOKING AT SOUTHWEST CORNER WITH BUILDING NO. 521, ETHER VAULT, AND BUILDING NO. 519-A, ETHER & ALOCOHL STORAGE TANKS, IN BACKGROUND RIGHT. - Picatinny Arsenal, 500 Area, Powder Factory & Power House, State Route 15 near I-80, Dover, Morris County, NJ

  13. 40 CFR 721.10069 - Ether amine phosphonate (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Ether amine phosphonate (generic). 721... Substances § 721.10069 Ether amine phosphonate (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as ether amine phosphonate (PMN...

  14. 40 CFR 721.3486 - Polyglycerin mono(4-nonylphenyl) ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Polyglycerin mono(4-nonylphenyl) ether... Substances § 721.3486 Polyglycerin mono(4-nonylphenyl) ether. (a) Chemical substance and significant new uses...-nonylphenyl) ether (PMN P-94-2230) is subject to reporting under this section for the significant new...

  15. 40 CFR 721.3480 - Halogenated biphenyl glycidyl ethers.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Halogenated biphenyl glycidyl ethers... Substances § 721.3480 Halogenated biphenyl glycidyl ethers. (a) Chemical substance and significant new uses... ethers (PMNs P-90-1844, P-90-1845, and P-90-1846) are subject to reporting under this section for...

  16. 40 CFR 721.3480 - Halogenated biphenyl glycidyl ethers.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Halogenated biphenyl glycidyl ethers... Substances § 721.3480 Halogenated biphenyl glycidyl ethers. (a) Chemical substance and significant new uses... ethers (PMNs P-90-1844, P-90-1845, and P-90-1846) are subject to reporting under this section for...

  17. 40 CFR 721.10069 - Ether amine phosphonate (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Ether amine phosphonate (generic). 721... Substances § 721.10069 Ether amine phosphonate (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as ether amine phosphonate (PMN...

  18. 40 CFR 721.3500 - Perhalo alkoxy ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Perhalo alkoxy ether. 721.3500 Section... Substances § 721.3500 Perhalo alkoxy ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as perhalo alkoxy ether (PMN P-83-1227)...

  19. 40 CFR 721.3420 - Brominated arylalkyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Brominated arylalkyl ether. 721.3420... Substances § 721.3420 Brominated arylalkyl ether. (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified generically as brominated arylalkyl ether (P-83-906)...

  20. 40 CFR 721.3465 - Stilbene diglycidyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Stilbene diglycidyl ether. 721.3465... Substances § 721.3465 Stilbene diglycidyl ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as stilbene diglycidyl ether (PMN P-96-1427) is subject...

  1. 40 CFR 721.3465 - Stilbene diglycidyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Stilbene diglycidyl ether. 721.3465... Substances § 721.3465 Stilbene diglycidyl ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as stilbene diglycidyl ether (PMN P-96-1427) is subject...

  2. 40 CFR 721.3438 - Chlorohydroxyalkyl butyl ether (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Chlorohydroxyalkyl butyl ether... Specific Chemical Substances § 721.3438 Chlorohydroxyalkyl butyl ether (generic). (a) Chemical substance... chlorohydroxyalkyl butyl ether (PMN P-99-1295) is subject to reporting under this section for the significant new...

  3. 40 CFR 721.3500 - Perhalo alkoxy ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Perhalo alkoxy ether. 721.3500 Section... Substances § 721.3500 Perhalo alkoxy ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as perhalo alkoxy ether (PMN P-83-1227)...

  4. 40 CFR 721.3430 - 4-Bromophenyl phenyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false 4-Bromophenyl phenyl ether. 721.3430... Substances § 721.3430 4-Bromophenyl phenyl ether. (a) Chemical substance and significant new use subject to reporting. (1) The chemical substance 4-bromophenyl phenyl ether (CAS No. 101-55-3) is subject to...

  5. 40 CFR 721.3520 - Aliphatic polyglycidyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Aliphatic polyglycidyl ether. 721.3520... Substances § 721.3520 Aliphatic polyglycidyl ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance aliphatic polyglycidyl ether (PMN P-89-1036) is subject...

  6. 40 CFR 721.3486 - Polyglycerin mono(4-nonylphenyl) ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Polyglycerin mono(4-nonylphenyl) ether... Substances § 721.3486 Polyglycerin mono(4-nonylphenyl) ether. (a) Chemical substance and significant new uses...-nonylphenyl) ether (PMN P-94-2230) is subject to reporting under this section for the significant new...

  7. 40 CFR 721.3550 - Dipropylene glycol dimethyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Dipropylene glycol dimethyl ether. 721... Substances § 721.3550 Dipropylene glycol dimethyl ether. (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified as dipropylene glycol dimethyl ether (PMN...

  8. 40 CFR 721.3420 - Brominated arylalkyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Brominated arylalkyl ether. 721.3420... Substances § 721.3420 Brominated arylalkyl ether. (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified generically as brominated arylalkyl ether (P-83-906)...

  9. 40 CFR 721.3438 - Chlorohydroxyalkyl butyl ether (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Chlorohydroxyalkyl butyl ether... Specific Chemical Substances § 721.3438 Chlorohydroxyalkyl butyl ether (generic). (a) Chemical substance... chlorohydroxyalkyl butyl ether (PMN P-99-1295) is subject to reporting under this section for the significant new...

  10. 40 CFR 721.3520 - Aliphatic polyglycidyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Aliphatic polyglycidyl ether. 721.3520... Substances § 721.3520 Aliphatic polyglycidyl ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance aliphatic polyglycidyl ether (PMN P-89-1036) is subject...

  11. 40 CFR 721.3550 - Dipropylene glycol dimethyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Dipropylene glycol dimethyl ether. 721... Substances § 721.3550 Dipropylene glycol dimethyl ether. (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified as dipropylene glycol dimethyl ether (PMN...

  12. 40 CFR 721.3430 - 4-Bromophenyl phenyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false 4-Bromophenyl phenyl ether. 721.3430... Substances § 721.3430 4-Bromophenyl phenyl ether. (a) Chemical substance and significant new use subject to reporting. (1) The chemical substance 4-bromophenyl phenyl ether (CAS No. 101-55-3) is subject to...

  13. 40 CFR 721.10551 - Bisphenol S mono ether (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Bisphenol S mono ether (generic). 721... Substances § 721.10551 Bisphenol S mono ether (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as bisphenol S mono ether (PMN...

  14. 40 CFR 721.10551 - Bisphenol S mono ether (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Bisphenol S mono ether (generic). 721... Substances § 721.10551 Bisphenol S mono ether (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as bisphenol S mono ether (PMN...

  15. Synthesis and characterizations of electrospun sulfonated poly (ether ether ketone) SPEEK nanofiber membrane

    NASA Astrophysics Data System (ADS)

    Hasbullah, N.; Sekak, K. A.; Ibrahim, I.

    2016-07-01

    A novel electrospun polymer electrolyte membrane (PEM) based on Sulfonated Poly (ether ether ketone) were prepared and characterized. The poly (ether ether ketone) PEEK was sulfonated using concentrated sulfuric acid at room temperature for 60 hours reaction time. The degree sulfonation (DS) of the SPEEK are 58% was determined by H1 NMR using area under the peak of the hydrogen shielding at aromatic ring of the SPEEK. Then, the functional group of the SPEEK was determined using Fourier transfer infrared (FTIR) showed O-H vibration at 3433 cm-1 of the sulfonated group (SO2-OH). The effect of the solvent and polymer concentration toward the electrospinning process was investigated which, the DMAc has electrospun ability compared to the DMSO. While, at 20 wt.% of the polymer concentration able to form a fine and uniform nanofiber, this was confirmed by FESEM that shown electrospun fiber mat SPEEK surface at nano scale diameter.

  16. Dimensionally Stable Ether-Containing Polyimide Copolymers

    NASA Technical Reports Server (NTRS)

    Fay, Catharine C. (Inventor); St.Clair, Anne K. (Inventor)

    1999-01-01

    Novel polyimide copolymers containing ether linkages were prepared by the reaction of an equimolar amount of dianhydride and a combination of diamines. The polyimide copolymers described herein possess the unique features of low moisture uptake, dimensional stability, good mechanical properties, and moderate glass transition temperatures. These materials have potential application as encapsulants and interlayer dielectrics.

  17. Elastic electron scattering by ethyl vinyl ether

    NASA Astrophysics Data System (ADS)

    Khakoo, M. A.; Hong, L.; Kim, B.; Winstead, C.; McKoy, V.

    2010-02-01

    We report measured and calculated results for elastic scattering of low-energy electrons by ethyl vinyl ether (ethoxyethene), a prototype system for studying indirect dissociative attachment processes that may play a role in DNA damage. The integral cross section displays the expected π* shape resonance. The agreement between the calculated and measured cross sections is generally good.

  18. POLYBROMINATED DIPHENYL ETHERS IN SOUTHERN MISSISSIPPI CATFISH

    EPA Science Inventory

    Polybrominated diphenyl ethers (PBDEs) are used as flame retardants in a wide variety of consumer products. Concerns surrounding these compounds are primarily due do their ubiquitous presence in the environment as well as in human tissue, such as milk, coupled with evidence indi...

  19. Methyl tert-butyl ether (MTBE)

    Integrated Risk Information System (IRIS)

    Methyl tert - butyl ether ( MTBE ) ; CASRN 1634 - 04 - 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 f

  20. Bis(2-chloro-1-methylethyl) ether

    Integrated Risk Information System (IRIS)

    Bis ( 2 - chloro - 1 - methylethyl ) ether ; CASRN 108 - 60 - 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 Assess

  1. Ethylene glycol monobutyl ether (EGBE) (2-Butoxyethanol)

    Integrated Risk Information System (IRIS)

    Ethylene glycol monobutyl ether ( EGBE ) ( 2 - Butoxyethanol ) ; CASRN 111 - 76 - 2 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 (

  2. Orphan enzymes in ether lipid metabolism.

    PubMed

    Watschinger, Katrin; Werner, Ernst R

    2013-01-01

    Ether lipids are an emerging class of lipids which have so far not been investigated and understood in every detail. They have important roles as membrane components of e.g. lens, brain and testis, and as mediators such as platelet-activating factor. The metabolic enzymes for biosynthesis and degradation have been investigated to some extent. As most involved enzymes are integral membrane proteins they are tricky to handle in biochemical protocols. The sequence of some ether lipid metabolising enzymes has only recently been reported and other sequences still remain obscure. Defined enzymes without assigned sequence are known as orphan enzymes. One of these enzymes with uncharacterised sequence is plasmanylethanolamine desaturase, a key enzyme for the biosynthesis of one of the most abundant phospholipids in our body, the plasmalogens. This review aims to briefly summarise known functions of ether lipids, give an overview on their metabolism including the most prominent members, platelet-activating factor and the plasmalogens. A special focus is set on the description of orphan enzymes in ether lipid metabolism and on the successful strategies how four previous orphans have recently been assigned a sequence. Only one of these four was characterised by classical protein purification and sequencing, whereas the other three required alternative strategies such as bioinformatic candidate gene selection and recombinant expression or development of an inhibitor and multidimensional metabolic profiling.

  3. Imide/arylene ether block copolymers

    NASA Technical Reports Server (NTRS)

    Jensen, B. J.; Hergenrother, P. M.; Bass, R. G.

    1991-01-01

    Two series of imide/arylene either block copolymers were prepared using an arylene ether block and either an amorphous or semi-crystalline imide block. The resulting copolymers were characterized and selected physical and mechanical properties were determined. These results, as well as comparisons to the homopolymer properties, are discussed.

  4. POLYBROMINATED DIPHENYL ETHERS IN US SOILS

    EPA Science Inventory

    Chemical analysis of thirty-three soil samples from 15 US states reveals Polybrominated Diphenyl Ethers (PBDEs), in every sample.PBDE concentrations rangefrom 0.09 to 1200 parts per billion by mass. These data are the first analysis of soil concentrations of PBDEs in soils from a...

  5. Enantioseparations of primary amino compounds by high-performance liquid chromatography using chiral crown ether-based chiral stationary phase.

    PubMed

    Hyun, Myung Ho

    2013-01-01

    Liquid chromatographic resolution of racemic compounds containing a primary amino group has been known to be most successful when chiral crown ether-based chiral stationary phases (CSPs) are used. Among various crown ether-based CSPs, the stationary phase based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid covalently bonded to silica gel has been successfully applied in the resolution of various racemic compounds containing primary amino groups. In this chapter, the preparation of the CSP based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid covalently bonded to silica gel and examples for the application to the enantioseparation of racemic compounds including α-amino acids, cyclic amines, amino alcohols, and chiral drugs are described.

  6. Enantioseparations of primary amino compounds by high-performance liquid chromatography using chiral crown ether-based chiral stationary phase.

    PubMed

    Hyun, Myung Ho

    2013-01-01

    Liquid chromatographic resolution of racemic compounds containing a primary amino group has been known to be most successful when chiral crown ether-based chiral stationary phases (CSPs) are used. Among various crown ether-based CSPs, the stationary phase based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid covalently bonded to silica gel has been successfully applied in the resolution of various racemic compounds containing primary amino groups. In this chapter, the preparation of the CSP based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid covalently bonded to silica gel and examples for the application to the enantioseparation of racemic compounds including α-amino acids, cyclic amines, amino alcohols, and chiral drugs are described. PMID:23283776

  7. Cyclic AMP in cervical mucus.

    PubMed

    Póvoa, H; Figueira, D R; Campos da Paz, A; Spichler, E R; Lopes, E R

    1981-01-01

    Cyclic adenosine monophosphate normally stimulates motility of spermatozoa. Its concentration in cervical mucus was studied by an isotopic competitive method in 15 normal women aged between 20 and 50 years. Values were very high, particularly in the periovulatory period, with a mean (+/-SD) value of 167.90 +/- 154.96 nmol/l. These are very high when compared with values in other biological fluids (blood serum and urine).

  8. Ruthenium(II) bipyridine complexes bearing new keto-enol azoimine ligands: Synthesis, structure, electrochemistry and DFT calculations

    NASA Astrophysics Data System (ADS)

    Al-Noaimi, Mousa; Awwadi, Firas F.; Mansi, Ahmad; Abdel-Rahman, Obadah S.; Hammoudeh, Ayman; Warad, Ismail

    2015-01-01

    The novel azoimine ligand, Phsbnd NHsbnd Ndbnd C(COCH3)sbnd NHPh(Ctbnd CH) (H2L), was synthesized and its molecular structure was determined by X-ray crystallography. Catalytic hydration of the terminal acetylene of H2L in the presence of RuCl3·3H2O in ethanol at reflux temperature yielded a ketone (L1 = Phsbnd Ndbnd Nsbnd C(COCH3)dbnd Nsbnd Ph(COCH3) and an enol (L2 = Phsbnd Ndbnd Nsbnd C(COCH3)dbnd Nsbnd PhC(OH)dbnd CH2) by Markovnikov addition of water. Two mixed-ligand ruthenium complexes having general formula, trans-[Ru(bpy)(Y)Cl2] (1-2) (where Y = L1 (1) and Y = L2 (2), bpy is 2.2‧-bipyrdine) were achieved by the stepwise addition of equimolar amounts of (H2L) and bpy ligands to RuCl3·3H2O in absolute ethanol. Theses complexes were characterized by elemental analyses and spectroscopic (IR, UV-Vis, and NMR (1D 1H NMR, 13C NMR, (DEPT-135), (DEPT-90), 2D 1H-1H and 13C-1H correlation (HMQC) spectroscopy)). The two complexes exhibit a quasi-reversible one electron Ru(II)/Ru(III) oxidation couple at 604 mV vs. ferrocene/ferrocenium (Cp2Fe0/+) couple along with one electron ligand reduction at -1010 mV. The crystal structure of complex 1 showed that the bidentate ligand L1 coordinates to Ru(II) by the azo- and imine-nitrogen donor atoms. The complex adopts a distorted trans octahedral coordination geometry of chloride ligands. The electronic spectra of 1 and 1+ in dichloromethane have been modeled by time-dependent density functional theory (TD-DFT).

  9. Ruthenium(II) bipyridine complexes bearing new keto-enol azoimine ligands: synthesis, structure, electrochemistry and DFT calculations.

    PubMed

    Al-Noaimi, Mousa; Awwadi, Firas F; Mansi, Ahmad; Abdel-Rahman, Obadah S; Hammoudeh, Ayman; Warad, Ismail

    2015-01-25

    The novel azoimine ligand, Ph-NH-N=C(COCH3)-NHPh(C≡CH) (H2L), was synthesized and its molecular structure was determined by X-ray crystallography. Catalytic hydration of the terminal acetylene of H2L in the presence of RuCl3·3H2O in ethanol at reflux temperature yielded a ketone (L1=Ph-N=N-C(COCH3)=N-Ph(COCH3) and an enol (L2=Ph-N=N-C(COCH3)=N-PhC(OH)=CH2) by Markovnikov addition of water. Two mixed-ligand ruthenium complexes having general formula, trans-[Ru(bpy)(Y)Cl2] (1-2) (where Y=L1 (1) and Y=L2 (2), bpy is 2.2'-bipyrdine) were achieved by the stepwise addition of equimolar amounts of (H2L) and bpy ligands to RuCl3·3H2O in absolute ethanol. Theses complexes were characterized by elemental analyses and spectroscopic (IR, UV-Vis, and NMR (1D (1)H NMR, (13)C NMR, (DEPT-135), (DEPT-90), 2D (1)H-(1)H and (13)C-(1)H correlation (HMQC) spectroscopy)). The two complexes exhibit a quasi-reversible one electron Ru(II)/Ru(III) oxidation couple at 604 mV vs. ferrocene/ferrocenium (Cp2Fe(0/+)) couple along with one electron ligand reduction at -1010 mV. The crystal structure of complex 1 showed that the bidentate ligand L1 coordinates to Ru(II) by the azo- and imine-nitrogen donor atoms. The complex adopts a distorted trans octahedral coordination geometry of chloride ligands. The electronic spectra of 1 and 1+ in dichloromethane have been modeled by time-dependent density functional theory (TD-DFT).

  10. Certain glycol ethers eliminated from toxic chemical release reporting requirements

    SciTech Connect

    1994-09-01

    Effective June 28, 1994, the U.S. Environmental Protection Agency (EPA) eliminated high molecular weight glycol ethers from the reporting requirements of section 313 of the Emergency Planning and Community Right-To-Know Act of 1986 (EPCRA). EPCRA (42 U.S.C. 11023) is also referred to as Title III of the Superfund Amendments and Reauthorization Act (SARA) of 1986. EPA redefined the glycol ethers category list of chemicals subject to reporting based on an EPA review of available human health data on short-chain glycol ethers. EPA is removing only the surfactant glycol ethers, which are high molecular weight glycol ethers, i.e., those with pendant alkyl groups and that typically have eight or more carbon atoms. The redefinition retains certain glycol ethers (i.e., ethylene glycol ethers where there are 1,2, or 3 repeating ethylene oxide groups) in the category. These are reasonably anticipated to cause adverse human health effects.

  11. One-Pot Domino Aldol Reaction of Indium Enolates Affording 6-Deoxy-α-D,L-altropyranose Derivatives: Synthesis, Mechanism, and Computational Results.

    PubMed

    Cinar, M Emin; Schmittel, Michael

    2015-08-21

    The domino-aldol-aldol-hemiacetal-reaction cascade of indium and other group 13 metal enolates furnished 6-deoxy-α-D,L-altropyranose derivatives in up to 99% yield under thermodynamic control. At lower temperature and thus under kinetic control, the reaction proceeded in a much less diastereoselective manner. The changeover from kinetic to thermodynamic control operating in this multistep domino-aldol-aldol-hemiacetal protocol was used for probing the efficiency of DFT computations. Calculations at the B3LYP/6-31G(d)/LANL2DZ level provided a mechanistic picture in full agreement with the experimental outcome. PMID:26258596

  12. Total Synthesis of Macrocarpines D and E via an Enolate-Driven Copper-Mediated Cross-Coupling Process: Replacement of Catalytic Palladium with Copper Iodide.

    PubMed

    Rahman, M Toufiqur; Deschamps, Jeffrey R; Imler, Gregory H; Schwabacher, Alan W; Cook, James M

    2016-09-01

    An enolate driven copper-mediated cross-coupling process enabled cheaper and greener access to the key pentacyclic intermediates required for the enantiospecific total synthesis of a number of C-19 methyl substituted sarpagine/macroline indole alkaloids. Replacement of palladium (60-68%) with copper iodide (82-89%) resulted in much higher yields. The formation of an unusual 7-membered cross-coupling product was completely inhibited by using TEMPO as a radical scavenger. Further functionalization led to the first enantiospecific total synthesis of macrocarpines D and E. PMID:27526647

  13. One-Pot Domino Aldol Reaction of Indium Enolates Affording 6-Deoxy-α-D,L-altropyranose Derivatives: Synthesis, Mechanism, and Computational Results.

    PubMed

    Cinar, M Emin; Schmittel, Michael

    2015-08-21

    The domino-aldol-aldol-hemiacetal-reaction cascade of indium and other group 13 metal enolates furnished 6-deoxy-α-D,L-altropyranose derivatives in up to 99% yield under thermodynamic control. At lower temperature and thus under kinetic control, the reaction proceeded in a much less diastereoselective manner. The changeover from kinetic to thermodynamic control operating in this multistep domino-aldol-aldol-hemiacetal protocol was used for probing the efficiency of DFT computations. Calculations at the B3LYP/6-31G(d)/LANL2DZ level provided a mechanistic picture in full agreement with the experimental outcome.

  14. Tactics for Probing Aryne Reactivity: Mechanistic Studies of Silicon-oxygen Bond Cleavage During the Trapping of (HDDA-generated) Benzynes by Silyl Ethers

    PubMed Central

    Hoye, Thomas R.; Baire, Beeraiah; Wang, Tao

    2014-01-01

    We report mechanistic aspects of the trapping of thermally (HDDA) generated benzyne derivatives by pendant silyl ether groups, which results in net insertion of the pair of benzyne Csp-hydribized carbon atoms into the silicon–oxygen sigma bond. Cross-over experiments using symmetrical, doubly labeled bis-silyl ether substrates established that the reaction is unimolecular in nature. Competition experiments involving either intramolecular or intermolecular dihydrogen transfer clock reactions (from within a TIPS isopropyl group or cyclooctane, respectively) vs. the silyl ether cyclization were used to gain additional insights. We evaluated effects of the steric bulk of the silyl ether trapping group and of the ring-size of the cyclic ether being formed (furan vs. pyran). These types of competition experiments allow the relative rates of various product-determining steps to be determined. This previously has only rarely been possible because aryne formation is typically rate-limiting, making it challenging to probe the kinetics of subsequent trapping reactions. Solvent effects (polarity of the medium) and computational studies were used to probe the question of stepwise vs. concerted pathways for the Si–O insertion. PMID:25419449

  15. Ether bridge formation in loline alkaloid biosynthesis

    PubMed Central

    Pan, Juan; Bhardwaj, Minakshi; Faulkner, Jerome R.; Nagabhyru, Padmaja; Charlton, Nikki D.; Higashi, Richard M.; Miller, Anne-Frances; Young, Carolyn A.; Grossman, Robert B.; Schardl, Christopher L.

