Effect of halogenated substituents on the metabolism and estrogenic effects of the equine estrogen, equilenin.

PubMed

Liu, Xuemei; Zhang, Fagen; Liu, Hong; Burdette, Joanna E; Li, Yan; Overk, Cassia R; Pisha, Emily; Yao, Jiaqin; van Breemen, Richard B; Swanson, Steven M; Bolton, Judy L

2003-06-01

Estrogen replacement therapy has been correlated with an increased risk for developing breast and endometrial cancers. One potential mechanism of estrogen carcinogenesis involves metabolism of estrogens to 2- and 4-hydroxylated catechols, which are further oxidized to electrophilic/redox active o-quinones that have the potential to both initiate and promote the carcinogenic process. Previously, we showed that the equine estrogens, equilin and equilenin, which are major components of the estrogen replacement formulation Premarin (Wyeth-Ayerst), are primarily metabolized to the catechol, 4-hydroxyequilenin. This catechol was found to autoxidize to an o-quinone causing oxidation and alkylation of DNA in vitro and in vivo. To block catechol formation from equilenin, 4-halogenated equilenin derivatives were synthesized. These derivatives were tested for their ability to bind to the estrogen receptor, induce estrogen sensitive genes, and their potential to form catechol metabolites. We found that the 4-fluoro derivatives were more estrogenic than the 4-chloro and 4-bromo derivatives as demonstrated by a higher binding affinity for estrogen receptors alpha and beta, an enhanced induction of alkaline phosphatase activity in Ishikawa cells, pS2 expression in S30 cells, and PR expression in Ishikawa cells. Incubation of these compounds with tyrosinase in the presence of GSH showed that the halogenated equilenin compounds formed less catechol GSH conjugates than the parent compounds, equilenin and 17beta-hydroxyequilenin. In addition, these halogenated compounds showed less cytotoxicity in the presence of tyrosinase than the parent compounds in S30 cells. Also, as stated above, the 4-fluoro derivatives showed similar estrogenic effects as compared with parent compounds; however, they were less toxic in S30 cells as compared to equilenin and 17beta-equilenin. Because 17beta-hydroxy-4-halogenated equilenin derivatives showed higher estrogenic effects than the halogenated equilenin derivatives in vitro, we studied the relative ability of the 17beta-hydroxy-4-halogenated equilenin derivatives to induce estrogenic effects in the ovariectomized rat model. The 4-fluoro derivative showed higher activity than 4-chloro and 4-bromo derivatives as demonstrated by inducing higher vaginal cellular differentiation, uterine growth, and mammary gland branching. However, 17beta-hydroxy-4-fluoroequilenin showed a lower estrogenic activity than 17beta-hydroxyequilenin and estradiol, which could be due to alternative pharmacokinetic properties for these compounds. These data suggest that the 4-fluoroequilenin derivatives have promise as alternatives to traditional estrogen replacement therapy due to their similar estrogenic properties with less overall toxicity.

Syntheses of halogen derivatives of L-tryptophan, L-tyrosine and L-phenylalanine labeled with hydrogen isotopes.

PubMed

Pająk, Małgorzata; Pałka, Katarzyna; Winnicka, Elżbieta; Kańska, Marianna

2016-01-01

Halogenated, labeled with tritium and doubly with deuterium and tritium, derivatives of L-tryptophan, i.e. 5'-bromo-[2-(3)H]-, 5'-bromo-[2-(2)H/(3)H]-, 5'-fluoro-[2-(3)H]-5'-fluoro-[2-(2)H/(3)H]-, 6'-fluoro-[2-(3)H]-, 6'-fluoro-[2-(2)H/(3)H]-L-tryptophan, as well as, L-tyrosine, i.e. 3'-fluoro-[2-(3)H]-, 3'-fluoro-[2-(2)H/(3)H]-, 3'-chloro-[2-(3)H]-, and 3'-chloro-[2-(2)H/(3)H]-L-tyrosine, and also L-phenylalanine, i.e. 2'-fluoro-[(3S)-(3)H]-, 2'-fluoro-[(3S)-(2)H/(3) H]-, 2'-chloro-[(3S)-(3)H]-, 2'-chloro-[(3S)-(2)H/(3)H]-, 4'-chloro-[(3S)-(3)H]-, and 4'-chloro-[(3S)-(2)H/(3)H]-L-phenylalanine were synthesized using enzymatic methods. Isotopomers of L-tryptophan were synthesized by coupling of halogenated indoles with S-methyl-L-cysteine carried out in deuteriated or tritiated incubation media. Labeled halogenated derivatives of L-tyrosine were obtained by the enzymatically supported exchange between halogenated L-tyrosine and isotopic water. Labeled halogenated isotopologues of L-Phe were synthesized by the enzymatic addition of ammonia to halogenated cinnamic acid. As a source of hydrogen tritiated water (HTO) and heavy water (D2O) with addition of HTO were used. Copyright © 2015 John Wiley & Sons, Ltd.

Concentration-dependent multiple chirality transition in halogen-bond-driven 2D self-assembly process

NASA Astrophysics Data System (ADS)

Miao, Xinrui; Li, Jinxing; Zha, Bao; Miao, Kai; Dong, Meiqiu; Wu, Juntian; Deng, Wenli

2018-03-01

The concentration-dependent self-assembly of iodine substituted thienophenanthrene derivative (5,10-DITD) is investigated at the 1-octanic acid/graphite interface using scanning tunneling microscopy. Three kinds of chiral arrangement and transition of 2D molecular assembly mainly driven by halogen bonding is clearly revealed. At high concentration the molecules self-assembled into a honeycomb-like chiral network. Except for the interchain van der Waals forces, this pattern is stabilized by intermolecular continuous Cdbnd O⋯I⋯S halogen bonds in each zigzag line. At moderate concentration, a chiral kite-like nanoarchitecture are observed, in which the Cdbnd O⋯I⋯S and I⋯Odbnd C halogen bonds, along with the molecule-solvent Cdbnd O⋯I⋯H halogen bonds are the dominated forces to determine the structural formation. At low concentration, the molecules form a chiral cyclic network resulting from the solvent coadsorption mainly by molecule-molecule Cdbnd O⋯I⋯S halogen bonds and molecule-solvent Cdbnd O⋯I⋯H halogen bonds. The density of molecular packing becomes lower with the decreasing of the solution concentration. The solution-concentration dependent self-assembly of thienophenanthrene derivative with iodine and ester chain moieties reveals that the type of intermolecular halogen bond and the number of the co-adsorbing 1-octanic acids by molecule-solvent Cdbnd O⋯I⋯H halogen bonds determine the formation and transformation of chirality. This research emphasizes the role of different types of halogen (I) bonds in the controllable supramolecular structures and provides an approach for the fabrication of chirality.

Halogen bond: a long overlooked interaction.

PubMed

Cavallo, Gabriella; Metrangolo, Pierangelo; Pilati, Tullio; Resnati, Giuseppe; Terraneo, Giancarlo

2015-01-01

Because of their high electronegativity, halogen atoms are typically considered, in most of their derivatives, as sites of high electron density and it is commonly accepted that they can form attractive interactions by functioning as the electron donor site (nucleophilic site). This is the case when they work as hydrogen bond acceptor sites. However, the electron density in covalently bound halogens is anisotropically distributed. There is a region of higher electron density, accounting for the ability of halogens to function as electron donor sites in attractive interactions, and a region of lower electron density where the electrostatic potential is frequently positive (mainly in the heavier halogens). This latter region is responsible for the ability of halogen atoms to function as the electron-acceptor site (electrophilic site) in attractive interactions formed with a variety of lone pair-possessing atoms, anions, and π-systems. This ability is quite general and is shown by a wide diversity of halogenated compounds (e.g., organohalogen derivatives and dihalogens). According to the definition proposed by the International Union of Pure and Applied Chemistry, any attractive interactions wherein the halogen atom is the electrophile is named halogen bond (XB). In this chapter, it is discussed how the practice and the concept of XB developed and a brief history of the interaction is presented. Papers (either from the primary or secondary literature) which have reported major experimental findings in the field or which have given important theoretical contributions for the development of the concept are recollected in order to trace how a unifying and comprehensive categorization emerged encompassing all interactions wherein halogen atoms function as the electrophilic site.

Evaluating the potential for halogen bonding in ketosteroid isomerase’s oxyanion hole using unnatural amino acid mutagenesis

PubMed Central

Kraut, Daniel A; Churchil, Michael J; Dawson, Phillip E

2009-01-01

There has recently been an increasing interest in controlling macromolecular conformations and interactions through halogen bonding. Halogen bonds are favorable electrostatic interactions between polarized, electropositive chlorine, bromine or iodine atoms and electronegative atoms such as oxygen or nitrogen. These interactions have been likened to hydrogen bonds both in terms of their favored acceptor molecules, their geometries, and their energetics. We asked whether a halogen bond could replace a hydrogen bond in the oxyanion hole of ketosteroid isomerase, using semi-synthetic enzyme containing para-halogenated phenylalanine derivatives to replace the tyrosine hydrogen bond donor. Formation of a halogen bond to the oxyanion in the transition state would be expected to rescue the effects of mutation to phenylalanine, but all of the halogenated enzymes were comparable in activity to the phenylalanine mutant. We conclude that, at least in this active site, a halogen bond cannot functionally replace a hydrogen bond. PMID:19260691

A Halogen-Containing Stilbene Derivative from the Leaves of Cajanus cajan that Induces Osteogenic Differentiation of Human Mesenchymal Stem Cells.

PubMed

Cai, Jia-Zhong; Tang, Rong; Ye, Gui-Fu; Qiu, Sheng-Xiang; Zhang, Nen-Ling; Hu, Ying-Jie; Shen, Xiao-Ling

2015-06-11

A new natural halogen-containing stilbene derivative was isolated from the leaves of Cajanus cajan (L.) Millsp. and identified as 3-O-(3-chloro-2-hydroxyl-propanyl)-longistylin A by comprehensive spectroscopic and chemical analysis, and named cajanstilbene H (1). It is the first halogen-containing stilbene derivative found from plants. In human mesenchymal stem cells (hMSC) from bone marrow, 1 did not promote cell proliferation, but distinctly enhanced osteogenic differentiation of hMSC in time- and dose-dependent manners. In six human cancer cell lines, 1 showed a moderate inhibitory effect on cell proliferation, with IC50 values of 21.42-25.85 μmol·L(-1).

Binding interactions of halogenated bisphenol A with mouse PPARα: In vitro investigation and molecular dynamics simulation.

PubMed

Zhang, Jie; Li, Tiezhu; Wang, Tuoyi; Guan, Tianzhu; Yu, Hansong; Li, Zhuolin; Wang, Yongzhi; Wang, Yongjun; Zhang, Tiehua

2018-02-01

The binding of bisphenol A (BPA) and its halogenated derivatives (halogenated BPAs) to mouse peroxisome proliferator-activated receptor α ligand binding domain (mPPARα-LBD) was examined by a combination of in vitro investigation and in silico simulation. Fluorescence polarization (FP) assay showed that halogenated BPAs could bind to mPPARα-LBD* as the affinity ligands. The calculated electrostatic potential (ESP) illustrated the different charge distributions of halogenated BPAs with altered halogenation patterns. As electron-attracting substituents, halogens decrease the positive electrostatic potential and thereby have a significant influence on the electrostatic interactions of halogenated BPAs with mPPARα-LBD*. The docking results elucidated that hydrophobic and hydrogen-bonding interactions may also contribute to stabilize the binding of the halogenated BPAs to their receptor molecule. Comparison of the calculated binding energies with the experimentally determined affinities yielded a good correlation (R 2 =0.6659) that could provide a rational basis for designing environmentally benign chemicals with reduced toxicities. This work can potentially be used for preliminary screening of halogenated BPAs. Copyright © 2017 Elsevier B.V. All rights reserved.

Benzoylurea Chitin Synthesis Inhibitors.

PubMed

Sun, Ranfeng; Liu, Chunjuan; Zhang, Hao; Wang, Qingmin

2015-08-12

Benzoylurea chitin synthesis inhibitors are widely used in integrated pest management (IPM) and insecticide resistance management (IRM) programs due to their low toxicity to mammals and predatory insects. In the past decades, a large number of benzoylurea derivatives have been synthesized, and 15 benzoylurea chitin synthesis inhibitors have been commercialized. This review focuses on the history of commercial benzolyphenylureas (BPUs), synthetic methods, structure-activity relationships (SAR), action mechanism research, environmental behaviors, and ecotoxicology. Furthermore, their disadvantages of high risk to aquatic invertebrates and crustaceans are pointed out. Finally, we propose that the para-substituents at anilide of benzoylphenylureas should be the functional groups, and bipartite model BPU analogues are discussed in an attempt to provide new insight for future development of BPUs.

α-Halogenated oxaphosphinanes: Synthesis, unexpected reactions and evaluation as inhibitors of cancer cell proliferation.

PubMed

Babouri, Rachida; Rolland, Marc; Sainte-Catherine, Odile; Kabouche, Zahia; Lecouvey, Marc; Bakalara, Norbert; Volle, Jean-Noël; Virieux, David; Pirat, Jean-Luc

2015-11-02

This paper describes the preparation and the biological evaluation of α-halogenated oxaphosphinanes. These halogen derivatives were synthetized from a short and stereoselective synthetic sequence starting by previously described hydroxy-precursors 1 and 2 with respectively a glucose and mannose-like configuration. The in vitro biological tests of these unnatural halogenated phosphinosugars, on several cell lines, highlighted, for some of them, their antiproliferative and anti migration and invasion properties at nanomolar concentration. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Experimental and computational evidence of halogen bonds involving astatine

NASA Astrophysics Data System (ADS)

Guo, Ning; Maurice, Rémi; Teze, David; Graton, Jérôme; Champion, Julie; Montavon, Gilles; Galland, Nicolas

2018-03-01

The importance of halogen bonds—highly directional interactions between an electron-deficient σ-hole moiety in a halogenated compound and an acceptor such as a Lewis base—is being increasingly recognized in a wide variety of fields from biomedicinal chemistry to materials science. The heaviest halogens are known to form stronger halogen bonds, implying that if this trend continues down the periodic table, astatine should exhibit the highest halogen-bond donating ability. This may be mitigated, however, by the relativistic effects undergone by heavy elements, as illustrated by the metallic character of astatine. Here, the occurrence of halogen-bonding interactions involving astatine is experimentally evidenced. The complexation constants of astatine monoiodide with a series of organic ligands in cyclohexane solution were derived from distribution coefficient measurements and supported by relativistic quantum mechanical calculations. Taken together, the results show that astatine indeed behaves as a halogen-bond donor—a stronger one than iodine—owing to its much more electrophilic σ-hole.

M-aminophenyltrialkylstannane

DOEpatents

Kassis, Amin I.; Khawli, Leslie A.

1990-01-01

m-Radiohalo-aniline is a stable intermediate for preparing biotin-m-radiohalo-anilide to be used as an imaging agent or therapeutic agent. The invention also contemplates m-aminophenyltrialkylstannane which can be radiohalogenated and linked to biotin.

M-aminophenyltrialkylstannane

DOEpatents

Kassis, A.I.; Khawli, L.A.

1990-12-11

m-Radiohalo-aniline is a stable intermediate for preparing biotin-m-radiohalo-anilide to be used as an imaging agent or therapeutic agent. The invention also contemplates m-aminophenyltrialkylstannane which can be radiohalogenated and linked to biotin. No Drawings

A mushroom-derived amino acid, ergothioneine, is a potential inhibitor of inflammation-related DNA halogenation.

PubMed

Asahi, Takashi; Wu, Xiaohong; Shimoda, Hiroshi; Hisaka, Shinsuke; Harada, Etsuko; Kanno, Tomomi; Nakamura, Yoshimasa; Kato, Yoji; Osawa, Toshihiko

2016-01-01

Myeloperoxidase (MPO)-generated halogenating molecules, such as hypochlorous acid and hypobromous acid (HOBr), in inflammatory regions are postulated to contribute to disease progression. In this study, we showed that ergothioneine (EGT), derived from an edible mushroom, inhibited MPO activity as well as the formation of 8-bromo-2'-deoxyguanosine in vitro. The HOBr scavenging effect of EGT is higher than those of ascorbic acid and glutathione. We initially observed that the administration of Coprinus comatus, an edible mushroom containing a high amount of EGT, inhibited the UV-B-induced inflammatory responses and DNA halogenation, suggesting that EGT is a promising anti-inflammatory agent from mushrooms.

Thermodynamics parameters for binding of halogenated benzotriazole inhibitors of human protein kinase CK2α.

PubMed

Winiewska, Maria; Kucińska, Katarzyna; Makowska, Małgorzata; Poznański, Jarosław; Shugar, David

2015-10-01

The interaction of human CK2α (hCK2α) with nine halogenated benzotriazoles, TBBt and its analogues representing all possible patterns of halogenation on the benzene ring of benzotriazole, was studied by biophysical methods. Thermal stability of protein-ligand complexes, monitored by calorimetric (DSC) and optical (DSF) methods, showed that the increase in the mid-point temperature for unfolding of protein-ligand complexes (i.e. potency of ligand binding to hCK2α) follow the inhibitory activities determined by biochemical assays. The dissociation constant for the ATP-hCK2α complex was estimated with the aid of microscale thermophoresis (MST) as 4.3±1.8 μM, and MST-derived dissociation constants determined for halogenated benzotriazoles, when converted according to known ATP concentrations, perfectly reconstruct IC50 values determined by the biochemical assays. Ligand-dependent quenching of tyrosine fluorescence, together with molecular modeling and DSC-derived heats of unfolding, support the hypothesis that halogenated benzotriazoles bind in at least two alternative orientations, and those that are efficient hCK2α inhibitors bind in the orientation which TBBt adopts in its complex with maize CK2α. DSC-derived apparent heat for ligand binding (ΔΔHbind) is driven by intermolecular electrostatic interactions between Lys68 and the triazole ring of the ligand, as indicated by a good correlation between ΔΔHbind and ligand pKa. Overall results, additionally supported by molecular modeling, confirm that a balance of hydrophobic and electrostatic interactions contribute predominantly (~40 kJ/mol), relative to possible intermolecular halogen/hydrogen bonding (less than 10 kJ/mol), in binding of halogenated benzotriazoles to the ATP-binding site of hCK2α. This article is part of a Special Issue entitled: Inhibitors of Protein Kinases. Copyright © 2015 Elsevier B.V. All rights reserved.

Metalloporphyrins and their uses as imageable tumor-targeting agents for radiation therapy

DOEpatents

Miura, Michiko; Slatkin, Daniel N.

2003-05-20

The present invention covers halogenated derivatives of boronated porphyrins containing multiple carborane cages having the formula ##STR1## which selectively accumulate in neoplastic tissue within the irradiation volume and thus can be used in cancer therapies including, but not limited to, boron neutron- capture therapy and photodynamic therapy. The present invention also covers methods for using these halogenated derivatives of boronated porphyrins in tumor imaging and cancer treatment.

Use of novel metalloporphyrins as imageable tumor-targeting agents for radiation therapy

DOEpatents

Miura, Michiko; Slatkin, Daniel N.

2005-10-04

The present invention covers halogenated derivatives of boronated phorphyrins containing multiple carborane cages having the formula ##STR1## which selectively accumulate in neoplastic tissue within the irradiation volume and thus can be used in cancer therapies including, but not limited to, boron neutron-capture therapy and photodynamic therapy. The present invention also covers methods for using these halogenated derivatives of boronated porphyrins in tumor imaging and cancer treatment.

Iodine(III) Derivatives as Halogen Bonding Organocatalysts.

PubMed

Heinen, Flemming; Engelage, Elric; Dreger, Alexander; Weiss, Robert; Huber, Stefan M

2018-03-26

Hypervalent iodine(III) derivatives are known as versatile reagents in organic synthesis, but there is only one previous report on their use as Lewis acidic organocatalysts. Herein, we present first strong indications for the crucial role of halogen bonding in this kind of catalyses. To this end, the solvolysis of benzhydryl chloride and the Diels-Alder reaction of cyclopentadiene with methyl vinyl ketone served as benchmark reactions for halide abstraction and the activation of neutral compounds. Iodolium compounds (cyclic diaryl iodonium species) were used as activators or catalysts, and we were able to markedly reduce or completely switch off their activity by sterically blocking one or two of their electrophilic axes. Compared with previously established bidentate cationic halogen bond donors, the monodentate organoiodine derivatives used herein are at least similarly active (in the Diels-Alder reaction) or even decidedly more active (in benzhydryl chloride solvolysis). © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and antimalarial evaluation of novel isocryptolepine derivatives.