    2014-01-01

    Lolines are potent insecticidal agents produced by endophytic fungi of cool-season grasses. These alkaloids are composed of a pyrrolizidine ring system and an uncommon ether bridge linking carbons 2 and 7. Previous results indicated that 1-aminopyrrolizidine was a pathway intermediate. We used RNA interference to knock down expression of lolO, resulting in the accumulation of a novel alkaloid identified as exo-1-acetamidopyrrolizidine based on high-resolution MS and NMR. Genomes of endophytes differing in alkaloid profiles were sequenced, revealing that those with mutated lolO accumulated exo-1-acetamidopyrrolizidine but no lolines. Heterologous expression of wild-type lolO complemented a lolO mutant, resulting in the production of N-acetylnorloline. These results indicated that the non-heme iron oxygenase, LolO, is required for ether bridge formation, probably through oxidation of exo-1-acetamidopyrrolizidine. PMID:24374065

  16. Synthesis and utility of fluorogenic acetoxymethyl ethers.

    PubMed

    Lavis, Luke D; Chao, Tzu-Yuan; Raines, Ronald T

    2011-01-01

    Phenolic fluorophores such as fluorescein, Tokyo Green, resorufin, and their derivatives are workhorses of biological science. Acylating the phenolic hydroxyl group(s) in these fluorophores masks their fluorescence. The ensuing ester is a substrate for cellular esterases, which can restore fluorescence. These esters are, however, notoriously unstable to hydrolysis, severely compromising their utility. The acetoxymethyl (AM) group is an esterase-sensitive motif that can mask polar functionalities in small molecules. Here, we report on the use of AM ether groups to mask phenolic fluorophores. The resulting profluorophores have a desirable combination of low background fluorescence, high chemical stability, and high enzymatic reactivity, both in vitro and in cellulo. These simple phenyl ether-based profluorophores could supplement or supplant the use of phenyl esters for imaging biochemical and biological systems.

  17. Poly(Arylene Ether Imidazole) Surface Films

    NASA Technical Reports Server (NTRS)

    Connell, John W.; Towell, Timothy W.; Tompkins, Stephen S.

    1993-01-01

    Films adhere well to some substrates, provide smooth surfaces, and facilitate release from molds. Thin films of thermoplastic poly(arylene ether imidazole)s (PAEI's) particularly suitable for use as surface modifiers for graphite/epoxy or graphite/bismaleimide composite panels. Molecule of PAEI includes imidazole groups along its backbone that co-cure with epoxies or bismaleimides during processing. Films thermally stable and resistant to bombardment by energetic electrons.

  18. Cyclic GMP and Cilia Motility

    PubMed Central

    Wyatt, Todd A.

    2015-01-01

    Motile cilia of the lungs respond to environmental challenges by increasing their ciliary beat frequency in order to enhance mucociliary clearance as a fundamental tenant of innate defense. One important second messenger in transducing the regulable nature of motile cilia is cyclic guanosine 3′,5′-monophosphate (cGMP). In this review, the history of cGMP action is presented and a survey of the existing data addressing cGMP action in ciliary motility is presented. Nitric oxide (NO)-mediated regulation of cGMP in ciliated cells is presented in the context of alcohol-induced cilia function and dysfunction. PMID:26264028

  19. Cyclic voltammetry of supported BLMs

    NASA Astrophysics Data System (ADS)

    Murgasova, Renata; Sabo, Jan; Ottova, Angelica L.; Tien, H. T.

    1996-06-01

    The transfer of an electron across a bilayer lipid membrane (BLM) is one of the BLMs most exciting processes. A number of well known electron mediators have been investigated using the method of cyclic voltammetry on a Teflon coated platinum wire, the tip of which has been modified by a self-assembled bilayer lipid membrane (s-BLM). The electrical capacitance of the s-BLM system was measured as a function of frequency. The results are discussed in terms of electron transfer and redox reactions.

  20. Nikola Tesla, the Ether and his Telautomaton

    NASA Astrophysics Data System (ADS)

    Milar, Kendall

    2014-03-01

    In the nineteenth century physicists' understanding of the ether changed dramatically. New developments in thermodynamics, energy physics, and electricity and magnetism dictated new properties of the ether. These have traditionally been examined from the perspective of the scientists re-conceptualizing the ether. However Nikola Tesla, a prolific inventor and writer, presents a different picture of nineteenth century physics. Alongside the displays that showcased his inventions he presented alternative interpretations of physical, physiological and even psychical research. This is particularly evident in his telautomaton, a radio remote controlled boat. This invention and Tesla's descriptions of it showcase some of his novel interpretations of physical theories. He offered a perspective on nineteenth century physics that focused on practical application instead of experiment. Sometimes the understanding of physical theories that Tesla reached was counterproductive to his own inventive work; other times he offered new insights. Tesla's utilitarian interpretation of physical theories suggests a more scientifically curious and invested inventor than previously described and a connection between the scientific and inventive communities.

  1. Promoting environmentally sound management of polybrominated diphenyl ethers in Asia.

    PubMed

    Li, Jinhui; Zhao, Nana; Liu, Xue; Wu, Xiaoyang

    2014-06-01

    Polybrominated diphenyl ethers with persistent organic pollutant properties are required to be controlled by the Stockholm Convention. Recently, polybrominated diphenyl ether contamination has become widespread in Asia, mainly because of the disposal and recycling processes of polybrominated diphenyl ether-containing wastes. The management status, production, usage, import/export, treatment, and disposal, as well as implementation deficiencies for the environmentally sound management of polybrominated diphenyl ethers and polybrominated diphenyl ether-containing materials in ten Asian countries were investigated and assessed in this study. This information could help the participating countries implement the Stockholm Convention and could promote the regional environmentally sound management of polybrominated diphenyl ether-containing articles and products. The results obtained were as follows. (1) Most of the countries studied lacked environmental policies and regulations, or even standards of polybrominated diphenyl ether pollution management and emission control actions. Accurate data on the consumption and importation of polybrominated diphenyl ether-containing materials, however, were not available for all the participating countries. In addition, there were no special treatment or disposal systems for polybrominated diphenyl ether-containing materials, or emission-cutting measures for the treatment of waste in these countries, owing to the lack of sufficient funding or technologies. (2) The improper dismantling of e-waste is a major source of polybrominated diphenyl ether emissions in these countries. (3) Proper e-waste management could result in a breakthrough in the environmentally sound management of this major polybrominated diphenyl ether-containing material flow, and could significantly reduce polybrominated diphenyl ether emissions. Finally, based on the study results, this article puts forward some recommendations for improving the environmentally

  2. Formation of α-SF5-Enolate Enables Preparation of 3-SF5-Quinolin-2-ones, 3-SF5-Quinolines, and 3-SF5-Pyridin-2-ones: Evaluation of their Physicochemical Properties.

    PubMed

    Joliton, Adrien; Plancher, Jean-Marc; Carreira, Erick M

    2016-02-01

    This study describes, for the first time, the generation of a SF5 -substituted ester enolate from benzyl SF5 -acetate under soft enolization conditions, which in turn participates in aldol addition reactions in high yield. The reaction was applied in the synthesis of 3-SF5 -quinolin-2-ones, 3-SF5 -quinolines, and 3-SF5 -pyridin-2-ones, none of which have previously been reported. To provide guidelines for their use in drug discovery, the physicochemical properties of these building blocks were determined and compared with those of their CF3 - and t-Bu-analogues. PMID:26732047

  3. Chemistry and adhesive properties of poly(arylene ether)s containing heterocyclic units

    NASA Technical Reports Server (NTRS)

    Connell, John W.

    1991-01-01

    Novel poly(arylene ether)s containing heterocyclic units were prepared, characterized, and evaluated as adhesives and composite matrices. The polymers were prepared by reacting a heterocyclic bisphenol with an activated aromatic dihalide in a polar aprotic solvent, using potassium carbonate. The polymerizations were generally carried out in N,N-dimethylacetamide at 155 C. In some cases, where the polymers were semicrystalline, higher temperatures and thus higher boiling solvents were necessary to keep the polymers in solution. Heterocyclic rings incorporated into the poly(arylene ether) backbone include phenylquinoxaline, phenylimidazole, benzimidazole, benzoxazole, 1,3,4-oxadiazole, and 1,2,4-triazole. The polymers were characterized by differential scanning calorimetry, solution viscosity, X-ray diffraction, thin film, and adhesive and (in some cases) composite properties. The glass transition temperatures, crystalline melt temperature, solubility, and mechanical properties varied depending upon the heterocyclic ring. The chemistry and properties of these materials are discussed.

  4. Cyclic statistics in rolling bearing diagnosis

    NASA Astrophysics Data System (ADS)

    Li, Li; Qu, Liangsheng

    2003-10-01

    Mechanical signals with amplitude modulated are characterized by periodic time-varying ensemble statistics and can be considered as cyclostationary. In this paper, the second order cyclic statistics, i.e. cyclic autocorrelation and cyclic spectrum, are introduced. A method of demodulation based on cyclic autocorrelation is derived from a signal model. The modulators and carrier are exhibited, respectively, in low- and high-frequency band of cyclic frequency domain. The three-dimensional spectral correlation figure, which represents cyclic frequency, frequency and spectral correlation strength simultaneously, is developed to express the demodulation results clearly. The method is tested by simulation signal and applied to diagnose rolling bearing faults. It obtained more information than other conventional methods, such as the frequency domain and the envelop detection. Furthermore, its effect is demonstrated by comparing with the wavelet envelope demodulation.

  5. Advances in targeting cyclic nucleotide phosphodiesterases.

    PubMed

    Maurice, Donald H; Ke, Hengming; Ahmad, Faiyaz; Wang, Yousheng; Chung, Jay; Manganiello, Vincent C

    2014-04-01

    Cyclic nucleotide phosphodiesterases (PDEs) catalyse the hydrolysis of cyclic AMP and cyclic GMP, thereby regulating the intracellular concentrations of these cyclic nucleotides, their signalling pathways and, consequently, myriad biological responses in health and disease. Currently, a small number of PDE inhibitors are used clinically for treating the pathophysiological dysregulation of cyclic nucleotide signalling in several disorders, including erectile dysfunction, pulmonary hypertension, acute refractory cardiac failure, intermittent claudication and chronic obstructive pulmonary disease. However, pharmaceutical interest in PDEs has been reignited by the increasing understanding of the roles of individual PDEs in regulating the subcellular compartmentalization of specific cyclic nucleotide signalling pathways, by the structure-based design of novel specific inhibitors and by the development of more sophisticated strategies to target individual PDE variants.

  6. Cyclic fatigue in silicon nitride ceramics

    SciTech Connect

    Choi, G.; Kawabe, Y. . Tsukuba Lab.); Horibe, S. . Dept. of Materials Science and Engineering)

    1994-04-01

    Static and cyclic fatigue behavior was investigated for two kinds of silicon nitride with different microstructures. These materials hardly show rising R-curve behavior. Nevertheless the considerable cyclic loading effect is obviously recognized in them. There has been observed an insignificant difference in the pure cyclic loading effect between coarse grained silicon nitride (SSN-1) and fine grained one (SSN-2). In addition, crack growth rate shows a transient acceleration or retardation when variable-amplitude cyclic loading is applied to SSN-1. Such a result implies the existence of a process zone near a crack tip which has a similar function to plastic zone in metals. Since the above cyclic crack behavior is inexplicable by the grain bridging degradation mechanisms, possible cyclic fatigue mechanisms are, thus, discussed.

  7. β-Keto-enol Tethered Pyridine and Thiophene: Synthesis, Crystal Structure Determination and Its Organic Immobilization on Silica for Efficient Solid-Liquid Extraction of Heavy Metals.

    PubMed

    Radi, Smaail; Tighadouini, Said; Bacquet, Maryse; Degoutin, Stephanie; Dacquin, Jean-Philippe; Eddike, Driss; Tillard, Monique; Mabkhot, Yahia N

    2016-07-07

    Molecules bearing β-keto-enol functionality are potential candidates for coordination chemistry. Reported herein is the first synthesis and use of a novel designed ligand based on β-keto-enol group embedded with pyridine and thiophene moieties. The product was prepared in a one-step procedure by mixed Claisen condensation and was characterized by EA, m/z, FT-IR, (¹H, (13)C) NMR and single-crystal X-ray diffraction analysis. The new structure was grafted onto silica particles to afford a chelating matrix which was well-characterized by EA, FT-IR, solid-state (13)C-NMR, BET, BJH, SEM and TGA. The newly prepared organic-inorganic material was used as an adsorbent for efficient solid-phase extraction (SPE) of Cu(II), Zn(II), Cd(II) and Pb(II) from aqueous solutions and showed a capture capacity of 104.12 mg·g(-1), 98.90 mg·g(-1), 72.02 mg·g(-1), and 65.54 mg·g(-1), respectively. The adsorption capacity was investigated, in a batch method, using time of contact, pH, initial concentration, kinetics (Langmuir and Freundlich models), and thermodynamic parameters (ΔG°, ΔH° and ΔS°) of the system effects.

  8. Solvent effects on the absorption spectrum and first hyperpolarizability of keto-enol tautomeric forms of anil derivatives: A Monte Carlo/quantum mechanics study.

    PubMed

    Adriano Junior, L; Fonseca, T L; Castro, M A

    2016-06-21

    Theoretical results for the absorption spectrum and electric properties of the enol and keto tautomeric forms of anil derivatives in the gas-phase and in solution are presented. The electronic properties in chloroform, acetonitrile, methanol, and water were determined by carrying out sequential Monte Carlo simulations and quantum mechanics calculations based on the time dependent density functional theory and on the second-order Møller-Plesset perturbation theory method. The results illustrate the role played by electrostatic interactions in the electronic properties of anil derivatives in a liquid environment. There is a significant increase of the dipole moment in solution (20%-100%) relative to the gas-phase value. Solvent effects are mild for the absorption spectrum and linear polarizability but they can be particularly important for first hyperpolarizability. A large first hyperpolarizability contrast between the enol and keto forms is observed when absorption spectra present intense lowest-energy absorption bands. Dynamic results for the first hyperpolarizability are in qualitative agreement with the available experimental results.

  9. Safety evaluation of the double mutant 5-enol pyruvylshikimate-3-phosphate synthase (2mEPSPS) from maize that confers tolerance to glyphosate herbicide in transgenic plants.

    PubMed

    Herouet-Guicheney, Corinne; Rouquié, David; Freyssinet, Martine; Currier, Thomas; Martone, Aris; Zhou, Junguo; Bates, Elizabeth E M; Ferullo, Jean-Marc; Hendrickx, Koen; Rouan, Dominique

    2009-07-01

    Glyphosate tolerance can be conferred by decreasing the herbicide's ability to inhibit the enzyme 5-enol pyruvylshikimate-3-phosphate synthase, which is essential for the biosynthesis of aromatic amino acids in all plants, fungi, and bacteria. Glyphosate tolerance is based upon the expression of the double mutant 5-enol pyruvylshikimate-3-phosphate synthase (2mEPSPS) protein. The 2mEPSPS protein, with a lower binding affinity for glyphosate, is highly resistant to the inhibition by glyphosate and thus allows sufficient enzyme activity for the plants to grow in the presence of herbicides that contain glyphosate. Based on both a review of published literature and experimental studies, the potential safety concerns related to the transgenic 2mEPSPS protein were assessed. The safety evaluation supports that the expressed protein is innocuous. The 2mEPSPS enzyme does not possess any of the properties associated with known toxins or allergens, including a lack of amino acid sequence similarity to known toxins and allergens, a rapid degradation in simulated gastric and intestinal fluids, and no adverse effects in mice after intravenous or oral administration (at 10 or 2000 mg/kg body weight, respectively). In conclusion, there is a reasonable certainty of no harm resulting from the inclusion of the 2mEPSPS protein in human food or in animal feed.

  10. Safety evaluation of the double mutant 5-enol pyruvylshikimate-3-phosphate synthase (2mEPSPS) from maize that confers tolerance to glyphosate herbicide in transgenic plants.

    PubMed

    Herouet-Guicheney, Corinne; Rouquié, David; Freyssinet, Martine; Currier, Thomas; Martone, Aris; Zhou, Junguo; Bates, Elizabeth E M; Ferullo, Jean-Marc; Hendrickx, Koen; Rouan, Dominique

    2009-07-01

    Glyphosate tolerance can be conferred by decreasing the herbicide's ability to inhibit the enzyme 5-enol pyruvylshikimate-3-phosphate synthase, which is essential for the biosynthesis of aromatic amino acids in all plants, fungi, and bacteria. Glyphosate tolerance is based upon the expression of the double mutant 5-enol pyruvylshikimate-3-phosphate synthase (2mEPSPS) protein. The 2mEPSPS protein, with a lower binding affinity for glyphosate, is highly resistant to the inhibition by glyphosate and thus allows sufficient enzyme activity for the plants to grow in the presence of herbicides that contain glyphosate. Based on both a review of published literature and experimental studies, the potential safety concerns related to the transgenic 2mEPSPS protein were assessed. The safety evaluation supports that the expressed protein is innocuous. The 2mEPSPS enzyme does not possess any of the properties associated with known toxins or allergens, including a lack of amino acid sequence similarity to known toxins and allergens, a rapid degradation in simulated gastric and intestinal fluids, and no adverse effects in mice after intravenous or oral administration (at 10 or 2000 mg/kg body weight, respectively). In conclusion, there is a reasonable certainty of no harm resulting from the inclusion of the 2mEPSPS protein in human food or in animal feed. PMID:19303906

  11. Solvent effects on the absorption spectrum and first hyperpolarizability of keto-enol tautomeric forms of anil derivatives: A Monte Carlo/quantum mechanics study

    NASA Astrophysics Data System (ADS)

    Adriano Junior, L.; Fonseca, T. L.; Castro, M. A.

    2016-06-01

    Theoretical results for the absorption spectrum and electric properties of the enol and keto tautomeric forms of anil derivatives in the gas-phase and in solution are presented. The electronic properties in chloroform, acetonitrile, methanol, and water were determined by carrying out sequential Monte Carlo simulations and quantum mechanics calculations based on the time dependent density functional theory and on the second-order Møller-Plesset perturbation theory method. The results illustrate the role played by electrostatic interactions in the electronic properties of anil derivatives in a liquid environment. There is a significant increase of the dipole moment in solution (20%-100%) relative to the gas-phase value. Solvent effects are mild for the absorption spectrum and linear polarizability but they can be particularly important for first hyperpolarizability. A large first hyperpolarizability contrast between the enol and keto forms is observed when absorption spectra present intense lowest-energy absorption bands. Dynamic results for the first hyperpolarizability are in qualitative agreement with the available experimental results.

  12. Cyclic Imide Dioxime: Formation and Hydrolytic Stability

    SciTech Connect

    Kang, S.O.; Vukovic, Sinisa; Custelcean, Radu; Hay, Benjamin

    2012-01-01

    Poly(acrylamidoximes) play an important role in the uranium extraction from seawater. The present work reports solution studies of simple analogs to address the formation and stability of two binding sites present in these polymers, open-chain amidoximes and cyclic imide dioximes, including: 1) conditions that maximize the formation of the cyclic form, 2) existence of a base-induced conversion from open-chain to cyclic form, and 3) degradation under acid and base conditions.

  13. [Cyclic Cushing's Syndrome - rare or rarely recognized].

    PubMed

    Kiałka, Marta; Doroszewska, Katarzyna; Mrozińska, Sandra; Milewicz, Tomasz; Stochmal, Ewa

    2015-01-01

    Cyclic Cushing's syndrome is a type of Cushing's disease which is characterized by alternating periods of increasing and decreasing levels of cortisol in the blood. The diagnostic criteria for cyclic Cushing's syndrome are at least three periods of hypercortisolism alternating with at least two episodes of normal levels of serum cortisol concentration. The epidemiology, signs, symptoms, pathogenesis and treatment of cyclic Cushing's syndrome have been discussed.

  14. Azidated Ether-Butadiene-Ether Block Copolymers as Binders for Solid Propellants

    NASA Astrophysics Data System (ADS)

    Cappello, Miriam; Lamia, Pietro; Mura, Claudio; Polacco, Giovanni; Filippi, Sara

    2016-07-01

    Polymeric binders for solid propellants are usually based on hydroxyl-terminated polybutadiene (HTPB), which does not contribute to the overall energy output. Azidic polyethers represent an interesting alternative but may have poorer mechanical properties. Polybutadiene-polyether copolymers may combine the advantages of both. Four different ether-butadiene-ether triblock copolymers were prepared and azidated starting from halogenated and/or tosylated monomers using HTPB as initiator. The presence of the butadiene block complicates the azidation step and reduces the storage stability of the azidic polymer. Nevertheless, the procedure allows modifying the binder properties by varying the type and lengths of the energetic blocks.

  15. Comparative Study of Ether-Based Electrolytes for Application in Lithium-Sulfur Battery.

    PubMed

    Carbone, Lorenzo; Gobet, Mallory; Peng, Jing; Devany, Matthew; Scrosati, Bruno; Greenbaum, Steve; Hassoun, Jusef

    2015-07-01

    Herein, we report the characteristics of electrolytes using various ether-solvents with molecular composition CH3O[CH2CH2O]nCH3, differing by chain length, and LiCF3SO3 as the lithium salt. The electrolytes, considered as suitable media for lithium-sulfur batteries, are characterized in terms of thermal properties (TGA, DSC), lithium ion conductivity, lithium interface stability, cyclic voltammetry, self-diffusion properties of the various components, and lithium transference number measured by NMR. Furthermore, the electrolytes are characterized in lithium cells using a sulfur-carbon composite cathode by galvanostatic charge-discharge tests. The results clearly evidence the influence of the solvent chain length on the species mobility within the electrolytes that directly affects the behavior in lithium sulfur cell. The results may effectively contribute to the progress of an efficient, high-energy lithium-sulfur battery.

  16. Comparative Study of Ether-Based Electrolytes for Application in Lithium-Sulfur Battery.

    PubMed

    Carbone, Lorenzo; Gobet, Mallory; Peng, Jing; Devany, Matthew; Scrosati, Bruno; Greenbaum, Steve; Hassoun, Jusef

    2015-07-01

    Herein, we report the characteristics of electrolytes using various ether-solvents with molecular composition CH3O[CH2CH2O]nCH3, differing by chain length, and LiCF3SO3 as the lithium salt. The electrolytes, considered as suitable media for lithium-sulfur batteries, are characterized in terms of thermal properties (TGA, DSC), lithium ion conductivity, lithium interface stability, cyclic voltammetry, self-diffusion properties of the various components, and lithium transference number measured by NMR. Furthermore, the electrolytes are characterized in lithium cells using a sulfur-carbon composite cathode by galvanostatic charge-discharge tests. The results clearly evidence the influence of the solvent chain length on the species mobility within the electrolytes that directly affects the behavior in lithium sulfur cell. The results may effectively contribute to the progress of an efficient, high-energy lithium-sulfur battery. PMID:26057152

  17. 40 CFR 721.10067 - Ether amine phosphonate salt (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Ether amine phosphonate salt (generic... Specific Chemical Substances § 721.10067 Ether amine phosphonate salt (generic). (a) Chemical substances... ether amine phosphonate salt (PMNs P-05-57, P-05-58, P-05-59, P-05-61, P-05-62, P-05-63, P-05-64, and...

  18. 40 CFR 721.10067 - Ether amine phosphonate salt (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Ether amine phosphonate salt (generic... Specific Chemical Substances § 721.10067 Ether amine phosphonate salt (generic). (a) Chemical substances... ether amine phosphonate salt (PMNs P-05-57, P-05-58, P-05-59, P-05-61, P-05-62, P-05-63, P-05-64, and...

  19. 40 CFR 721.10067 - Ether amine phosphonate salt (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Ether amine phosphonate salt (generic... Specific Chemical Substances § 721.10067 Ether amine phosphonate salt (generic). (a) Chemical substances... ether amine phosphonate salt (PMNs P-05-57, P-05-58, P-05-59, P-05-61, P-05-62, P-05-63, P-05-64, and...

  20. 40 CFR 721.10067 - Ether amine phosphonate salt (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Ether amine phosphonate salt (generic... Specific Chemical Substances § 721.10067 Ether amine phosphonate salt (generic). (a) Chemical substances... ether amine phosphonate salt (PMNs P-05-57, P-05-58, P-05-59, P-05-61, P-05-62, P-05-63, P-05-64, and...

  1. 40 CFR 721.10067 - Ether amine phosphonate salt (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Ether amine phosphonate salt (generic... Specific Chemical Substances § 721.10067 Ether amine phosphonate salt (generic). (a) Chemical substances... ether amine phosphonate salt (PMNs P-05-57, P-05-58, P-05-59, P-05-61, P-05-62, P-05-63, P-05-64, and...

  2. Antioxidant activity of alkyl hydroxytyrosyl ethers in unsaturated lipids.

    PubMed

    Cert, Rosa; Madrona, Andrés; Espartero, José Luis; Pérez-Camino, M Carmen

    2015-06-01

    The antioxidant activity of ethyl and octyl hydroxytyrosyl ethers toward lipids was determined using the Rancimat and open cup methods at high temperatures and 50 °C, respectively. The effect of the unsaturation of the matrix was evaluated using sunflower, soya, and fish refined oils. The antioxidant activities of alkyl hydroxytyrosyl ethers (HTy ethers), hydroxytyrosyl esters, and free hydroxytyrosol are similar, and are much higher than that of α-tocopherol at the same millimolar concentration. The relationship between the induction period and the concentration of the HTy ethers is a sigmoidal curve; an accurate concentration of HTy ethers is necessary to achieve maximum activity, as it increases with the level of matrix unsaturation. The presence of tocopherols in commercial oils affects the antioxidant effect of HTy ethers. Thus, the addition of a low concentration of HTy ethers results in a positive effect, whereas the effect of the addition of high amounts of ethers is slightly less than that of the phenol alone. The addition of HTy ethers to commercial refined oils increases the stability of the oils and preserves tocopherols and polyunsaturated fatty acids from oxidation, enabling the oils to maintain their nutritional properties for longer periods of time.

  3. Divinyl ether synthase gene, and protein and uses thereof

    DOEpatents

    Howe, Gregg A.; Itoh, Aya

    2006-12-26

    The present invention relates to divinyl ether synthase genes, proteins, and methods of their use. The present invention encompasses both native and recombinant wild-type forms of the synthase, as well as mutants and variant forms, some of which possess altered characteristics relative to the wild-type synthase. The present invention also relates to methods of using divinyl ether synthase genes and proteins, including in their expression in transgenic organisms and in the production of divinyl ether fatty acids, and to methods of suing divinyl ether fatty acids, including in the protection of plants from pathogens.

  4. Divinyl ether synthase gene and protein, and uses thereof

    DOEpatents

    Howe, Gregg A.; Itoh, Aya

    2011-09-13

    The present invention relates to divinyl ether synthase genes, proteins, and methods of their use. The present invention encompasses both native and recombinant wild-type forms of the synthase, as well as mutants and variant forms, some of which possess altered characteristics relative to the wild-type synthase. The present invention also relates to methods of using divinyl ether synthase genes and proteins, including in their expression in transgenic organisms and in the production of divinyl ether fatty acids, and to methods of suing divinyl ether fatty acids, including in the protection of plants from pathogens.

  5. Computational Study of Nanosized Drug Delivery from Cyclodextrins, Crown Ethers and Hyaluronan in Pharmaceutical Formulations.

    PubMed

    Torrens, Francisco; Castellano, Gloria

    2015-01-01

    The problem in this work is the computational characterization of cyclodextrins, crown ethers and hyaluronan (HA) as hosts of inclusion complexes for nanosized drug delivery vehicles in pharmaceutical formulations. The difficulty is addressed through a computational study of some thermodynamic, geometric and topological properties of the hosts. The calculated properties of oligosaccharides of D-glucopyranoses allow these to act as co-solvents of polyanions in water. In crown ethers, the central channel is computed. Mucoadhesive polymer HA in formulations releases drugs in mucosas. Geometric, topological and fractal analyses are carried out with code TOPO. Reference calculations are performed with code GEPOL. From HA to HA·3Ca and hydrate, the hydrophilic solvent-accessible surface varies with the count of H-bonds. The fractal dimension rises. The dimension of external atoms rises resulting 1.725 for HA. It rises going to HA·3Ca and hydrate. Nonburied minus molecular dimension rises and decays. Hydrate globularity is lower than O(water), Ca(2+) and O(HA). Ca(2+) rugosity is smaller than for hydrate, O(HA) and O(water). Ca(2+) and O(water) accessibilities are greater than hydrate. Conclusions are drawn on: (1) the relative stability of linear/cyclic and shorter/larger polymers; (2) the atomic analysis of properties allows determining the atoms with maximum reactivity.

  6. Nonlinear, nonbinary cyclic group codes

    NASA Technical Reports Server (NTRS)

    Solomon, G.

    1992-01-01

    New cyclic group codes of length 2(exp m) - 1 over (m - j)-bit symbols are introduced. These codes can be systematically encoded and decoded algebraically. The code rates are very close to Reed-Solomon (RS) codes and are much better than Bose-Chaudhuri-Hocquenghem (BCH) codes (a former alternative). The binary (m - j)-tuples are identified with a subgroup of the binary m-tuples which represents the field GF(2 exp m). Encoding is systematic and involves a two-stage procedure consisting of the usual linear feedback register (using the division or check polynomial) and a small table lookup. For low rates, a second shift-register encoding operation may be invoked. Decoding uses the RS error-correcting procedures for the m-tuple codes for m = 4, 5, and 6.

  7. Cell reorientation under cyclic stretching

    PubMed Central

    Livne, Ariel; Bouchbinder, Eran; Geiger, Benjamin

    2014-01-01

    Mechanical cues from the extracellular microenvironment play a central role in regulating the structure, function and fate of living cells. Nevertheless, the precise nature of the mechanisms and processes underlying this crucial cellular mechanosensitivity remains a fundamental open problem. Here we provide a novel framework for addressing cellular sensitivity and response to external forces by experimentally and theoretically studying one of its most striking manifestations – cell reorientation to a uniform angle in response to cyclic stretching of the underlying substrate. We first show that existing approaches are incompatible with our extensive measurements of cell reorientation. We then propose a fundamentally new theory that shows that dissipative relaxation of the cell’s passively-stored, two-dimensional, elastic energy to its minimum actively drives the reorientation process. Our theory is in excellent quantitative agreement with the complete temporal reorientation dynamics of individual cells, measured over a wide range of experimental conditions, thus elucidating a basic aspect of mechanosensitivity. PMID:24875391

  8. Facile cleavage of triethylsilyl (TES) ethers using o-iodoxybenzoic acid (IBX) without affecting tert-butyldimethylsilyl (TBS) ethers.

    PubMed

    Wu, Yikang; Huang, Jia-Hui; Shen, Xin; Hu, Qi; Tang, Chao-Jun; Li, Liang

    2002-06-27

    [reaction: see text] In DMSO cleavage of triethylsilyl (TES) ethers by o-iodoxybenzoic acid (IBX) was significantly faster than cleavage of tert-butyldimethylsilyl (TBS) ethers or further oxidation into carbonyl compounds. In most cases, TES protecting groups could be removed in good to excellent yields within 1 h, whereas similar TBS protecting groups remained intact under the same conditions. The procedure also could be adapted for direct one-pot conversion of TES ethers into carbonyl compounds.

  9. Brominated-chlorinated diphenyl ethers formed by thermolysis of polybrominated diphenyl ethers at low temperatures.

    PubMed

    Rupp, Silke; Metzger, Jörg W

    2005-09-01

    Polybrominated diphenyl ethers (PBDEs) are a group of brominated flame retardants (BFRs) used mainly as additives in different kinds of plastic material. Various PBDEs are found in all environmental compartments as well as in tissue and blood serum of animals and humans due to their persistence and tendency to bioaccumulate. Emission of PBDEs into the environment can occur during recycling of PBDE-containing plastic material or during their uncontrolled or insufficient combustion as e.g. in accidental fires or landfill fires. Under these circumstances, PBDEs can also function as precursor molecules for the formation of polybrominated dibenzodioxins (PBDDs) and dibenzofurans (PBDFs). In this study, we qualitatively investigated the reaction of two PBDE congeners, 2,2',4,4'-tetrabromo diphenyl ether (BDE 47) and 2,2',4,4',5,5'-hexabromo diphenyl ether (BDE 153), as well as hexabromobenzene (HBB), a flame retardant used in the past, when exposed to temperatures between 250 degrees C and 500 degrees C. The formed reaction products were analysed by high resolution gas chromatography-low resolution mass spectrometry (HRGC-LRMS). Among others brominated-chlorinated diphenyl ethers were formed by chlorodebromination of the PBDEs. In addition, thermolysis of BDE 47 and BDE 153 in the presence of tetrachloromethane as model substance for an organic chlorine source was studied. Thermal treatment of HBB resulted in the formation of brominated-chlorinated benzenes. PMID:16083771

  10. Antifungal ether diglycosides from Matayba guianensis Aublet.

    PubMed

    de Assis, Polyana A; Theodoro, Phellipe N E T; de Paula, José E; Araújo, Ana J; Costa-Lotufo, Letícia V; Michel, Sylvie; Grougnet, Raphaël; Kritsanida, Marina; Espindola, Laila S

    2014-03-01

    Since the 1960s, fungal infections have become a major worldwide public health problem. Antifungal treatments have many limitations, such as toxicity and resistance. Matayba guianensis Aublet (Sapindaceae) was chemically investigated as part of our ongoing search for lead molecules against fungi in the Brazilian Cerrado biome. The ethanolic extract of M. guianensis root bark revealed the presence of two previously unreported ether diglycosides: matayoside E (1) and F (2) with anti Candida activity, along with two known compounds: cupanioside (3) and stigmasterol (4).

  11. Antifungal activity of some diaryl ethers.

    PubMed

    Xu, Hui; Jian, Kun-Zhong; Guan, Qiu; Ye, Fei; Lv, Min

    2007-12-01

    Several diaryl ethers were synthesized and tested in vitro against seven phytopathogenic fungi, namely Fusarium graminearum, Alternaria alternate, Helminthosporium sorokinianum, Pyricularia oryzae, Fusarium oxysporum f. sp. vasinfectum, Fusarium oxysporum f. sp. cucumarinum and Alternaria brassicae. Compared to a commercial agricultural fungicide, hymexazol, especially compounds a, b, e, g and k were found to be more effective at 50 mug/ml against F. graminearum, F. oxysporum f. sp. vasinfectum and F. oxysporum f. sp. cucumarinum. Meantime, some structure-activity relationships were also observed. PMID:18057754

  12. Cyclic malyl anthocyanins in Dianthus caryophyllus.

    PubMed

    Nakayama, M; Koshioka, M; Yoshida, H; Kan, Y; Fukui, Y; Koike, A; Yamaguchi, M

    2000-12-01

    3,5-Di-O-(beta-glucopyranosyl) pelargonidin 6''-O-4,6'''-O-1-cyclic malate and a previously reported cyanidin equivalent, 3,5-di-O-(beta-glucopyranosyl) cyanidin 6''-O-4,6'''-O-1-cyclic malate were identified from petals of deep pink and red-purple flower cultivars of Dianthus caryophyllus, respectively.

  13. Cyclic Linearization and Island Repair in Sluicing

    ERIC Educational Resources Information Center

    Qiu, Chunan

    2009-01-01

    Cyclic Linearization is adopted to account for the island repair of Sluicing in English. The extraction of wh-phrase out of certain islands undergoes non-successive-cyclic movement, which yields conflicting ordering statements. The derivation can be rescued by deleting all ordering statements in IP, including those conflicting ones. Two arguments…

  14. 77 FR 39236 - Nanomaterial Case Study: A Comparison of Multiwalled Carbon Nanotubes and Decabromodiphenyl Ether...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-02

    ... AGENCY Nanomaterial Case Study: A Comparison of Multiwalled Carbon Nanotubes and Decabromodiphenyl Ether... Study: A Comparison of Multiwalled Carbon Nanotubes and Decabromodiphenyl Ether Flame-Retardant Coatings... ``Nanomaterial Case Study: A Comparison of Multiwalled Carbon Nanotubes and Decabromodiphenyl Ether...

  15. Low temperature (550-700 K) oxidation pathways of cyclic ketones: dominance of HO2-elimination channels yielding conjugated cyclic coproducts.

    PubMed

    Scheer, Adam M; Welz, Oliver; Vasu, Subith S; Osborn, David L; Taatjes, Craig A

    2015-05-14

    The low-temperature oxidation of three cyclic ketones, cyclopentanone (CPO; C5H8=O), cyclohexanone (CHO; C6H10=O), and 2-methyl-cyclopentanone (2-Me-CPO; CH3-C5H7=O), is studied between 550 and 700 K and at 4 or 8 Torr total pressure. Initial fuel radicals R are formed via fast H-abstraction from the ketones by laser-photolytically generated chlorine atoms. Intermediates and products from the subsequent reactions of these radicals in the presence of excess O2 are probed with time and isomeric resolution using multiplexed photoionization mass spectrometry with tunable synchrotron ionizing radiation. For CPO and CHO the dominant product channel in the R + O2 reactions is chain-terminating HO2-elimination yielding the conjugated cyclic coproducts 2-cyclopentenone and 2-cyclohexenone, respectively. Results on oxidation of 2-Me-CPO also show a dominant contribution from HO2-elimination. The photoionization spectrum of the co-product suggests formation of 2-methyl-2-cyclopentenone and/or 2-cyclohexenone, resulting from a rapid Dowd-Beckwith rearrangement, preceding addition to O2, of the initial (2-oxocyclopentyl)methyl radical to 3-oxocyclohexyl. Cyclic ethers, markers for hydroperoxyalkyl radicals (QOOH), key intermediates in chain-propagating and chain-branching low-temperature combustion pathways, are only minor products. The interpretation of the experimental results is supported by stationary point calculations on the potential energy surfaces of the associated R + O2 reactions at the CBS-QB3 level. The calculations indicate that HO2-elimination channels are energetically favored and product formation via QOOH is disfavored. The prominence of chain-terminating pathways linked with HO2 formation in low-temperature oxidation of cyclic ketones suggests little low-temperature reactivity of these species as fuels in internal combustion engines. PMID:25877515

  16. Low temperature (550-700 K) oxidation pathways of cyclic ketones: Dominance of HO2-elimination channels yielding conjugated cyclic coproducts

    DOE PAGESBeta

    Scheer, Adam M.; Welz, Oliver; Vasu, Subith S.; Osborn, David L.; Taatjes, Craig A.

    2015-04-13

    The low-temperature oxidation of three cyclic ketones, cyclopentanone (CPO; C5H8O), cyclohexanone (CHO; C6H10 O), and 2-methyl-cyclopentanone (2-Me-CPO; CH3–C5H7 O), is studied between 550 and 700 K and at 4 or 8 Torr total pressure. Initial fuel radicals R are formedvia fast H-abstraction from the ketones by laser-photolytically generated chlorine atoms. Intermediates and products from the subsequent reactions of these radicals in the presence of excess O2 are probed with time and isomeric resolution using multiplexed photoionization mass spectrometry with tunable synchrotron ionizing radiation. For CPO and CHO the dominant product channel in the R + O2 reactions is chain-terminating HO2-eliminationmore » yielding the conjugated cyclic coproducts 2-cyclopentenone and 2-cyclohexenone, respectively. Results on oxidation of 2-Me-CPO also show a dominant contribution from HO2-elimination. Moreover, the photoionization spectrum of the co-product suggests formation of 2-methyl-2-cyclopentenone and/or 2-cyclohexenone, resulting from a rapid Dowd–Beckwith rearrangement, preceding addition to O2, of the initial (2-oxocyclopentyl)methyl radical to 3-oxocyclohexyl. Cyclic ethers, markers for hydroperoxyalkyl radicals (QOOH), key intermediates in chain-propagating and chain-branching low-temperature combustion pathways, are only minor products. The interpretation of the experimental results is supported by stationary point calculations on the potential energy surfaces of the associated R + O2 reactions at the CBS-QB3 level. Furthermore, the calculations indicate that HO2-elimination channels are energetically favored and product formation via QOOH is disfavored. Lastly, the prominence of chain-terminating pathways linked with HO2 formation in low-temperature oxidation of cyclic ketones suggests little low-temperature reactivity of these species as fuels in internal combustion engines.« less

  17. Phase behaviors of cyclic diblock copolymers.

    PubMed

    Zhang, Guojie; Fan, Zhongyong; Yang, Yuliang; Qiu, Feng

    2011-11-01

    A spectral method of self-consistent field theory has been applied to AB cyclic block copolymers. Phase behaviors of cyclic diblock copolymers, such as order-disorder transition, order-order transition, and domain spacing size, have been studied, showing good consistency with previous experimental and theoretical results. Compared to linear diblocks, cyclic diblocks are harder to phase separate due to the topological constraint of the ring structure. A direct disorder-to-cylinder transition window is observed in the phase diagram, which is significantly different from the mean field phase diagram of linear diblock copolymers. The domain spacing size ratio between cyclic and linear diblock copolymers is typically close to 0.707, indicating in segregation that the cyclic polymer can be considered to be made up of linear diblocks with half of the original chain length. PMID:22070321

  18. Extraction, purification, identification and metabolism of 3',5'-cyclic UMP, 3',5'-cyclic IMP and 3',5'-cyclic dTMP from rat tissues.

    PubMed Central

    Newton, R P; Kingston, E E; Hakeem, N A; Salih, S G; Beynon, J H; Moyse, C D

    1986-01-01

    The large-scale extraction and partial purification of endogenous 3',5'-cyclic UMP, 3',5'-cyclic IMP and 3',5'-cyclic dTMP are described. Rat liver, kidney, heart, spleen and lung tissues were subjected to a sequential purification procedure involving freeze-clamping, perchlorate extraction, alumina and Sephadex ion-exchange chromatography and preparative electrophoresis. The samples thus obtained co-chromatographed with authentic cyclic UMP, cyclic IMP and cyclic dTMP on t.l.c. and h.p.l.c. and the u.v. spectra of the extracted samples were identical with those of the standards. Fast atom bombardment of the three cyclic nucleotide standards yielded mass spectra containing a molecular protonated ion in each case; mass-analysed ion kinetic-energy spectrometry ('m.i.k.e.s') of these ions produced a spectrum unique to the parent cyclic nucleotide. The extracted putative cyclic UMP, cyclic IMP and cyclic dTMP each produced a m.i.k.e.s. identical with that obtained with the corresponding cyclic nucleotide standard. Rat liver, heart, kidney, brain, intestine, spleen, testis and lung protein preparations were each found capable of the synthesis of cyclic UMP, cyclic IMP and cyclic dTMP from the corresponding nucleoside triphosphate, of the hydrolysis of these cyclic nucleotides and of their binding, with the exception that cyclic dTMP was not synthesized by the kidney preparation. PMID:3019316

  19. Activation energies of sigmatropic shifts in propene and acetone enolate from the anti-Hermitian contracted Schrödinger equation

    NASA Astrophysics Data System (ADS)

    Foley, Jonathan J.; Rothman, Adam E.; Mazziotti, David A.

    2009-05-01

    The hydrogen [1,3]-sigmatropic shift in propene is predicted by the Woodward-Hoffman rules to occur by an antarafacial pathway, yet the lack of experimental evidence suggests that this pathway is not favorable. Two natural questions arise: (i) can the [1,3]-shift be made more favorable by a symmetry-forbidden multistep pathway, and (ii) can the energetics be influenced by a substituent on propene? As in many chemical reactions, describing the energetics of these reactions requires a balanced treatment of both single-reference and multireference electron correlations, and yet traditional wave function methods often excel in treating only one kind of correlation. An equitable description of correlation effects, however, can be achieved, at a cost similar to efficient single-reference methods, by computing the two-electron reduced density matrix (2-RDM) from the anti-Hermitian part of the contracted Schrödinger equation (ACSE) [D. A. Mazziotti, Phys. Rev. Lett. 97, 143002 (2006)]. As with the contracted Schrödinger equation, the indeterminacy of the ACSE is removed without the many-electron wave function by reconstructing the 3-RDM from the 2-RDM via cumulant theory [D. A. Mazziotti, Chem. Phys. Lett. 289, 419 (1998)]. In this paper we apply the ACSE to study sigmatropic shifts in both propene and acetone enolate while extending its formalism to treat doublet spin states. In the 6-311G∗∗ basis set the ACSE predicts the activation energy of the trimethylene-to-propene rearrangement to be 8.8 kcal/mol while multireference perturbation theory yields a smaller barrier of 2.2 kcal/mol and coupled cluster singles-doubles predicts a negative barrier. We further find that the [1,3]-shift in acetone enolate is more favorable by ≈30 kcal/mol than the [1,3]-shift in propene, which is consistent with a prior theoretical investigation as well as experimental observations of these shifts in 2-butanone enolate.

  20. Short and stereoselective total synthesis of furano lignans (+/-)-dihydrosesamin, (+/-)-lariciresinol dimethyl ether, (+/-)-acuminatin methyl ether, (+/-)-sanshodiol methyl ether, (+/-)-lariciresinol, (+/-)-acuminatin, and (+/-)-lariciresinol monomethyl ether and furofuran lignans (+/-)-sesamin, (+/-)-eudesmin, (+/-)-piperitol methyl ether, (+/-)-pinoresinol, (+/-)-piperitol, and (+/-)-pinoresinol monomethyl ether by radical cyclization of epoxides using a transition-metal radical source.

    PubMed

    Roy, Subhas Chandra; Rana, Kalyan Kumar; Guin, Chandrani

    2002-05-17

    Intramolecular radical cyclization of suitably substituted epoxy ethers 4a-g using bis(cyclopentadienyl)titanium(III) chloride as the radical source resulted in trisubstituted tetrahydrofurano lignans and 2,6-diaryl-3,7-dioxabicyclo[3.3.0]octane lignans depending on the reaction conditions. The titanium(III) species was prepared in situ from commercially available titanocene dichloride and activated zinc dust in THF. Upon radical cyclization followed by acidic workup, epoxy olefinic ethers 4a-g afforded furano lignans dihydrosesamin 1a, lariciresinol dimethyl ether 1b, acuminatin methyl ether 1e, and sanshodiol methyl ether 1g directly and lariciresinol 1h, acuminatin 1i, and lariciresinol monomethyl ether 1j after removal of the benzyl protecting group by controlled hydrogenolysis of the corresponding cyclized products. The furofuran lignans sesamin 2a, eudesmin 2b, and piperitol methyl ether 2e were also prepared directly by using the same precursors 4a-f on radical cyclization followed by treatment with iodine and pinoresinol 2h, piperitol 2i, and pinoresinol monomethyl ether 2j after controlled hydrogenolysis of the benzyl protecting group of the corresponding cyclized products. Two naturally occurring acyclic lignans, secoisolariciresinol 5h and secoisolariciresinol dimethyl ether 5b, have also been prepared by exhaustive hydrogenolysis of 2h and 2b, respectively.

  1. [Aerobic microbial degradation of polybrominated diphenyl ethers].