PubMed

Whittell, Louise R; Batty, Kevin T; Wong, Rina P M; Bolitho, Erin M; Fox, Simon A; Davis, Timothy M E; Murray, Paul E

2011-12-15

A series of mono- and di-substituted analogues of isocryptolepine have been synthesized and evaluated for in vitro antimalarial activity against chloroquine sensitive (3D7) and resistant (W2mef) Plasmodium falciparum and for cytotoxicity (3T3 cells). Di-halogenated compounds were the most potent derivatives and 8-bromo-2-chloroisocryptolepine displayed the highest selectivity index (106; the ratio of cytotoxicity (IC(50)=9005 nM) to antimalarial activity (IC(50)=85 nM)). Our evaluation of novel isocryptolepine compounds has demonstrated that di-halogenated derivatives are promising antimalarial lead compounds. Copyright © 2011 Elsevier Ltd. All rights reserved.

Prediction of enthalpy and standard Gibbs energy of vaporization of haloaromatics from atomic properties.

PubMed

Monte, M J S; Almeida, A R R P; Liebman, J F

2015-11-01

Halogenated benzenes form a class of pollutants with a huge number of members - 1504 distinct benzene compounds, where one or more hydrogen atoms are replaced by halogens, may exist theoretically. This study presents a user friendly method for accurate prediction of vapor pressures and enthalpies of vaporization, at 298.15 K, of any mono or poly halobenzene compound. The derived equations for the prediction of those vaporization properties depend just on the number of each constituent halogen atom. This is a consequence of the absence of intramolecular interactions between the halogen atoms, revealed after examining vaporization results of ca. 40 halogenated benzenes. In order to rationalize the estimation equations, the contribution of the halogen atoms for the referred to above properties of vaporization was decomposed into two atomic properties - the volume and electron affinity. Extension of the applicability of the estimation method to substituted benzenes containing other substituent groups beyond halogen atoms as well as to some polycyclic aromatic species was tested with success. Copyright © 2015 Elsevier Ltd. All rights reserved.

Competition of hydrogen bonds and halogen bonds in complexes of hypohalous acids with nitrogenated bases.

PubMed

Alkorta, Ibon; Blanco, Fernando; Solimannejad, Mohammad; Elguero, Jose

2008-10-30

A theoretical study of the complexes formed by hypohalous acids (HOX, X = F, Cl, Br, I, and At) with three nitrogenated bases (NH 3, N 2, and NCH) has been carried out by means of ab initio methods, up to MP2/aug-cc-pVTZ computational method. In general, two minima complexes are found, one with an OH...N hydrogen bond and the other one with a X...N halogen bond. While the first one is more stable for the smallest halogen derivatives, the two complexes present similar stabilities for the iodine case and the halogen-bonded structure is the most stable one for the hypoastatous acid complexes.

Metal-Mediated Halogen Exchange in Aryl and Vinyl Halides: A Review

PubMed Central

Evano, Gwilherm; Nitelet, Antoine; Thilmany, Pierre; Dewez, Damien F.

2018-01-01

Halogenated arenes and alkenes are of prime importance in many areas of science, especially in the pharmaceutical, agrochemical, and chemical industries. While the simplest ones are commercially available, some of them are still hardly accessible depending on their substitution patterns and the nature of the halogen atom. Reactions enabling the selective and efficient replacement of the halogen atom of an aryl or alkenyl halide by another one, lighter, or heavier, are therefore of major importance since they can be used for example to turn a less reactive aryl/alkenyl chloride into the more reactive iodinated derivatives or, in a reversed sense, to block an undesired reactivity, for late-stage modifications or for the introduction of a radionuclide. If some halogen exchange reactions are possible with activated substrates, they usually require catalysis with metal complexes. Remarkably efficient processes have been developed for metal-mediated halogen exchange in aryl and vinyl halides: they are overviewed, in a comprehensive manner, in this review article. PMID:29755967

Metal-Mediated Halogen Exchange in Aryl and Vinyl Halides: a Review

NASA Astrophysics Data System (ADS)

Evano, Gwilherm; Nitelet, Antoine; Thilmany, Pierre; Dewez, Damien F.

2018-04-01

Halogenated arenes and alkenes are of prime importance in many areas of science, especially in the pharmaceutical, agrochemical and chemical industries. While the simplest ones are commercially available, some of them are still hardly accessible depending on their substitution patterns and the nature of the halogen atom. Reactions enabling the selective and efficient replacement of the halogen atom of an aryl or alkenyl halide by another one, lighter or heavier, are therefore of major importance since they can be used for example to turn a less reactive aryl/alkenyl chloride into the more reactive iodinated derivatives or, in a reversed sense, to block an undesired reactivity, for late-stage modifications or for the introduction of a radionuclide. If some halogen exchange reactions are possible with activated substrates, they usually require catalysis with metal complexes. Remarkably efficient processes have been developed for metal-mediated halogen exchange in aryl and vinyl halides: they are overviewed, in a comprehensive manner, in this review article.

Phosphorylated lignin as a halogen-free flame retardant additive for epoxy composites

Treesearch

Gamini P. Mendis; Sydney G. Weiss; Matthew Korey; Charles R. Boardman; Mark Dietenberger; Jeffrey P. Youngblood; John A. Howarter

2016-01-01

Sustainable, non-halogenated flame retardants are desired for a variety of industry applications. Lignin, as an industrially processed wood derivative, has been examined as a potential sustainable flame retardant additive to polymer systems. Here, the lignin is phosphorylated using a pyridine-catalysed esterification reaction with diphenyl phosphoryl chloride to...

Tuning the electronic structure of graphene through alkali metal and halogen atom intercalation

NASA Astrophysics Data System (ADS)

Ahmad, Sohail; Miró, Pere; Audiffred, Martha; Heine, Thomas

2018-04-01

The deposition, intercalation and co-intercalation of heavy alkali metals and light halogens atoms in graphene mono- and bilayers have been studied using first principles density-functional calculations. Both the deposition and the intercalation of alkali metals gives rise to n-type doping due to the formation of M+-C- pairs. The co-intercalation of a 1:1 ratio of alkali metals and halogens derives into the formation of ionic pairs among the intercalated species, unaltering the electronic structure of the layered material.

Development and application of a sampling method for the determination of reactive halogen species in volcanic gas emissions.

PubMed

Rüdiger, Julian; Bobrowski, Nicole; Liotta, Marcello; Hoffmann, Thorsten

2017-10-01

Volcanoes release large amounts of reactive trace gases including sulfur and halogen-containing species into the atmosphere. The knowledge of halogen chemistry in volcanic plumes can deliver information about subsurface processes and is relevant for the understanding of the impact of volcanoes on atmospheric chemistry. In this study, a gas diffusion denuder sampling method using 1,3,5-trimethoxybenzene (1,3,5-TMB)-coated glass tubes for the in situ derivatization of reactive halogen species (RHS) was characterized by a series of laboratory experiments. The coating proved to be applicable to collect selectively gaseous bromine species with oxidation states (OS) of +1 or 0 (such as Br 2 , BrCl, HOBr, BrO, and BrONO 2 ) while being unreactive to HBr (OS -1). The reaction of 1,3,5-TMB with reactive bromine species forms 1-bromo-2,4,6-TMB-other halogens give corresponding derivatives. Solvent elution of the derivatives followed by analysis with GC-MS results in absolute detection limits of a few nanograms for Br 2 , Cl 2 , and I 2 . In 2015, the technique was applied on volcanic gas plumes at Mt. Etna (Italy) measuring reactive bromine mixing ratios between 0.8 and 7.0 ppbv. Total bromine mixing ratios between 4.7 and 27.5 ppbv were derived from alkaline trap samples, simultaneously taken by a Raschig tube and analyzed with IC and ICP-MS. This leads to the first results of the reactive bromine contribution to total bromine in volcanic emissions, spanning over a range between 12% (±1) and 36% (±2). Our finding is in an agreement with previous model studies, which imply values <44% for plume ages <1 min, which is consistent with the assumed plume age at the sampling sites. Graphical abstract Illustration of the measurement procedure for the determination of reactive halogen species in volcanic plumes.

GC-MS Study of Mono- and Bishaloethylphosphonates Related to Schedule 2.B.04 of the Chemical Weapons Convention: The Discovery of a New Intramolecular Halogen Transfer

NASA Astrophysics Data System (ADS)

Picazas-Márquez, Nerea; Sierra, María; Nova, Clara; Moreno, Juan Manuel; Aboitiz, Nuria; de Rivas, Gema; Sierra, Miguel A.; Martínez-Álvarez, Roberto; Gómez-Caballero, Esther

2016-09-01

A new class of compounds, mono- and bis-haloethylphosphonates (HAPs and bisHAPs, respectively), listed in Schedule 2.B.04 of the Chemical Weapons Convention (CWC), has been synthesized and studied by GC-MS with two aims. First, to improve the identification of this type of chemicals by the Organization for the Prohibition of Chemical Weapons, (OPCW). Second, to study the synergistic effect of halogen and silicon atoms in molecules undergoing mass spectrometry. Fragmentation patterns of trimethylsilyl derivatives of HAPs were found to depend on the nature of the halogen atom; this was in agreement with DFT-calculations. The data suggest that a novel intramolecular halogen transfer takes place during the fragmentation process.

GC-MS Study of Mono- and Bishaloethylphosphonates Related to Schedule 2.B.04 of the Chemical Weapons Convention: The Discovery of a New Intramolecular Halogen Transfer.

PubMed

Picazas-Márquez, Nerea; Sierra, María; Nova, Clara; Moreno, Juan Manuel; Aboitiz, Nuria; de Rivas, Gema; Sierra, Miguel A; Martínez-Álvarez, Roberto; Gómez-Caballero, Esther

2016-09-01

A new class of compounds, mono- and bis-haloethylphosphonates (HAPs and bisHAPs, respectively), listed in Schedule 2.B.04 of the Chemical Weapons Convention (CWC), has been synthesized and studied by GC-MS with two aims. First, to improve the identification of this type of chemicals by the Organization for the Prohibition of Chemical Weapons, (OPCW). Second, to study the synergistic effect of halogen and silicon atoms in molecules undergoing mass spectrometry. Fragmentation patterns of trimethylsilyl derivatives of HAPs were found to depend on the nature of the halogen atom; this was in agreement with DFT-calculations. The data suggest that a novel intramolecular halogen transfer takes place during the fragmentation process. Graphical Abstract ᅟ.

Tannins and Tannin-Related Derivatives Enhance the (Pseudo-)Halogenating Activity of Lactoperoxidase.

PubMed

Gau, Jana; Prévost, Martine; Van Antwerpen, Pierre; Sarosi, Menyhárt-Botond; Rodewald, Steffen; Arnhold, Jürgen; Flemmig, Jörg

2017-05-26

Several hydrolyzable tannins, proanthocyanidins, tannin derivatives, and a tannin-rich plant extract of tormentil rhizome were tested for their potential to regenerate the (pseudo-)halogenating activity, i.e., the oxidation of SCN - to hypothiocyanite - OSCN, of lactoperoxidase (LPO) after hydrogen peroxide-mediated enzyme inactivation. Measurements were performed using 5-thio-2-nitrobenzoic acid in the presence of tannins and related substances in order to determine kinetic parameters and to trace the LPO-mediated - OSCN formation. The results were combined with docking studies and molecular orbital analysis. The - OSCN-regenerating effect of tannin derivatives relates well with their binding properties toward LPO as well as their occupied molecular orbitals. Especially simple compounds like ellagic acid or methyl gallate and the complex plant extract were found as potent enzyme-regenerating compounds. As the (pseudo-)halogenating activity of LPO contributes to the maintenance of oral bacterial homeostasis, the results provide new insights into the antibacterial mode of action of tannins and related compounds. Furthermore, chemical properties of the tested compounds that are important for efficient enzyme-substrate interaction and regeneration of the - OSCN formation by LPO were identified.

Remarkable effect of halogenation of aromatic compounds on efficiency of nanowire formation through polymerization/crosslinking by high-energy single particle irradiation

NASA Astrophysics Data System (ADS)

Horio, Akifumi; Sakurai, Tsuneaki; Kayama, Kazuto; Lakshmi, G. B. V. S.; Kumar Avasthi, Devesh; Sugimoto, Masaki; Yamaki, Tetsuya; Chiba, Atsuya; Saito, Yuichi; Seki, Shu

2018-01-01

Irradiation of high-energy ion particles on organic films induced solid-state polymerization and crosslinking reactions of the materials along the ion trajectories, resulting in the formation of insoluble uniform nanowires with a precise diameter. The nanowires were isolated by the development process i.e. the irradiated film was immersed in organic solvents, and their morphology was visualized by atomic force microscopy. The target organic materials are 4-vinyltriphenylamine, poly(4-vinyltriphenylamine), and polystyrene derivatives with/without the partial substitutions by halogen atoms. It was found that 4-vinyltriphenylamines, in spite of their small molecular sizes, afforded nanowires more clearly than poly(4-vinyltriphenylamine)s. Moreover, the efficiency of demonstrated polymerization/crosslinking reactions obviously depends on the substituted halogen atom species. The averaged diameters of nanowires from bromo- or iodo- substituted 4-vinyltriphenylamine (9.3 and 9.4 nm, respectively) were larger than that obtained from simple 4-vinyltriphenylamine (6.8 nm). The remarkable effect of halogenation of aromatic compounds on the efficiency of the radiation-induced reactions was also observed for polystyrene derivatives. This contrast was considered to originate from the sum of the efficiency of elementary reactions including dissociative electron attachment.

Modulation of the fibrillogenesis inhibition properties of two transthyretin ligands by halogenation.

PubMed

Cotrina, Ellen Y; Pinto, Marta; Bosch, Lluís; Vilà, Marta; Blasi, Daniel; Quintana, Jordi; Centeno, Nuria B; Arsequell, Gemma; Planas, Antoni; Valencia, Gregorio

2013-11-27

The amyloidogenic protein transthyretin (TTR) is thought to aggregate into amyloid fibrils by tetramer dissociation which can be inhibited by a number of small molecule compounds. Our analysis of a series of crystallographic protein-inhibitor complexes has shown no clear correlation between the observed molecular interactions and the in vitro activity of the inhibitors. From this analysis, it emerged that halogen bonding (XB) could be mediating some key interactions. Analysis of the halogenated derivatives of two well-known TTR inhibitors has shown that while flufenamic acid affinity for TTR was unchanged by halogenation, diflunisal gradually improves binding up to 1 order of magnitude after iodination through interactions that can be interpreted as a suboptimal XB (carbonyl Thr106: I...O distance 3.96-4.05 Å; C-I...O angle 152-156°) or as rather optimized van der Waals contacts or as a mixture of both. These results illustrate the potential of halogenation strategies in designing and optimizing TTR fibrillogenesis inhibitors.

Novel Halogenated Pyrazine-Based Chalcones as Potential Antimicrobial Drugs.

PubMed

Kucerova-Chlupacova, Marta; Vyskovska-Tyllova, Veronika; Richterova-Finkova, Lenka; Kunes, Jiri; Buchta, Vladimir; Vejsova, Marcela; Paterova, Pavla; Semelkova, Lucia; Jandourek, Ondrej; Opletalova, Veronika

2016-10-27

Chalcones, i.e., compounds with the chemical pattern of 1,3-diphenylprop-2-en-1-ones, exert a wide range of bio-activities, e.g., antioxidant, anti-inflammatory, anticancer, anti-infective etc. Our research group has been focused on pyrazine analogues of chalcones; several series have been synthesized and tested in vitro on antifungal and antimycobacterial activity. The highest potency was exhibited by derivatives with electron withdrawing groups (EWG) in positions 2 and 4 of the ring B. As halogens also have electron withdrawing properties, novel halogenated derivatives were prepared by Claisen-Schmidt condensation. All compounds were submitted for evaluation of their antifungal and antibacterial activity, including their antimycobacterial effect. In the antifungal assay against eight strains of selected fungi, growth inhibition of Candida glabrata and Trichophyton interdigitale (formerly T. mentagrophytes ) was shown by non-alkylated derivatives with 2-bromo or 2-chloro substitution. In the panel of selected bacteria, 2-chloro derivatives showed the highest inhibitory effect on Staphylococcus sp. In addition, all products were also screened for their antimycobacterial activity against Mycobacterium tuberculosis H37RV My 331/88, M. kansasii My 235/80, M. avium 152/80 and M. smegmatis CCM 4622. Some of the examined compounds, inhibited growth of M. kansasii and M. smegmatis with minimum inhibitory concentrations (MICs) comparable with those of isoniazid.

ORGANIC REACTIONS IN THE SOLID STATE AND IN SOLID SOLUTIONS.

DTIC Science & Technology

on the reactions of phthalic acid and acetanilide , various acyl anilides, and ring-substituted acetanilides . Exploratory experiments were also...performed between ring-substituted acetanilides and succinic, glutaric, maleic and fumaric acids. The influence of imidazole as a catalyst of the...transacylation reaction of phthalic anhydride and acetanilide is also reported. (Author)

Utilization of Boron Compounds for the Modification of Suberoyl Anilide Hydroxamic Acid as Inhibitor of Histone Deacetylase Class II Homo sapiens

PubMed Central

Bakri, Ridla; Parikesit, Arli Aditya; Satriyanto, Cipta Prio; Kerami, Djati; Tambunan, Usman Sumo Friend

2014-01-01

Histone deacetylase (HDAC) has a critical function in regulating gene expression. The inhibition of HDAC has developed as an interesting anticancer research area that targets biological processes such as cell cycle, apoptosis, and cell differentiation. In this study, an HDAC inhibitor that is available commercially, suberoyl anilide hydroxamic acid (SAHA), has been modified to improve its efficacy and reduce the side effects of the compound. Hydrophobic cap and zinc-binding group of these compounds were substituted with boron-based compounds, whereas the linker region was substituted with p-aminobenzoic acid. The molecular docking analysis resulted in 8 ligands with ΔG binding value more negative than the standards, SAHA and trichostatin A (TSA). That ligands were analyzed based on the nature of QSAR, pharmacological properties, and ADME-Tox. It is conducted to obtain a potent inhibitor of HDAC class II Homo sapiens. The screening process result gave one best ligand, Nova2 (513246-99-6), which was then further studied by molecular dynamics simulations. PMID:25214833

A Survey of Electron Impact Cross-Sections for Halogens and Halogen Compounds of Interest to Plasma Processing

NASA Technical Reports Server (NTRS)

Sharma, S. P.; Rao, M. V. V. S.; Arnold, James O. (Technical Monitor)

1998-01-01

Published electron impact cross section data on halogens Cl2, F2, and halogen containing compounds such as Cx Fy, HCl, Cx Cly Fz are reviewed and critically evaluated based on the information provided by various researchers. The present work reports data on electron impact excitation, ionization, dissociation, electron attachment, electron detachment, and photo detachment. Elastic scattering cross sections and data on bulk properties such as diffusion coefficients in various background gases are also evaluated. Since some of the cross sectional data is derived from indirect measurements such as drift velocity, care has been taken to reconcile the differences among the reported data with due attention to the measurement technique. In conclusion, the processes with no or very limited amount of data and questionable set of data are identified and recommendation for further research direction is made.

Synthesis and biological evaluation of 2-arylimino-3-pyridin-thiazolineone derivatives as antibacterial agents.

PubMed

Cai, Ming-Guang; Wu, Yang; Chang, Jun

2016-05-15

With an intention to find more potent antibacterial agents, four halogen disubstituted thiazolineone derivatives (2a-d), five halogen monosubstituted thiazolineone derivatives (2e-i), and eleven 2-arylimino-3-pyridin-thiazolineone derivatives (2j-t) were synthesized and screened for their antibacterial activity, bactericidal activity, cytotoxicity, and erythrocyte hemolysis. Most of the synthesized derivatives showed antibacterial activity in inhibiting the growth of S. epidermidis and MRSA, and exhibited safety in the cytotoxicity study on the Vero cells and hemolytic activities test on healthy human erythrocytes. 2-Arylimino-3-pyridin-thiazolineone derivatives not only improved the clog P, but also showed potent antibacterial activity in inhibiting the growth of S. epidermidis and MRSA. In particularly, several compounds (2f, 2i, 2r and 2t) showed bactericidal activity, in which compound 2r displayed the best inhibitory capacity among the synthesized compounds, and further druggability research is on going. Copyright © 2016 Elsevier Ltd. All rights reserved.

Dehalogenases: From Improved Performance to Potential Microbial Dehalogenation Applications.

PubMed

Ang, Thiau-Fu; Maiangwa, Jonathan; Salleh, Abu Bakar; Normi, Yahaya M; Leow, Thean Chor

2018-05-07

The variety of halogenated substances and their derivatives widely used as pesticides, herbicides and other industrial products is of great concern due to the hazardous nature of these compounds owing to their toxicity, and persistent environmental pollution. Therefore, from the viewpoint of environmental technology, the need for environmentally relevant enzymes involved in biodegradation of these pollutants has received a great boost. One result of this great deal of attention has been the identification of environmentally relevant bacteria that produce hydrolytic dehalogenases—key enzymes which are considered cost-effective and eco-friendly in the removal and detoxification of these pollutants. These group of enzymes catalyzing the cleavage of the carbon-halogen bond of organohalogen compounds have potential applications in the chemical industry and bioremediation. The dehalogenases make use of fundamentally different strategies with a common mechanism to cleave carbon-halogen bonds whereby, an active-site carboxylate group attacks the substrate C atom bound to the halogen atom to form an ester intermediate and a halide ion with subsequent hydrolysis of the intermediate. Structurally, these dehalogenases have been characterized and shown to use substitution mechanisms that proceed via a covalent aspartyl intermediate. More so, the widest dehalogenation spectrum of electron acceptors tested with bacterial strains which could dehalogenate recalcitrant organohalides has further proven the versatility of bacterial dehalogenators to be considered when determining the fate of halogenated organics at contaminated sites. In this review, the general features of most widely studied bacterial dehalogenases, their structural properties, basis of the degradation of organohalides and their derivatives and how they have been improved for various applications is discussed.

A facile approach towards increasing the nitrogen-content in nitrogen-doped carbon nanotubes via halogenated catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ombaka, L.M.; Ndungu, P.G.; Department of Applied Chemistry, Doornfontein Campus, University of Johannesburg, P.O. Box 17011, Johannesburg 2028

Nitrogen-doped carbon nanotubes (N-CNTs) have been synthesized at 850 °C via a CVD deposition technique by use of three ferrocenyl derivative catalysts, i.e. para-CN, -CF{sub 3} and -Cl substituted-phenyl rings. The synthesized catalysts have been characterized by NMR, IR, HR-MS and XRD. The XRD analysis of the para-CF{sub 3} catalyst indicates that steric factors influence the X-ray structure of 1,1′-ferrocenylphenyldiacrylonitriles. Acetonitrile or pyridine was used as carbon and nitrogen sources to yield mixtures of N-CNTs and carbon spheres (CS). The N-CNTs obtained from the para-CF{sub 3} catalysts, in pyridine, have the highest nitrogen-doping level, show a helical morphology and aremore » less thermally stable compared with those synthesized by use of the para-CN and -Cl as catalyst. This suggests that fluorine heteroatoms enhance nitrogen-doping in N-CNTs and formation of helical-N-CNTs (H-N-CNTs). The para-CF{sub 3} and para-Cl catalysts in acetonitrile yielded iron-filled N-CNTs, indicating that halogens promote encapsulation of iron into the cavity of N-CNT. The use of acetonitrile, as carbon and nitrogen source, with the para-CN and -Cl as catalysts also yielded a mixture of N-CNTs and carbon nanofibres (CNFs), with less abundance of CNFs in the products obtained using para-Cl catalysts. However, para-CF{sub 3} catalyst in acetonitrile gave N-CNTs as the only shaped carbon nanomaterials. - Graphical abstract: Graphical abstract showing the synthesis of N-CNTs using halogenated-ferrocenyl derivatives as catalyst with pyridine or acetonitrile as nitrogen and carbon sources via the chemical vapour deposition technique. - Highlights: • N-CNTs were synthesized from halogenated ferrocenyl catalysts. • Halogenated catalysts promote nitrogen-doping and pyridinic nitrogen in N-CNTs. • Halogenated catalysts facilitate iron filling of N-CNTs.« less

Halogens, Barium and Uranium in Mantle Fluid Inclusions

NASA Astrophysics Data System (ADS)

Villa, I. M.; Peverelli, V.; Oglialoro, E.; Pettke, D. T.; Frezzotti, M. L.

2016-12-01

Halogens are an underexplored geochemical marker. A way to measure halogens at ng/g levels is measuring Ar, Kr and Xe in irradiated samples [1,2]. We derive absolute halogen amounts from rare gas amounts via scapolite monitor SY [2]. Kr-Xe systematics also yield Ba and U concentrations. We combined irradiation with stepheating on carbonate-sulfate-rich fluid inclusions (FI)-bearing xe­no­liths from El Hierro, Canarias: spinel harzburgite XML-7 and spinel dunite XML-1 [3]. Three components are recognized in the rare gas release. (1) Atmospheric surface contamination occurs up to 1000 °C. (2) FI decrepitation by laboratory heating occurs above 1200 °C [4], corresponding to the release of 80,82Kr and 128Xe in the 1200 and 1400 °C steps. Br whole-rock concentrations are 3-8 ng/g; the molar Br/Cl and I/Cl ratios in the harzburgite FI, 9 E-4 resp. 2 E-4, are identical to those in the dunite FI. This sets the halogens in our FI apart from MORB [2]. Halogen-derived rare gases are closely associated to artificial 131Xe from Ba; Ba has a high affinity of for CO2-rich fluids. Daughter minerals in multiphase FI were identified by Raman micro­spectroscopy [4]. The calculated Ba concentrations are 2-6 µg/g. (3) The third component is U-derived 134,136Xe and 86Kr released in a spike at 1000 °C, decoupled from FI. This requires a different carrier than FI, e.g. Ti oxides. As U concentrations are 10-20 pg/g, the U-bearing phase needs to be below a ppm, invisible by petro­graphy. The 136Xe/134Xe ratio > 1 suggests retention of radio­genic Xe. However, analysis of an unirradiated sample detected no radiogenic Xe. It is likely that Xe-U produced in the core of the McMaster reactor (thermal, epithermal and fast neutrons) has a different isotopic composition from that in textbooks, as proposed by [2].[1] Jeffery & Reynolds (1961) J.Geophys. Res. 66, 3582 [2] Kendrick (2012) Chem. Geol. 292, 116 [3] Oglialoro et al (2015) AGU Fall Meeting abstract V21C-3046 [4] Roedder (1965) Am. Min. 50, 1746

Discovery, SAR, and Radiolabeling of Halogenated Benzimidazole Carboxamide Antagonists as Useful Tools for (alpha)4(beta)1 Integrin Expressed on T- and B-cell Lymphomas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carpenter, R D; Natarajan, A; Lau, E Y

2010-02-08

The cell surface receptor {alpha}{sub 4}{beta}{sub 1} integrin is an attractive yet poorly understood target for selective diagnosis and treatment of T- and B-cell lymphomas. This report focuses on the rapid microwave preparation of medicinally pertinent benzimidazole heterocycles, structure-activity relationships (SAR) of novel halobenzimidazole carboxamide antagonists 3-6, and preliminary biological evaluation of radioiodinated agents 7, 8, and 18. The I-125 derivative 18 had good tumor uptake (12 {+-} 1% ID/g at 24 h; 4.5 {+-} 1% ID/g at 48 h) and tumor:kidney ratio ({approx}4:1 at 24 h; 2.5:1 at 48 h) in xenograft murine models of B-cell lymphoma. Molecular homologymore » models of {alpha}{sub 4}{beta}{sub 1} integrin have predicted that docked halobenzimidazole carboxamides have the halogen atom in a suitable orientation for halogen-hydrogen bonding. These high affinity ({approx} pM binding) halogenated ligands are attractive tools for medicinal and biological use; the fluoro and iodo derivatives are potential radiodiagnostic ({sup 18}F) or radiotherapeutic ({sup 131}I) agents, whereas the chloro and bromo analogues could provide structural insight into integrin-ligand interactions through photoaffinity cross-linking/mass spectroscopy experiments, as well as co-crystallization X-ray studies.« less

Photolytic dehalogenation of disinfection byproducts in water by natural sunlight irradiation.

PubMed

Abusallout, Ibrahim; Hua, Guanghui

2016-09-01

The aqueous photolysis of halogenated disinfection byproducts (DBPs) by natural sunlight irradiation was studied to determine their photolytic dehalogenation kinetics. Total organic halogen analysis was used to quantify the dehalogenation extents of DBPs during outdoor photolysis experiments. Dichloroacetamide, chloral hydrate, chloroform, dichloroacetonitrile, monochloro-, monobromo-, dichloro-, dibromo-, and trichloroacetic acids were generally resistant to photolytic dehalogenation and showed less than 10% reduction after 6 h sunlight irradiation. Monoiodoacetic acid, tribromoacetic acid, bromoform, dibromoacetonitrile, and trichloronitromethane showed moderate to high dehalogenation degrees with half-lives of 4.0-19.3 h. Diiodoacetic acid, triiodoacetic acid, and iodoform degraded rapidly under the sunlight irradiation and exhibited half-lives of 5.3-10.2 min. In general, the photosensitive cleavage of carbon-halogen bonds of DBPs increased with increasing number of halogens (tri- > di- > mono-halogenated) and size of the substituted halogens (I > Br > Cl). Nitrate, nitrite, and pH had little impact on the photodehalogenation of DBPs under typical levels in surface waters. The presence of natural organic matter (NOM) inhibited the photodehalogenation of DBPs by light screening. The NOM inhibiting effects were more pronounced for the fast degrading iodinated DBPs. The results of this study improve our understanding about the photolytic dehalogenation of wastewater-derived DBPs in surface waters during water reuse. Published by Elsevier Ltd.

Structure and biocatalytic scope of thermophilic flavin-dependent halogenase and flavin reductase enzymes.

PubMed

Menon, Binuraj R K; Latham, Jonathan; Dunstan, Mark S; Brandenburger, Eileen; Klemstein, Ulrike; Leys, David; Karthikeyan, Chinnan; Greaney, Michael F; Shepherd, Sarah A; Micklefield, Jason

2016-10-04

Flavin-dependent halogenase (Fl-Hal) enzymes have been shown to halogenate a range of synthetic as well as natural aromatic compounds. The exquisite regioselectively of Fl-Hal enzymes can provide halogenated building blocks which are inaccessible using standard halogenation chemistries. Consequently, Fl-Hal are potentially useful biocatalysts for the chemoenzymatic synthesis of pharmaceuticals and other valuable products, which are derived from haloaromatic precursors. However, the application of Fl-Hal enzymes, in vitro, has been hampered by their poor catalytic activity and lack of stability. To overcome these issues, we identified a thermophilic tryptophan halogenase (Th-Hal), which has significantly improved catalytic activity and stability, compared with other Fl-Hal characterised to date. When used in combination with a thermostable flavin reductase, Th-Hal can efficiently halogenate a number of aromatic substrates. X-ray crystal structures of Th-Hal, and the reductase partner (Th-Fre), provide insights into the factors that contribute to enzyme stability, which could guide the discovery and engineering of more robust and productive halogenase biocatalysts.

Regional atmospheric emissions determined from measurements at Jeju Island, Korea: Halogenated compounds from China

NASA Astrophysics Data System (ADS)

Kim, Jooil; Li, Shanlan; Kim, Kyung-Ryul; Stohl, Andreas; Mühle, Jens; Kim, Seung-Kyu; Park, Mi-Kyung; Kang, Dong-Jin; Lee, Gangwoong; Harth, Christina M.; Salameh, Peter K.; Weiss, Ray F.

2010-06-01

High-frequency in-situ measurements of a wide range of halogenated compounds including chlorofluorocarbons (CFCs), halons, hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), perfluorinated compounds (PFCs), sulfur hexafluoride (SF6), and other chlorinated and brominated compounds have been made at Gosan (Jeju Island, Korea). Regional emissions of HCFC-22 (CHClF2) calculated from inverse modeling were combined with interspecies correlation methods to estimate national emissions for China, a major emitter of industrial halogenated gases. Our results confirm the signs of successful phase-out of primary ozone-depleting species such as CFCs, halons and many chlorinated or brominated compounds, along with substantial emissions of replacement HCFCs. Emissions derived for HFCs, PFCs, and SF6 were compared to published estimates and found to be a significant fraction of global totals. Overall, Chinese emissions of the halogenated compounds discussed here represent 19(14-17)% and 20(15-26)% of global emissions when evaluated in terms of their Ozone Depletion Potentials and 100-year Global Warming Potentials, respectively.

Lipase-catalyzed synthesis of palmitanilide: Kinetic model and antimicrobial activity study.

PubMed

Liu, Kuan-Miao; Liu, Kuan-Ju

2016-01-01

Enzymatic syntheses of fatty acid anilides are important owing to their wide range of industrial applications in detergents, shampoo, cosmetics, and surfactant formulations. The amidation reaction of Mucor miehei lipase Lipozyme IM20 was investigated for direct amidation of triacylglycerol in organic solvents. The process parameters (reaction temperature, substrate molar ratio, enzyme amount) were optimized to achieve the highest yield of anilide. The maximum yield of palmitanilide (88.9%) was achieved after 24 h of reaction at 40 °C at an enzyme concentration of 1.4% (70 mg). Kinetics of lipase-catalyzed amidation of aniline with tripalmitin has been investigated. The reaction rate could be described in terms of the Michaelis-Menten equation with a Ping-Pong Bi-Bi mechanism and competitive inhibition by both the substrates. The kinetic constants were estimated by using non-linear regression method using enzyme kinetic modules. The enzyme operational stability study showed that Lipozyme IM20 retained 38.1% of the initial activity for the synthesis of palmitanilide (even after repeated use for 48 h). Palmitanilide, a fatty acid amide, exhibited potent antimicrobial activity toward Bacillus cereus. Copyright © 2015 Elsevier Inc. All rights reserved.

Halogen atom effect on the photophysical properties of substituted aza-BODIPY derivatives.

PubMed

De Simone, B C; Mazzone, G; Pirillo, J; Russo, N; Sicilia, E

2017-01-18

The influence of halogen atom substitution (Br and I), in different amounts and positions in an aza-BODIPY skeleton, on the photophysical properties of some aza-BODIPY derivatives has been investigated by using density functional theory and its time-dependent extension. The heavy atom effect on excitation energies, singlet-triplet energy gaps and spin-orbit matrix elements has been considered. The maximum absorption within the therapeutic window has been confirmed for all the aza-BODIPY derivatives. The feasible intersystem spin crossing pathways for the population of the lowest triplet state, that will depend on the values of the spin-orbit matrix elements, the energy gap as well as the orbital composition of the involved states have been found to most likely involve the S 1 and T 1 or T 2 states. The outcomes of computations support the potential therapeutic use of these compounds as photosensitizers in photodynamic therapy.

Estrogenicity of halogenated bisphenol A: in vitro and in silico investigations.

PubMed

Zhang, Jie; Li, Tiezhu; Wang, Tuoyi; Yuan, Cuiping; Zhong, Shuning; Guan, Tianzhu; Li, Zhuolin; Wang, Yongzhi; Yu, Hansong; Luo, Quan; Wang, Yongjun; Zhang, Tiehua

2018-03-01

The binding interactions of bisphenol A (BPA) and its halogenated derivatives (halogenated BPAs) to human estrogen receptor α ligand binding domain (hERα-LBD) was investigated using a combined in vitro and in silico approach. First, the recombinant hERα-LBD was prepared as a soluble protein in Escherichia coli BL21(DE3)pLysS. A native fluorescent phytoestrogen, coumestrol, was employed as tracer for the fluorescence polarization assay. The results of the in vitro binding assay showed that bisphenol compounds could bind to hERα-LBD as the affinity ligands. All the tested halogenated BPAs exhibited weaker receptor binding than BPA, which might be explained by the steric effect of substituents. Molecular docking studies elucidated that the halogenated BPAs adopted different conformations in the flexible hydrophobic ligand binding pocket (LBP), which is mainly dependent on their distinct halogenation patterns. The compounds with halogen substituents on the phenolic rings and on the bridging alkyl moiety acted as agonists and antagonists for hERα, respectively. Interestingly, all the compounds in the agonist conformation of hERα formed a hydrogen bond with His524, while the compounds in the antagonist conformation formed a hydrogen bond with Thr347. These docking results suggested a pivotal role of His524/Thr347 in maintaining the hERα structure in the biologically active agonist/antagonist conformation. Comparison of the calculated binding energies vs. experimental binding affinities yielded a good correlation, which might be applicable for the structure-based design of novel bisphenol compounds with reduced toxicities and for environmental risk assessment. In addition, based on hERα-LBD as a recognition element, the proposed fluorescence polarization assay may offer an alternative to chromatographic techniques for the multi-residue determination of bisphenol compounds.

MISTRA mechanism development: A new mechanism focused on marine environments

NASA Astrophysics Data System (ADS)

Bräuer, Peter; Sommariva, Roberto; von Glasow, Roland

2015-04-01

The tropospheric multiphase chemistry of halogen compounds plays a key role in marine environments. Moreover, halogen compounds have an impact on the tropospheric oxidation capacity and climate. With more than two thirds of the Earth's surface covered with oceans, effects are of global importance. Various conditions are found in marine environments ranging from pristine regions to polluted regimes in the continental outflow. Furthermore, there are important sources for halogen compounds over land, such as volcanoes, salt lakes, or emissions from industrial processes. To assess the impact of halogen chemistry with numerical models under these distinct conditions, a multiphase mechanism has been developed in the last decades and applied successfully in numerous box and 1D model studies. Contributions from these model studies helped to identify important chemical cycles affecting the composition and chemistry of the troposphere. However, several discrepancies between model results and field measurements remain. Therefore, a major revision of the chemical mechanism has been performed including an update of the kinetic data and the addition of new reaction cycles. The extended mechansims have been evaluated in several model studies with the 1D model MISTRA. Current work focuses at the identification of the most important reaction cycles, which led to significant changes in the concentration-time profiles of several halogen species. Subsequently, the mechanism will be reduced to the most imporatant reactions, which are currently investigated. As regional and global model studies become more important to identify the importance of tropospheric halogen multiphase chemistry, the goal is to derive parameterisations for the most important halogen chemistry cycles, which can than be implemented in regional and global 3D models. In the reduction process, the extented MISTRA version will serve as a benchmark to assess the quality and accuracy of the reduced mechansim versions.

Synthesis and biological evaluation of some novel thiazole compounds as potential anti-inflammatory agents.

PubMed

Helal, M H M; Salem, M A; El-Gaby, M S A; Aljahdali, M

2013-07-01

In the present investigation, furo[2,3-d]thiazol-5(2H)-one 5 was obtained from reaction of thiosemicarbazone derivative 2 with diethyl acetylene dicarboxylate. A series of newly synthesized 2-(hydrazinyl)thiazol-4(5H)-one 6, 7 &8 and 2-(4-(substituted)-thiazol-2-yl)hydrazono derivatives 9a, b &10 were synthesized from treatment of thiosemicarbazone derivative 2 with appropriate α-halogenated compounds. Also, a one pot synthesis of thiazole derivatives 13 &15 was achieved from three components reaction of hydrazone derivative 11 with phenyl isothiocyanate and α-halogenated compounds catalyzed by DMF/KOH. 4-(4-Morpholino phenyl) thiazol-2-amino 17 was obtained via the reaction of acetophenone derivative 1 with thiourea in presence of iodine. The reactivity of 2-aminothiazole 17 toward some electrophilic reagents was investigated. The structure of the newly compounds was confirmed on the basis of elemental analysis and spectral data. The antibacterial activity towards two Gram negative (Proteus mirabilis &Serratia marcesens) and two Gram positive (Staphylococcus aureus &Bacillus cereus) bacteria was investigated. The anti-inflammatory activity was also investigated and the inhibition of the carrageenin-induced oedema by these compounds was established. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

Synthesis of Thieno[3,2-b]indoles via Halogen Dance and Ligand-Controlled One-Pot Sequential Coupling Reaction.

PubMed

Hayashi, Yuki; Okano, Kentaro; Mori, Atsunori

2018-02-16

A two-pot synthesis of thieno[3,2-b]indole from 2,5-dibromothiophene is described. A halogen dance of 2,5-dibromothiophene was performed with LDA, and subsequent Negishi coupling was performed with 2-iodoaniline derivatives to provide the corresponding coupling products. The resulting two bromo groups have different reactivities, which were utilized for the one-pot Suzuki-Miyaura coupling/intramolecular Buchwald-Hartwig amination to produce thieno[3,2-b]indole via an assisted tandem catalysis that involved in situ ligand exchange.