    PubMed

    Ding, Juan; Zhou, Juan; Jiang, Wei-Ying; Gao, Shi-Xiang

    2008-11-01

    The biodegradation of 4, 4'-dibromodipheny ether (BDE15) and decabromodiphenyl ether (BDE209) by white rot fungi under aerobic conditions was studied. Effects of non-ionic surfactant Tween 80 and beta-cyclodextrin as solubilizers on the apparent solubilities and biodegradation rates of BDE15 and BDE209 were also evaluated. The results showed that both BDE15 and BDE209 were efficiently degraded by white rot fungi. The degradation rates were 43.0% and 62.5% for BDE209 and BDE15, respectively, after 10 d incubation. The degradation of BDE209 was greatly enhanced by addition of Tween 80 (< or = 700 mg/L) and beta-cyclodextrin, which may own to their solubilization effects on BDE209. However, Tween 80 at a high concentration (900 mg/L) would restrain the fungal growth, thereby decrease the degradation of BDE209. Addition of Tween 80 and beta-cyclodextrin exhibited some negative effects on the degradation of BDE15, which may due to decreased concentration of free BDE15 in water solution resulted from inclusion function of Tween 80 micelles and beta-cyclodextrin cavity, although the apparent solubility of BDE15 was drastically increased by both of them. PMID:19186824

  2. Biosynthesis of archaeal membrane ether lipids

    PubMed Central

    Jain, Samta; Caforio, Antonella; Driessen, Arnold J. M.

    2014-01-01

    A vital function of the cell membrane in all living organism is to maintain the membrane permeability barrier and fluidity. The composition of the phospholipid bilayer is distinct in archaea when compared to bacteria and eukarya. In archaea, isoprenoid hydrocarbon side chains are linked via an ether bond to the sn-glycerol-1-phosphate backbone. In bacteria and eukarya on the other hand, fatty acid side chains are linked via an ester bond to the sn-glycerol-3-phosphate backbone. The polar head groups are globally shared in the three domains of life. The unique membrane lipids of archaea have been implicated not only in the survival and adaptation of the organisms to extreme environments but also to form the basis of the membrane composition of the last universal common ancestor (LUCA). In nature, a diverse range of archaeal lipids is found, the most common are the diether (or archaeol) and the tetraether (or caldarchaeol) lipids that form a monolayer. Variations in chain length, cyclization and other modifications lead to diversification of these lipids. The biosynthesis of these lipids is not yet well understood however progress in the last decade has led to a comprehensive understanding of the biosynthesis of archaeol. This review describes the current knowledge of the biosynthetic pathway of archaeal ether lipids; insights on the stability and robustness of archaeal lipid membranes; and evolutionary aspects of the lipid divide and the LUCA. It examines recent advances made in the field of pathway reconstruction in bacteria. PMID:25505460

  3. Imide/arylene ether copolymers with pendent trifluoromethyl groups

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J.; Havens, Stephen J.

    1992-01-01

    A series of imide/arylene ether block copolymers were prepared using an arylene ether block containing a hexafluoroisopropylidene group and an imide block containing a hexafluoroisopropylidene and a trifluoromethyl group in the polymer backbone. The copolymers were characterized and mechanical properties were determined and compared to the homopolymers.

  4. Process for producing dimethyl ether from synthesis gas

    DOEpatents

    Pierantozzi, R.

    1985-06-04

    This invention pertains to a Fischer Tropsch process for converting synthesis gas to an oxygenated hydrocarbon with particular emphasis on dimethyl ether. Synthesis gas comprising carbon monoxide and hydrogen are converted to dimethyl ether by carrying out the reaction in the presence of an alkali metal-manganese-iron carbonyl cluster incorporated onto a zirconia-alumina support.

  5. 40 CFR 721.3485 - Hydrofluorocarbon alkyl ether.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Hydrofluorocarbon alkyl ether. 721... Substances § 721.3485 Hydrofluorocarbon alkyl ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as a hydrofluorocarbon alkyl...

  6. 40 CFR 721.3485 - Hydrofluorocarbon alkyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Hydrofluorocarbon alkyl ether. 721... Substances § 721.3485 Hydrofluorocarbon alkyl ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as a hydrofluorocarbon alkyl...

  7. 40 CFR 721.3485 - Hydrofluorocarbon alkyl ether.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Hydrofluorocarbon alkyl ether. 721... Substances § 721.3485 Hydrofluorocarbon alkyl ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as a hydrofluorocarbon alkyl...

  8. 40 CFR 721.3485 - Hydrofluorocarbon alkyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Hydrofluorocarbon alkyl ether. 721... Substances § 721.3485 Hydrofluorocarbon alkyl ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as a hydrofluorocarbon alkyl...

  9. 40 CFR 721.3485 - Hydrofluorocarbon alkyl ether.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Hydrofluorocarbon alkyl ether. 721... Substances § 721.3485 Hydrofluorocarbon alkyl ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as a hydrofluorocarbon alkyl...

  10. Responsive supramolecular gels constructed by crown ether based molecular recognition.

    PubMed

    Ge, Zhishen; Hu, Jinming; Huang, Feihe; Liu, Shiyong

    2009-01-01

    Responsive supramolecular gels were constructed from crown ether terminated four-arm star poly(epsilon-caprolactone) (PCL-DB24C8) and dibenzylammonium-terminated two-arm PCL-DBAS (see scheme), exploiting the formation of pseudorotaxane linkages between crown ether and ammonium moieties. The resultant supramolecular gels exhibit thermo- and pH-induced reversible gel-sol transition.

  11. Preparation of highly fluorinated diols containing ether linkages.

    NASA Technical Reports Server (NTRS)

    Rochow, S. E.; Stump, E. C., Jr.

    1970-01-01

    Hydroxy-terminated perfluoroethers and polyurethane resins derived from ethers have outstanding chemical resistance and good thermal properties. They can be used as potting compounds, coatings, and seals. The hydroxy-terminated ethers serve as intermediates in the synthesis of highly fluorinated elastomers and adhesives.

  12. IRIS Toxicological Review of Decabromodiphenyl Ether (2008 Final)

    EPA Science Inventory

    EPA is announcing the release of the final report, Toxicological Review of Decabromodiphenyl Ether: in support of the Integrated Risk Information System (IRIS). The updated Summary for Decabromodiphenyl Ether and accompanying Quickview have also been added to the IRIS Data...

  13. 47. BUILDING NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, INTERIOR, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    47. BUILDING NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, INTERIOR, 4TH LEVEL, LOOKING NORTH AT TOPS OF ALCOHOL AND ETHER DISTILLATION TOWERS. - Picatinny Arsenal, 500 Area, Powder Factory & Power House, State Route 15 near I-80, Dover, Morris County, NJ

  14. 48. BUILDING NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, INTERIOR, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    48. BUILDING NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, INTERIOR, 5TH LEVEL, LOOKING NORTH AT ETHER AND ALCOHOL CONDENSERS AT TOP OF TOWER. - Picatinny Arsenal, 500 Area, Powder Factory & Power House, State Route 15 near I-80, Dover, Morris County, NJ

  15. 46. BUILDING NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, INTERIOR, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    46. BUILDING NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, INTERIOR, CONTROL PANEL LEVEL (2ND DECK) OF ETHER AND ALCOHOL STILL BUILDING, LOOKING NORTH, SHOWING TWO ALCOHOL DISTILLATION TOWERS BEHIND 'MIXED SOLVENT UNIT' CONTROL PANEL. - Picatinny Arsenal, 500 Area, Powder Factory & Power House, State Route 15 near I-80, Dover, Morris County, NJ

  16. 29 CFR 1926.1106 - Methyl chloromethyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 8 2011-07-01 2011-07-01 false Methyl chloromethyl ether. 1926.1106 Section 1926.1106 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION... § 1926.1106 Methyl chloromethyl ether. Note: The requirements applicable to construction work under...

  17. 29 CFR 1915.1006 - Methyl chloromethyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 7 2011-07-01 2011-07-01 false Methyl chloromethyl ether. 1915.1006 Section 1915.1006 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION... Hazardous Substances § 1915.1006 Methyl chloromethyl ether. Note: The requirements applicable to...

  18. 29 CFR 1926.1106 - Methyl chloromethyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 8 2010-07-01 2010-07-01 false Methyl chloromethyl ether. 1926.1106 Section 1926.1106 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION... § 1926.1106 Methyl chloromethyl ether. Note: The requirements applicable to construction work under...

  19. 29 CFR 1910.1006 - Methyl chloromethyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 6 2010-07-01 2010-07-01 false Methyl chloromethyl ether. 1910.1006 Section 1910.1006 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION... Substances § 1910.1006 Methyl chloromethyl ether. See § 1910.1003, 13 carcinogens....

  20. 29 CFR 1910.1006 - Methyl chloromethyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 6 2011-07-01 2011-07-01 false Methyl chloromethyl ether. 1910.1006 Section 1910.1006 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION... Substances § 1910.1006 Methyl chloromethyl ether. See § 1910.1003, 13 carcinogens....

  1. 29 CFR 1910.1008 - bis-Chloromethyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 6 2011-07-01 2011-07-01 false bis-Chloromethyl ether. 1910.1008 Section 1910.1008 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR... bis-Chloromethyl ether. See § 1910.1003, 13 carcinogens....

  2. 29 CFR 1910.1008 - bis-Chloromethyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 6 2010-07-01 2010-07-01 false bis-Chloromethyl ether. 1910.1008 Section 1910.1008 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR... bis-Chloromethyl ether. See § 1910.1003, 13 carcinogens....

  3. 29 CFR 1915.1008 - bis-Chloromethyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 7 2011-07-01 2011-07-01 false bis-Chloromethyl ether. 1915.1008 Section 1915.1008 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR... § 1915.1008 bis-Chloromethyl ether. Note: The requirements applicable to shipyard employment under...

  4. 29 CFR 1915.1006 - Methyl chloromethyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 7 2010-07-01 2010-07-01 false Methyl chloromethyl ether. 1915.1006 Section 1915.1006 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION... Hazardous Substances § 1915.1006 Methyl chloromethyl ether. Note: The requirements applicable to...

  5. 40 CFR 721.825 - Certain aromatic ether diamines.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Certain aromatic ether diamines. 721.825 Section 721.825 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) TOXIC... Substances § 721.825 Certain aromatic ether diamines. (a) Chemical substances and significant new...

  6. 29 CFR 1915.1008 - bis-Chloromethyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 7 2010-07-01 2010-07-01 false bis-Chloromethyl ether. 1915.1008 Section 1915.1008 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR... § 1915.1008 bis-Chloromethyl ether. Note: The requirements applicable to shipyard employment under...

  7. 29 CFR 1926.1108 - bis-Chloromethyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 8 2010-07-01 2010-07-01 false bis-Chloromethyl ether. 1926.1108 Section 1926.1108 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR...-Chloromethyl ether. Note: The requirements applicable to construction work under this section are identical...

  8. 29 CFR 1926.1108 - bis-Chloromethyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 8 2011-07-01 2011-07-01 false bis-Chloromethyl ether. 1926.1108 Section 1926.1108 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR...-Chloromethyl ether. Note: The requirements applicable to construction work under this section are identical...

  9. The Ether Wind and the Global Positioning System.

    ERIC Educational Resources Information Center

    Muller, Rainer

    2000-01-01

    Explains how students can perform a refutation of the ether theory using information from the Global Positioning System (GPS). Discusses the functioning of the GPS, qualitatively describes how position determination would be affected by an ether wind, and illustrates the pertinent ideas with a simple quantitative model. (WRM)

  10. 40 CFR 721.825 - Certain aromatic ether diamines.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Certain aromatic ether diamines. 721... Substances § 721.825 Certain aromatic ether diamines. (a) Chemical substances and significant new uses...,5-benzenetetracarboxylic acid, diethyl ester, compound with 4,4′- -2,5-diylbis(oxy)]bis (1:1) (PMN...

  11. Process for producing dimethyl ether form synthesis gas

    DOEpatents

    Pierantozzi, Ronald

    1985-01-01

    This invention pertains to a Fischer Tropsch process for converting synthesis gas to an oxygenated hydrocarbon with particular emphasis on dimethyl ether. Synthesis gas comprising carbon monoxide and hydrogen are converted to dimethyl ether by carrying out the reaction in the presence of an alkali metal-manganese-iron carbonyl cluster incorporated onto a zirconia-alumina support.

  12. A Chitosan Derivative Containing Both Carboxylic Acid and Quaternary Ammonium Moieties for the Synthesis of Cyclic Carbonates.

    PubMed

    Besse, Vincent; Illy, Nicolas; David, Ghislain; Caillol, Sylvain; Boutevin, Bernard

    2016-08-23

    Chitosan, a renewable feedstock, is modified and used as a catalytic support in the presence of potassium iodide. The system is highly efficient towards the incorporation of carbon dioxide (CO2 ) into epoxides. It demonstrates very good thermal stability and is recyclable more than five times without loss of activity. The optimal reaction conditions were determined using allylglycidyl ether as a model and extended to a wide range of other epoxides. Cyclic carbonates were obtained with very high yield in a few hours under mild conditions (2-7 bar≈0.2-0.7 MPa, 80 °C) and no solvent. PMID:27440310

  13. Practical asymmetric synthesis of a potent PDE4 inhibitor via stereoselective enolate alkylation of a chiral aryl-heteroaryl secondary tosylate.

    PubMed

    O'Shea, Paul D; Chen, Cheng-yi; Chen, Weirong; Dagneau, Philippe; Frey, Lisa F; Grabowski, Edward J J; Marcantonio, Karen M; Reamer, Robert A; Tan, Lushi; Tillyer, Richard D; Roy, Amélie; Wang, Xin; Zhao, Dalian

    2005-04-15

    A practical, chromatography-free catalytic asymmetric synthesis of a potent and selective PDE4 inhibitor (L-869,298, 1) is described. Catalytic asymmetric hydrogenation of thiazole ketone 5a afforded the corresponding alcohol 3b in excellent enantioselectivity (up to 99.4% ee). Activation of alcohol 3b via formation of the corresponding p-toluenesulfonate followed by an unprecedented displacement with the lithium enolate of ethyl 3-pyridylacetate N-oxide 4a generated the required chiral trisubstituted methane. The displacement reaction proceeded with inversion of configuration and without loss of optical purity. Conversion of esters 2b to 1 was accomplished via a one-pot deprotection, saponification, and decarboxylation sequence in excellent overall yield.

  14. Subtle trade-off existing between (anti)aromaticity, push-pull interaction, keto-enol tautomerism, and steric hindrance when defining the electronic properties of conjugated structures.

    PubMed

    Kleinpeter, Erich; Bölke, Ute; Koch, Andreas

    2010-07-22

    The spatial magnetic properties (through space NMR shieldings, TSNMRS) of conjugated structures (benzenoid/quinonoid keto/enol tautomers, 1,3-dihydroxyaryl-2-aldehydes, Don-pi-Acc chromophores with trade-off existing push-pull vs aromatic behavior) have been calculated by the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept, and visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The TSNMRS values, thus obtained, can be successfully employed to quantify and visualize (anti)aromaticity and to identify readily hereby zwitterionic structures due to push-pull behavior of the compounds studied. In addition, the push-pull behavior was quantified by the quotient (pi*/pi) approach of the central partial C=C double bond. PMID:20586465

  15. A study of interstellar aldehydes and enols as tracers of a cosmic ray-driven nonequilibrium synthesis of complex organic molecules.

    PubMed

    Abplanalp, Matthew J; Gozem, Samer; Krylov, Anna I; Shingledecker, Christopher N; Herbst, Eric; Kaiser, Ralf I

    2016-07-12

    Complex organic molecules such as sugars and amides are ubiquitous in star- and planet-forming regions, but their formation mechanisms have remained largely elusive until now. Here we show in a combined experimental, computational, and astrochemical modeling study that interstellar aldehydes and enols like acetaldehyde (CH3CHO) and vinyl alcohol (C2H3OH) act as key tracers of a cosmic-ray-driven nonequilibrium chemistry leading to complex organics even deep within low-temperature interstellar ices at 10 K. Our findings challenge conventional wisdom and define a hitherto poorly characterized reaction class forming complex organic molecules inside interstellar ices before their sublimation in star-forming regions such as SgrB2(N). These processes are of vital importance in initiating a chain of chemical reactions leading eventually to the molecular precursors of biorelevant molecules as planets form in their interstellar nurseries. PMID:27382172

  16. A study of interstellar aldehydes and enols as tracers of a cosmic ray-driven nonequilibrium synthesis of complex organic molecules.

    PubMed

    Abplanalp, Matthew J; Gozem, Samer; Krylov, Anna I; Shingledecker, Christopher N; Herbst, Eric; Kaiser, Ralf I

    2016-07-12

    Complex organic molecules such as sugars and amides are ubiquitous in star- and planet-forming regions, but their formation mechanisms have remained largely elusive until now. Here we show in a combined experimental, computational, and astrochemical modeling study that interstellar aldehydes and enols like acetaldehyde (CH3CHO) and vinyl alcohol (C2H3OH) act as key tracers of a cosmic-ray-driven nonequilibrium chemistry leading to complex organics even deep within low-temperature interstellar ices at 10 K. Our findings challenge conventional wisdom and define a hitherto poorly characterized reaction class forming complex organic molecules inside interstellar ices before their sublimation in star-forming regions such as SgrB2(N). These processes are of vital importance in initiating a chain of chemical reactions leading eventually to the molecular precursors of biorelevant molecules as planets form in their interstellar nurseries.

  17. Mixed Strategies in cyclic competition

    NASA Astrophysics Data System (ADS)

    Intoy, Ben; Pleimling, Michel

    2015-03-01

    Physicists have been using evolutionary game theory to model and simulate cyclically competing species, with applications to lizard mating strategies and competing bacterial strains. However these models assume that each agent plays the same strategy, which is called a pure strategy in game theory, until they are beaten by a better strategy which they immediately adopt. We relax this constraint of an agent playing a single strategy by instead letting the agent pick its strategy randomly from a probability distribution, which is called a mixed strategy in game theory. This scheme is very similar to multiple occupancy models seen in the literature, the major difference being that interactions happen between sites rather than within them. Choosing strategies out of a distribution also has applications to economic/social systems such as the public goods game. We simulate a model of mixed strategy and cylic competition on a one-dimensional lattice with three and four strategies and find interesting spatial and stability properties depending on how discretized the choice of strategy is for the agents. This work is supported by the US National Science Foundation through Grant DMR-1205309.

  18. 2-Acetylcyclopentanone, an Enolate-Forming 1,3-Dicarbonyl Compound, Is Cytoprotective in Warm Ischemia-Reperfusion Injury of Rat Liver

    PubMed Central

    Kosharskyy, Boleslav; Vydyanathan, Amaresh; Zhang, Lihai; Shaparin, Naum; Geohagen, Brian C.; Bivin, William; Liu, Qiang; Gavin, Terrence

    2015-01-01

    We have previously shown that 2-acetylcyclopentanone (2-ACP), an enolate-forming 1,3-dicarbonyl compound, provides protection in cell culture and animal models of oxidative stress. The pathophysiology of ischemia-reperfusion injury (IRI) involves oxidative stress, and, therefore, we determined the ability of 2-ACP to prevent this injury in a rat liver model. IRI was induced by clamping the portal vasculature for 45 minutes (ischemia phase), followed by recirculation for 180 minutes (reperfusion phase). This sequence was associated with substantial derangement of plasma liver enzyme activities, histopathological indices, and markers of oxidative stress. The 2-ACP (0.80–2.40 mmol/kg), administered by intraperitoneal injection 10 minutes prior to reperfusion, provided dose-dependent cytoprotection, as indicated by normalization of the IRI-altered liver histologic and biochemical parameters. The 2-ACP (2.40 mmol/kg) was also hepatoprotective when injected before clamping the circulation (ischemia phase). In contrast, an equimolar dose of N-acetylcysteine (2.40 mmol/kg) was not hepatoprotective when administered prior to reperfusion. Our studies to date suggest that during reperfusion the enolate nucleophile of 2-ACP limits the consequences of mitochondrial-based oxidative stress through scavenging unsaturated aldehyde electrophiles (e.g., acrolein) and chelation of metal ions that catalyze the free radical-generating Fenton reaction. The ability of 2-ACP to reduce IRI when injected prior to ischemia most likely reflects the short duration of this experimental phase (45 minutes) and favorable pharmacokinetics that maintain effective 2-ACP liver concentrations during subsequent reperfusion. These results provide evidence that 2-ACP or an analog might be useful in treating IRI and other conditions that have oxidative stress as a common molecular etiology. PMID:25659651

  19. Asymmetric cyclic evolution in polymerised cosmology

    SciTech Connect

    Hrycyna, Orest; Mielczarek, Jakub; Szydłowski, Marek E-mail: jakub.mielczarek@uj.edu.pl

    2009-12-01

    The dynamical systems methods are used to study evolution of the polymerised scalar field cosmologies with the cosmological constant. We have found all evolutional paths admissible for all initial conditions on the two-dimensional phase space. We have shown that the cyclic solutions are generic. The exact solution for polymerised cosmology is also obtained. Two basic cases are investigated, the polymerised scalar field and the polymerised gravitational and scalar field part. In the former the division on the cyclic and non-cyclic behaviour is established following the sign of the cosmological constant. The value of the cosmological constant is upper bounded purely from the dynamical setting.

  20. Processable Cyclic Peptide Nanotubes with Tunable Interiors

    SciTech Connect

    Hourani, Rami; Zhang, Chen; van der Weegen, Rob; Ruiz, Luis; Li, Changyi; Keten, Sinan; Helms, Brett A.; Xu, Ting

    2011-09-06

    A facile route to generate cyclic peptide nanotubes with tunable interiors is presented. By incorporating 3-amino-2-methylbenzoic acid in the d,l-alternating primary sequence of a cyclic peptide, a functional group can be presented in the interior of the nanotubes without compromising the formation of high aspect ratio nanotubes. The new design of such a cyclic peptide also enables one to modulate the nanotube growth process to be compatible with the polymer processing window without compromising the formation of high aspect ratio nanotubes, thus opening a viable approach toward molecularly defined porous membranes.

  1. [Recent development of research on the biotribology of carbon fiber reinforced poly ether ether ketone composites].

    PubMed

    Chen, Yan; Pan, Yusong

    2014-12-01

    Carbon fiber reinforced poly ether ether ketone (CF/PEEK) composite possesses excellent biocompatible, biomechanical and bioribological properties. It is one of the most promising implant materials for artificial joint. Many factors influence the bioribological properties of CF/PEEK composites. In this paper, the authors reviewed on the biotribology research progress of CF/PEEK composites. The influences of various factors such as lubricant, reinforcement surface modification, functional particles, friction counterpart and friction motion modes on the bio-tribological properties of CF/PEEK composites are discussed. Based on the recent research, the authors suggest that the further research should be focused on the synergistic effect of multiple factors on the wear and lubrication mechanism of CF/PEEK. PMID:25868268

  2. A sulfonated poly (aryl ether ether ketone ketone) isomer: synthesis and DMFC performance

    SciTech Connect

    Kim, Yu Seung; Liu, Baijun; Hu, Wei; Jiang, Zhenhua; Robertson, Gilles; Guiver, Michael

    2009-01-01

    A sulfonated poly(aryl ether ether ketone ketone) (PEEKK) having a well-defined rigid homopolymer-like chemical structure was synthesized from a readily-prepared PEEKK post-sulfonation with concentrated sulfuric acid at room temperature within several hours. The polymer electrolyte membrane (PEM) cast from the resulting polymer exhibited an excellent combination of thermal resistance, oxidative and dimensional stability, low methanol fuel permeability and high proton conductivity. Furthermore, membrane electrode assemblies (MEAs) were successfully fabricated and good direct methanol fuel cell (DMFC) performance was observed. At 2 M MeOH feed, the current density at 0.5 V reached 165 mA/cm, which outperformed our reported analogues and eveluated Nafion membranes.

  3. The effect of high-energy electron radiation on poly(arylene ether)s

    NASA Technical Reports Server (NTRS)

    Connell, J. W.; Siochi, E. J.; Croall, C. I.