Investigating Planetary Volatile Accretion Mechanisms Using the Halogens

NASA Astrophysics Data System (ADS)

Ballentine, C. J.; Clay, P. L.; Burgess, R.; Busemann, H.; Ruzié, L.; Joachim, B.; Day, J. M.

2014-12-01

Depletion of the volatile elements in the Earth relative to the CI chondrites is roughly correlated with volatility, or decreasing condensation temperature. For the heavy halogen group elements (Cl, Br and I), volatility alone does not account for their apparent depletion, which early data has suggested is far greater than predicted [1-2]. Such depletion has been used to argue for the preferential loss of halogens by, amongst other processes, impact-driven erosive loss from Earth's surface [2]. Little consensus exists as to why the halogens should exhibit such preferential behavior during accretionary processes. Early efforts to constrain halogen abundance and understand their behavior in both Earth and planetary materials [3-6] have been hampered by their typically low abundance (ppb level) in most geologic materials. We present the results of halogen analysis of 23 chondrite samples, selected to represent diverse groups and petrologic type. Halogen abundances were measured by neutron irradiation noble gas mass spectrometry (NI-NGMS). Significant concentration heterogeneity is observed within some samples. However, a single Br/Cl and I/Cl ratio of 1.9 ± 0.2 (x 10-3) and 335 ± 10 (x 10-6) can be defined for carbonaceous chondrites with a good correlation between Br and Cl (R2 = 0.97) and between I and Cl (R2 = 0.84). Ratios of I/Cl overlap with terrestrial estimates of Bulk Silicate Earth and Mid Ocean Ridge Basalts. Similarly, good correlations are derived for enstatite (E) chondrites and a sulfide- and halogen- rich subset of E-chondrites. Chlorine abundances of CI (Orgueil) in this study are lower by factor of ~ 3 than the value of ~ 700 ppm Cl (compilation in [1]). Our results are similar to early discarded low values for Ivuna and Orgueil from [5,6] and agree more closely with values for CM chondrites. Halogens may not be as depleted in Earth as previously suggested, or a high degree of heterogeneity in the abundance of these volatile elements in carbonaceous chondrites should be considered when we assess Earth's halogen abundance relative to CI. [1] Lodders (2003) Astr J 591:1220-47. [2] Sharp et al. (2013) EPSL 369/70: 71-7. [3] Dreibus et al. (1979) Phys Chem Earth 11:33-8. [4] Goles et al. (1967) GCA 31: 1771-7. [5] Reed and Allen (1966) GCA 30: 779-800. [6] Greenland & Lovering (1965) GCA 29: 821-58.

Covalent binding of aniline to humic substances. 2. 15N NMR studies of nucleophilic addition reactions

USGS Publications Warehouse

Thorn, K.A.; Pettigrew, P.J.; Goldenberg, W.S.; Weber, E.J.

1996-01-01

Aromatic amines are known to undergo covalent binding with humic substances in the environment. Although previous studies have examined reaction conditions and proposed mechanisms, there has been no direct spectroscopic evidence for the covalent binding of the amines to the functional groups in humic substances. In order to further elucidate the reaction mechanisms, the Suwannee River and IHSS soil fulvic and humic acids were reacted with 15N-labeled aniline at pH 6 and analyzed using 15N NMR spectrometry. Aniline underwent nucleophilic addition reactions with the quinone and other carbonyl groups in the samples and became incorporated in the form of anilinohydroquinone, anilinoquinone, anilide, imine, and heterocyclic nitrogen, the latter comprising 50% or more of the bound amine. The anilide and anilinohydroquinone nitrogens were determined to be susceptible to chemical exchange by ammonia. In the case of Suwannee River fulvic acid, reaction under anoxic conditions and pretreatment with sodium borohydride or hydroxylamine prior to reaction under oxic conditions resulted in a decrease in the proportion of anilinohydroquinone nitrogen incorporated. The relative decrease in the incorporation of anilinohydroquinone nitrogen with respect to anilinoquinone nitrogen under anoxic conditions suggested that inter- or intramolecular redox reactions accompanied the nucleophilic addition reactions.

Rational design of an orthogonal noncovalent interaction system at the MUPP1 PDZ11 complex interface with CaMKIIα-derived peptides in human fertilization.

PubMed

Zhang, Yi-Le; Han, Zhao-Feng

2017-09-26

The recognition and association between the Ca 2+ /calmodulin-activated protein kinase II-α (CaMKIIα) and the multi-PDZ domain protein 1 (MUPP1) plays an important role in the sperm acrosome reaction and human fertilization. Previously, we have demonstrated that the MUPP1 PDZ11 domain is the primary binding partner of the CaMKIIα C-terminal tail, which can be targeted by a rationally designed sia peptide with nanomolar affinity. Here, we further introduced an orthogonal noncovalent interaction (ONI) system between a native hydrogen bond and a designed halogen bond across the complex interface of the PDZ11 domain with the sia [Asn-1Phe] peptide mutant, where the halogen bond was formed by substituting the o-hydrogen atom of the benzene ring of the peptide Phe-1 residue with a halogen atom (F, Cl, Br or I). Molecular dynamics simulations and high-level theoretical calculations suggested that bromine (Br) is a good compromise between the halogen-bonding strength and steric hindrance effect due to introduction of a bulkier halogen atom into the tightly packed complex interface. Fluorescence spectroscopy assays revealed that the resulting o-Br-substituted peptide (K d = 18 nM) exhibited an ∼7.6-fold affinity increase relative to its native counterpart (K d = 137 nM). In contrast, the p-Br-substituted peptide, a negative control that is unable to establish the ONI according to structure-based analysis, has decreased affinity (K d = 210 nM) upon halogenation.

Carbide-derived carbons - From porous networks to nanotubes and graphene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Presser, V.; Heon, M.; Gogotsi, Y.

2011-02-09

Carbide-derived carbons (CDCs) are a large family of carbon materials derived from carbide precursors that are transformed into pure carbon via physical (e.g., thermal decomposition) or chemical (e.g., halogenation) processes. Structurally, CDC ranges from amorphous carbon to graphite, carbon nanotubes or graphene. For halogenated carbides, a high level of control over the resulting amorphous porous carbon structure is possible by changing the synthesis conditions and carbide precursor. The large number of resulting carbon structures and their tunability enables a wide range of applications, from tribological coatings for ceramics, or selective sorbents, to gas and electrical energy storage. In particular, themore » application of CDC in supercapacitors has recently attracted much attention. This review paper summarizes key aspects of CDC synthesis, properties, and applications. It is shown that the CDC structure and properties are sensitive to changes of the synthesis parameters. Understanding of processing–structure–properties relationships facilitates tuning of the carbon material to the requirements of a certain application.« less

Influence of the chemical structure on odor qualities and odor thresholds of halogenated guaiacol-derived odorants

NASA Astrophysics Data System (ADS)

Juhlke, Florian; Lorber, Katja; Wagenstaller, Maria; Buettner, Andrea

2017-12-01

Chlorinated guaiacol derivatives are found in waste water of pulp mills using chlorine in the bleaching process of wood pulp. They can also be detected in fish tissue, possibly causing off-odors. To date, there is no systematic investigation on the odor properties of halogenated guaiacol derivatives. To close this gap, odor thresholds in air and odor qualities of 14 compounds were determined by gas chromatography-olfactometry. Overall, the investigated compounds elicited smells that are characteristic for guaiacol, namely smoky, sweet, vanilla-like, but also medicinal and plaster-like. Their odor thresholds in air were, however, very low, ranging from 0.00072 to 23 ng/Lair. The lowest thresholds were found for 5-chloro- and 5-bromoguaiacol, followed by 4,5-dichloro- and 6-chloroguaiacol. Moreover, some inter-individual differences in odor threshold values could be observed, with the highest variations having been recorded for the individual values of 5-iodo- and 4-bromoguaiacol.

3D-QSAR based on quantum-chemical molecular fields: toward an improved description of halogen interactions.

PubMed

Güssregen, Stefan; Matter, Hans; Hessler, Gerhard; Müller, Marco; Schmidt, Friedemann; Clark, Timothy

2012-09-24

Current 3D-QSAR methods such as CoMFA or CoMSIA make use of classical force-field approaches for calculating molecular fields. Thus, they can not adequately account for noncovalent interactions involving halogen atoms like halogen bonds or halogen-π interactions. These deficiencies in the underlying force fields result from the lack of treatment of the anisotropy of the electron density distribution of those atoms, known as the "σ-hole", although recent developments have begun to take specific interactions such as halogen bonding into account. We have now replaced classical force field derived molecular fields by local properties such as the local ionization energy, local electron affinity, or local polarizability, calculated using quantum-mechanical (QM) techniques that do not suffer from the above limitation for 3D-QSAR. We first investigate the characteristics of QM-based local property fields to show that they are suitable for statistical analyses after suitable pretreatment. We then analyze these property fields with partial least-squares (PLS) regression to predict biological affinities of two data sets comprising factor Xa and GABA-A/benzodiazepine receptor ligands. While the resulting models perform equally well or even slightly better in terms of consistency and predictivity than the classical CoMFA fields, the most important aspect of these augmented field-types is that the chemical interpretation of resulting QM-based property field models reveals unique SAR trends driven by electrostatic and polarizability effects, which cannot be extracted directly from CoMFA electrostatic maps. Within the factor Xa set, the interaction of chlorine and bromine atoms with a tyrosine side chain in the protease S1 pocket are correctly predicted. Within the GABA-A/benzodiazepine ligand data set, PLS models of high predictivity resulted for our QM-based property fields, providing novel insights into key features of the SAR for two receptor subtypes and cross-receptor selectivity of the ligands. The detailed interpretation of regression models derived using improved QM-derived property fields thus provides a significant advantage by revealing chemically meaningful correlations with biological activity and helps in understanding novel structure-activity relationship features. This will allow such knowledge to be used to design novel molecules on the basis of interactions additional to steric and hydrogen-bonding features.

Conformational equilibrium of phenylacetic acid and its halogenated analogues through theoretical studies, NMR and IR spectroscopy

NASA Astrophysics Data System (ADS)

Levandowski, Mariana N.; Rozada, Thiago C.; Melo, Ulisses Z.; Basso, Ernani A.; Fiorin, Barbara C.

2017-03-01

This paper presents a study on the conformational preferences of phenylacetic acid (PA) and its halogenated analogues (FPA, CPA, BPA). To clarify the effects that rule these molecules' behaviour, theoretical calculations were used, for both the isolated phase and solution, combined with nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy. Most conformations of phenylacetic acid and its halogenated derivatives are stabilized through the hyperconjugative effect, which rules the conformational preference. NMR analyses showed that even with the variation in medium polarity, there was no significant change in the conformation population. Infrared spectroscopy showed similar results for all compounds under study. In most spectra, two bands were found through the carbonyl deconvolution, which is in accordance with the theoretical data. It was possible to prove that variation in the nature of the substituent in the ortho position had no significant influence on the conformational equilibrium.

Fluoroalkenylphosphonates

NASA Astrophysics Data System (ADS)

Kadyrov, A. A.; Rokhlin, E. M.

1988-09-01

In this review we survey the methods for the preparation of derivatives of fluoroalkenylphosphonic acid and their reactions. The main methods for obtaining these compounds are based on the reactions of fluoroolefins with phosphites and also on the elimination of halogens, hydrogen halides and alkyl halides from fluoroalkylphosphonates or fluorine-containing phosphorus ylides. The chemical properties of fluoroalkenylphosphonates are due to the combined effect of the fluorine atoms and the phosphonate group. Their reactions with different reagents leads to modifications of the phosphonate group, addition to the C=C bond, replacement of the vinyl halogen atom, and cleavage of the C-P bond. The bibliography includes 96 references.

Room-Temperature Phosphorescence in Pure Organic Materials: Halogen Bonding Switching Effects.

PubMed

Xiao, Lu; Wu, Yishi; Yu, Zhenyi; Xu, Zhenzhen; Li, Jinbiao; Liu, Yanping; Yao, Jiannian; Fu, Hongbing

2018-02-06

Organic room-temperature phosphorescence (ORTP), when combined with external stimuli-responsive capability, is very attractive for sensors and bio-imaging devices, but remains challenging. Herein, by doping two β-iminoenamine-BF 2 derivatives (S-2CN and S-2I) into a 4-iodoaniline (I-Ph-NH 2 ) crystalline matrix, the formation of S-2CN⋅⋅⋅I-Ph-NH 2 and S-2I⋅⋅⋅I-Ph-NH 2 halogen bonds leads to bright-red RTP emissions from these two host-guest doped crystals (hgDCs) with quantum efficiencies up to 13.43 % and 15.96 %, respectively. Upon treatment with HCl, the competition of I-Ph-NH 2 ⋅HCl formation against S-2I⋅⋅⋅I-Ph-NH 2 halogen bonding switches off the red RTP from S-2I/I-Ph-NH 2 hgDCs, whereas the stable halogen-bonded S-2CN⋅⋅⋅I-Ph-NH 2 ensures red RTP from S-2CN/I-Ph-NH 2 hgDCs remains unchanged. A security protection luminescence pattern by using these different HCl-responsive RTP behaviors was designed. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

QSPR models of n-octanol/water partition coefficients and aqueous solubility of halogenated methyl-phenyl ethers by DFT method.

PubMed

Zeng, Xiao-Lan; Wang, Hong-Jun; Wang, Yan

2012-02-01

The possible molecular geometries of 134 halogenated methyl-phenyl ethers were optimized at B3LYP/6-31G(*) level with Gaussian 98 program. The calculated structural parameters were taken as theoretical descriptors to establish two new novel QSPR models for predicting aqueous solubility (-lgS(w,l)) and n-octanol/water partition coefficient (lgK(ow)) of halogenated methyl-phenyl ethers. The two models achieved in this work both contain three variables: energy of the lowest unoccupied molecular orbital (E(LUMO)), most positive atomic partial charge in molecule (q(+)), and quadrupole moment (Q(yy) or Q(zz)), of which R values are 0.992 and 0.970 respectively, their standard errors of estimate in modeling (SD) are 0.132 and 0.178, respectively. The results of leave-one-out (LOO) cross-validation for training set and validation with external test sets both show that the models obtained exhibited optimum stability and good predictive power. We suggests that two QSPR models derived here can be used to predict S(w,l) and K(ow) accurately for non-tested halogenated methyl-phenyl ethers congeners. Copyright © 2011 Elsevier Ltd. All rights reserved.

Singlet versus Triplet Excited State Mediated Photoinduced Dehalogenation Reactions of Itraconazole in Acetonitrile and Aqueous Solutions.

PubMed

Zhu, Ruixue; Li, Ming-de; Du, Lili; Phillips, David Lee

2017-04-06

Photoinduced dehalogenation of the antifungal drug itraconazole (ITR) in acetonitrile (ACN) and ACN/water mixed solutions was investigated using femtosecond and nanosecond time-resolved transient absorption (fs-TA and ns-TA, respectively) and nanosecond time-resolved resonance Raman spectroscopy (ns-TR 3 ) experiments. An excited resonance energy transfer is found to take place from the 4-phenyl-4,5-dihydro-3H-1,2,4-triazol-3-one part of the molecule to the 1,3-dichlorobenzene part of the molecule when ITR is excited by ultraviolet light. This photoexcitation is followed by a fast carbon-halogen bond cleavage that leads to the generation of radical intermediates via either triplet and/or singlet excited states. It is found that the singlet excited state-mediated carbon-halogen cleavage is the predominant dehalogenation process in ACN solvent, whereas a triplet state-mediated carbon-halogen cleavage prefers to occur in the ACN/water mixed solutions. The singlet-to-triplet energy gap is decreased in the ACN/water mixed solvents and this helps facilitate an intersystem crossing process, and thus, the carbon-halogen bond cleavage happens mostly through an excited triplet state in the aqueous solutions examined. The ns-TA and ns-TR 3 results also provide some evidence that radical intermediates are generated through a homolytic carbon-halogen bond cleavage via predominantly the singlet excited state pathway in ACN but via mainly the triplet state pathway in the aqueous solutions. In strong acidic solutions, protonation at the oxygen and/or nitrogen atoms of the 1,2,4-triazole-3-one group appears to hinder the dehalogenation reactions. This may offer the possibility that the phototoxicity of ITR due to the generation of aryl or halogen radicals can be reduced by protonation of certain moieties in suitably designed ITR halogen-containing derivatives.

Synthetic procedure for N-Fmoc amino acyl-N-sulfanylethylaniline linker as crypto-peptide thioester precursor with application to native chemical ligation.

PubMed

Sakamoto, Ken; Sato, Kohei; Shigenaga, Akira; Tsuji, Kohei; Tsuda, Shugo; Hibino, Hajime; Nishiuchi, Yuji; Otaka, Akira

2012-08-17

N-sulfanylethylanilide (SEAlide) peptides 1, obtainable using Fmoc-based solid-phase peptide synthesis (Fmoc SPPS), function as crypto-thioesters in native chemical ligation (NCL), yielding a wide variety of peptides/proteins. Their acylating potential with N-terminal cysteinyl peptides 2 can be tuned by the presence or absence of phosphate salts, leading to one-pot/multifragment ligation, operating under kinetically controlled conditions. SEAlide peptides have already been shown to be promising for use in protein synthesis; however, a widely applicable method for the synthesis of N-Fmoc amino acyl-N-sulfanylethylaniline linkers 4, required for the preparation of SEAlide peptides, is unavailable. The present study addresses the development of efficient condensation protocols of 20 naturally occurring amino acid derivatives to the N-sulfanylethylaniline linker 5. N-Fmoc amino acyl aniline linkers 4 of practical use in NCL chemistry, except in the case of the proline- or aspartic acid-containing linker, were successfully synthesized by coupling of POCl(3)- or SOCl(2)-activated Fmoc amino acid derivatives with sodium anilide species 6, without accompanying racemization and loss of side-chain protection. Furthermore, SEAlide peptides 7 possessing various C-terminal amino acids (Gly, His, Phe, Ala, Asn, Ser, Glu, and Val) were shown to be of practical use in NCL chemistry.

Impacts of halogen additions on mercury oxidation, in a slipstream selective catalyst reduction (SCR), reactor when burning sub-bituminous coal.

PubMed

Cao, Yan; Gao, Zhengyang; Zhu, Jiashun; Wang, Quanhai; Huang, Yaji; Chiu, Chengchung; Parker, Bruce; Chu, Paul; Pant, Wei-Ping

2008-01-01

This paper presents a comparison of impacts of halogen species on the elemental mercury (Hg(0)) oxidation in a real coal-derived flue gas atmosphere. It is reported there is a higher percentage of Hg(0) in the flue gas when burning sub-bituminous coal (herein Powder River Basin (PRB) coal) and lignite, even with the use of selective catalytic reduction (SCR). The higher Hg(0)concentration in the flue gas makes it difficult to use the wet-FGD process for the mercury emission control in coal-fired utility boilers. Investigation of enhanced Hg(0) oxidation by addition of hydrogen halogens (HF, HCl, HBr, and HI) was conducted in a slipstream reactor with and without SCR catalysts when burning PRB coal. Two commercial SCR catalysts were evaluated. SCR catalyst no. 1 showed higher efficiencies of both NO reduction and Hg(0) oxidation than those of SCR catalyst no. 2. NH3 addition seemed to inhibit the Hg(0) oxidation, which indicated competitive processes between NH3 reduction and Hg(0) oxidation on the surface of SCR catalysts. The hydrogen halogens, in the order of impact on Hg(0) oxidation, were HBr, HI, and HCl or HF. Addition of HBr at approximately 3 ppm could achieve 80% Hg(0) oxidation. Addition of HI at approximately 5 ppm could achieve 40% Hg(0) oxidation. In comparison to the empty reactor, 40% Hg(0) oxidation could be achieved when HCl addition was up to 300 ppm. The enhanced Hg(0) oxidation by addition of HBr and HI seemed not to be correlated to the catalytic effects by both evaluated SCR catalysts. The effectiveness of conversion of hydrogen halogens to halogen molecules or interhalogens seemed to be attributed to their impacts on Hg(0) oxidation.

Effect of halogenated impurities on lifetime of organic light emitting diode

NASA Astrophysics Data System (ADS)

Yamawaki, Hayato; Suzuki, Kunihiko; Kubota, Tomohiro; Watabe, Takeyoshi; Ishigaki, Ayumi; Nakamura, Rina; Inoue, Hideko; Nakashima, Harue; Horikoshi, Nozomi; Nowatari, Hiromi; Kataishi, Riho; Hamada, Toshiki; Sasaki, Toshiki; Suzuki, Tsunenori; Seo, Satoshi

2016-09-01

We investigated a correlation between lifetime and the halogen element concentration in an organic light-emitting diode (OLED) and conducted experiments and simulations to discuss degradation mechanisms due to the halogen. OELD is generally formed of high-purity materials. Since the synthesis of high-purity materials takes time and cost, quantitative understanding of the kind, amount, and influence of impurities in OLED devices is expected. The results of combustion ion chromatography show that, if the chlorine concentration in the host material is more than several parts per million, the lifetime of the device is drastically reduced. The chlorine element, which is derived from the chlorinated by-product of the host material, is found to be transferred from the chloride to other materials (e.g., an emissive dopant) according to the results of LC-MS analysis. In addition, the electron transport layer including such impurities is also found to adversely affect the lifetime. The results of TOF-SIMS analysis suggest that the dissociated chlorine element diffuse to the light-emitting layer side when the device is driven. The results of simulations (Gaussian 09) and electrochemical analyses (cyclic voltammetry and electrolysis) reveal that the halogen element is easy to dissociate from halide by excitation or reduction. The halogen element can repeat reactions with the peripheral materials by excitation or reduction and cause damages, e.g., generate radicals or further reaction products due to the radicals. The results of simulation suggest that, such compounds have low energy level and become quenchers.

Halogens in normal- and enriched-basalts from Central Indian Ridge (18-20°S): Testing the E-MORB subduction origin hypothesis

NASA Astrophysics Data System (ADS)

Ruzie, L.; Burgess, R.; Hilton, D. R.; Ballentine, C. J.

2012-12-01

Basalts emitted along oceanic ridges have often been subdivided into two categories: the Normal-MORB and the Enriched-MORB, anomalously enriched in highly incompatible elements. Donnelly et al. (2004) proposed that the formation of enriched sources is related to two stages of melting. The first one occurs in subduction zones where the mantle wedge is enriched by the addition of low-degree melts of subducted slab. The second stage of melting occurs beneath ocean ridges. Because of their incompatibility, relatively high concentrations and distinct elemental compositions in surface reservoirs, the heavy halogens (Cl, Br, I) are good tracers to detect the slab contribution in E-MORB sources. However, the halogen systematics in mantle reservoirs remains poorly constrained mainly because of their very low abundance in materials of interest. An innovative halogen analytical technique, developed at the University of Manchester, involving neutron irradiation of samples to convert halogens to noble gases provides detection limits unmatched by any other technique studies [Johnson et al. 2000]. For the first time Cl, Br and I can now be determined in appropriate samples. We focus on the content of halogens in the glassy margins of basalts erupted along the CIR from 18-20°S and the off-axis Gasitao Ridge. Our set of samples contains both N- and E-MORB and is fully described in terms of major and trace elements, as well as 3He/4He ratios and water concentrations [Murton et al., 2005; Nauret et al., 2006; Füri et al., 2011; Barry et al., in prep.]. The halogen concentration range is between 10 and 140 ppm for Cl, 30 and 500 ppb for Br and 0.8 and 10 ppb for I. The higher concentrations are found in E-MORB samples from the northern part of ridge axis. Comparing our data with previous halogen studies, our sample suites fall within the range of N-MORB from East Pacific Ridge (EPR) and Mid-Atlantic Ridge (MAR) [Jambon et al. 1995; Deruelle et al. 1992] and in the lower range of E-MORB from Macquarie Island [Kendrick et al., 2012]. The concentrations are not related to superficial processes. The on-axis samples display a relatively restricted range (6.9-8.6wt%) of MgO contents, suggesting no control of the crystallisation processes. The basalts were erupted between 3900-2000 m bsl, so no appreciable degassing of halogens would be expected. The strong correlation, which exists between the halogens and other incompatible elements (e.g., Rb, La), also rules out seawater assimilation. Therefore, concentrations and elemental ratios can be directly linked to melting and source features. Estimates of halogens abundances in the depleted-mantle source are 4 ppm Cl, 14 ppb Br and 0.3 ppb I. These low abundances, which are in agreement with values derived for sub-continental mantle from coated diamonds [Burgess et al., 2002], suggest that, like noble gases, the upper mantle is degassed of its halogens. Critically, the halogen elemental ratios show no significant variations along the axial ridge and off-axis ridge or between N-MORB and E-MORB: Br/Cl=0.00147±0.00014, I/Cl=0.000021±0.000005; I/Br=0.0142±0.0036. These ratios are similar to E-MORB from Macquarie Island [Kendrick et al., 2012]. This observation is thus not consistent with subduction as a source of halogen enrichment in E-MORB.

Atmosphere-Ocean Coupling through Trace Gases

NASA Astrophysics Data System (ADS)

Tegtmeier, S.; Atlas, E. L.; Krüger, K.; Lennartz, S. T.; Marandino, C. A.; Patra, P. K.; Quack, B.; Schlundt, C.

2017-12-01

Halogen- and sulfur-containing trace gases, as well as other volatile organic compounds (VOCs, such as isoprene) from biogeochemical marine sources are important constituents of the ocean and the atmosphere. These compounds exert wide-ranging influence on atmospheric chemical processes and climate interactions, as well as on human health in coastal regions. In their reactive form, they can affect the oxidizing capacity of the air and lead to the formation of new particles or the growth of existing ones. In this contribution, marine derived halogen-, sulfur-, and oxygen-containing compounds will be discussed. Their net flux into the atmosphere and their impact on atmospheric processes is analyzed based on observations and model simulations.

The Suzuki-Miyaura Cross-Coupling Reaction of Halogenated Aminopyrazoles: Method Development, Scope, and Mechanism of Dehalogenation Side Reaction.

PubMed

Jedinák, Lukáš; Zátopková, Renáta; Zemánková, Hana; Šustková, Alena; Cankař, Petr

2017-01-06

The efficient Suzuki-Miyaura cross-coupling reaction of halogenated aminopyrazoles and their amides or ureas with a range of aryl, heteroaryl, and styryl boronic acids or esters has been developed. The method allowed incorporation of problematic substrates: aminopyrazoles bearing protected or unprotected pyrazole NH, as well as the free amino or N-amide group. Direct comparison of the chloro, bromo, and iodopyrazoles in the Suzuki-Miyaura reaction revealed that Br and Cl derivatives were superior to iodopyrazoles, as a result of reduced propensity to dehalogenation. Moreover, the mechanism and factors affecting the undesired dehalogenation side reaction were revealed.

Nonthmicin, a Polyether Polyketide Bearing a Halogen-Modified Tetronate with Neuroprotective and Antiinvasive Activity from Actinomadura sp.

PubMed

Igarashi, Yasuhiro; Matsuoka, Noriaki; In, Yasuko; Kataura, Tetsushi; Tashiro, Etsu; Saiki, Ikuo; Sudoh, Yuri; Duangmal, Kannika; Thamchaipenet, Arinthip

2017-03-17

Nonthmicin (1), a new polyether polyketide bearing a chlorinated tetronic acid, was isolated from the culture extract of a soil-derived Actinomadura strain. The structure of 1 was elucidated by interpretation of NMR and MS spectroscopic data, and the absolute configuration of 1 was proposed on the basis of the crystal structure of its dechloro congener ecteinamycin (2) also isolated from the same strain. Tetronic acids modified by halogenation have never been reported from natural products. Compounds 1 and 2 were found to have neuroprotective activity and antimetastatic properties at submicromolar concentrations in addition to antibacterial activity.

Engineering of new-to-nature halogenated indigo precursors in plants.

PubMed

Fräbel, Sabine; Wagner, Bastian; Krischke, Markus; Schmidts, Volker; Thiele, Christina M; Staniek, Agata; Warzecha, Heribert

2018-03-01

Plants are versatile chemists producing a tremendous variety of specialized compounds. Here, we describe the engineering of entirely novel metabolic pathways in planta enabling generation of halogenated indigo precursors as non-natural plant products. Indican (indolyl-β-D-glucopyranoside) is a secondary metabolite characteristic of a number of dyers plants. Its deglucosylation and subsequent oxidative dimerization leads to the blue dye, indigo. Halogenated indican derivatives are commonly used as detection reagents in histochemical and molecular biology applications; their production, however, relies largely on chemical synthesis. To attain the de novo biosynthesis in a plant-based system devoid of indican, we employed a sequence of enzymes from diverse sources, including three microbial tryptophan halogenases substituting the amino acid at either C5, C6, or C7 of the indole moiety. Subsequent processing of the halotryptophan by bacterial tryptophanase TnaA in concert with a mutant of the human cytochrome P450 monooxygenase 2A6 and glycosylation of the resulting indoxyl derivatives by an endogenous tobacco glucosyltransferase yielded corresponding haloindican variants in transiently transformed Nicotiana benthamiana plants. Accumulation levels were highest when the 5-halogenase PyrH was utilized, reaching 0.93 ± 0.089 mg/g dry weight of 5-chloroindican. The identity of the latter was unambiguously confirmed by NMR analysis. Moreover, our combinatorial approach, facilitated by the modular assembly capabilities of the GoldenBraid cloning system and inspired by the unique compartmentation of plant cells, afforded testing a number of alternative subcellular localizations for pathway design. In consequence, chloroplasts were validated as functional biosynthetic venues for haloindican, with the requisite reducing augmentation of the halogenases as well as the cytochrome P450 monooxygenase fulfilled by catalytic systems native to the organelle. Thus, our study puts forward a viable alternative production platform for halogenated fine chemicals, eschewing reliance on fossil fuel resources and toxic chemicals. We further contend that in planta generation of halogenated indigoid precursors previously unknown to nature offers an extended view on and, indeed, pushes forward the established frontiers of biosynthetic capacity of plants. Copyright © 2018 International Metabolic Engineering Society. Published by Elsevier Inc. All rights reserved.

Source regions of stratospheric VSLS in the Indian Ocean

NASA Astrophysics Data System (ADS)

Quack, Birgit; Hepach, Helmke; Atlas, Elliot; Bracher, Astrid; Endres, Sonja; Arevalo-Martinez, Damian; Bange, Hermann; Lennartz, Sinikka; Steinhoff, Tobias; Booge, Dennis; Zarvasky, Alexander; Marandino, Christa; Patey, Matt; Achterberg, Eric; Dengler, Markus; Fiehn, Alina; Tegtmeier, Susann; Krüger, Kirstin

2016-04-01

Halogenated very-short-lived substances (VSLS), which are naturally produced in the ocean, play a significant role in present day ozone depletion, in particular in combination with enhanced stratospheric sulfate aerosol, which is also partly derived from oceanic VSLS. The decline of anthropogenic chlorine in the stratosphere within the 21st century will increase the relative importance of the natural emissions on stratospheric ozone destruction. Especially, oceanic sources and source regions of the compounds need to be better constrained, in order to improve the future prediction. During boreal summer the Asian monsoon circulation transports air masses from the Indian Ocean to the stratosphere, while the contribution of VSLS from this ocean to stratospheric halogen and sulfur is unknown. During the research cruises SO 234/2 and SO 235 in July-August 2014 onboard RV SONNE oceanic and atmospheric halogenated VSLS such as bromoform (CHBr3), dibromomethane (CH2Br2) and methyl iodide (CH3I) were measured in the subtropical and tropical West Indian Ocean for the first time. Here we present the oceanic sources of the halogenated compounds and their relation to other biogeochemical parameters (short- and longlived trace gases, phytoplankton and nutrients) along the cruise track, which covered coastal, upwelling and open ocean regimes and the Seychelles-Chagos thermocline ridge as important source region for stratospheric bromine.

Force Field Model of Periodic Trends in Biomolecular Halogen Bonds

PubMed Central

Scholfield, Matthew R.; Ford, Melissa Coates; Vander Zanden, Crystal M.; Billman, M. Marie; Ho, P. Shing; Rappé, Anthony K.

2016-01-01

The study of the noncovalent interaction now defined as a halogen bond (X-bond) has become one of the fastest growing areas in experimental and theoretical chemistry—its applications as a design tool are highly extensive. The significance of the interaction in biology has only recently been recognized, but has now become important in medicinal chemistry. We had previously derived a set of empirical potential energy functions to model the structure-energy relationships for bromines in biomolecular X-bonds (BXBs). Here, we have extended this force field for BXBs (ffBXB) to the halogens (Cl, Br, and I) that are commonly seen to form stable X-bonds. The ffBXB calculated energies show a remarkable one-to-one linear relationship to explicit BXB energies determined from an experimental DNA junction system, thereby validating the approach and the model. The resulting parameters allow us to interpret the stabilizing effects of BXBs in terms of well-defined physical properties of the halogen atoms, including their size, shape, and charge, showing periodic trends that are predictable along the Group VII column of elements. Consequently, we have established the ffBXB as accurate computational tool that can be applied to, for example, for the design of new therapeutic compounds against clinically important targets and new biomolecular based materials. PMID:25338128

An ab initio MO study of heavy atom effects on the zero-field splitting tensors of high-spin nitrenes: how the spin-orbit contributions are affected.

PubMed

Sugisaki, Kenji; Toyota, Kazuo; Sato, Kazunobu; Shiomi, Daisuke; Kitagawa, Masahiro; Takui, Takeji

2014-05-21

The CASSCF and the hybrid CASSCF-MRMP2 methods are applied to the calculations of spin-spin and spin-orbit contributions to the zero-field splitting tensors (D tensors) of the halogen-substituted spin-septet 2,4,6-trinitrenopyridines, focusing on the heavy atom effects on the spin-orbit term of the D tensors (D(SO) tensors). The calculations reproduced experimentally determined |D| values within an error of 15%. Halogen substitutions at the 3,5-positions are less influential in the spin-spin dipolar (D(SS)) term of 2,4,6-trinitrenopyridines, although the D(SO) terms are strongly affected by the introduction of heavier halogens. The absolute sign of the D(SO) value (D = D(ZZ) - (D(XX) + D(YY))/2) of 3,5-dibromo derivative 3 is predicted to be negative, which contradicts the Pederson-Khanna (PK) DFT result previously reported. The large negative contributions to the D(SO) value of 3 arise from the excited spin-septet states ascribed mainly to the excitations of in-plane lone pair of bromine atoms → SOMO of π nature. The importance of the excited states involving electron transitions from the lone pair orbital of the halogen atom is also confirmed in the D(SO) tensors of halogen-substituted para-phenylnitrenes. A new scheme based on the orbital region partitioning is proposed for the analysis of the D(SO) tensors as calculated by means of the PK-DFT approach.

A refined method for calculating equivalent effective stratospheric chlorine

NASA Astrophysics Data System (ADS)

Engel, Andreas; Bönisch, Harald; Ostermöller, Jennifer; Chipperfield, Martyn P.; Dhomse, Sandip; Jöckel, Patrick

2018-01-01

Chlorine and bromine atoms lead to catalytic depletion of ozone in the stratosphere. Therefore the use and production of ozone-depleting substances (ODSs) containing chlorine and bromine is regulated by the Montreal Protocol to protect the ozone layer. Equivalent effective stratospheric chlorine (EESC) has been adopted as an appropriate metric to describe the combined effects of chlorine and bromine released from halocarbons on stratospheric ozone. Here we revisit the concept of calculating EESC. We derive a refined formulation of EESC based on an advanced concept of ODS propagation into the stratosphere and reactive halogen release. A new transit time distribution is introduced in which the age spectrum for an inert tracer is weighted with the release function for inorganic halogen from the source gases. This distribution is termed the release time distribution. We show that a much better agreement with inorganic halogen loading from the chemistry transport model TOMCAT is achieved compared with using the current formulation. The refined formulation shows EESC levels in the year 1980 for the mid-latitude lower stratosphere, which are significantly lower than previously calculated. The year 1980 is commonly used as a benchmark to which EESC must return in order to reach significant progress towards halogen and ozone recovery. Assuming that - under otherwise unchanged conditions - the EESC value must return to the same level in order for ozone to fully recover, we show that it will take more than 10 years longer than estimated in this region of the stratosphere with the current method for calculation of EESC. We also present a range of sensitivity studies to investigate the effect of changes and uncertainties in the fractional release factors and in the assumptions on the shape of the release time distributions. We further discuss the value of EESC as a proxy for future evolution of inorganic halogen loading under changing atmospheric dynamics using simulations from the EMAC model. We show that while the expected changes in stratospheric transport lead to significant differences between EESC and modelled inorganic halogen loading at constant mean age, EESC is a reasonable proxy for modelled inorganic halogen on a constant pressure level.

40 CFR 65.154 - Halogen scrubbers and other halogen reduction devices.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 15 2011-07-01 2011-07-01 false Halogen scrubbers and other halogen... Routing to a Fuel Gas System or a Process § 65.154 Halogen scrubbers and other halogen reduction devices. (a) Halogen scrubber and other halogen reduction device equipment and operating requirements. (1) An...

Absolute configuration and crystal packing chirality for three conglomerate-forming ortho-halogen substituted phenyl glycerol ethers

NASA Astrophysics Data System (ADS)

Bredikhin, Alexander A.; Gubaidullin, Aidar T.; Bredikhina, Zemfira A.

2010-06-01

Three conglomerate-forming ortho-Hal (Hal = Cl, Br, I) substituted phenyl glycerol ethers 1- 3 were investigated by single-crystal X-ray analysis, and the absolute configuration for all substances was established. The molecular structures and crystal packing details for halogen derivatives were compared with the same characteristics for ortho-OCH 3 and ortho-CH 3 analogues. Two different types of crystal packing were evaluated for these very much alike compounds. The interplay of the supramolecular crystal organization chirality sense and the single molecule absolute configuration was demonstrated. Some stabilizing and destabilizing interactions involving the ortho-substituents were revealed. The resolution of rac-2 by entrainment procedure was successfully realized.

Volatile composition of microinclusions in diamonds from the Panda kimberlite, Canada: Implications for chemical and isotopic heterogeneity in the mantle

NASA Astrophysics Data System (ADS)

Burgess, Ray; Cartigny, Pierre; Harrison, Darrell; Hobson, Emily; Harris, Jeff

2009-03-01

In order to better investigate the compositions and the origins of fluids associated with diamond growth, we have carried-out combined noble gas (He and Ar), C and N isotope, K, Ca and halogen (Cl, Br, I) determinations on fragments of individual microinclusion-bearing diamonds from the Panda kimberlite, North West Territories, Canada. The fluid concentrations of halogens and noble gases in Panda diamonds are enriched by several orders of magnitude over typical upper mantle abundances. However, noble gas, C and N isotopic ratios ( 3He/ 4He = 4-6 Ra, 40Ar/ 36Ar = 20,000-30,000, δ 13C = -4.5‰ to -6.9‰ and δ 15N = -1.2‰ to -8.8‰) are within the worldwide range determined for fibrous diamonds and similar to the mid ocean ridge basalt (MORB) source value. The high 36Ar content of the diamonds (>1 × 10 -9 cm 3/g) is at least an order of magnitude higher than any previously reported mantle sample and enables the 36Ar content of the subcontinental lithospheric mantle to be estimated at ˜0.6 × 10 -12 cm 3/g, again similar to estimates for the MORB source. Three fluid types distinguished on the basis of Ca-K-Cl compositions are consistent with carbonatitic, silicic and saline end-members identified in previous studies of diamonds from worldwide sources. These fluid end-members also have distinct halogen ratios (Br/Cl and I/Cl). The role of subducted seawater-derived halogens, originally invoked to explain some of the halogen ratio variations in diamonds, is not considered an essential component in the formation of the fluids. In contrast, it is considered that large halogen fractionation of a primitive mantle ratio occurs during fluid-melt partitioning in forming silicic fluids, and during separation of an immiscible saline fluid.

Synthesis and characterization of tetra phenoxy-substituted halogen-rich metallophthalocyanine derivatives: A study on their LCD color filter requirements

NASA Astrophysics Data System (ADS)

Muthukumar, Palanisamy; Kim, Hak-Soo; Jeong, Jong Woo; Son, Young-A.

2016-09-01

This study addresses the synthesis and characterization of new tetra phenoxy-substituted halogen-rich metallophthalocyanine derivatives (MPcs) 4-7 (M = Co, Ni, Cu and Zn). The synthesized new compounds were characterized using UV-Vis, FT-IR, MALDI-TOF, 1H NMR and elemental analyses. In addition, the basic requirements such as aggregation behavior, thermal stability, transmittance and solubility in propylene glycol monomethyl ether acetate (PGMEA) of MPcs 4-7 were investigated for their usage as a green color filter in Liquid Crystal Displays (LCDs). All of the MPcs showed thermal stability and sufficient solubility in PGMEA. However, the addition of binder into PGMEA solution of MPcs 5 and 6 leads to precipitation. Among the four MPcs, zinc phthalocyanine (7) showed higher transmittance. The higher transmittance of zinc phthalocyanine (7) along with its thermal stability and sufficient solubility in PGMEA are promising for its application as a green color filter in LCDs.