    1993-01-01

    Thin films of four experimental poly(arylene ether)s of similar chemical structure were exposed to 1 MeV electrons while under high vacuum. The films received total exposures of 5 x 10 exp 7 and 1 x 10 exp 9 rads at a dose rate of 5 x 10 exp 7 rads/h and a pressure of 2 x 10 exp -7 torr. Films exposed to 5 x 10 exp 7 rads showed dramatic changes in molecular weight distribution. After exposures of 1 x 10 exp 9 rads the films were only partially soluble in chloroform and exhibited no detectable changes in the glass transition temperatures. Thin-film tensile properties were also altered by the exposure to electron radiation. The effect of the exposures as determined by various analyses is discussed.

  4. Origin of mechanical modifications in poly (ether ether ketone)/carbon nanotube composite

    SciTech Connect

    Pavlenko, Ekaterina; Puech, Pascal; Bacsa, Wolfgang; Boyer, François; Olivier, Philippe; Sapelkin, Andrei; King, Stephen; Heenan, Richard; Pons, François; Gauthier, Bénédicte; Cadaux, Pierre-Henri

    2014-06-21

    Variations in the hardness of a poly (ether ether ketone) beam electrically modified with multi-walled carbon nanotubes (MWCNT, 0.5%-3%) are investigated. It is shown that both rupture and hardness variations correlate with the changes in carbon nanotube concentration when using micro indentation and extended Raman imaging. Statistical analysis of the relative spectral intensities in the Raman image is used to estimate local tube concentration and polymer crystallinity. We show that the histogram of the Raman D band across the image provides information about the amount of MWCNTs and the dispersion of MWCNTs in the composite. We speculate that we have observed a local modification of the ordering between pure and modified polymer. This is partially supported by small angle neutron scattering measurements, which indicate that the agglomeration state of the MWCNTs is the same at the concentrations studied.

  5. A New Analogue of Echinomycin and a New Cyclic Dipeptide from a Marine-Derived Streptomyces sp. LS298

    PubMed Central

    Zhen, Xin; Gong, Ting; Liu, Fu; Zhang, Pei-Cheng; Zhou, Wan-Qi; Li, Yan; Zhu, Ping

    2015-01-01

    Quinomycin G (1), a new analogue of echinomycin, together with a new cyclic dipeptide, cyclo-(l-Pro-4-OH-l-Leu) (2), as well as three known antibiotic compounds tirandamycin A (3), tirandamycin B (4) and staurosporine (5), were isolated from Streptomyces sp. LS298 obtained from a marine sponge Gelliodes carnosa. The planar and absolute configurations of compounds 1 and 2 were established by MS, NMR spectral data analysis and Marfey’s method. Furthermore, the differences in NMR data of keto-enol tautomers in tirandamycins were discussed for the first time. Antibacterial and anti-tumor activities of compound 1 were measured against 15 drug-sensitive/resistant strains and 12 tumor cell lines. Compound 1 exhibited moderate antibacterial activities against Staphylococcuse pidermidis, S. aureus, Enterococcus faecium, and E. faecalis with the minimum inhibitory concentration (MIC) values ranged from 16 to 64 μg/mL. Moreover, it displayed remarkable anti-tumor activities; the highest activity was observed against the Jurkat cell line (human T-cell leukemia) with an IC50 value of 0.414 μM. PMID:26593927

  6. A New Analogue of Echinomycin and a New Cyclic Dipeptide from a Marine-Derived Streptomyces sp. LS298.

    PubMed

    Zhen, Xin; Gong, Ting; Liu, Fu; Zhang, Pei-Cheng; Zhou, Wan-Qi; Li, Yan; Zhu, Ping

    2015-11-01

    Quinomycin G (1), a new analogue of echinomycin, together with a new cyclic dipeptide, cyclo-(l-Pro-4-OH-l-Leu) (2), as well as three known antibiotic compounds tirandamycin A (3), tirandamycin B (4) and staurosporine (5), were isolated from Streptomyces sp. LS298 obtained from a marine sponge Gelliodes carnosa. The planar and absolute configurations of compounds 1 and 2 were established by MS, NMR spectral data analysis and Marfey's method. Furthermore, the differences in NMR data of keto-enol tautomers in tirandamycins were discussed for the first time. Antibacterial and anti-tumor activities of compound 1 were measured against 15 drug-sensitive/resistant strains and 12 tumor cell lines. Compound 1 exhibited moderate antibacterial activities against Staphylococcuse pidermidis, S. aureus, Enterococcus faecium, and E. faecalis with the minimum inhibitory concentration (MIC) values ranged from 16 to 64 μg/mL. Moreover, it displayed remarkable anti-tumor activities; the highest activity was observed against the Jurkat cell line (human T-cell leukemia) with an IC50 value of 0.414 μM. PMID:26593927

  7. Methoxy-ether and crown-ether derivatives of tetrahomodioxa- and octahomotetraoxacalix[4]arenes.

    PubMed

    Masci, B; Saccheo, S; Fonsi, M; Varrone, M; Finelli, M; Nierlich, M; Thuéry, P

    2001-08-01

    Three methoxy-ether and one methoxy-ether/crown-ether derivatives of p-tert-butyltetrahomodioxa- and p-R-octahomotetraoxacalix[4]arenes (R = methyl, tert-butyl, H) have been investigated. The first three compounds, 7,15,21,27-tetra-tert-butyl-29,30,31,32-tetramethoxy-3,11-dioxapentacyclo[23.3.1.1(5,9).1(13,17).1(19,23)]ditriaconta-1(29),5,7,9(30),13,15,-17(31),19,21,23(32),25,27-dodecaene, C(50)H(68)O(6), 33,34,35,36-tetramethoxy-7,15,23,31-tetramethyl-3,11,19,27-tetraoxapentacyclo[27.3.1.1(5,9).1(13,17).1(21,25)]hexatriaconta-1(33),5,7,9(34),13,15,17(35),21,23,25(36),29,31-dodecaene, C(40)H(48)O(8), and 7,23-di-tert-butyl-33,34,35,36-tetramethoxy-3,11,19,27-tetraoxapentacyclo[27.3.1.1(5,9).1(13,17).1(21,25)]hexatriaconta-1(33),5,7,9(34),13,15,17(35),- 21,23,25(36),29,31-dodecaene, C(44)H(56)O(8), in the partial-cone or 1,2-alternate conformations, present the common feature of methoxy-ether self-inclusion, while the fourth, 42,43-dimethoxy-7,15,23,31-tetramethyl-3,11,19,27,34,37,40-heptaoxahexacyclo[15.15.9.1(5,9).1(21,25).0(13,41).0(29,33)]tritetraconta-5(42),6,8,13(41),14,16,21(43),22,24,29(33),30,32-dodecaene, C(42)H(50)O(9), adopts the 1,3-alternate conformation owing to the presence of a 1,3-polyether chain.

  8. Development of specialty chemicals from dimethyl ether

    SciTech Connect

    Tartamella, T.L.; Lee, S.

    1996-12-31

    Dimethyl ether (DME) may be efficiently produced from coal-bases syngas in a high pressure, mechanically agitated slurry reactor. DME synthesis occurs in the liquid phase using a dual catalyst. By operating in a dual catalyst mode, DME may be converted from in-situ produced methanol resulting in higher methyl productivities and syngas conversions over methanol conversion alone. The feasibility of utilizing DME as a building block for more valuable specialty chemicals has been examined. A wide variety of petrochemicals may be produced from DME including light olefins, gasoline range hydrocarbons, oxygenates, and glycol precursors. These chemicals represent an important part of petroleum industries inventory of fine chemicals. Carbonylation, hydrocarbonylation, and oxidative dimerization are but a few of the reactions in which DME may undergo conversion. DME provides an additional route for the production of industrially important petrochemicals.

  9. High temperature fuel cell membranes based on poly(arylene ether)s containing benzimidazole groups

    SciTech Connect

    Kim, Dae Sik; Kim, Yu Seung; Lee, Kwan - Soo; Boncella, James M; Kuiper, David; Guiver, Michael D

    2009-01-01

    Development of new high-performance polymer membranes that retain their proton conductivity under low humidity conditions is one of the most critical requirements to commercialize PEMFC systems. Current sulfonated proton exchange membranes acquire proton conductivity by water that solvates ion and carries proton. Consequently, a loss of water under low RH conditions immediately results in a loss of proton conductivity. One approach to maintain proton conductivity under low RH conditions is to replace water with a less volatile proton solvent. Kreuer has pointed out the possibility to develop fully polymeric proton-conducting membranes based on nitrogen-containing heterocycles such as imidazole, benzimidazole, and pyrazole. We have attempted to blend those less volatile proton solvent with sulfonated copolymers such as polystyrene sulfonic acid, Nafion, poly(arylene ether sulfone, BPSH-xx). [Ref. DOE review meeting 2007 and 2008] However, we observed that imidazole was slowly sublimated out as temperature and humidity increases which could cause poisoning of electro-catalyst, corrosion and losing conductivity. In this presentation, we report the synthesis of novel poly(arylene ether sulfone)s containing benzimidazole groups These benzimidazole containing polymer was blended with sulfonated poly(arylene ether sulfone). In the blend system, benzimidazole group attached to the polysulfone acts as a medium through the basic nitrogen for transfer of protons between the sulfonic acid groups. Proton conductivity of the blend membranes was investigated as a function of water content at 80 C and compared the performance with water based proton conduction system.

  10. Formulating liquid ethers for microtubular SOFCs

    NASA Astrophysics Data System (ADS)

    Kendall, Kevin; Slinn, Matthew; Preece, John

    One of the key problems of applying solid oxide fuel cells (SOFCs) in transportation is that conventional fuels like kerosene and diesel do not operate directly in SOFCs without prereforming to hydrogen and carbon monoxide which can be handled by the nickel cermet anode. SOFCs can internally reform certain hydrocarbon molecules such as methanol and methane. However, other liquid fuels usable in petrol or diesel internal combustion engines (ICEs) have not easily been reformable directly on the anode. This paper describes a search for liquid fuels which can be mixed with petrol or diesel and also injected directly into an SOFC without destroying the nickel anode. When fuel molecules such as octane are injected onto the conventional nickel/yttria stabilised zirconia (Ni/YSZ) SOFC fuel electrode, the anode rapidly becomes blocked by carbon deposition and the cell power drops to near zero in minutes. This degeneration of the anode can be inhibited by injection of air or water into the anode or by some upstream reforming just before entry to the SOFC. Some smaller molecules such as methane, methanol and methanoic acid produce a slight tendency to carbon deposition but not sufficient to prevent long term operation. In this project we have investigated a large number of molecules and now found that some liquid ethers do not significantly damage the anode when directly injected. These molecules and formulations with other components have been evaluated in this study. The theory put forward in this paper is that carbon-carbon bonds in the fuel are the main reason for anode damage. By testing a number of fuels without such bonds, particularly liquid ethers such as methyl formate and dimethoxy methane, it has been shown that SOFCs can run without substantial carbon formation. The proposal is that conventional fuels can be doped with these molecules to allow hybrid operation of an ICE/SOFC device.

  11. Development of Stereocontrolled Palladium(II)-Catalyzed Domino Heck/Suzuki β,α-Diarylation Reactions with Chelating Vinyl Ethers and Arylboronic Acids

    PubMed Central

    Trejos, Alejandro; Odell, Luke R; Larhed, Mats

    2012-01-01

    A stereoselective and 1,4-benzoquinone-mediated palladium(II)-catalyzed Heck/Suzuki domino reaction involving metal coordinating cyclic methylamino vinyl ethers and a number of electronically diverse arylboronic acids has been developed and studied. Diastereomeric ratios up to 39:1 and 78 % isolated yields were obtained. The stereoselectivity of the reaction was found to be highly dependent on the nature of the arylboronic acid and the amount of water present in the reaction mixture. Thus, a domino β,α-diarylation–reduction of chelating vinyl ethers can now be accomplished and stereochemically controlled, given that optimized conditions and an appropriate chiral auxiliary are used. To the best of our knowledge, this represents the first example of a stereoselective, oxidative Heck/Suzuki domino reaction in the literature. PMID:24551492

  12. The structures of cyclic dihydronium cations.

    PubMed

    Wallace, Sonjae; Huang, Lulu; Massa, Lou; Mukhopadhyay, Uday; Bernal, Ivan; Karle, Jerome

    2007-10-23

    Recent experimental discoveries have revealed the existence of hitherto unexpected cyclic hydronium di-cations trapped within crystal structures. The molecular formulas are (H(14)O(6))(2+), present as two isomers, four- and six-member cyclic structures, and (H(18)O(8))(2+), an eight-member cyclic structure. As these unprecedented hydronium species are stabilized by the crystal structures in which they are captured, the question arises whether they could be stable as independent species as, for example, in solution or gas phase. Quantum mechanical density functional theory calculations are used to investigate this question. We find these doubly charged cyclic hydronium structures to be energetically stable and, as between the four- and six-member structures, the former has more binding energy than the latter. We also determine the theoretically optimized structures for all three ions and give their calculated atomic charges for both their crystal and optimized geometries.

  13. Synchronization in chaotic oscillators by cyclic coupling

    NASA Astrophysics Data System (ADS)

    Olusola, O. I.; Njah, A. N.; Dana, S. K.

    2013-07-01

    We introduce a type of cyclic coupling to investigate synchronization of chaotic oscillators. We derive analytical solutions of the critical coupling for stable synchronization under the cyclic coupling for the Rössler system and the Lorenz oscillator as paradigmatic illustration. Based on the master stability function (MSF) approach, the analytical results on critical coupling are verified numerically. An enhancing effect in terms of lowering the critical coupling or enlarging the synchronization window in a critical coupling space is noticed. The cyclic coupling is also applied in other models, Hindmarsh-Rose model, Sprott system, Chen system and forced Duffing system to confirm the enhancing effect. The cyclic coupling allows tuning of two coupling constants in reverse directions when an optimal control of synchronization is feasible.

  14. Mortar constituent of concrete under cyclic compression

    NASA Astrophysics Data System (ADS)

    Maher, A.; Darwin, D.

    1980-10-01

    The behavior of the mortar constituent of concrete under cyclic compression was studied and a simple analytic model was developed to represent its cyclic behavior. Experimental work consisted of monotonic and cyclic compressive loading of mortar. Two mixes were used, with proportions corresponding to concretes having water cement ratios of 0.5 and 0.6. Forty-four groups of specimens were tested at ages ranging from 5 to 70 days. complete monotonic and cyclic stress strain envelopes were obtained. A number of loading regimes were investigated, including cycles to a constant maximum strain. Major emphasis was placed on tests using relatively high stress cycles. Degradation was shown to be a continuous process and a function of both total strain and load history. No stability or fatigue limit was apparent.

  15. Cyclic loading in knee ligament injuries.

    PubMed

    Weisman, G; Pope, M H; Johnson, R J

    1980-01-01

    The effect of cyclic loading on knee ligaments was studied both in vivo and in vitro. The compliance of the medial collateral ligaments of athletes participating in hockey, basketball, soccer, and downhill skiing was determined by using a specially built machine. Tests were conducted before and after participation in the various sports. Most subjects tested showed an increased compliance after their respective sporting activities. This observation was confirmed in the laboratory by imparting cyclic loading to 10 people under controlled conditions. The in vitro studies were conducted on the medial collateral ligaments of rats. These were tested to determine the effect of cyclic loading on the strength and stiffness of the ligaments. Results show a clear relationship between decreased stiffness or softening and a reduction in strength of the ligament. The amount of softening was related to the cyclic stress in the ligament.

  16. Prenyl Ethers: Novel Fungal Volatiles Formed by Penicillium digitatum.

    PubMed

    Amrein, Thomas M; Frey, Peter; Meier, Roberto; Baumann, Heidi; Tanner, Miriam; Gassenmeier, Klaus F

    2014-10-01

    Prenyl ethyl ether (PEE) was previously described as the cause for a solvent-like off-note in ground hazelnuts, but its origin remained unclear. Investigations were carried out by analytical groups of Coop and Givaudan over four years to elucidate this phenomenon. From mouldy citrus fruits a strain of Penicillium digitatum was isolated and found to form PEE. Formation on citrus and other fruits was prominent and contributed to the particular smell of decayed fruits. Several strains of P. digitatum formed PEE, while other fungal species did not. In contrast to citrus fruit, prenyl methyl ether (PME) was formed as dominant prenyl ether on hazelnuts while only small amounts of PEE were found. PME has not been previously described as volatile metabolite of fungi or as a food-taint. Spiking experiments with deuterated ethanol showed that the ethyl group is likely incorporated into PEE via the aldehyde form. On hazelnuts strongly decayed by P. digitatum yet another prenyl ether was tentatively identified: Prenyl isopropyl ether. Prenyl ethers present a novel group of volatile metabolites of P. digitatum. They are likely typical for this species and have not been described before. Prenyl ethers seem to play a significant role in the smell of food decayed by P. digitatum and should be considered in cases of off-notes and taints. PMID:25437159

  17. Crown Ethers in Nonaqueous Electrolytes for Lithium/Air Batteries

    SciTech Connect

    Xu, Wu; Xiao, Jie; Wang, Deyu; Zhang, Jian; Zhang, Jiguang

    2010-02-04

    The effects of three crown ethers, 12-crown-4, 15-crown-5, and 18-crown-6, as additives and co-solvents in non-aqueous electrolytes on the cell performance of primary Li/air batteries operated in a dry air environment were investigated. Crown ethers have large effects on the discharge performance of non-aqueous electrolytes in Li/air batteries. A small amount (normally less than 10% by weight or volume in electrolytes) of 12-Crown-4 and 15-crown-5 reduces the battery performance and a minimum discharge capacity appears at the crown ether content of ca. 5% in the electrolytes. However, when the content increases to about 15%, both crown ethers improve the capacity of Li/air cells by about 28% and 16%, respectively. 15-Crown-5 based electrolytes even show a maximum discharge capacity in the crown ether content range from 10% to 15%. On the other hand, the increase of 18-crown-6 amount in the electrolytes continuously lowers of the cell performance. The different battery performances of these three crown ethers in electrolytes are explained by the combined effects from the electrolytes’ contact angle, oxygen solubility, viscosity, ionic conductivity, and the stability of complexes formed between crown ether molecules and lithium ions.

  18. Characterization of Microsolvated Crown Ethers from Broadband Rotational Spectroscopy

    NASA Astrophysics Data System (ADS)

    Perez, Cristobal; Schnell, Melanie; Blanco, Susana; Lopez, Juan Carlos

    2016-06-01

    Since they were first synthetized, crown ethers have been extensively used in organometallic chemistry due to their unparalleled binding selectivity with alkali metal cations. From a structural point of view, crown ethers are heterocycles containing oxygen and/or other heteroatoms, although the most common ones are formed from ethylene oxide unit. Crown ethers are conventionally seen as being hydrophilic inside and hydrophobic outside when the structures found for the metal cation complexes are considered. However, crown ethers are extremely flexible and in isolation may present a variety of stable conformations so that their structure may be easily adapted in presence of a strong ligand as an alkali metal cation minimize the energy of the resulting complex. Water can be considered a soft ligand which interacts with crown ethers through moderate hydrogen bonds. It is thus interesting to investigate which conformers are selected by water to form complexes, the preferred interaction sites and the possible conformational changes due to the presence of one or more water molecules. Previous studies identified microsolvated crown ethers but in all cases with a chromophore group attached to the structure. Here we present a broadband rotational spectroscopy study of microsolvated crown ethers produced in a pulsed molecular jet expansion. Several 1:1 and 1:2 crown ether:water aggregates are presented for 12-crown-4, 15-crown-5 and 18-crown-6. Unambiguous identification of the structures has been achieved using isotopic substitution within the water unit. The subtle changes induced in the structures of the crown ether monomer upon complexation and the hydrogen-bonding network that hold them together will be also discussed. F. Gámez, B. Martínez-Haya, S. Blanco,J. C. López and J. L. Alonso, Phys. Chem. Chem. Phys. 2014, 14 12912-12918 V. A. Shubert, C.W. Müller and T. Zwier, J. Phys. Chem. A 2009, 113 8067-8079

  19. Antimicrobial cyclic peptides for plant disease control.

    PubMed

    Lee, Dong Wan; Kim, Beom Seok

    2015-03-01

    Antimicrobial cyclic peptides derived from microbes bind stably with target sites, have a tolerance to hydrolysis by proteases, and a favorable degradability under field conditions, which make them an attractive proposition for use as agricultural fungicides. Antimicrobial cyclic peptides are classified according to the types of bonds within the ring structure; homodetic, heterodetic, and complex cyclic peptides, which in turn reflect diverse physicochemical features. Most antimicrobial cyclic peptides affect the integrity of the cell envelope. This is achieved through direct interaction with the cell membrane or disturbance of the cell wall and membrane component biosynthesis such as chitin, glucan, and sphingolipid. These are specific and selective targets providing reliable activity and safety for non-target organisms. Synthetic cyclic peptides produced through combinatorial chemistry offer an alternative approach to develop antimicrobials for agricultural uses. Those synthesized so far have been studied for antibacterial activity, however, the recent advancements in powerful technologies now promise to provide novel antimicrobial cyclic peptides that are yet to be discovered from natural resources.

  20. Antimicrobial Cyclic Peptides for Plant Disease Control

    PubMed Central

    Lee, Dong Wan; Kim, Beom Seok

    2015-01-01

    Antimicrobial cyclic peptides derived from microbes bind stably with target sites, have a tolerance to hydrolysis by proteases, and a favorable degradability under field conditions, which make them an attractive proposition for use as agricultural fungicides. Antimicrobial cyclic peptides are classified according to the types of bonds within the ring structure; homodetic, heterodetic, and complex cyclic peptides, which in turn reflect diverse physicochemical features. Most antimicrobial cyclic peptides affect the integrity of the cell envelope. This is achieved through direct interaction with the cell membrane or disturbance of the cell wall and membrane component biosynthesis such as chitin, glucan, and sphingolipid. These are specific and selective targets providing reliable activity and safety for non-target organisms. Synthetic cyclic peptides produced through combinatorial chemistry offer an alternative approach to develop antimicrobials for agricultural uses. Those synthesized so far have been studied for antibacterial activity, however, the recent advancements in powerful technologies now promise to provide novel antimicrobial cyclic peptides that are yet to be discovered from natural resources. PMID:25774105

  1. Cyclic behaviors of amorphous shape memory polymers.

    PubMed

    Yu, Kai; Li, Hao; McClung, Amber J W; Tandon, Gyaneshwar P; Baur, Jeffery W; Qi, H Jerry

    2016-04-01

    Cyclic loading conditions are commonly encountered in the applications of shape memory polymers (SMPs), where the cyclic characteristics of the materials determine their performance during the service life, such as deformation resistance, shape recovery speed and shape recovery ratio. Recent studies indicate that in addition to the physical damage or some other irreversible softening effects, the viscoelastic nature could also be another possible reason for the degraded cyclic behavior of SMPs. In this paper, we explore in detail the influence of the viscoelastic properties on the cyclic tension and shape memory (SM) behavior of an epoxy based amorphous thermosetting polymer. Cyclic experiments were conducted first, which show that although the epoxy material does not have any visible damage or irreversible softening effect during deformation, it still exhibits obvious degradation in the cyclic tension and SM behaviors. A linear multi-branched model is utilized to assist in the prediction and understanding of the mechanical responses of amorphous SMPs. Parametric studies based on the applied model suggest that the shape memory performance can be improved by adjusting programming and recovery conditions, such as lowering the loading rate, increasing the programming temperature, and reducing the holding time. PMID:26924339

  2. Cyclic behaviors of amorphous shape memory polymers.

    PubMed

    Yu, Kai; Li, Hao; McClung, Amber J W; Tandon, Gyaneshwar P; Baur, Jeffery W; Qi, H Jerry

    2016-04-01

    Cyclic loading conditions are commonly encountered in the applications of shape memory polymers (SMPs), where the cyclic characteristics of the materials determine their performance during the service life, such as deformation resistance, shape recovery speed and shape recovery ratio. Recent studies indicate that in addition to the physical damage or some other irreversible softening effects, the viscoelastic nature could also be another possible reason for the degraded cyclic behavior of SMPs. In this paper, we explore in detail the influence of the viscoelastic properties on the cyclic tension and shape memory (SM) behavior of an epoxy based amorphous thermosetting polymer. Cyclic experiments were conducted first, which show that although the epoxy material does not have any visible damage or irreversible softening effect during deformation, it still exhibits obvious degradation in the cyclic tension and SM behaviors. A linear multi-branched model is utilized to assist in the prediction and understanding of the mechanical responses of amorphous SMPs. Parametric studies based on the applied model suggest that the shape memory performance can be improved by adjusting programming and recovery conditions, such as lowering the loading rate, increasing the programming temperature, and reducing the holding time.

  3. The synthesis of nonlinear optical (NLO) poly(hydroxy ethers)

    SciTech Connect

    Brennan, D.J.; Gulotty, R.J.; Inbasekaran, M.

    1995-12-31

    New poly(hydroxy ethers) have been prepared which exhibit an excellent combination of (a) high second-order nonlinear optical (NLO) activity (d{sub 33} of 20-28 x 10{sup -9} esu, 1064 nm, after parallel plate poling at E=0.5 MV/cm), (b) high glass transition temperatures Tg=150-200{degrees}C, (c) persistence of activity at 100{degrees}C, and (d) excellent processability. The NLO poly(hydroxy ethers) are prepared by the reactions of aromatic diglycidyl ethers with bisphenols that contain dipolar moieties based on nitrophenylhydrazones and other chromophores.

  4. Synthesis and biological activity of gem-dichlorocyclopropyl ethers

    SciTech Connect

    Shostakovskii, S.M.; Mochalov, V.N.; Larionov, G.M.

    1986-09-01

    In order to examine the antimicrobial activity of oxygenated cyclopropanes, the authors have synthesized the bis-gem-dichlorocyclopropyl ether of ethylene glycol, the meso- and dl- forms of bis-gem-dichlorocyclopropyl ether, and the gem-dichlorocyclopropyl alkyl ethers. The physiocochemical properties of compounds obtained are presented. The authors conclude that in the case of gem-dichlorocyclopropane compounds, decontamination of microorganisms occurs at the pre-metabolic stage, and results in the denaturation of the protein components of the cell wall and external membranes and of the specific peptides of the peptide-glycan layer.

  5. The envelope-based cyclic periodogram

    NASA Astrophysics Data System (ADS)

    Borghesani, P.

    2015-06-01

    Cyclostationary analysis has proven effective in identifying signal components for diagnostic purposes. A key descriptor in this framework is the cyclic power spectrum, traditionally estimated by the averaged cyclic periodogram and the smoothed cyclic periodogram. A lengthy debate about the best estimator finally found a solution in a cornerstone work by Antoni, who proposed a unified form for the two families, thus allowing a detailed statistical study of their properties. Since then, the focus of cyclostationary research has shifted towards algorithms, in terms of computational efficiency and simplicity of implementation. Traditional algorithms have proven computationally inefficient and the sophisticated "cyclostationary" definition of these estimators slowed their spread in the industry. The only attempt to increase the computational efficiency of cyclostationary estimators is represented by the cyclic modulation spectrum. This indicator exploits the relationship between cyclostationarity and envelope analysis. The link with envelope analysis allows a leap in computational efficiency and provides a "way in" for the understanding by industrial engineers. However, the new estimator lies outside the unified form described above and an unbiased version of the indicator has not been proposed. This paper will therefore extend the analysis of envelope-based estimators of the cyclic spectrum, proposing a new approach to include them in the unified form of cyclostationary estimators. This will enable the definition of a new envelope-based algorithm and the detailed analysis of the properties of the cyclic modulation spectrum. The computational efficiency of envelope-based algorithms will be also discussed quantitatively for the first time in comparison with the averaged cyclic periodogram. Finally, the algorithms will be validated with numerical and experimental examples.

  6. Measuring Cyclic Error in Laser Heterodyne Interferometers

    NASA Technical Reports Server (NTRS)

    Ryan, Daniel; Abramovici, Alexander; Zhao, Feng; Dekens, Frank; An, Xin; Azizi, Alireza; Chapsky, Jacob; Halverson, Peter

    2010-01-01

    An improved method and apparatus have been devised for measuring cyclic errors in the readouts of laser heterodyne interferometers that are configured and operated as displacement gauges. The cyclic errors arise as a consequence of mixing of spurious optical and electrical signals in beam launchers that are subsystems of such interferometers. The conventional approach to measurement of cyclic error involves phase measurements and yields values precise to within about 10 pm over air optical paths at laser wavelengths in the visible and near infrared. The present approach, which involves amplitude measurements instead of phase measurements, yields values precise to about .0.1 microns . about 100 times the precision of the conventional approach. In a displacement gauge of the type of interest here, the laser heterodyne interferometer is used to measure any change in distance along an optical axis between two corner-cube retroreflectors. One of the corner-cube retroreflectors is mounted on a piezoelectric transducer (see figure), which is used to introduce a low-frequency periodic displacement that can be measured by the gauges. The transducer is excited at a frequency of 9 Hz by a triangular waveform to generate a 9-Hz triangular-wave displacement having an amplitude of 25 microns. The displacement gives rise to both amplitude and phase modulation of the heterodyne signals in the gauges. The modulation includes cyclic error components, and the magnitude of the cyclic-error component of the phase modulation is what one needs to measure in order to determine the magnitude of the cyclic displacement error. The precision attainable in the conventional (phase measurement) approach to measuring cyclic error is limited because the phase measurements are af-

  7. Solvent extraction of cesium by substituted crown ethers

    SciTech Connect

    Sachleben, R.A.; Deng, Y.; Palmer, D.A.; Moyer, B.A.

    1996-12-31

    The extraction of alkali metal nitrates by 18-crown-6, 21-crown-7, and 24-crown-8 ethers, bearing cyclohexano, benzo-, t-alkylbenzo, and furano- substituents, in 1,2-dichloroethane has been surveyed. Introduction of a furano substituent onto the macrocyclic ring of 18-crown-6 or 21 crown-7 ethers causes a significant reduction in both extraction efficiency and selectivity. Addition of an additional benzo group to dibenzo-21 -crown-7, to give tribenzo-21 -crown-7, decreases both extraction efficiency and selectivity, whereas addition of one or two additional benzo groups to dibenzo-24-crown-8 increases the extraction efficiency and selectivity for the larger ions Rb+ and Cs{sup +} Detailed equilibrium modeling of the extraction by lipophilic 21 -crown-7 ethers indicates that the addition of t-alkyl substituents onto the benzo groups has only a minor effect on the extraction of cesium nitrate by dibenzo-21 -crown-7 ethers.

  8. 46 CFR 151.50-42 - Ethyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... shall be designed and tested to meet the rules of the American Bureau of Shipping for a head of water at... liquid. (g) Precautions shall be taken to prevent the contamination of ethyl ether by strong...

  9. Tough poly(arylene ether) thermoplastics as modifiers for bismaleimides

    NASA Technical Reports Server (NTRS)

    Stenzenberger, H. D.; Roemer, W.; Hergenrother, P. M.; Jensen, B. J.

    1989-01-01

    Several aspects of research on thermoplastics as toughness modifiers are discussed, including the contribution of the backbone chemistry and the concentration of the poly(arylene ether) thermoplastic to fracture toughness, influence of the molecular weight of the poly(arylene ether) thermoplastic on neat resin fracture toughness, and the morphology of the thermoplastic modified networks. The results show that fracture toughness of brittle bismaleimide resins can be improved significantly with poly(arylene ether) thermoplastic levels of 20 percent by weight, and that high molecular weight poly(arylene ether) based on bisphenol A provides the highest degree of toughening. Preliminary composite evaluation shows that improvements in neat resin toughness translate into carbon fabric composite.

  10. POLYBROMINATED DIPHENYL ETHERS IN HOUSE DUST AND CLOTHES DRYER LINT

    EPA Science Inventory

    Polybrominated diphenyl ether (PBDE) flame retardants are now considered ubiquitous and persistent pollutants. Few studies have examined the concentrations of these chemicals in the home and here we report measurements of PBDEs in house dust samples collected from the Washington...

  11. 36. BUILDINGS NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    36. BUILDINGS NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, AND NO. 523, REFRIGERATION PLANT BUILDING, LOOKING EAST. - Picatinny Arsenal, 500 Area, Powder Factory & Power House, State Route 15 near I-80, Dover, Morris County, NJ

  12. 44. BUILDING NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, INTERIOR, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    44. BUILDING NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, INTERIOR, LOOKING UP DISTILLATION TOWER FROM 2ND LEVEL. - Picatinny Arsenal, 500 Area, Powder Factory & Power House, State Route 15 near I-80, Dover, Morris County, NJ

  13. POLYBROMINATED DIPHENYL ETHERS (PBDES) CONTAMINATION OF UNITED STATES FOOD

    EPA Science Inventory

    Elevated levels of polybrominated diphenyl ethers (PBDEs), a type of brominated flame retardant, were recently detected in United States (U.S.) nursing mothers' milk. These halogenated compounds chemically and toxicologically resemble others such as polychlorinated biphenyls (PC...

  14. A short synthesis of ±-cherylline dimethyl ether.

    PubMed

    Kale, Bhima Y; Shinde, Ananta D; Sonar, Swapnil S; Shingate, Bapurao B; Kumar, Sanjeev; Ghosh, Samir; Venugopal, Soodamani; Shingare, Murlidhar S

    2009-01-01

    A synthesis of ±-cherylline dimethyl ether is reported. The key steps involved are Michael-type addition, radical azidonation of an aldehyde, Curtius rearrangement, and reduction of an isocyanate intermediate followed by Pictet-Spengler cyclization.

  15. Partial cone calix[4]arene-crown-6-ethers

    SciTech Connect

    Das, G.; Sachleben, R.A.; Descazeaud, T.; Bryan, J.C.; Moyer, B.A.

    1997-12-31

    Partial cone calix[4] arene crown ethers represents a new category of lariat ethers. In general, calix arene crown ethers have been previously shown to be efficient extractants for metal cations. Appropriately substituted cone and 1, 3-alt conformers of calix crowns exhibit selectivities for Na{sup +} and Cs{sup +}, respectively. The partial cone conformers have not been as throughly studied. We have developed an efficient method of synthesis of partial cone calix[4]arene-crown ethers and have synthesized a variety of partial cone calix[4]arene crowns. Solution and solid-state structures of representative examples have been determined by {sup 1}H NMR spectroscopy and X-ray crystallography. Relative affinities of these partial cone calix[4]arene crowns for alkali metal ions have been investigated by solvent extraction techniques.

  16. Effect of diethyl ether on the biliary excretion of acetaminophen.

    PubMed

    Watkins, J B; Siegers, C P; Klaassen, C D

    1984-10-01

    The biliary and renal excretion of acetaminophen and its metabolites over 8 hr was determined in rats exposed to diethyl ether by inhalation for 1 hr. Additional rats were anesthetized with urethane (1 g/kg ip) while control animals were conscious throughout the experiment (surgery was performed under hexobarbital narcosis: 150 mg/kg ip; 30-min duration). The concentration of UDP-glucuronic acid was decreased 80% in livers from ether-anesthetized rats but was not reduced in urethane-treated animals when compared to that in control rats. The concentration of reduced glutathione was not affected by either urethane or diethyl ether. Basal bile flow was not altered by the anesthetic agents. Bile flow rate after acetaminophen injection (100 mg/kg iv) was increased slightly over basal levels for 2 hr in hexobarbital-treated control rats, was unaltered in urethane-anesthetized animals, and was decreased throughout the 8-hr experiment in rats exposed to diethyl ether for 1 hr. In control and urethane-anesthetized animals, approximately 30-35% of the total acetaminophen dose (100 mg/kg iv) was excreted into bile in 8 hr, while only 16% was excreted in rats anesthetized with diethyl ether. Urinary elimination (60-70% of the dose) was not altered by exposure to ether. Separation of metabolites by reverse-phase high-pressure liquid chromatography showed that ether decreased the biliary elimination of unchanged acetaminophen and its glucuronide, sulfate, and glutathione conjugates by 47, 40, 49, and 73%, respectively, as compared to control rats. Excretion of unchanged acetaminophen and the glutathione conjugate into bile was depressed in urethane-anesthetized animals by 45 and 66%, respectively, whereas elimination of the glucuronide and sulfate conjugates was increased by 27 and 50%, respectively. These results indicate that biliary excretion is influenced by the anesthetic agent and that diethyl ether depresses conjugation with sulfate and glutathione as well as glucuronic

  17. Development of a Vinyl Ether-Functionalized Polyphosphoester as a Template for Multiple Postpolymerization Conjugation Chemistries and Study of Core Degradable Polymeric Nanoparticles

    PubMed Central

    2015-01-01

    A novel polyphosphoester (PPE) with vinyl ether side chain functionality was developed as a versatile template for postpolymerization modifications, and its degradability and biocompatibility were evaluated. An organocatalyzed ring-opening polymerization of ethylene glycol vinyl ether-pendant cyclic phosphotriester monomer allowed for construction of poly(ethylene glycol vinyl ether phosphotriester) (PEVEP). This vinyl ether-functionalized PPE scaffold was coupled with hydroxyl- or thiol-containing model small molecules via three different types of conjugation chemistries—thiol–ene “click” reaction, acetalization, or thio-acetalization reaction—to afford modified polymers that accommodated either stable thio–ether or hydrolytically labile acetal or thio–acetal linkages. Amphiphilic diblock copolymers of poly(ethylene glycol) and PEVEP formed well-defined micelles with a narrow and monomodal size distribution in water, as confirmed by dynamic light scattering (DLS), transmission electron microscopy, and atomic force microscopy. The stability of the micelles and the hydrolytic degradability of the backbone and side chains of the PEVEP block segment were assessed by DLS and nuclear magnetic resonance spectroscopy (1H and 31P), respectively, in aqueous buffer solutions at pH values of 5.0 and 7.4 and at temperatures of 25 and 37 °C. The hydrolytic degradation products of the PEVEP segments of the block copolymers were then identified by electrospray ionization, gas chromatography, and matrix-assisted laser desorption/ionization mass spectrometry. The parent micelles and their degradation products were found to be non-cytotoxic at concentrations up to 3 mg/mL, when evaluated with RAW 264.7 mouse macrophages and OVCAR-3 human ovarian adenocarcinoma cells. PMID:25601803

  18. Aircraft control by propeller cyclic blades

    NASA Technical Reports Server (NTRS)

    Deyoung, J.

    1979-01-01

    A theory is developed for aircraft control obtained from the propeller forces and moments generated by blade angle variation during a blade revolution. The propeller blade is pitched harmonically one cycle per propeller revolution which results in vehicle control forces and moments, termed cyclic-control. Using a power series respresentation of an arbitrary function of cyclic-blade angle, cyclic-control theory is developed which leads to exact solutions in terms of derivatives of steady-state thrust and power with respect to blade angle. An alternative solution, when the cyclic-blade angle function is limited to a sinusoidal cycle, is in terms of Bessel functions. An estimate of non-steady azimuth angle change or lag is presented. Cyclic-control analysis applied to the counter-rotating propeller shows that control forces or moments can be uniquely isolated from each other. Thus the dual rotor, in hovering mode, has propulsion without rotor tilt or moments, or, when in propeller mode at the tail of an air ship or submarine, vehicle control with no vehicle movement. Control isolation is also attainable from three or more propellers in-line.

  19. Novel pH-Sensitive Cyclic Peptides.

    PubMed

    Weerakkody, Dhammika; Moshnikova, Anna; El-Sayed, Naglaa Salem; Adochite, Ramona-Cosmina; Slaybaugh, Gregory; Golijanin, Jovana; Tiwari, Rakesh K; Andreev, Oleg A; Parang, Keykavous; Reshetnyak, Yana K

    2016-01-01

    A series of cyclic peptides containing a number of tryptophan (W) and glutamic acid (E) residues were synthesized and evaluated as pH-sensitive agents for targeting of acidic tissue and pH-dependent cytoplasmic delivery of molecules. Biophysical studies revealed the molecular mechanism of peptides action and localization within the lipid bilayer of the membrane at high and low pHs. The symmetric, c[(WE)4WC], and asymmetric, c[E4W5C], cyclic peptides translocated amanitin, a polar cargo molecule of similar size, across the lipid bilayer and induced cell death in a pH- and concentration-dependent manner. Fluorescently-labelled peptides were evaluated for targeting of acidic 4T1 mammary tumors in mice. The highest tumor to muscle ratio (5.6) was established for asymmetric cyclic peptide, c[E4W5C], at 24 hours after intravenous administration. pH-insensitive cyclic peptide c[R4W5C], where glutamic acid residues (E) were replaced by positively charged arginine residues (R), did not exhibit tumor targeting. We have introduced a novel class of cyclic peptides, which can be utilized as a new pH-sensitive tool in investigation or targeting of acidic tissue. PMID:27515582

  20. Novel pH-Sensitive Cyclic Peptides

    PubMed Central

    Weerakkody, Dhammika; Moshnikova, Anna; El-Sayed, Naglaa Salem; Adochite, Ramona-Cosmina; Slaybaugh, Gregory; Golijanin, Jovana; Tiwari, Rakesh K.; Andreev, Oleg A.; Parang, Keykavous; Reshetnyak, Yana K.

    2016-01-01

    A series of cyclic peptides containing a number of tryptophan (W) and glutamic acid (E) residues were synthesized and evaluated as pH-sensitive agents for targeting of acidic tissue and pH-dependent cytoplasmic delivery of molecules. Biophysical studies revealed the molecular mechanism of peptides action and localization within the lipid bilayer of the membrane at high and low pHs. The symmetric, c[(WE)4WC], and asymmetric, c[E4W5C], cyclic peptides translocated amanitin, a polar cargo molecule of similar size, across the lipid bilayer and induced cell death in a pH- and concentration-dependent manner. Fluorescently-labelled peptides were evaluated for targeting of acidic 4T1 mammary tumors in mice. The highest tumor to muscle ratio (5.6) was established for asymmetric cyclic peptide, c[E4W5C], at 24 hours after intravenous administration. pH-insensitive cyclic peptide c[R4W5C], where glutamic acid residues (E) were replaced by positively charged arginine residues (R), did not exhibit tumor targeting. We have introduced a novel class of cyclic peptides, which can be utilized as a new pH-sensitive tool in investigation or targeting of acidic tissue. PMID:27515582

  1. Cyclic transformation of orbital angular momentum modes

    NASA Astrophysics Data System (ADS)

    Schlederer, Florian; Krenn, Mario; Fickler, Robert; Malik, Mehul; Zeilinger, Anton

    2016-04-01

    The spatial modes of photons are one realization of a QuDit, a quantum system that is described in a D-dimensional Hilbert space. In order to perform quantum information tasks with QuDits, a general class of D-dimensional unitary transformations is needed. Among these, cyclic transformations are an important special case required in many high-dimensional quantum communication protocols. In this paper, we experimentally demonstrate a cyclic transformation in the high-dimensional space of photonic orbital angular momentum (OAM). Using simple linear optical components, we show a successful four-fold cyclic transformation of OAM modes. Interestingly, our experimental setup was found by a computer algorithm. In addition to the four-cyclic transformation, the algorithm also found extensions to higher-dimensional cycles in a hybrid space of OAM and polarization. Besides being useful for quantum cryptography with QuDits, cyclic transformations are key for the experimental production of high-dimensional maximally entangled Bell-states.

  2. Recovery of cyclic antidepressants with gastric lavage.

    PubMed

    Watson, W A; Leighton, J; Guy, J; Bergman, R; Garriott, J C

    1989-01-01

    The role of lavage fluid volume in recovery of cyclic antidepressant with gastric lavage was determined in 13 patients treated for moderate to severe cyclic antidepressant intoxication. An orogastric tube was placed, gastric contents aspirated, and gastric lavage performed with 60 to 180 mL aliquots of tap water or 0.9% NaCl for irrigation. A volume of 12.8 +/- 4.4 liters of lavage fluid was instilled, and 97.6 +/- 6.9% of this volume was recovered. The recovered aspirate and lavage fluid were inspected for the presence of particulate matter and saved in 4 to 5 liter collections. Determination of cyclic antidepressant and metabolite concentrations was performed using gas chromatography-mass spectrometry, and the amount of cyclic antidepressant recovered was calculated. The mean total amount recovered was 110 mg and ranged from 2.4 mg to 342 mg. Of the total amount recovered, 88% +/- 13% was recovered in the first 4 to 5 liters of lavage fluid. An estimate of the dose ingested was available in 7 patients, with 8.7% (0.4% to 21.7%) of the estimated dose recovered by lavage. There were no cases of significant drug recovery in clear lavage fluid. We conclude that if gastric lavage is undertaken in cyclic antidepressant intoxications, it should utilize 5 liters initially and then continue only if particulate matter is seen.

  3. Cyclic nucleotides of cone-dominant retinas. Reduction of cyclic AMP levels by light and by cone degeneration.

    PubMed

    Farber, D B; Souza, D W; Chase, D G; Lolley, R N

    1981-01-01

    Dark-adapted retinas or whole eyes of 13-line ground squirrels (Citellus tridecemlineatus) and western fence lizards (Sceloporus occidentalis) contain higher levels of cyclic AMP than of cyclic GMP. In these cone-dominant retinas, light reduces cyclic AMP content selectively. Freezing of dark- or light-adapted retinas or eyes also reduces cyclic AMP content, with only minimal changes in cyclic GMP levels. In addition, exposure of frozen retinas of dark-adapted ground squirrel to light results in a significant decrease in cyclic AMP content. The destruction of cone visual cells of ground squirrel retina by iodoacetic acid injection decreases the cyclic nucleotide content of the dark-adapted retina. Considering the relative loss of cyclic nucleotides from cone degeneration, we estimate that the content of cyclic AMP in visual cells of ground squirrel retina is about four times greater than that of cyclic GMP. PMID:6256308

  4. Dimethyl ether (DME) as an alternative fuel

    NASA Astrophysics Data System (ADS)

    Semelsberger, Troy A.; Borup, Rodney L.; Greene, Howard L.

    With ever growing concerns on environmental pollution, energy security, and future oil supplies, the global community is seeking non-petroleum based alternative fuels, along with more advanced energy technologies (e.g., fuel cells) to increase the efficiency of energy use. The most promising alternative fuel will be the fuel that has the greatest impact on society. The major impact areas include well-to-wheel greenhouse gas emissions, non-petroleum feed stocks, well-to-wheel efficiencies, fuel versatility, infrastructure, availability, economics, and safety. Compared to some of the other leading alternative fuel candidates (i.e., methane, methanol, ethanol, and Fischer-Tropsch fuels), dimethyl ether appears to have the largest potential impact on society, and should be considered as the fuel of choice for eliminating the dependency on petroleum. DME can be used as a clean high-efficiency compression ignition fuel with reduced NO x, SO x, and particulate matter, it can be efficiently reformed to hydrogen at low temperatures, and does not have large issues with toxicity, production, infrastructure, and transportation as do various other fuels. The literature relevant to DME use is reviewed and summarized to demonstrate the viability of DME as an alternative fuel.