40 CFR 63.994 - Halogen scrubbers and other halogen reduction devices.

Code of Federal Regulations, 2012 CFR

2012-07-01

... halogen scrubber or other halogen reduction technique used to reduce the vent stream halogen atom mass... subpart shall determine the halogen atom mass emission rate prior to the combustion device according to...

40 CFR 63.994 - Halogen scrubbers and other halogen reduction devices.

Code of Federal Regulations, 2014 CFR

2014-07-01

... halogen scrubber or other halogen reduction technique used to reduce the vent stream halogen atom mass... subpart shall determine the halogen atom mass emission rate prior to the combustion device according to...

40 CFR 63.994 - Halogen scrubbers and other halogen reduction devices.

Code of Federal Regulations, 2010 CFR

2010-07-01

... halogen scrubber or other halogen reduction technique used to reduce the vent stream halogen atom mass... subpart shall determine the halogen atom mass emission rate prior to the combustion device according to...

40 CFR 63.994 - Halogen scrubbers and other halogen reduction devices.

Code of Federal Regulations, 2013 CFR

2013-07-01

... halogen scrubber or other halogen reduction technique used to reduce the vent stream halogen atom mass... subpart shall determine the halogen atom mass emission rate prior to the combustion device according to...

40 CFR 63.994 - Halogen scrubbers and other halogen reduction devices.

Code of Federal Regulations, 2011 CFR

2011-07-01

... halogen scrubber or other halogen reduction technique used to reduce the vent stream halogen atom mass... subpart shall determine the halogen atom mass emission rate prior to the combustion device according to...

Donor impurity incorporation during layer growth of Zn II-VI semiconductors

NASA Astrophysics Data System (ADS)

Barlow, D. A.

2017-12-01

The maximum halogen donor concentration in Zn II-VI semiconductors during layer growth is studied using a standard model from statistical mechanics. Here the driving force for incorporation is an increase in entropy upon mixing of the donor impurity into the available anion lattice sites in the host binary. A formation energy opposes this increase and thus equilibrium is attained at some maximum concentration. Considering the halogen donor impurities within the Zn II-VI binary semiconductors ZnO, ZnS, ZnSe and ZnTe, a heat of reaction obtained from reported diatomic bond strengths is shown to be directly proportional to the log of maximum donor concentration. The formation energy can then be estimated and an expression for maximum donor concentration derived. Values for the maximum donor concentration with each of the halogen impurities, within the Zn II-VI compounds, are computed. This model predicts that the halogens will serve as electron donors in these compounds in order of increasing effectiveness as: F, Br, I, Cl. Finally, this result is taken to be equivalent to an alternative model where donor concentration depends upon impurity diffusion and the conduction band energy shift due to a depletion region at the growing crystal's surface. From this, we are able to estimate the diffusion activation energy for each of the impurities mentioned above. Comparisons are made with reported values and relevant conclusions presented.

Theoretical studies of weak interactions of formamide with methanol and its derivates

NASA Astrophysics Data System (ADS)

Zheng, Xiao-Wen; Wang, Lu; Han, Shu-Min; Cui, Xiang-Yang; Du, Chong-Yang; Liu, Tao

2015-08-01

Theoretical calculations have been performed for the complexes of formamide (FA) with methanol and its derivates (MAX, X = F, Cl, Br, NO2, H, OH, CH3, and NH2) to study their structures and properties. Substituent effects on the hydrogen bond (H-bond) strength and cooperative effect by using water and its derivatives (HOZ, Z = H, NH2, and Br) as weak interaction probe were also explored. The calculation results show that electron-donating groups strengthen the weak interaction between formamide with methanol whereas electron-withdrawing groups weaken it. The cooperativity is present for the N-HïO H-bond in MAX-FA-HOZ and the cooperative effect increases in a series HONH2, HOH, and HOBr. In addition, we investigated the interaction between FA with hypohalous acids HOY (Y = F, Cl, and Br). It was found that the weak interaction between FA and HOY became stronger with the increase of the size of halogen atom. The nature of the halogen atom has negligible impact on the strength of the H-bond in MAX-FA (X = F, Cl, and Br), whereas it has an obvious influence on the strength of the H-bond in HOY-FA (Y = F, Cl, and Br).

Synthesis and in vitro biological evaluation of novel coumarin derivatives containing isoxazole moieties on melanin synthesis in B16 cells and inhibition on bacteria.

PubMed

Pang, Guang Xian; Niu, Chao; Mamat, Nuramina; Aisa, Haji Akber

2017-06-15

A novel series of coumarin derivatives 6a-o, bearing isoxazole moieties were designed and synthesized. After that, they were evaluated for melanin synthesis in murine B16 cells and inhibitory effect on the growth of CA (Candida albicans), EC (Escherichia coli), SA (Staphylococcus aureus). It was found that eleven compounds (6b-f, 6j-o) showed a better activity on melanin synthesis than positive control (8-MOP). Among them, compounds 6d (242%) and 6f (390%), with nearly 1.6 and 2.6-fold potency compared with 8-MOP (149%) respectively, were recognized as the most promising candidate hits for further pharmacological study of anti-vitiligo. Seven halogen substituted compounds exhibited moderate antimicrobial activity against CA. It is interesting that 6e-f and 6l-m, which had two halogens on the benzene showed a comparable activity with Amphotericin B against CA. The evaluation of melanin synthesis in B16 cells and inhibitory effect on bacteria of above structurally diverse derivatives had also led to an outline of structure-activity relationship. Copyright © 2017 Elsevier Ltd. All rights reserved.

Monohalogenated maleimides as potential agents for the inhibition of Pseudomonas aeruginosa biofilm.

PubMed

Carteau, David; Soum-Soutéra, Emmanuelle; Faÿ, Fabienne; Dufau, Chrystèle; Cérantola, Stéphane; Vallée-Réhel, Karine

2010-01-01

New monohalogenated maleimide derivatives (with bromine, chlorine or iodine) were synthesized to test the effect of halogen atoms in inhibiting the formation of Pseudomonas aeruginosa biofilm. The evaluation of their biological activities clearly defines a structure-activity relationship. In this study, the bactericidal action of the three compounds was observed at the concentration range 0.3-5.0 mM on Luria-Bertani agar plates. The halogen atom of these molecules was critical in modulating the antibacterial activity, with a slightly higher effectiveness for chlorine. Confocal laser scanning microscopy was used to examine P. aeruginosa biofilms cultivated in flow cells. At concentration as low as 40 microM, the bromine and iodine compounds displayed a total inhibition towards the formation of bacterial biofilm. At this concentration, the bacterial attachment to glass surfaces was strongly affected by the presence of bromine and iodine whereas the chlorine derivative behaved as a bactericidal compound. A bioluminescent reporter strain was then used to detect the effect of the chemically synthesized maleimides on quorum sensing (QS) in P. aeruginosa. At the concentration range 10-100 microM, bioluminescence assays reveal that halogenated maleimides were able to interfere with the QS of the bacterium. Although the relationship between the weak inhibition of cell-to-cell communication (15-55% of the signal) and the high inhibition of biofilm formation has not been elucidated clearly, the results demonstrate that bromo- and iodo-N-substituted maleimides bromine and iodine may be used as new potent inhibitors that control bacterial biofilms.

Synthesis and Characterization of New Poly(alkyl/arylphosphazenes)

DTIC Science & Technology

1991-11-26

substituted (silylamino) phosphines , 7, (eq 4) in good yields as thermally stable, distillable liquids. Subsequent oxidative halogenation to 8a, followed by...have been prepared simply by treating the anion with aldehydes or ketones, including those with potentially electroactive groups such as ferrocene 2 1...i.e., x:y = 2:1), but is as high as 45% for the ferrocene and thiophene derivatives. The T values of the alcohol derivatives show the expected

Method and apparatus for vapor detection

NASA Technical Reports Server (NTRS)

Lerner, Melvin (Inventor); Hood, Lyal V. (Inventor); Rommel, Marjorie A. (Inventor); Pettitt, Bruce C. (Inventor); Erikson, Charles M. (Inventor)

1980-01-01

The method disclosed herein may be practiced by passing the vapors to be sampled along a path with halogen vapor, preferably chlorine vapor, heating the mixed vapors to halogenate those of the sampled vapors subject to halogenation, removing unreacted halogen vapor, and then sensing the vapors for organic halogenated compounds. The apparatus disclosed herein comprises means for flowing the vapors, both sample and halogen vapors, into a common path, means for heating the mixed vapors to effect the halogenation reaction, means for removing unreacted halogen vapor, and a sensing device for sensing halogenated compounds. By such a method and means, the vapors of low molecular weight hydrocarbons, ketones and alcohols, when present, such as methane, ethane, acetone, ethanol, and the like are converted, at least in part, to halogenated compounds, then the excess halogen removed or trapped, and the resultant vapors of the halogenated compounds sensed or detected. The system is highly sensitive. For example, acetone in a concentration of 30 parts per billion (volume) is readily detected.

Halogen speciation in volcanic plumes - Development of compact denuder sampling techniques with in-situ derivatization followed by gas chromatography-mass spectrometry and their application at Mt. Etna, Mt. Nyiragongo and Mt. Nyamulagira in 2015.

NASA Astrophysics Data System (ADS)

Rüdiger, Julian; Bobrowski, Nicole; Hoffmann, Thorsten

2016-04-01

Volcanoes are a large source for several reactive atmospheric trace gases including sulfur and halogen containing species. The detailed knowledge of volcanic plume chemistry can give insights into subsurface processes and can be considered as a useful geochemical tool for monitoring of volcanic activity, especially halogen to sulfur ratios (e.g. Bobrowski and Giuffrida, 2012; Donovan et al., 2014). The reactive bromine species bromine monoxide (BrO) is of particular interest, because BrO as well as SO2 are readily measurable by UV spectrometer at a safe distance. Furthermore it is formed in the plume by a multiphase reaction mechanism under depletion of ozone in the plume. The abundance of BrO changes as a function of the reaction time and therefore distance from the vent as well as the spatial position in the plume. The precursor substance for the formation of BrO is HBr with Br2as an intermediate product. The reaction of HBr to BrO involves heterogeneous reactions involving aerosol particles, while Br2 reacts directly with O3 to form BrO in a UV radiation induced mechanism. Due to the lack of analytical approaches for the species analysis of halogens (HBr, Br2, Br, BrCl, HOBr) there are still uncertainties about the magnitude of volcanic halogen emissions and in particular their speciation and therefore also in the understanding of the bromine chemistry in volcanic plumes (Bobrowski et al., 2007). In this study a gas diffusion denuder sampling method using a 1,3,5-trimethoxybenzene (1,3,5-TMB) coating for the derivatization of reactive halogen species (Rüdiger et al., 2015) was characterized by reaction chamber experiments. The coating proved to be suitable to collect selectively gaseous bromine species with oxidation states of +1 or 0 (such as Br2, BrCl, BrO(H) and BrONO2), while being ignorant to HBr (OS -1). The reaction of 1,3,5-TMB with reactive bromine species gives 1-bromo-2,4,6-trimethoxybenzene (1-bromo-2,4,6-TMB) - other halogens give corresponding products. The diffusion denuder technique allows sampling of gaseous compounds exclusively without collecting particulate matter. Solvent elution of the derivatized analytes and subsequent analysis with gas chromatography-mass spectrometry gives a limit of detection below 1 ng of bromine. The method was applied in 2015 on volcanic gas plumes at Mt. Etna (Italy), Mt. Nyiragongo and Mt. Nyamulagira (DR Congo) giving reactive bromine mixing ratios from 0.3 ppb (Nyiragongo) up to 22 ppb (Etna, NEC). Compared with total halogen data derived by alkaline trap sampling (Raschig-tube) and ion-chromatography analysis the reactive bromine mixing ratios allow the investigation of the conversion of HBr into reactive species due to plume chemistry with progressing plume age. The new method will be described in detail and the first results on the reactive halogen to total halogen output will be discussed (for bromine and chlorine) and compared to earlier volcanic plume chemistry model studies. References Bobrowski, N. and G. Giuffrida: Bromine monoxide / sulphur dioxide ratios in relation to volcanological observations at Mt. Etna 2006-2009. Solid Earth, 3, 433-445, 2012 Bobrowski, N., R. von Glasow, A. Aiuppa, S. Inguaggiato, I. Louban, O. W. Ibrahim and U. Platt: Reactive halogen chemistry in volcanic plumes. J. Geophys. Res., 112, 2007 Donovan A., V. Tsanev, C. Oppenheimer and M. Edmonds: Reactive halogens (BrO and OClO) detected in the plume of Soufrière Hills Volcano during an eruption hiatus. Geochem. Geophys. Geosyst., 15, 3346-3363, 2014 Rüdiger, J., N. Bobrowski, T. Hoffmann (2015), Development and application of compact denuder sampling techniques with in situ derivatization followed by gas chromatography-mass spectrometry for halogen speciation in volcanic plumes (EGU2015-2392-2), EGU General Assembly 2015

Cloning and characterization of a novel amidase from Paracoccus sp. M-1, showing aryl acylamidase and acyl transferase activities.

PubMed

Shen, Weiliang; Chen, Honghong; Jia, Kaizhi; Ni, Jun; Yan, Xin; Li, Shunpeng

2012-05-01

A novel amidase gene, designated pamh, was cloned from Paracoccus sp. M-1. Site-directed mutagenesis and bioinformatic analysis showed that the PamH protein belonged to the amidase signature enzyme family. PamH was expressed in Escherichia coli, purified, and characterized. The molecular mass of PamH was determined to be 52 kDa with an isoelectric point of 5.13. PamH displayed its highest enzymatic activity at 45°C and at pH 8.0 and was stable within a pH range of 5.0-10.0. The PamH enzyme exhibited amidase activity, aryl acylamidase activity, and acyl transferase activity, allowing it to function across a very broad substrate spectrum. PamH was highly active on aromatic and short-chain aliphatic amides (benzamide and propionamide), moderately active on amino acid amides, and possessed weak urease activity. Of the anilides examined, only propanil was a good substrate for PamH. For propanil, the k (cat) and K (m) were 2.8 s(-1) and 158 μM, respectively, and the catalytic efficiency value (k (cat)/K (m)) was 0.018 μM(-1) s(-1). In addition, PamH was able to catalyze the acyl transfer reaction to hydroxylamine for both amide and anilide substrates, including acetamide, propanil, and 4-nitroacetanilide; the highest reaction rate was shown with isobutyramide. These characteristics make PamH an excellent candidate for environmental remediation and an important enzyme for the biosynthesis of novel amides.

Structure-toxicity relationship study of para-halogenated styrene analogues in CYP2E1 transgenic cells

PubMed Central

Chung, Jou-Ku; Shen, Shuijie; Jiang, Zhiteng; Yuan, Wei; Zheng, Jiang

2012-01-01

Styrene is one of the most important industrial intermediates consumed in the world and is mainly used as a monomer for reinforced plastics and rubber. Styrene has been found to be hepatotoxic and pneumotoxic in humans and experimental animals. The toxicity of styrene is suggested to be metabolism-dependent. Styrene-7,8-oxide has been considered as the major metabolite responsible for styrene-induced cytotoxicity. The objective of the study was to investigate the correlation between cytotoxicity of styrene and chemical and biochemical properties of the vinyl group of styrene by development of structure activity relationships (SAR). 4-Fluorostyrene, 4-chlorostyrene and 4-bromostyrene were selected for the SAR study. Cytotoxicity of styrene and the halogenated styrene derivatives with an order of 4-bromostyrene > 4-chlorostyrene > 4-fluorostyrene ≈ styrene was observed in CYP2E1 transgenic cells. Similar orders in the efficiency of the metabolism of styrene and the halogenated styrene analogues to their oxides and in the electrophilicity of the corresponding oxides were observed. Additionally, the order of the potency of cellular glutathione depletion and the degree of protein adduction induced by styrene and the halogenated styrenes were consistent with that of their cytotoxicities. The wild-type cells were less susceptible to the toxicity of the corresponding model compounds than CYP2E1 cells. The present study provided insight into the roles of the biochemical and chemical properties of styrene in its cytotoxicity. PMID:22366341

Process for removal of hydrogen halides or halogens from incinerator gas

DOEpatents

Huang, Hann S.; Sather, Norman F.

1988-01-01

A process for reducing the amount of halogens and halogen acids in high temperature combustion gases and through their removal, the formation of halogenated organics at lower temperatures, with the reduction being carried out electrochemically by contacting the combustion gas with the negative electrode of an electrochemical cell and with the halogen and/or halogen acid being recovered at the positive electrode.

Process for removal of hydrogen halides or halogens from incinerator gas

DOEpatents

Huang, H.S.; Sather, N.F.

1987-08-21

A process for reducing the amount of halogens and halogen acids in high temperature combustion gas and through their removal, the formation of halogenated organics at lower temperatures, with the reduction being carried out electrochemically by contacting the combustion gas with the negative electrode of an electrochemical cell and with the halogen and/or halogen acid being recovered at the positive electrode.

Is halogen content the most important factor in the removal of halogenated trace organics by MBR treatment?

PubMed

Hai, Faisal I; Tadkaew, Nichanan; McDonald, James A; Khan, Stuart J; Nghiem, Long D

2011-05-01

This study investigated the relationship between physicochemical properties (namely halogen content and hydrophobicity) of halogenated trace organics and their removal efficiencies by a laboratory scale membrane bioreactor (MBR) under stable operating conditions. The reported results demonstrated a combined effect of halogen content and hydrophobicity on the removal. Compounds with high halogen content (>0.3) were well removed (>85%) when they possessed high hydrophobicity (Log D>3.2), while those with lower Log D values were also well removed if they had low halogen content (<0.1). General indices such as the BIOWIN index (which is based on only biodegradation) or a more specific index such as the halogen content (which captures a chemical aspect) appeared insufficient to predict the removal efficiency of halogenated compounds in MBR. Experimental data confirmed that the ratio of halogen content and Log D, which incorporates two important physico-chemical properties, is comparatively more suitable. Copyright © 2011 Elsevier Ltd. All rights reserved.

Indomethacin Analogs: Synthesis and Anti-inflammatory and Analgesic Activities of Indoline Derivatives.

PubMed

Amin, Mohamed M; Shaaban, Mohamed R; Al-Qurashi, Nadia T; Mahmoud, Huda K; Farghaly, Thoraya A

2018-03-29

Short reaction time and high yield was achieved for the synthesis of new hydrazonoindolines having thiazole moiety under microwave irradiation via the reaction of hydrazonoyl chlorides or halogenated activemethylene derivatives with thiosemicarbazone derivatives. Also, the utility of the versatile indoline-2,3-dione derivatives in the design of new multifunctional building blocks using condensation with hydrazine derivatives was demonstrated. The information derived from the spectral data of the formed compounds were confirmed their structures. Also, the analgesic and anti-inflammatory activities of the designed derivatives were screened and the results obtained indicated that six derivatives 4g, 9b, 4c, 10b, 4d and 11a revealed the highest anti-inflammatory and analgesic effects. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Electrochemical oxidation of tramadol in low-salinity reverse osmosis concentrates using boron-doped diamond anodes.

PubMed

Lütke Eversloh, Christian; Schulz, Manoj; Wagner, Manfred; Ternes, Thomas A

2015-04-01

The electrochemical treatment of low-salinity reverse osmosis (RO) concentrates was investigated using tramadol (100 μM) as a model substance for persistent organic contaminants. Galvanostatic degradation experiments using boron-doped diamond electrodes at different applied currents were conducted in RO concentrates as well as in ultra-pure water containing either sodium chloride or sodium sulfate. Kinetic investigations revealed a significant influence of in-situ generated active chlorine besides direct anodic oxidation. Therefore, tramadol concentrations decreased more rapidly at elevated chloride content. Nevertheless, reduction of total organic carbon (TOC) was found to be comparatively low, demonstrating that transformation rather than mineralization was taking place. Early stage product formation could be attributed to both direct and indirect processes, including demethylation, hydroxylation, dehydration, oxidative aromatic ring cleavage and halogenation reactions. The latter led to various halogenated derivatives and resulted in AOX (adsorbable organic halogens) formation in the lower mg/L-range depending on the treatment conditions. Characterisation of transformation products (TPs) was achieved via MS(n) experiments and additional NMR measurements. Based on identification and quantification of the main TPs in different matrices and on additional potentiostatic electrolysis, a transformation pathway was proposed. Copyright © 2014 Elsevier Ltd. All rights reserved.