  5. Polybrominated diphenyl ether (PBDE) flame retardants.

    PubMed

    Rahman, F; Langford, K H; Scrimshaw, M D; Lester, J N

    2001-07-25

    Polybrominated diphenyl ether, PBDE, flame retardants are now a world-wide pollution problem reaching even remote areas. They have been found to bioaccumulate and there are concerns over the health effects of exposure to PBDEs, they also have potential endocrine disrupting properties. They are lipophilic compounds so are easily removed from the aqueous environment and are predicted to sorb onto sediments and particulate matter or to fatty tissue, aiding their distribution throughout the environment. PBDEs are structurally similar to PCBs and DDT and, therefore, their chemical properties, persistence and distribution in the environment follow similar patterns. Concentrations of PBDEs found in environmental samples are now higher than those of PCBs. Evidence to date demonstrates that PBDEs are a growing problem in the environment and concern over their fate and effects is warranted. The manufacture of reactive and additive flame retardants is briefly discussed and their fate and behaviour in the environment is assessed. PBDE toxicology is reviewed and methods of analysis are evaluated.

  6. Influence of Solvent Polarizability on the Keto-Enol Equilibrium in 4-[5-(naphthalen-1-ylmethyl)-1,3,4-thiadiazol-2-yl]benzene-1,3-diol.

    PubMed

    Matwijczuk, Arkadiusz; Górecki, Andrzej; Kamiński, Daniel; Myśliwa-Kurdziel, Beata; Fiedor, Leszek; Niewiadomy, Andrzej; Karwasz, Grzegorz P; Gagoś, Mariusz

    2015-11-01

    This work presents spectroscopic studies of the keto-enol equilibrium induced by solvent polarizability in 4-[5-(naphthalen-1-ylmethyl)-1,3,4-thiadiazol-2-yl]benzene-1,3-diol a strong antiproliferative and anticancer thiadiazol derivative. Electronic absorption, steady state and time resolved fluorescence, and infrared spectroscopies were applied to investigate the keto and enol forms of this compound in a series of polar and non-polar solvents. The enol form dominates in polar solvents while, surprisingly, the keto form dominates in non-polar solvents with high average electric dipole polarizability e.g. n-alkenes. The electronic absorption spectrum of this derivative is more dependent on spatially averaged electric dipole polarizability of the solvent than on Kirkwood's correlation or on Lorenz-Lorenz electric polarizability. By analogy of n-alkanes to the alkyl parts of lipids, one can expect that the transformation of 1,3,4-thiadiazoles to the keto form may be facilitated in the hydrophobic core of the lipid membrane. Such a transition may be of great practical importance for the design of biologically active pharmaceutics, which are able to interact with the hydrophobic regions of cell membranes in a specific manner.

  7. Molecular structure, vibrational and electronic properties of 4-Phenyl-3H-1,3-thiazol-2-ol using density functional theory and comparison of drug efficacy of keto and enol forms by QSAR analysis

    NASA Astrophysics Data System (ADS)

    Sachan, Alok K.; Pathak, Shilendra K.; Chand, Satish; Srivastava, Ruchi; Prasad, Onkar; Belaidi, Salah; Sinha, Leena

    2014-11-01

    4-Phenyl-3H-1,3-thiazol-2-ol can exist in two tautomeric forms - keto and enol. Comprehensive investigation of molecular geometry and electronic structure in ground as well as in the first excited state of 4-Phenyl-3H-1,3-thiazol-2-ol (enol) has been carried out. To determine lowest-energy molecular conformation of the title molecule, the selected torsion angles were varied in steps of 10° and molecular energy profile was calculated from -180° to +180°. Experimental FT-IR and FT-Raman spectra of title compound were compared with the spectral data obtained by DFT/B3LYP method. Dipole moment, polarizability, first static hyperpolarizability and molecular electrostatic potential surface map have been calculated to get a better insight of the properties of title molecule. Natural bond orbital (NBO) analysis has been done to study the stability of the molecule arising from charge delocalization. UV-Vis spectrum of the title compound was also recorded and electronic properties such as frontier orbitals and band gap energies were calculated by TD-DFT approach. To compare the drug efficacy of enolic and keto forms, QSAR properties of both forms have also been computed and discussed.

  8. Measurement of Polybrominated Diphenyl Ethers and Metabolites in Mouse Plasma after Exposure to a Commercial Pentabromodiphenyl Ether Mixture

    PubMed Central

    Qiu, Xinghua; Mercado-Feliciano, Minerva; Bigsby, Robert M.; Hites, Ronald A.

    2007-01-01

    Background Previous studies have shown that polybrominated diphenyl ethers (PBDEs) behave as weak estrogens in animal and cell culture bioassays. In vivo metabolites of PBDEs are suspected to cause these effects. Objectives To identify candidate metabolites, mouse plasma samples were collected after continuous oral and subcutaneous exposure to DE-71, a widely used commercial pentabromodiphenyl ether product, for 34 days. Methods Samples were extracted, separated into neutral and phenolic fractions, and analyzed by gas chromatographic mass spectrometry. Results In the plasma samples of orally treated animals, 2,2′,4,4′,5,5′-hexabromodiphenyl ether (BDE-153) represented 52% of total measurable PBDEs, whereas it represented only 4.3% in the DE-71 mixture. This suggested that BDE-153 was more persistent than other congeners in mice. Several metabolites were detected and quantitated: 2,4-dibromophenol, 2,4,5-tribromophenol, and six hydroxylated PBDEs. The presence of the two phenols suggested cleavage of the ether bond of 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) and 2,2′,4,4′,5-pentabromodiphenyl ether (BDE-99), respectively. The hydroxylated (HO)-PBDEs might come from hydroxylation or debromination/hydroxylation. Among the quantitated hydroxylated metabolites, the most abundant was 4-HO-2,2′,3,4′-tetra-BDE, which suggested that there was a bromine shift during the hydroxylation process. para-HO-PBDEs have been proposed to behave as endocrine disruptors. Conclusions There seem to be three metabolic pathways: cleavage of the diphenyl ether bond, hydroxylation, and debromination/hydroxylation. The cleavage of the diphenyl ether bond formed bromophenols, and the other two pathways formed hydroxylated PBDEs, of which para-HO-PBDEs are most likely formed from BDE-47. These metabolites may be the most thyroxine-like and/or estrogen-like congeners among the HO-PBDEs. PMID:17637922

  9. Cyclic and low temperature effects on microcircuits

    NASA Technical Reports Server (NTRS)

    Weissflug, V. A.; Sisul, E. V.

    1977-01-01

    Cyclic temperature and low temperature operating life tests, and pre-/post-life device evaluations were used to determine the degrading effects of thermal environments on microcircuit reliability. Low power transistor-transistor-logic gates and linear devices were included in each test group. Device metallization systems included aluminum metallization/aluminum wire, aluminum metallization/gold wire, and gold metallization/gold wire. Fewer than 2% electrical failures were observed during the cyclic and low temperature life tests and the post-life evaluations revealed approximately 2% bond pull failures. Reconstruction of aluminum die metallization was observed in all devices and the severity of the reconstruction appeared to be directly related to the magnitude of the temperature excursion. All types of bonds except the gold/gold bonds were weakened by exposure to repeated cyclic temperature stress.

  10. Holographic dark energy in a cyclic universe

    NASA Astrophysics Data System (ADS)

    Zhang, Jingfei; Zhang, Xin; Liu, Hongya

    2007-11-01

    In this paper we study the cosmological evolution of the holographic dark energy in a cyclic universe, generalizing the model of holographic dark energy proposed by Li. The holographic dark energy with c<1 can realize a quintom behavior; namely, it evolves from a quintessence-like component to a phantom-like one. The holographic phantom energy density grows rapidly and dominates the late-time expanding phase, helping to realize a cyclic universe scenario in which the high energy regime is modified by the effects of quantum gravity, causing a turn-around (and a bounce) of the universe. The dynamical evolution of holographic dark energy in the regimes of low energy and high energy is governed by two differential equations, respectively. It is of importance to link the two regimes for this scenario. We propose a link condition giving rise to a complete picture of holographic evolution of a cyclic universe.

  11. Cyclic entropy: An alternative to inflationary cosmology

    NASA Astrophysics Data System (ADS)

    Frampton, Paul Howard

    2015-07-01

    We address how to construct an infinitely cyclic universe model. A major consideration is to make the entropy cyclic which requires the entropy to be reset to zero in each cycle expansion → turnaround → contraction → bounce → etc. Here, we reset entropy at the turnaround by selecting the introverse (visible universe) from the extroverse which is generated by the accelerated expansion. In the model, the observed homogeneity is explained by the low entropy at the bounce. The observed flatness arises from the contraction together with the reduction in size between the expanding and contracting universe. The present flatness is predicted to be very precise.

  12. Cyclic Polymer with Alternating Monomer Sequence.

    PubMed

    Zhu, Wen; Li, Zi; Zhao, Youliang; Zhang, Ke

    2015-11-01

    Cyclic polymers with alternating monomer sequence are synthesized for the first time based on the ring-closure strategy. Well-defined telechelic alternating polymers are synthesized by reversible addition-fragmentation chain transfer polymerization by copolymerizing the electron acceptor monomer of N-benzylmaleimide and donor monomer of styrene with a feed ratio of 1 between them. The corresponding cyclic alternating polymers are then produced by the UV-induced Diels-Alder click reaction to ring-close the linear alternating polymer precursors under highly diluted reaction solution.

  13. A novel sulfonated poly(ether ether ketone) and cross-linked membranes for fuel cells

    NASA Astrophysics Data System (ADS)

    Li, Hongtao; Zhang, Gang; Wu, Jing; Zhao, Chengji; Zhang, Yang; Shao, Ke; Han, Miaomiao; Lin, Haidan; Zhu, Jing; Na, Hui

    A novel poly(ether ether ketone) (PEEK) containing pendant carboxyl groups has been synthesized by a nucleophilic polycondensation reaction. Sulfonated polymers (SPEEKs) with different ion exchange capacity are then obtained by post-sulfonation process. The structures of PEEK and SPEEKs are characterized by both FT-IR and 1H NMR. The properties of SPEEKs as candidates for proton exchange membranes are studied. The cross-linking reaction is performed at 140 °C using poly(vinyl alcohol) (PVA) as the cross-linker. In comparison with the non-cross-linked membranes, some properties of the cross-linked membranes are significantly improved, such as water uptake, methanol resistance, mechanical and oxidative stabilities, while the proton conductivity decreases. The effect of PVA content on proton conductivity, water uptake, swelling ratio, and methanol permeability is also investigated. Among all the membranes, SPEEK-C-8 shows the highest selectivity of 50.5 × 10 4 S s cm -3, which indicates that it is a suitable candidate for applications in direct methanol fuel cells.

  14. Investigation of crystalline morphology in poly (ether ether ketone) using dielectric relaxation spectroscopy

    SciTech Connect

    Kalika, D.S.; Krishnaswamy, R.K.

    1993-12-31

    The relaxation behavior of poly (ether ether ketone) [PEEK] has been investigated using dielectric relaxation spectroscopy; the glass-rubber ({alpha}) relaxation and a sub-glass ({beta}) relaxation were examined for the amorphous material and both cold-crystallized and melt-crystallized specimens. Analysis of the data using the Cole-Cole modification of the Debye equation allowed determination of the dielectric relaxation strength and relaxation broadening parameter for both transitions as a function of material crystallization history. The crystallized specimens displayed a positive offset in isochronal loss temperature for both the {alpha} and {beta} relaxations, with the {alpha} relaxation broadened significantly. The measured dipolar response was interpreted using a three-phase morphological model encompassing a crystalline phase, a mobile amorphous phase, and a rigid amorphous phase. Determination of phase fractions based on dipolar mobilization across the glass-rubber relaxation revealed a finite rigid amorphous phase fraction for both the cold-crystallized specimens which was relatively insensitive to thermal history and degree of crystallinity (W{sub RAP}40.20).

  15. Copoly(arlene ether)s containing pendant sulfonic acid groups as proton exchange membrane

    SciTech Connect

    Kim, Yu Seung; Kim, Dae Sik; Robertson, Gilles; Guiver, Michael

    2008-01-01

    A copoly(arylene ether) (PAE) with high fluorine content and a copoly(arylene ether nitrile) (PAEN) with high nitrile content, each containing pendant phenyl sulfonic acids were synthesized. The P AE and PAEN were prepared from decafluorobiphenyl (DFBP) and difluorobenzonitrile (DFBN) respectively, by polycondensation with 2-phenylhydroquinone (PHQ) by conventional aromatic nucleophilic substitution reactions. The sulfonic acid groups were introduced by mild post-sulfonation exclusively on the para-position of the pendant phenyl ring in PHQ. The membrane properties of the resulting sulfonated copolymers sP AE and sP AEN were compared for fuel cell applications. The copolymers sPAE and sPAEN, each having a degree of sulfonation (DS) of 1.0 had high ion exchange capacities (IEC{sub v}(wet) (volume-based, wet state)) of 1.77 and 2.55 meq./cm{sup 3}, high proton conductivities of 135.4 and 140.1 mS/cm at 80 C, and acceptable volume-based water uptake of 44.5-51.9 vol% at 80 C, respectively, compared to Nafion. The data points of these copolymer membranes are located in the area of outstanding properties in the trade-off plot of alternative hydrocarbon polyelectrolyte membranes (PEM) for the relationship between proton conductivity versus water uptake (weight based or volume based). Furthermore, the relative selectivity derived from proton conductivity and methanol permeability is higher than that of Nafion.

  16. Electrical conductivity of sulfonated poly(ether ether ketone) based composite membranes containing sulfonated polyhedral oligosilsesquioxane

    NASA Astrophysics Data System (ADS)

    Celso, Fabricio; Mikhailenko, Serguei D.; Rodrigues, Marco A. S.; Mauler, Raquel S.; Kaliaguine, Serge

    2016-02-01

    Composite proton exchange membranes (PEMs) intended for fuel cell applications were prepared by embedding of various amounts of dispersed tri-sulfonic acid ethyl POSS (S-Et-POSS) and tri-sulfonic acid butyl POSS (S-Bu-POSS) in thin films of sulfonated poly ether-ether ketone. The electrical properties of the PEMs were studied by Impedance spectroscopy and it was found that their conductivity σ changes with the filler content following a curve with a maximum. The water uptake of these PEMs showed the same dependence. The investigation of initial isolated S-POSS substances revealed the properties of typical electrolytes, which however in both cases possessed low conductivities of 1. 17 × 10-5 S cm-1 (S-Et-POSS) and 3.52 × 10-5 S cm-1 (S-Bu-POSS). At the same time, the insoluble in water S-POSS was found forming highly conductive interface layer when wetted with liquid water and hence producing a strong positive impact on the conductivity of the composite PEM. Electrical properties of the composites were analysed within the frameworks of effective medium theory and bounding models, allowing to evaluate analytically the range of possible conductivity values. It was found that these approaches produced quite good approximation of the experimental data and constituted a fair basis for interpretation of the observed relationship.

  17. Molecular sieve/sulfonated poly(ether ketone ether sulfone) composite membrane as proton exchange membrane

    NASA Astrophysics Data System (ADS)

    Changkhamchom, Sairung; Sirivat, Anuvat

    2012-02-01

    A proton exchange membrane (PEM) is an electrolyte membrane used in both polymer electrolyte membrane fuel cells (PEMFC) and direct methanol fuel cells (DMFCs). Currently, PEMs typically used for PEMFCs are mainly the commercially available Nafion^ membranes, which is high cost and loss of proton conductivity at elevated temperature. In this work, the Sulfonated poly(ether ketone ether sulfone), (S-PEKES), was synthesized by the nucleophilic aromatic substitution polycondensation between bisphenol S and 4,4'-dichlorobenzophenone, and followed by the sulfonation reaction with concentrated sulfuric acid. The molecular sieve was added in the S-PEKES matrix at various ratios to form composite membranes to be the candidate for PEM. Properties of both pure sulfonated polymer and composite membranes were compared with the commercial Nafion^ 117 membrane from Dupont. S-PEKES membranes cast from these materials were evaluated as a polymer electrolyte membrane for direct methanol fuel cells. The main properties investigated were the proton conductivity, methanol permeability, thermal, chemical, oxidative, and mechanical stabilities by using a LCR meter, Gas Chromatography, Thermogravimetric Analysis, Fourier Transform Infrared Spectroscopy, Fenton's reagent, and Universal Testing Machine. The addition of the molecular sieve helped to increase both the proton conductivity and the methanol stability. These composite membranes are shown as to be potential candidates for use as a Proton Exchange Membrane (PEM).

  18. The acid-catalyzed decompostion of phenacylcobalamin: evidence for the formation of an enol-Co(III) pi-complex intermediate.

    PubMed

    Brown, K L; Chu, M M; Ingraham, L L

    1976-04-01

    Phenacylcobalamin has been synthesized and characterized by thin-layer chromatography and uv-visible spectroscopy, as well as identification of the cobalt-containing and organic products of its cleavage in acid and base and by aerobic photolysis. The major organic product from all three cleavage reactions is acetophenone and the cobalt-containing product is aquacobalamin (or hydroxocobalamin, its conjugate base). In aqueous acidic solution (pH 0 to 7.3, ionic strength 1.0 M, and 25.0 degrees C), the kinetics of the formation of aquacobalamin are biphasic representing the linear sum of two exponential terms. The pH dependence of the first-order rate constant of both phases shows a first-order dependence on proton concentration but with an inflection point ot pH 3.55 for the faster phase and at pH 4.03 for the slower phase. This behavior is interpreted in terms of the specific acid catalyzed formation of an intermediate from both "base on" and "base off" phenacylcobalamin with different second-order rate constants for each form, followed by an intermediate decompotion step with a similar formal mechanism. The nature of the intermediate is discussed and it is concluded to be a pi-complex between cob(III)alamin and the enol of acetophenone. PMID:4086

  19. Spectrophotometric tool for the determination of the total carboxylate content in proteins; molar extinction coefficient of the enol ester from Woodward's reagent K reacted with protein carboxylates.

    PubMed

    Kosters, Hans A; de Jongh, Harmen H J

    2003-05-15

    A number of relevant properties of Woodward's reagent K have been determined, such as the stability of the reactant and the optimal reaction conditions of the reactant with protein carboxylates. A Woodward's reagent K stock solution was stable at 4 degrees C for prolonged time, whereas upon storage at 22 degrees C, almost 20% of the reactive compound was lost within 1 week. The pH-dependency of the spontaneous degradation reaction of Woodward's reagent K was studied and was shown to be base-mediated. A molar extinction coefficient of 3150 M(-1) cm(-1) at 269 nm for the enol ester resulting from the reaction between Woodward's reagent K and the protein carboxylates was established using the conditions laid out in this work. This value was validated using a variety of proteins that were modified by Woodward's reagent K. In addition, upon methylation of the carboxylates of a single protein, ovalbumin in this case, the degree of modification could be determined accurately and was confirmed by cation exchange chromatography elution profiles.

  20. Finding of 13(2) , 17(3) -cyclopheophorbide a enol as a degradation product of chlorophyll in shrunk zooxanthellae of the coral Montipora digitata.

    PubMed

    Suzuki, Toshiyuki; Casareto, Beatriz Estela; Shioi, Yuzo; Ishikawa, Yoshio; Suzuki, Yoshimi

    2015-02-01

    We examined the morphology and pigment composition of zooxanthellae in corals subjected to normal temperature (27°C) and thermal stress (32°C). We observed several normal and abnormal morphological types of zooxanthellar cells. Normal cells were intact and their chloroplasts were unbroken (healthy); abnormal cells were shrunken and had partially degraded or broken chloroplasts, or they were bleached and without chloroplasts. At 27°C, most healthy zooxanthellar cells were retained in the coral tissue, whereas shrunken zooxanthellae were expelled. Under thermal stress, the abundance of healthy zooxanthellae declined and the proportion of shrunken/abnormal cells increased in coral tissues. The rate of algal cell expulsion was reduced under thermal stress. Within the shrunken cells, we detected the presence of a chl-like pigment that is not ordinarily found in healthy zooxanthellae. Analysis of the absorption spectrum, absorption maxima, and retention time (by HPLC) indicated that this pigment was 13(2) , 17(3) -cyclopheophorbide a enol (cPPB-aE), which is frequently found in marine and lacustrine sediments, and in protozoans that graze on phytoplankton. The production of cPPB-aE in shrunken zooxanthellae suggests that the chls have been degraded to cPPB-aE, a compound that is not fluorescent. The lack of a fluorescence function precludes the formation of reactive oxygen species. We therefore consider the formation of cPPB-aE in shrunken zooxanthellae to be a mechanism for avoiding oxidative stress. PMID:26986257

  1. Divergent properties and phylogeny of cyanobacterial 5-enol-pyruvyl-shikimate-3-phosphate synthases: evidence for horizontal gene transfer in the Nostocales.

    PubMed

    Forlani, Giuseppe; Bertazzini, Michele; Barillaro, Donatella; Rippka, Rosmarie

    2015-01-01

    As it represents the target of the successful herbicide glyphosate, great attention has been paid to the shikimate pathway enzyme 5-enol-pyruvyl-shikimate-3-phosphate (EPSP) synthase. However, inconsistent results have been reported concerning the sensitivity of the enzyme from cyanobacteria, and consequent inhibitory effects on cyanobacterial growth. The properties of EPSP synthase were investigated in a set of 42 strains representative of the large morphological diversity of these prokaryotes. Publicly available protein sequences were analyzed, and related to enzymatic features. In most cases, the native protein showed an unusual homodimeric composition and a general sensitivity to micromolar doses of glyphosate. By contrast, eight out of 15 Nostocales strains were found to possess a monomeric EPSP synthase, whose activity was inhibited only at concentrations exceeding 1 mM. Sequence analysis showed that these two forms are only distantly related, the latter clustering separately in a clade composed of diverse bacterial phyla. The results are consistent with the occurrence of a horizontal gene transfer event involving an evolutionarily distant organism. Moreover, data suggest that the existence of class I (glyphosate-sensitive) and class II (glyphosate-tolerant) EPSP synthases representing two distinct phylogenetic clades is an oversimplification because of the limited number of analyzed samples. PMID:25229999

  2. Distinguishing between keto-enol and acid-base forms of firefly oxyluciferin through calculation of excited-state equilibrium constants.

    PubMed

    Falklöf, Olle; Durbeej, Bo

    2014-11-15

    Although recent years have seen much progress in the elucidation of the mechanisms underlying the bioluminescence of fireflies, there is to date no consensus on the precise contributions to the light emission from the different possible forms of the chemiexcited oxyluciferin (OxyLH2) cofactor. Here, this problem is investigated by the calculation of excited-state equilibrium constants in aqueous solution for keto-enol and acid-base reactions connecting six neutral, monoanionic and dianionic forms of OxyLH2. Particularly, rather than relying on the standard Förster equation and the associated assumption that entropic effects are negligible, these equilibrium constants are for the first time calculated in terms of excited-state free energies of a Born-Haber cycle. Performing quantum chemical calculations with density functional theory methods and using a hybrid cluster-continuum approach to describe solvent effects, a suitable protocol for the modeling is first defined from benchmark calculations on phenol. Applying this protocol to the various OxyLH2 species and verifying that available experimental data (absorption shifts and ground-state equilibrium constants) are accurately reproduced, it is then found that the phenolate-keto-OxyLH(-) monoanion is intrinsically the preferred form of OxyLH2 in the excited state, which suggests a potential key role for this species in the bioluminescence of fireflies.

  3. Formation of δ-Lactones by Cerium-Catalyzed, Baeyer-Villiger-Type Coupling of β-Oxoesters, Enol Acetates, and Dioxygen.

    PubMed

    Geibel, Irina; Dierks, Anna; Schmidtmann, Marc; Christoffers, Jens

    2016-09-01

    Formation of δ-lactones is observed when cyclopentanone-2-carboxylates are converted in a cerium-catalyzed reaction with α-aryl vinyl acetates under oxidative conditions. The products of this transformation possess a 1,4-dicarbonyl constitution together with a quaternary carbon center. Atmospheric oxygen is the oxidant in this process, which can be regarded as ideal from economic and ecological points of view. Further advantages of this new C-C coupling and oxidation reaction are its operational simplicity and the application of nontoxic and inexpensive CeCl3·7 H2O as precatalyst. This so far unprecedented reaction is proposed to proceed via 1,2-dioxane derivatives, which decompose under formation of an oxycarbenium cation in a Baeyer-Villiger-type pathway. This mechanistic picture is supported by the observation that electron-rich (donor substituted or heteroaromatic) enol esters give higher yields than electron deficient congeners. Apart from 1,4-diketones and α-hydroxylated β-oxoesters formed as byproducts, the yields of δ-lactones range from moderate to good (up to 74%). PMID:27494288

  4. Why do crown ethers activate enzymes in organic solvents?

    PubMed

    van Unen, Dirk-Jan; Engbersen, Johan F J; Reinhoudt, David N

    2002-02-01

    One of the major drawbacks of enzymes in nonaqueous solvents is that their activity is often dramatically low compared to that in water. This limitation can be largely overcome by crown ether treatment of enzymes. In this paper, we describe a number of carefully designed new experiments that have improved the insights into the mechanisms that are operative in the crown ether activation of enzymes in organic solvents. The enhancement of enzyme activity upon addition of 18-crown-6 to the organic solvent can be reconciled with a mechanism in which macrocyclic interactions of 18-crown-6 with the enzyme play an important role. Macrocyclic interactions (e.g., complexation with lysine ammonium groups of the enzyme) can lead to a reduced formation of inter- and intramolecular salt bridges and, consequently, to lowering of the kinetic conformational barriers, enabling the enzyme to refold into thermodynamically stable, catalytically (more) active conformations. This assumption is supported by the observation that the crown-ether-enhanced enzyme activity is retained after removal of the crown by washing with a dry organic solvent. A much stronger crown ether activation is observed when 18-crown-6 is added prior to lyophilization, and this can be explained by a combination of two effects: the before-mentioned macrocyclic complexation effect, and a less specific, nonmacrocyclic, lyoprotecting effect. The magnitude of the total crown ether effect depends on the polarity and thermodynamic water activity of the solvent, the activation being highest in dry and apolar media, where kinetic conformational barriers are highest. By determination of the specific activity of crown-ether-lyophilized enzyme as a function of the enzyme concentration, the macrocyclic crown ether (linearly dependent on the enzyme concentration) and the nonmacrocyclic lyoprotection effect (not dependent on the enzyme concentration) could be separated. These measurements reveal that the contribution of the

  5. Mutagenicity testing of diethylene glycol monobutyl ether.

    PubMed Central

    Thompson, E D; Coppinger, W J; Valencia, R; Iavicoli, J

    1984-01-01

    The mutagenic potential of diethylene glycol monobutyl ether (diEGBE) was examined with a Tier I battery of in vitro assays followed by a Tier II in vivo Drosophila sex-linked recessive lethal assay. The in vitro battery consisted of: the Salmonella mutagenicity test, the L5178Y mouse lymphoma test, a cytogenetics assay using Chinese hamster ovary cells and the unscheduled DNA synthesis (UDS) assay in rat hepatocytes. Results of the Salmonella mutagenicity test, the cytogenetics test, and the rat hepatocyte assay were negative at concentrations up to 20 microL/plate, 7.92 microL/mL, and 4.4 microL/mL, respectively. Toxicity was clearly demonstrated at all high doses. A weak, but dose-related increase in the mutation frequency (4-fold increase over the solvent control at 5.6 microL/mL with 12% survival) was obtained in the L5178Y lymphoma test in the absence of metabolic activation. Results of the mouse lymphoma assay were negative in the presence of the S-9 activation system. The significance of the mouse lymphoma assay were negative in the presence of the S-9 activation system. The significance of the mouse lymphoma assay results were assessed by performing the Tier II sex-linked recessive lethal assay in Drosophila in which the target tissue is maturing germinal cells. Both feeding (11,000 ppm for 3 days) and injection (0.3 microL of approximately 14,000 ppm solution) routes of administration were employed in the Drosophila assay. Approximately 11,000 individual crosses with an equal number of negative controls were performed for each route of administration. diEGBE produced no increase in recessive lethals under these conditions.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:6389113

  6. Low temperature (550-700 K) oxidation pathways of cyclic ketones: Dominance of HO2-elimination channels yielding conjugated cyclic coproducts

    SciTech Connect

    Scheer, Adam M.; Welz, Oliver; Vasu, Subith S.; Osborn, David L.; Taatjes, Craig A.

    2015-04-13

    The low-temperature oxidation of three cyclic ketones, cyclopentanone (CPO; C5H8O), cyclohexanone (CHO; C6H10 O), and 2-methyl-cyclopentanone (2-Me-CPO; CH3–C5H7 O), is studied between 550 and 700 K and at 4 or 8 Torr total pressure. Initial fuel radicals R are formedvia fast H-abstraction from the ketones by laser-photolytically generated chlorine atoms. Intermediates and products from the subsequent reactions of these radicals in the presence of excess O2 are probed with time and isomeric resolution using multiplexed photoionization mass spectrometry with tunable synchrotron ionizing radiation. For CPO and CHO the dominant product channel in the R + O2 reactions is chain-terminating HO2-elimination yielding the conjugated cyclic coproducts 2-cyclopentenone and 2-cyclohexenone, respectively. Results on oxidation of 2-Me-CPO also show a dominant contribution from HO2-elimination. Moreover, the photoionization spectrum of the co-product suggests formation of 2-methyl-2-cyclopentenone and/or 2-cyclohexenone, resulting from a rapid Dowd–Beckwith rearrangement, preceding addition to O2, of the initial (2-oxocyclopentyl)methyl radical to 3-oxocyclohexyl. Cyclic ethers, markers for hydroperoxyalkyl radicals (QOOH), key intermediates in chain-propagating and chain-branching low-temperature combustion pathways, are only minor products. The interpretation of the experimental results is supported by stationary point calculations on the potential energy surfaces of the associated R + O2 reactions at the CBS-QB3 level. Furthermore, the calculations indicate that HO2-elimination channels are energetically favored and product formation via QOOH is disfavored. Lastly, the prominence of chain-terminating pathways linked with HO2 formation in low-temperature oxidation of cyclic ketones suggests little low

  7. Cyclic Cratonic Carbonates and Phanerozoic Calcite Seas.

    ERIC Educational Resources Information Center

    Wilkinson, Bruce H.

    1982-01-01

    Discusses causes of cyclicity in cratonic carbonate sequences and evidence for and potential significance of postulated primary calcite sediment components in past Paleozoic seas, outlining problems, focusing on models explaining existing data, and identifying background. Future sedimentary geologists will need to address these and related areas…

  8. A model for cyclic mechanical reinforcement

    PubMed Central

    Li, Zhenhai; Kong, Fang; Zhu, Cheng

    2016-01-01

    Mechanical force regulates a broad range of molecular interactions in biology. Three types of counterintuitive mechanical regulation of receptor–ligand dissociation have been described. Catch bonds are strengthened by constant forces, as opposed to slip bonds that are weakened by constant forces. The phenomenon that bonds become stronger with prior application of cyclic forces is termed cyclic mechanical reinforcement (CMR). Slip and catch bonds have respectively been explained by two-state models. However, they assume fast equilibration between internal states and hence are inadequate for CMR. Here we propose a three-state model for CMR where both loading and unloading regulate the transition of bonds among the short-lived, intermediate, and long-lived state. Cyclic forces favor bonds in the long-lived state, hence greatly prolonging their lifetimes. The three-state model explains the force history effect and agrees with the experimental CMR effect of integrin α5β1–fibronectin interaction. This model helps decipher the distinctive ways by which molecular bonds are mechanically strengthened: catch bonds by constant forces and CMR by cyclic forces. The different types of mechanical regulation may enable the cell to fine tune its mechanotransduction via membrane receptors. PMID:27786286

  9. Scale invariant density perturbations from cyclic cosmology

    NASA Astrophysics Data System (ADS)

    Frampton, Paul Howard

    2016-04-01

    It is shown how quantum fluctuations of the radiation during the contraction era of a comes back empty (CBE) cyclic cosmology can provide density fluctuations which re-enter the horizon during the subsequent expansion era and at lowest order are scale invariant, in a Harrison-Zel’dovich-Peebles sense. It is necessary to be consistent with observations of large scale structure.

  10. Integrated process for the production of diisopropyl ether and gasoline

    SciTech Connect

    Owen, H.; Harandi, M.N.

    1992-04-07

    This patent describes an integrated process for the production of diisopropyl ether and C{sub 5+} gasoline boiling range hydrocarbons. It comprises contacting C{sub 3} hydrocarbon feedstock and high pressure separator aqueous effluent recycle stream with acidic hydration and etherification catalyst in an etherification zone under etherification conditions to produce an effluent stream containing diisopropyl ether, isopropanol, unreacted water, unreacted C{sub 3} hydrocarbons and higher olefinic hydrocarbons; separating and extracting the effluent stream in a high pressure separation zone in contact with fresh water feed-stream to produce the aqueous effluent recycle stream containing a portion of the isopropanol and unreacted water and a separation zone effluent stream containing diisopropyl ether, unextracted isopropanol, unreacted C{sub 3} hydrocarbons and higher olefinic hydrocarbons; heating and flashing the separator effluent stream at a temperature sufficient to further separate the separator effluent to produce a flash evaporator overhead vapor stream for compression and recycle to the etherification zone, the recycle stream containing a major portion of the unreacted C{sub 3} hydrocarbons, and an evaporator bottom steam containing diisopropyl ether, unextracted isopropanol, a minor portion of the unreacted C{sub 3} hydrocarbons and higher olefinic hydrocarbons; separating the evaporator bottom stream to produce diisopropyl ether, a first stream containing C{sub 3} hydrocarbons and a second stream containing isopropanol and higher olefinic hydrocarbons.

  11. A cyclic GMP-dependent signalling pathway regulates bacterial phytopathogenesis.

    PubMed

    An, Shi-Qi; Chin, Ko-Hsin; Febrer, Melanie; McCarthy, Yvonne; Yang, Jauo-Guey; Liu, Chung-Liang; Swarbreck, David; Rogers, Jane; Maxwell Dow, J; Chou, Shan-Ho; Ryan, Robert P

    2013-09-11

    Cyclic guanosine 3',5'-monophosphate (cyclic GMP) is a second messenger whose role in bacterial signalling is poorly understood. A genetic screen in the plant pathogen Xanthomonas campestris (Xcc) identified that XC_0250, which encodes a protein with a class III nucleotidyl cyclase domain, is required for cyclic GMP synthesis. Purified XC_0250 was active in cyclic GMP synthesis in vitro. The linked gene XC_0249 encodes a protein with a cyclic mononucleotide-binding (cNMP) domain and a GGDEF diguanylate cyclase domain. The activity of XC_0249 in cyclic di-GMP synthesis was enhanced by addition of cyclic GMP. The isolated cNMP domain of XC_0249 bound cyclic GMP and a structure-function analysis, directed by determination of the crystal structure of the holo-complex, demonstrated the site of cyclic GMP binding that modulates cyclic di-GMP synthesis. Mutation of either XC_0250 or XC_0249 led to a reduced virulence to plants and reduced biofilm formation in vitro. These findings describe a regulatory pathway in which cyclic GMP regulates virulence and biofilm formation through interaction with a novel effector that directly links cyclic GMP and cyclic di-GMP signalling.

  12. Cyclic hardening in copper described in terms of combined monotonic and cyclic stress-strain curves

    SciTech Connect

    Chandler, H.D. . School of Mechanical Engineering)

    1995-01-01

    Hardening of polycrystalline copper subjected to tension-compression loading cycles in the plastic region is discussed with reference to changes in flow stress determined from equations describing dislocation glide. It is suggested that hardening is as a result of the accumulation of strain on a monotonic stress-strain curve. On initial loading, the behavior is monotonic. On stress reversal, a characteristic cyclic stress-strain curve is followed until the stress reaches a value in reverse loading corresponding to the maximum attained during the preceding half cycle. Thereafter, the monotonic path is followed until strain reversal occurs at completion of the half cycle. Repetition of the process results in cyclic hardening. Steady state cyclic behavior is reached when a stress associated with the monotonic stress-strain curve is reached which is equal to the stress associated with the cyclic stress-strain curve corresponding to the imposed strain amplitude.

  13. Methyl tertiary hexyl ether and methyl tertiary octyl ether as gasoline oxygenates: assessing risks from atmospheric dispersion and deposition.

    PubMed

    Snelling, Jeff; Barnett, Mark O; Zhao, Dongye; Arey, J Samuel

    2006-10-01

    Methyl tertiary hexyl ether (MtHxE) and methyl tertiary octyl ether (MtOcE) are currently being developed as replacement oxygenates for methyl tertiary butyl ether (MtBE) in gasoline. As was the case with MtBE, the introduction of these ethers into fuel supplies guarantees their introduction into the environment as well. In this study, a screening-level risk assessment was performed by comparing predicted environmental concentrations (PEC) of these ethers to concentrations that might cause adverse effects to humans or ecosystems. A simple box model that has successfully estimated urban air concentrations of MtBE was adapted to predict atmospheric concentrations of MtHxE and MtOcE. Expected atmospheric concentrations of these ethers were also estimated using the European Union System for the Evaluation of Substances (EUSES) multimedia fate model, which simultaneously calculates PECs in the various environmental compartments of air, water, soil, and sediment. Because little or no data are available on the physicochemical, environmental, and toxicological properties of MtHxE and MtOcE, estimation methods were used in conjunction with EUSES to predict both the PECs and the concentrations at which these ethers might pose a threat. The results suggest that these ethers would contaminate the air of a moderately sized U.S. city (Boston, MA) at levels similar to those found previously for MtBE. The risk assessment module in EUSES predicted risk characterization ratios of 10(-3) and 10(-2) for MtHxE and MtOcE, respectively, in Boston, and 10(-2) and 10(-1) in very large urban centers, suggesting that these ethers pose only a minimal threat to ecosystems at the anticipated environmental concentrations. The assessment also indicates that these compounds are possible human carcinogens and that they may be present in urban air at concentrations that pose an unacceptable cancer risk. Therefore, testing of the toxicological properties of these compounds is recommended before they

  14. Copoly(arylene ether)s containing pendant sulfonic acid groups as proton exchange membranes

    SciTech Connect

    Dae Sik, Kim; Yu Seung, Kim; Gilles, Robertson; Guiver, Michael D

    2009-01-01

    A copoly(arylene ether) (PAE) with high fluorine content and a copoly(arylene ether nitrile) (PAEN) with high nitrile content, each containing pendant phenyl sulfonic acids were synthesized. The PAE and P AEN were prepared from decafluorobiphenyl (DFBP) and difluorobenzonitrile (DFBN) respectively, by polycondensation with 2phenylhydroquinone (PHQ) by conventional aromatic nucleophilic substitution reactions. sulfonic acid groups were introduced by mild post-sulfonation exclusively on the para-position of the pendant phenyl ring in PHQ. The membrane properties of the resulting sulfonated copolymers sPAE and sPAEN were compared for fuel cell applications. The copolymers sPAE and sPAEN, each having a degree of sulfonation (OS) of 1.0 had high ion exchange capacities (IEC{sub v})(wet) (volume-based, wet state) of 1.77 and 2.55 meq./cm3, high proton conductivities of 135.4 and 140.1 mS/cm at 80 C, and acceptable volume-based water uptake of 44.5 -51.9 vol% at 80 C, respectively, compared to Nafion. The data points of these copolymer membranes are located in the upper left-hand corner in the trade-off plot of alternative hydrocarbon polyelectrolyte membranes (PEM) for the relationship between proton conductivity versus water uptake (weight based or volume based), i.e., high proton conductivity and low water uptake. Furthermore, the relative selectivity derived from proton conductivity and methanol permeability is higher than that of Nafion.

  15. Safety assessment of alkyl PEG ethers as used in cosmetics.

    PubMed

    Fiume, Monice M; Heldreth, Bart; Bergfeld, Wilma F; Belsito, Donald V; Hill, Ronald A; Klaassen, Curtis D; Liebler, Daniel; Marks, James G; Shank, Ronald C; Slaga, Thomas J; Snyder, Paul W; Andersen, F Alan

    2012-01-01

    The CIR Expert Panel assessed the safety of Alkyl PEG Ethers as used in cosmetics. These ingredients primarily function in cosmetics as surfactants, and some have additional functions as skin-conditioning agents, fragrance ingredients, and emulsion stabilizers. The Panel reviewed available relevant animal and clinical data, as well as information from previous CIR reports; when data were not available for individual ingredients, the Panel extrapolated from the existing data to support safety. The Panel concluded that the Alkyl PEG ethers are safe as used when formulated to be nonirritating, and the same applies to future alkyl PEG ether cosmetic ingredients that vary from those ingredients recited herein only by the number of ethylene glycol repeat units.

  16. Conversion of light hydrocarbons to ether rich gasoline

    SciTech Connect

    Bell, W.K.; Haag, W.O.; Harandi, M.N.; Owen, H.

    1991-05-07

    This patent describes an integrated process for the production of ether-rich rich liquid fuels. It comprises: contacting a fresh mixture of lower alkanol and a light hydrocarbon feedstock containing linear olefins and C{sub 4} + tertiary olefins; separating the etherification effluent stream consisting of ether rich C{sub 5} + and C{sub 5{minus}}; contacting second stream with an acidic catalyst in a second etherification zone under conditions effective to etherify the linear olefinic hydrocarbons; recovering a first stream comprising C{sub 5} + gasoline containing lower alkyl ethers of the C{sub 5{minus}}; and passing the second stream to an olefins to higher molecular weight hydrocarbons conversion zone.

  17. Laboratory Method for Analysis of Small Concentrations of Methyl tert-Butyl Ether and Other Ether Gasoline Oxygenates in Water

    USGS Publications Warehouse

    Rose, Donna L.; Connor, Brooke F.; Abney, Sonja R.; Raese, Jon W.

    1998-01-01

    This Fact Sheet presents data for analysis of nanogram-per-liter concentrations of methyl tert-butyl ether (MTBE) and three other ether gasoline oxygenates, including methyl tert-pentyl ether (TAME), diisopropyl ether (DIPE), and ethyl tert-butyl ether (ETBE), by purge- and-trap capillary-column gas chromatography. Long-term method detection levels (LT-MDLs) for MTBE, TAME, DIPE, and ETBE ranged from 15 to 83 nanograms per liter (0.015 to 0.083 microgram per liter). Nanogram-per-liter-concentration detections are reported if all of the identification criteria are met, whereas previous methods censored detections at a pre-determined method reporting level. The reporting level for this method is defined as two times the LT-MDL, does not censor detections at less than this concentration, and is referred to as the nondetection value (NDV). Bias and variability data from multiple analyses, analysts, and instruments over a 60-day period show the oxygenate recoveries ranging from 100 to 109 percent, with 6 to 8 percent relative standard deviation. MTBE, TAME, DIPE, and ETBE were not detected in the analysis of 225 laboratory reagent blanks from January to December 1997. A preservation study in ground water and surface water indicates that all the oxygenates are stable at pH 2 for up to 216 days, with recoveries ranging from 94 to 115 percent on day 216, and relative standard deviations ranging from 5 to 9 percent for the duration of the study.

  18. Significance of ether lipids derived from methanogens in sediments from modern and ancient basins

    SciTech Connect

    Shouten, S.; Sinninghe Damste, J.S.; Hoefs, M.J.L.; De Leeuw, J.W. Netherlands and Utrecht Univ. )

    1996-01-01

    High amounts of biphytanyl carbon skeletons with 0-3 cyclopentyl rings and low amounts of 2, 6, 10, 14, 18-pentamethyleicosane (PME) were detected after treatment with hydrogen iodide of fractions of several sediment extracts. These compounds are biosynthesized by archaebacteria only. Since the sediments were deposited in normal marine environments, these lipids are derived from methanogenic bacteria and more specifically Methanosarcina barkeri. In recent sediments from in and below the extensive oxygen-minimum zone in the Arabian Sea high amounts were detected in surface sediment samples where oxygen is still present. Our data suggest that these ether-bound compounds may be indicators for methane-production in the upper part of the water column and possibly an extensive oxygen-minimum zone. The concentrations varied strongly (2 orders of magnitude) in the Miocene Monterey Formation suggesting significant variations in water column methanogenic activity. The stable carbon isotopic compositions of the acyclic and cyclic biphytane carbon skeletons are several per mil heavier than those of compounds derived from photoautotrophic organisms whereas the stable carbon isotopic compositions of PME are several per mil lighter. This indicates the presence of different species of methanogens utilizing different carbon substrates.

  19. Significance of ether lipids derived from methanogens in sediments from modern and ancient basins

    SciTech Connect

    Shouten, S.; Sinninghe Damste, J.S.; Hoefs, M.J.L.; De Leeuw, J.W. |

    1996-12-31

    High amounts of biphytanyl carbon skeletons with 0-3 cyclopentyl rings and low amounts of 2, 6, 10, 14, 18-pentamethyleicosane (PME) were detected after treatment with hydrogen iodide of fractions of several sediment extracts. These compounds are biosynthesized by archaebacteria only. Since the sediments were deposited in normal marine environments, these lipids are derived from methanogenic bacteria and more specifically Methanosarcina barkeri. In recent sediments from in and below the extensive oxygen-minimum zone in the Arabian Sea high amounts were detected in surface sediment samples where oxygen is still present. Our data suggest that these ether-bound compounds may be indicators for methane-production in the upper part of the water column and possibly an extensive oxygen-minimum zone. The concentrations varied strongly (2 orders of magnitude) in the Miocene Monterey Formation suggesting significant variations in water column methanogenic activity. The stable carbon isotopic compositions of the acyclic and cyclic biphytane carbon skeletons are several per mil heavier than those of compounds derived from photoautotrophic organisms whereas the stable carbon isotopic compositions of PME are several per mil lighter. This indicates the presence of different species of methanogens utilizing different carbon substrates.

  20. Effects of microstructural inclusions on fatigue life of polyether ether ketone (PEEK).

    PubMed

    Simsiriwong, Jutima; Shrestha, Rakish; Shamsaei, Nima; Lugo, Marcos; Moser, Robert D

    2015-11-01

    In this study, the effects of microstructural inclusions on fatigue life of polyether ether ketone (PEEK) was investigated. Due to the versatility of its material properties, the semi-crystralline PEEK polymer has been increasingly adopted in a wide range of applications particularly as a biomaterial for orthopedic, trauma, and spinal implants. To obtain the cyclic behavior of PEEK, uniaxial fully-reversed strain-controlled fatigue tests were conducted at ambient temperature and at 0.02 mm/mm to 0.04 mm/mm strain amplitudes. The microstructure of PEEK was obtained using the optical and the scanning electron microscope (SEM) to determine the microstructural inclusion properties in PEEK specimen such as inclusion size, type, and nearest neighbor distance. SEM analysis was also conducted on the fracture surface of fatigue specimens to observe microstructural inclusions that served as the crack incubation sites. Based on the experimental strain-life results and the observed microstructure of fatigue specimens, a microstructure-sensitive fatigue model was used to predict the fatigue life of PEEK that includes both crack incubation and small crack growth regimes. Results show that the employed model is applicable to capture microstructural effects on fatigue behavior of PEEK.