Transition from metal-ligand bonding to halogen bonding involving a metal as halogen acceptor a study of Cu, Ag, Au, Pt, and Hg complexes

NASA Astrophysics Data System (ADS)

Oliveira, Vytor; Cremer, Dieter

2017-08-01

Utilizing all-electron Dirac-exact relativistic calculations with the Normalized Elimination of the Small Component (NESC) method and the local vibrational mode approach, the transition from metal-halide to metal halogen bonding is determined for Au-complexes interacting with halogen-donors. The local stretching force constants of the metal-halogen interactions reveal a smooth transition from weak non-covalent halogen bonding to non-classical 3-center-4-electron bonding and finally covalent metal-halide bonding. The strongest halogen bonds are found for dialkylaurates interacting with Cl2 or FCl. Differing trends in the intrinsic halogen-metal bond strength, the binding energy, and the electrostatic potential are explained.

Treatment System for Removing Halogenated Compounds from Contaminated Sources

NASA Technical Reports Server (NTRS)

Clausen, Christian A. (Inventor); Yestrebsky, Cherie L. (Inventor); Quinn, Jacqueline W. (Inventor)

2015-01-01

A treatment system and a method for removal of at least one halogenated compound, such as PCBs, found in contaminated systems are provided. The treatment system includes a polymer blanket for receiving at least one non-polar solvent. The halogenated compound permeates into or through a wall of the polymer blanket where it is solubilized with at least one non-polar solvent received by said polymer blanket forming a halogenated solvent mixture. This treatment system and method provides for the in situ removal of halogenated compounds from the contaminated system. In one embodiment, the halogenated solvent mixture is subjected to subsequent processes which destroy and/or degrade the halogenated compound.

Effect of halogen dopants on the properties of Li2O2: is chloride special?

PubMed

Cortes, Henry A; Vildosola, Verónica L; Barral, María Andrea; Corti, Horacio R

2018-05-18

There is consensus on the fact that one of the main limitations of Li air batteries (LABs) is the insulating character of Li2O2 and that it becomes crucial to explore new conduction paths. Recent studies indicate that doping with chloride increases the ion conductivity of Li2O2, although to a much lesser extent than expected if chloride is assumed to be a donor dopant [Gerbig et al., Adv. Mater., 2013, 25, 3129]. Subsequently, it has been shown that the addition of lithium chloride, LiCl, to the battery electrolyte increases its discharge capacity, while this effect is not observed with other halogens [Matsuda et al., J. Phys. Chem. C, 2016, 120, 13360]. This fact was attributed to an increase in the conductivity of Cl-doped Li2O2, but still the responsible mechanism is not clear. In this work, we have performed first principle calculations to study the effect of the different halogens (F, Cl, Br, I) as substitutional defects on the electronic and transport properties of Li2O2. We have calculated the formation energies of the different defects and impurities and we analysed how they affect the activation barriers and diffusion coefficients. We have demonstrated that the chloride does not behave like a donor dopant, thus explaining the meager increase of the ionic conductivity experimentally observed, and neither does it promote polaron formation and mobility. We have also found that chloride does not present any special behaviour among the halogen series. Our results reveal that all the studied configurations associated with the halogen defects do not derive metallic states nor extra polarons that would increase considerably the electronic conductivity. This is mainly due to the ionic characteristics of the Li2O2 crystal and the capability of the oxygen dimers to adapt its valence rather than to the nature of the dopant itself.

Comment on "Cosmic-ray-driven reaction and greenhouse effect of halogenated molecules: Culprits for atmospheric ozone depletion and global climate change"

NASA Astrophysics Data System (ADS)

Müller, Rolf; Grooß, Jens-Uwe

2014-04-01

Lu's "cosmic-ray-driven electron-induced reaction (CRE) theory" is based on the assumption that the CRE reaction of halogenated molecules (e.g., chlorofluorocarbons (CFCs), HCl, ClONO2) adsorbed or trapped in polar stratospheric clouds in the winter polar stratosphere is the key step in forming photoactive halogen species that are the cause of the springtime ozone hole. This theory has been extended to a warming theory of halogenated molecules for climate change. In this comment, we discuss the chemical and physical foundations of these theories and the conclusions derived from the theories. First, it is unclear whether the loss rates of halogenated molecules induced by dissociative electron attachment (DEA) observed in the laboratory can also be interpreted as atmospheric loss rates, but even if this were the case, the impact of DEA-induced reactions on polar chlorine activation and ozone loss in the stratosphere is limited. Second, we falsify several conclusions that are reported on the basis of the CRE theory: There is no polar ozone loss in darkness, there is no apparent 11-year periodicity in polar total ozone measurements, the age of air in the polar lower stratosphere is much older than 1-2 years, and the reported detection of a pronounced recovery (by about 20-25%) in Antarctic total ozone measurements by the year 2010 is in error. There are also conclusions about the future development of sea ice and global sea level which are fundamentally flawed because Archimedes' principle is neglected. Many elements of the CRE theory are based solely on correlations between certain datasets which are no substitute for providing physical and chemical mechanisms causing a particular behavior noticeable in observations. In summary, the CRE theory cannot be considered as an independent, alternative mechanism for polar stratospheric ozone loss and the conclusions on recent and future surface temperature and global sea level change do not have a physical basis.

Anti-human immunodeficiency virus (HIV) activities of halogenated gomisin J derivatives, new nonnucleoside inhibitors of HIV type 1 reverse transcriptase.

PubMed

Fujihashi, T; Hara, H; Sakata, T; Mori, K; Higuchi, H; Tanaka, A; Kaji, H; Kaji, A

1995-09-01

Halogenated gomisin J (a derivative of lignan compound), represented by the bromine derivative 1506 [(6R, 7S, S-biar)-4,9-dibromo-3,10-dihydroxy-1,2,11,12-tetramethoxy-6, 7-dimethyl-5,6,7,8- tetrahydrodibenzo[a,c]cyclo-octene], was found to be a potent inhibitor of the cytopathic effects of human immunodeficiency virus type 1 (HIV-1) on MT-4 human T cells (50% effective dose, 0.1 to 0.5 microM). Gomisin J derivatives were active in preventing p24 production from acutely HIV-1-infected H9 cells. The selective indices (toxic dose/effective dose) of these compounds were as high as > 300 in some systems. 1506 was active against 3'-azido-3'-deoxythymidine-resistant HIV-1 and acted synergistically with AZT and 2',3'-ddC. 1506 inhibited HIV-1 reverse transcriptase (RT) in vitro but not HIV-1 protease. From the time-of-addition experiment, 1506 was found to inhibit the early phase of the HIV life cycle. A 1506-resistant HIV mutant was selected and shown to possess a mutation within the RT-coding region (at position 188 [Tyr to Leu]). The mutant RT expressed in Escherichia coli was resistant to 1506 in the in vitro RT assay. Some of the HIV strains resistant to other nonnucleoside HIV-1 RT inhibitors were also resistant to 1506. Comparison of various gomisin J derivatives with gomisin J showed that iodine, bromine, and chlorine in the fourth and ninth positions increased RT inhibitory activity as well as cytoprotective activity.

Detection of Aryl Hydrocarbon Receptor Activation by Some Chemicals in Food Using a Reporter Gene Assay

PubMed Central

Amakura, Yoshiaki; Tsutsumi, Tomoaki; Yoshimura, Morio; Nakamura, Masafumi; Handa, Hiroshi; Matsuda, Rieko; Teshima, Reiko; Watanabe, Takahiro

2016-01-01

The purpose of this study was to examine whether a simple bioassay used for the detection of dioxins (DXNs) could be applied to detect trace amounts of harmful DXN-like substances in food products. To identify substances with possible DXN-like activity, we assessed the ability of various compounds in the environment to bind the aryl hydrocarbon receptor (AhR) that binds specifically to DXNs. The compounds tested included 19 polycyclic aromatic hydrocarbons (PAHs), 20 PAH derivatives (nitrated, halogenated, and aminated derivatives), 23 pesticides, six amino acids, and eight amino acid metabolites. The AhR binding activities (AhR activity) of these compounds were measured using the chemical activated luciferase gene expression (CALUX) reporter gene assay system. The majority of the PAHs exhibited marked AhR activity that increased in a concentration-dependent manner. Furthermore, there was a positive link between AhR activity and the number of aromatic rings in the PAH derivatives. Conversely, there appeared to be a negative correlation between AhR activity and the number of chlorine residues present on halogenated PAH derivatives. However, there was no correlation between AhR activity and the number and position of substituents among nitrated and aminated derivatives. Among the pesticides tested, the indole-type compounds carbendazim and thiabendazole showed high levels of activity. Similarly, the indole compound tryptamine was the only amino acid metabolite to induce AhR activity. The results are useful in understanding the identification and characterization of AhR ligands in the CALUX assay. PMID:28231110

Synthesis, characterization and biological approach of metal chelates of some first row transition metal ions with halogenated bidentate coumarin Schiff bases containing N and O donor atoms.

PubMed

Prabhakara, Chetan T; Patil, Sangamesh A; Toragalmath, Shivakumar S; Kinnal, Shivashankar M; Badami, Prema S

2016-04-01

The impregnation of halogen atoms in a molecule is an emerging trend in pharmaceutical chemistry. The presence of halogens (Cl, Br, I and F) increases the lipophilic nature of molecule and improves the penetration of lipid membrane. The presence of electronegative halogen atoms increases the bio- activity of core moiety. In the present study, Co(II), Ni(II) and Cu(II) complexes are synthesised using Schiff bases (HL(I) and HL(II)), derived from 8-formyl-7-hydroxy-4-methylcoumarin/3-chloro-8-formyl-7-hydroxy-4-methylcoumarin with 2,4-difluoroaniline/o-toluidine respectively. The synthesized compounds were characterized by spectral (IR, NMR, UV-visible, Mass, ESI-MS, ESR), thermal, fluorescence and molar conductivity studies. All the synthesized metal complexes are completely soluble in DMF and DMSO. The non-electrolytic nature of the metal complexes was confirmed by molar conductance studies. Elemental analysis study suggest [ML2(H2O)2] stoichiometry, here M=Co(II), Ni(II) and Cu(II), L=deprotonated ligand. The obtained IR data supports the binding of metal ion to Schiff base. Thermal study suggests the presence of coordinated water molecules. Electronic spectral results reveal six coordinated geometry for the synthesized metal complexes. The Schiff bases and their metal complexes were evaluated for antibacterial (Pseudomonas aureginosa and Proteus mirabilis), antifungal (Aspergillus niger and Rhizopus oryzae), anthelmintic (Pheretima posthuma) and DNA cleavage (Calf Thymus DNA) activities. Copyright © 2016 Elsevier B.V. All rights reserved.

A new class of halogen bonds that avoids the σ-hole

NASA Astrophysics Data System (ADS)

Zhang, Yu; Ma, Ning; Wang, Weizhou

2012-04-01

A new class of halogen bonds of the type X = Hal⋯Y has been investigated by using the density functional theory calculations. The strength of this new class of halogen bonds is in the range of 90-120 kcal/mol, which is greatly larger than that of the conventional halogen bond of the type X-Hal⋯Y. The geometry of this new class of halogen bonds is not determined by the halogen's positive σ-hole. Natural bond orbital analysis shows it is the n → π∗ interaction that determines the geometry of this new class of halogen bonds. Experimental results are in good agreement with the theoretical predictions.

The Halogen Bond in the Design of Functional Supramolecular Materials: Recent Advances

PubMed Central

2013-01-01

Halogen bonding is an emerging noncovalent interaction for constructing supramolecular assemblies. Though similar to the more familiar hydrogen bonding, four primary differences between these two interactions make halogen bonding a unique tool for molecular recognition and the design of functional materials. First, halogen bonds tend to be much more directional than (single) hydrogen bonds. Second, the interaction strength scales with the polarizability of the bond-donor atom, a feature that researchers can tune through single-atom mutation. In addition, halogen bonds are hydrophobic whereas hydrogen bonds are hydrophilic. Lastly, the size of the bond-donor atom (halogen) is significantly larger than hydrogen. As a result, halogen bonding provides supramolecular chemists with design tools that cannot be easily met with other types of noncovalent interactions and opens up unprecedented possibilities in the design of smart functional materials. This Account highlights the recent advances in the design of halogen-bond-based functional materials. Each of the unique features of halogen bonding, directionality, tunable interaction strength, hydrophobicity, and large donor atom size, makes a difference. Taking advantage of the hydrophobicity, researchers have designed small-size ion transporters. The large halogen atom size provided a platform for constructing all-organic light-emitting crystals that efficiently generate triplet electrons and have a high phosphorescence quantum yield. The tunable interaction strengths provide tools for understanding light-induced macroscopic motions in photoresponsive azobenzene-containing polymers, and the directionality renders halogen bonding useful in the design on functional supramolecular liquid crystals and gel-phase materials. Although halogen bond based functional materials design is still in its infancy, we foresee a bright future for this field. We expect that materials designed based on halogen bonding could lead to applications in biomimetics, optics/photonics, functional surfaces, and photoswitchable supramolecules. PMID:23805801

Halogen Chemistry in the CMAQ Model

EPA Science Inventory

Halogens (iodine and bromine) emitted from oceans alter atmospheric chemistry and influence atmospheric ozone mixing ratio. We previously incorporated a representation of detailed halogen chemistry and emissions of organic and inorganic halogen species into the hemispheric Commun...

Method of dehalogenation using diamonds

DOEpatents

Farcasiu, Malvina; Kaufman, Phillip B.; Ladner, Edward P.; Anderson, Richard R.

2000-01-01

A method for preparing olefins and halogenated olefins is provided comprising contacting halogenated compounds with diamonds for a sufficient time and at a sufficient temperature to convert the halogenated compounds to olefins and halogenated olefins via elimination reactions.

Method of producing nano-scaled graphene and inorganic platelets and their nanocomposites

DOEpatents

Jang, Bor Z [Centerville, OH; Zhamu, Aruna [Centerville, OH

2011-02-22

Disclosed is a method of exfoliating a layered material (e.g., graphite and graphite oxide) to produce nano-scaled platelets having a thickness smaller than 100 nm, typically smaller than 10 nm, and often between 0.34 nm and 1.02 nm. The method comprises: (a) subjecting the layered material in a powder form to a halogen vapor at a first temperature above the melting point or sublimation point of the halogen at a sufficient vapor pressure and for a duration of time sufficient to cause the halogen molecules to penetrate an interlayer space of the layered material, forming a stable halogen-intercalated compound; and (b) heating the halogen-intercalated compound at a second temperature above the boiling point of the halogen, allowing halogen atoms or molecules residing in the interlayer space to exfoliate the layered material to produce the platelets. Alternatively, rather than heating, step (a) is followed by a step of dispersing the halogen-intercalated compound in a liquid medium which is subjected to ultrasonication for exfoliating the halogen-intercalated compound to produce the platelets, which are dispersed in the liquid medium. The halogen can be readily captured and re-used, thereby significantly reducing the impact of halogen to the environment. The method can further include a step of dispersing the platelets in a polymer or monomer solution or suspension as a precursor step to nanocomposite fabrication.

Method of producing nano-scaled graphene and inorganic platelets and their nanocomposites

DOEpatents

Jang, Bor Z [Centerville, OH; Zhamu, Aruna [Centerville, OH

2012-02-14

Disclosed is a method of exfoliating a layered material (e.g., graphite and graphite oxide) to produce nano-scaled platelets having a thickness smaller than 100 nm, typically smaller than 10 nm, and often between 0.34 nm and 1.02 nm. The method comprises: (a) subjecting the layered material in a powder form to a halogen vapor at a first temperature above the melting point or sublimation point of the halogen at a sufficient vapor pressure and for a duration of time sufficient to cause the halogen molecules to penetrate an interlayer space of the layered material, forming a stable halogen-intercalated compound; and (b) heating the halogen-intercalated compound at a second temperature above the boiling point of the halogen, allowing halogen atoms or molecules residing in the interlayer space to exfoliate the layered material to produce the platelets. Alternatively, rather than heating, step (a) is followed by a step of dispersing the halogen-intercalated compound in a liquid medium which is subjected to ultrasonication for exfoliating the halogen-intercalated compound to produce the platelets, which are dispersed in the liquid medium. The halogen can be readily captured and re-used, thereby significantly reducing the impact of halogen to the environment. The method can further include a step of dispersing the platelets in a polymer or monomer solution or suspension as a precursor step to nanocomposite fabrication.

Biosynthesis of coral settlement cue tetrabromopyrrole in marine bacteria by a uniquely adapted brominase–thioesterase enzyme pair

PubMed Central

El Gamal, Abrahim; Agarwal, Vinayak; Diethelm, Stefan; Rahman, Imran; Schorn, Michelle A.; Sneed, Jennifer M.; Louie, Gordon V.; Whalen, Kristen E.; Mincer, Tracy J.; Noel, Joseph P.; Paul, Valerie J.; Moore, Bradley S.

2016-01-01

Halogenated pyrroles (halopyrroles) are common chemical moieties found in bioactive bacterial natural products. The halopyrrole moieties of mono- and dihalopyrrole-containing compounds arise from a conserved mechanism in which a proline-derived pyrrolyl group bound to a carrier protein is first halogenated and then elaborated by peptidic or polyketide extensions. This paradigm is broken during the marine pseudoalteromonad bacterial biosynthesis of the coral larval settlement cue tetrabromopyrrole (1), which arises from the substitution of the proline-derived carboxylate by a bromine atom. To understand the molecular basis for decarboxylative bromination in the biosynthesis of 1, we sequenced two Pseudoalteromonas genomes and identified a conserved four-gene locus encoding the enzymes involved in its complete biosynthesis. Through total in vitro reconstitution of the biosynthesis of 1 using purified enzymes and biochemical interrogation of individual biochemical steps, we show that all four bromine atoms in 1 are installed by the action of a single flavin-dependent halogenase: Bmp2. Tetrabromination of the pyrrole induces a thioesterase-mediated offloading reaction from the carrier protein and activates the biosynthetic intermediate for decarboxylation. Insights into the tetrabrominating activity of Bmp2 were obtained from the high-resolution crystal structure of the halogenase contrasted against structurally homologous halogenase Mpy16 that forms only a dihalogenated pyrrole in marinopyrrole biosynthesis. Structure-guided mutagenesis of the proposed substrate-binding pocket of Bmp2 led to a reduction in the degree of halogenation catalyzed. Our study provides a biogenetic basis for the biosynthesis of 1 and sets a firm foundation for querying the biosynthetic potential for the production of 1 in marine (meta)genomes. PMID:27001835

Independent Evolution of Six Families of Halogenating Enzymes.

PubMed

Xu, Gangming; Wang, Bin-Gui

2016-01-01

Halogenated natural products are widespread in the environment, and the halogen atoms are typically vital to their bioactivities. Thus far, six families of halogenating enzymes have been identified: cofactor-free haloperoxidases (HPO), vanadium-dependent haloperoxidases (V-HPO), heme iron-dependent haloperoxidases (HI-HPO), non-heme iron-dependent halogenases (NI-HG), flavin-dependent halogenases (F-HG), and S-adenosyl-L-methionine (SAM)-dependent halogenases (S-HG). However, these halogenating enzymes with similar biological functions but distinct structures might have evolved independently. Phylogenetic and structural analyses suggest that the HPO, V-HPO, HI-HPO, NI-HG, F-HG, and S-HG enzyme families may have evolutionary relationships to the α/β hydrolases, acid phosphatases, peroxidases, chemotaxis phosphatases, oxidoreductases, and SAM hydroxide adenosyltransferases, respectively. These halogenating enzymes have established sequence homology, structural conservation, and mechanistic features within each family. Understanding the distinct evolutionary history of these halogenating enzymes will provide further insights into the study of their catalytic mechanisms and halogenation specificity.

Impacts of bromine and iodine chemistry on tropospheric OH and HO2: comparing observations with box and global model perspectives

NASA Astrophysics Data System (ADS)

Stone, Daniel; Sherwen, Tomás; Evans, Mathew J.; Vaughan, Stewart; Ingham, Trevor; Whalley, Lisa K.; Edwards, Peter M.; Read, Katie A.; Lee, James D.; Moller, Sarah J.; Carpenter, Lucy J.; Lewis, Alastair C.; Heard, Dwayne E.

2018-03-01

The chemistry of the halogen species bromine and iodine has a range of impacts on tropospheric composition, and can affect oxidising capacity in a number of ways. However, recent studies disagree on the overall sign of the impacts of halogens on the oxidising capacity of the troposphere. We present simulations of OH and HO2 radicals for comparison with observations made in the remote tropical ocean boundary layer during the Seasonal Oxidant Study at the Cape Verde Atmospheric Observatory in 2009. We use both a constrained box model, using detailed chemistry derived from the Master Chemical Mechanism (v3.2), and the three-dimensional global chemistry transport model GEOS-Chem. Both model approaches reproduce the diurnal trends in OH and HO2. Absolute observed concentrations are well reproduced by the box model but are overpredicted by the global model, potentially owing to incomplete consideration of oceanic sourced radical sinks. The two models, however, differ in the impacts of halogen chemistry. In the box model, halogen chemistry acts to increase OH concentrations (by 9.8 % at midday at the Cape Verde Atmospheric Observatory), while the global model exhibits a small increase in OH at the Cape Verde Atmospheric Observatory (by 0.6 % at midday) but overall shows a decrease in the global annual mass-weighted mean OH of 4.5 %. These differences reflect the variety of timescales through which the halogens impact the chemical system. On short timescales, photolysis of HOBr and HOI, produced by reactions of HO2 with BrO and IO, respectively, increases the OH concentration. On longer timescales, halogen-catalysed ozone destruction cycles lead to lower primary production of OH radicals through ozone photolysis, and thus to lower OH concentrations. The global model includes more of the longer timescale responses than the constrained box model, and overall the global impact of the longer timescale response (reduced primary production due to lower O3 concentrations) overwhelms the shorter timescale response (enhanced cycling from HO2 to OH), and thus the global OH concentration decreases. The Earth system contains many such responses on a large range of timescales. This work highlights the care that needs to be taken to understand the full impact of any one process on the system as a whole.

Passivation of quartz for halogen-containing light sources

DOEpatents

Falkenstein, Zoran

1999-01-01

Lifetime of halogen containing VUV, UV, visible or IR light sources can be extended by passivating the quartz or glass gas containers with halogens prior to filling the quartz with the halogen and rare gas mixtures used to produce the light.

Method and apparatus for low temperature destruction of halogenated hydrocarbons

DOEpatents

Reagen, William Kevin; Janikowski, Stuart Kevin

1999-01-01

A method and apparatus for decomposing halogenated hydrocarbons are provided. The halogenated hydrocarbon is mixed with solvating agents and maintained in a predetermined atmosphere and at a predetermined temperature. The mixture is contacted with recyclable reactive material for chemically reacting with the recyclable material to create dehalogenated hydrocarbons and halogenated inorganic compounds. A feature of the invention is that the process enables low temperature destruction of halogenated hydrocarbons.

Halogen lamp experiment, HALEX

NASA Technical Reports Server (NTRS)

Schmitt, G.; Stapelmann, J.

1986-01-01

The main purpose of the Halogen Lamp Experiment (HALEX) was to investigate the operation of a halogen lamp during an extended period in a microgravity environment and to prove its behavior in space. The Mirror Heating Facilities for Crystal Growth and Material Science Experiments in space relies on one or two halogen lamps as a furnace to melt the specimens. The HALEX aim is to verify: full power operation of a halogen lamp for a period of about 60 hours; achievement of about 10% of its terrestrial life span; and operation of the halogen lamp under conditions similar to furnace operation.

The Important Role of Halogen Bond in Substrate Selectivity of Enzymatic Catalysis

NASA Astrophysics Data System (ADS)

Jiang, Shuiqin; Zhang, Lujia; Cui, Dongbin; Yao, Zhiqiang; Gao, Bei; Lin, Jinping; Wei, Dongzhi

2016-10-01

The use of halogen bond is widespread in drug discovery, design, and clinical trials, but is overlooked in drug biosynthesis. Here, the role of halogen bond in the nitrilase-catalyzed synthesis of ortho-, meta-, and para-chlorophenylacetic acid was investigated. Different distributions of halogen bond induced changes of substrate binding conformation and affected substrate selectivity. By engineering the halogen interaction, the substrate selectivity of the enzyme changed, with the implication that halogen bond plays an important role in biosynthesis and should be used as an efficient and reliable tool in enzymatic drug synthesis.

Halogen bonding in solution: thermodynamics and applications.

PubMed

Beale, Thomas M; Chudzinski, Michael G; Sarwar, Mohammed G; Taylor, Mark S

2013-02-21

Halogen bonds are noncovalent interactions in which covalently bound halogens act as electrophilic species. The utility of halogen bonding for controlling self-assembly in the solid state is evident from a broad spectrum of applications in crystal engineering and materials science. Until recently, it has been less clear whether, and to what extent, halogen bonding could be employed to influence conformation, binding or reactivity in the solution phase. This tutorial review summarizes and interprets solution-phase thermodynamic data for halogen bonding interactions obtained over the past six decades and highlights emerging applications in molecular recognition, medicinal chemistry and catalysis.

Comparison of stratospheric NO2 profiles above Kiruna, Sweden retrieved from ground-based zenith sky DOAS measurements, SAOZ balloon measurements and SCIAMACHY limb observations

NASA Astrophysics Data System (ADS)

Gu, Myojeong; Enell, Carl-Fredrik; Hendrick, François; Pukite, Janis; Van Roozendael, Michel; Platt, Ulrich; Raffalski, Uwe; Wagner, Thomas

2015-04-01

Stratospheric NO2 not only destroys ozone but acts as a buffer against halogen catalyzed ozone loss by converting halogen species into stable nitrates. These two roles of stratospheric NO2 depend on the altitude. Hence, the objective of this study is to investigate the vertical distribution of stratospheric NO2. We compare the NO2 profiles derived from the zenith sky DOAS with those obtained from, SAOZ balloon measurements and satellite limb observations. Vertical profiles of stratospheric NO2 are retrieved from ground-based zenith sky DOAS observations operated at Kiruna, Sweden (68.84°N, 20.41°E) since 1996. To determine the profile of stratospheric NO2 measured from ground-based zenith sky DOAS, we apply the Optimal Estimation Method (OEM) to retrieval of vertical profiles of stratospheric NO2 which has been developed by IASB-BIRA. The basic principle behind this profiling approach is the dependence of the mean scattering height on solar zenith angle (SZA). We compare the retrieved profiles to two additional datasets of stratospheric NO2 profile. The first one is derived from satellite limb observations by SCIAMACHY (Scanning Imaging Absorption spectrometer for Atmospheric CHartographY) on EnviSAT. The second is derived from the SAOZ balloon measurements (using a UV/Visible spectrometer) performed at Kiruna in Sweden.

Tests of halogen photochemistry using in situ measurements of ClO and BrO in the lower polar stratosphere

NASA Astrophysics Data System (ADS)

Avallone, Linnea M.; Toohey, Darin W.

2001-05-01

In situ observations of the halogen oxides ClO and BrO made from the NASA ER-2 during the Airborne Arctic Stratospheric Expedition (AASE) I and II missions are used to test current understanding of photochemical parameters. Measurements of ClO obtained during AASE I in the dark perturbed polar vortex are analyzed with respect to temperature to derive the equilibrium expression for the ClO/Cl2O2 system. Assuming photochemical steady state and complete activation of chlorine (ClO + 2Cl2O2 = Cly), observations of ClO made during AASE II are used to derive the photolysis rate of Cl2O2. The photolysis rate derived from atmospheric observations is compared to J values calculated with a photochemical model and various values for the absorption cross section of Cl2O2. The photolysis rate calculated with the cross section of Huder and DeMore [1995] is shown to be systematically too small, while those of Burkholder et al. [1990] and Cox and Hayman [1988] are too large to be consistent with atmospheric observations. Observations of BrO made during AASE II indicate that our understanding of the inorganic bromine budget in the polar regions is incomplete. A possible role for the adduct BrOOCl is investigated.

Complementary π-π interactions induce multicomponent coassembly into functional fibrils.

PubMed

Ryan, Derek M; Doran, Todd M; Nilsson, Bradley L

2011-09-06

Noncovalent self-assembled materials inspired by amyloid architectures are useful for biomedical applications ranging from regenerative medicine to drug delivery. The selective coassembly of complementary monomeric units to provide ordered multicomponent fibrils is a possible strategy for enhancing the sophistication of these noncovalent materials. Herein we report that complementary π-π interactions can be exploited to promote the coassembly of phenylalanine (Phe) derivatives that possess complementary aromatic side-chain functionality. Specifically, equimolar mixtures of Fmoc-Phe and Fmoc-F(5)-Phe, which possess side-chain groups with complementary quadrupole electronics, readily coassemble to form two-component fibrils and hydrogels under conditions where Fmoc-Phe alone fails to self-assemble. In addition, it was found that equimolar mixtures of Fmoc-Phe with monohalogenated (F, Cl, and Br) Fmoc-Phe derivatives also coassembled into two-component fibrils. These results collectively indicate that face-to-face quadrupole stacking between benzyl side-chain groups does not account for the molecular recognition between Phe and halogenated Phe derivatives that promote cofibrillization but that coassembly is mediated by more subtle π-π effects arising from the halogenation of the benzyl side chain. The use of complementary π-π interactions to promote the coassembly of two distinct monomeric units into ordered two-component fibrils dramatically expands the repertoire of noncovalent interactions that can be used in the development of sophisticated noncovalent materials. © 2011 American Chemical Society

The Influence of a Presence of a Heavy Atom on (13)C Shielding Constants in Organomercury Compounds and Halogen Derivatives.

PubMed

Wodyński, Artur; Gryff-Keller, Adam; Pecul, Magdalena

2013-04-09

(13)C nuclear magnetic resonance shielding constants have been calculated by means of density functional theory (DFT) for several organomercury compounds and halogen derivatives of aliphatic and aromatic compounds. Relativistic effects have been included through the four-component Dirac-Kohn-Sham (DKS) method, two-component Zeroth Order Regular Approximation (ZORA) DFT, and DFT with scalar effective core potentials (ECPs). The relative shieldings have been analyzed in terms of the position of carbon atoms with respect to the heavy atom and their hybridization. The results have been compared with the experimental values, some newly measured and some found in the literature. The main aim of the calculations has been to evaluate the magnitude of heavy atom effects on the (13)C shielding constants and to check what are the relative contributions of scalar relativistic effects and spin-orbit coupling. Another object has been to compare the DKS and ZORA results and to check how the approximate method of accounting for the heavy-atom-on-light-atom (HALA) relativistic effect by means of scalar effective core potentials on heavy atoms performs in comparison with the more rigorous two- and four-component treatment.

Squaraine dyes for photodynamic therapy: study of their cytotoxicity and genotoxicity in bacteria and mammalian cells.

PubMed

Ramaiah, Danaboyina; Eckert, Inge; Arun, Kalliat T; Weidenfeller, Lydia; Epe, Bernd

2002-12-01

Halogenated squaraine dyes are characterized by long wavelength absorption (>600 nm) and high triplet yields and therefore represent new types of photosensitizers that could be useful for photodynamic therapy. We have analyzed the cytotoxicity and genotoxicity of the bromo derivative 1, the iodo derivative 2 and the corresponding nonhalogenated dye 3 in the absence and presence of visible light. At concentrations of 1-2 microM, 1 and 2 reduced the cloning efficiency of AS52 Chinese hamster ovary cells to less than 1% under conditions that were well tolerated in the dark. Similarly, the proliferation of L5178Y mouse lymphoma cells was inhibited by photoexcited 1 and 2 with high selectivity. The squaraine 3 was much less efficient. Both 1 and 2 induced only few mutations in the gpt locus of the AS52 cells in the presence of light and were not mutagenic in the dark. No mutagenicity with and without irradiation was observed in Salmonella typhimurium TA100 and TA2638. However, both 1 and 2 plus light increased the frequency of micronuclei in AS52 cells. The results indicate that halogenated squaraines exhibit photobiological properties in vitro that are favorable for photodynamic therapeutical applications.

Implementation of marine halogen chemistry into the Community Multiscale Air Quality (CMAQ) model

NASA Astrophysics Data System (ADS)

Gantt, B.; Sarwar, G.

2017-12-01

In two recent studies (Sarwar et al, 2015 and Gantt et al., 2017), the impact of marine halogen (bromine and iodine) chemistry on air quality has been evaluated using the Community Multiscale Air Quality (CMAQ) model. We found that marine halogen chemistry not only has the expected effect of reducing marine boundary layer ozone concentrations, but also reduces ozone in the free troposphere and inland from the coast. In Sarwar et al. (2015), the impact of the halogen chemistry without and with photochemical reactions of higher iodine oxides over the Northern Hemisphere was examined using the coarse horizontal grids of a hemispheric domain. Halogen chemistry without and with the photochemical reactions of higher iodine oxides reduces ozone over seawater by 15% and 48%, respectively. Using the results of the chemistry without the photochemical reactions of higher iodine oxides, we developed a simple first order ozone loss rate and implemented it into the public version of CMAQv52. In Gantt et al. (2017), the impact of the simple first order loss rate as well as the full halogen chemistry without photochemical reactions of higher iodine oxides over the continental United States was examined using finer horizontal grids of the regional domain and boundary conditions from the hemispheric domain with and without marine halogen chemistry. The boundary conditions obtained with the halogen chemistry as well as the simple halogen chemistry reduces ozone along the coast where CMAQ typically overpredicts the concentrations. Development of halogen chemistry in CMAQ has continued with the implementation of several heterogeneous reactions of bromine and iodine species, revised reactions of higher iodine oxides, and a refined marine halogen emissions inventory. Our latest version of halogen chemistry with photochemical reactions of higher iodine oxides reduces ozone by 23% over the seawater. This presentation will discuss the previous and ongoing implementation of revised halogen chemistry in CMAQ and its impacts on air quality.

Technology for radiation efficiency measurement of high-power halogen tungsten lamp used in calibration of high-energy laser energy meter.

PubMed

Wei, Ji Feng; Hu, Xiao Yang; Sun, Li Qun; Zhang, Kai; Chang, Yan

2015-03-20

The calibration method using a high-power halogen tungsten lamp as a calibration source has many advantages such as strong equivalence and high power, so it is very fit for the calibration of high-energy laser energy meters. However, high-power halogen tungsten lamps after power-off still reserve much residual energy and continually radiate energy, which is difficult to be measured. Two measuring systems were found to solve the problems. One system is composed of an integrating sphere and two optical spectrometers, which can accurately characterize the radiative spectra and power-time variation of the halogen tungsten lamp. This measuring system was then calibrated using a normal halogen tungsten lamp made of the same material as the high-power halogen tungsten lamp. In this way, the radiation efficiency of the halogen tungsten lamp after power-off can be quantitatively measured. In the other measuring system, a wide-spectrum power meter was installed far away from the halogen tungsten lamp; thus, the lamp can be regarded as a point light source. The radiation efficiency of residual energy from the halogen tungsten lamp was computed on the basis of geometrical relations. The results show that the halogen tungsten lamp's radiation efficiency was improved with power-on time but did not change under constant power-on time/energy. All the tested halogen tungsten lamps reached 89.3% of radiation efficiency at 50 s after power-on. After power-off, the residual energy in the halogen tungsten lamp gradually dropped to less than 10% of the initial radiation power, and the radiation efficiency changed with time. The final total radiation energy was decided by the halogen tungsten lamp's radiation efficiency, the radiation efficiency of residual energy, and the total power consumption. The measuring uncertainty of total radiation energy was 2.4% (here, the confidence factor is two).

Enzymatic Halogenation and Dehalogenation Reactions: Pervasive and Mechanistically Diverse.

PubMed

Agarwal, Vinayak; Miles, Zachary D; Winter, Jaclyn M; Eustáquio, Alessandra S; El Gamal, Abrahim A; Moore, Bradley S

2017-04-26

Naturally produced halogenated compounds are ubiquitous across all domains of life where they perform a multitude of biological functions and adopt a diversity of chemical structures. Accordingly, a diverse collection of enzyme catalysts to install and remove halogens from organic scaffolds has evolved in nature. Accounting for the different chemical properties of the four halogen atoms (fluorine, chlorine, bromine, and iodine) and the diversity and chemical reactivity of their organic substrates, enzymes performing biosynthetic and degradative halogenation chemistry utilize numerous mechanistic strategies involving oxidation, reduction, and substitution. Biosynthetic halogenation reactions range from simple aromatic substitutions to stereoselective C-H functionalizations on remote carbon centers and can initiate the formation of simple to complex ring structures. Dehalogenating enzymes, on the other hand, are best known for removing halogen atoms from man-made organohalogens, yet also function naturally, albeit rarely, in metabolic pathways. This review details the scope and mechanism of nature's halogenation and dehalogenation enzymatic strategies, highlights gaps in our understanding, and posits where new advances in the field might arise in the near future.

Independent Evolution of Six Families of Halogenating Enzymes

PubMed Central

Xu, Gangming; Wang, Bin-Gui

2016-01-01

Halogenated natural products are widespread in the environment, and the halogen atoms are typically vital to their bioactivities. Thus far, six families of halogenating enzymes have been identified: cofactor-free haloperoxidases (HPO), vanadium-dependent haloperoxidases (V-HPO), heme iron-dependent haloperoxidases (HI-HPO), non-heme iron-dependent halogenases (NI-HG), flavin-dependent halogenases (F-HG), and S-adenosyl-L-methionine (SAM)-dependent halogenases (S-HG). However, these halogenating enzymes with similar biological functions but distinct structures might have evolved independently. Phylogenetic and structural analyses suggest that the HPO, V-HPO, HI-HPO, NI-HG, F-HG, and S-HG enzyme families may have evolutionary relationships to the α/β hydrolases, acid phosphatases, peroxidases, chemotaxis phosphatases, oxidoreductases, and SAM hydroxide adenosyltransferases, respectively. These halogenating enzymes have established sequence homology, structural conservation, and mechanistic features within each family. Understanding the distinct evolutionary history of these halogenating enzymes will provide further insights into the study of their catalytic mechanisms and halogenation specificity. PMID:27153321

Halogenation of microcapsule walls

NASA Technical Reports Server (NTRS)

Davis, T. R.; Schaab, C. K.; Scott, J. C.

1972-01-01

Procedure for halogenation of confining walls of both gelatin and gelatin-phenolic resin capsules is similar to that used for microencapsulation. Ten percent halogen content renders capsule wall nonburning; any higher content enhances flame-retardant properties of selected internal phase material. Halogenation decreases permeability of wall material to encapsulated materials.

Halogens are key cofactors in building of collagen IV scaffolds outside the cell.

PubMed

Brown, Kyle L; Hudson, Billy G; Voziyan, Paul A

2018-05-01

The purpose of this review is to highlight recent advances in understanding the molecular assembly of basement membranes, as exemplified by the glomerular basement membrane (GBM) of the kidney filtration apparatus. In particular, an essential role of halogens in the basement membrane formation has been discovered. Extracellular chloride triggers a molecular switch within non collagenous domains of collagen IV that induces protomer oligomerization and scaffold assembly outside the cell. Moreover, bromide is an essential cofactor in enzymatic cross-linking that reinforces the stability of scaffolds. Halogenation and halogen-induced oxidation of the collagen IV scaffold in disease states damage scaffold function. Halogens play an essential role in the formation of collagen IV scaffolds of basement membranes. Pathogenic damage of these scaffolds by halogenation and halogen-induced oxidation is a potential target for therapeutic interventions.

Design and verification of halogen-bonding system at the complex interface of human fertilization-related MUP PDZ5 domain with CAMK's C-terminal peptide.

PubMed

Wang, Juan; Guo, Yunjie; Zhang, Xue

2018-02-01

Calmodulin-dependent protein kinase (CAMK) is physiologically activated in fertilized human oocytes and is involved in the Ca 2+ response pathways that link the fertilization calmodulin signal to meiosis resumption and cortical granule exocytosis. The kinase has an unstructured C-terminal tail that can be recognized and bound by the PDZ5 domain of its cognate partner, the multi-PDZ domain protein (MUP). In the current study, we reported a rational biomolecular design of halogen-bonding system at the complex interface of CAMK's C-terminal peptide with MUP PDZ5 domain by using high-level computational approaches. Four organic halogens were employed as atom probes to explore the structural geometry and energetic property of designed halogen bonds in the PDZ5-peptide complex. It was found that the heavier halogen elements such as bromine Br and iodine I can confer stronger halogen bond but would cause bad atomic contacts and overlaps at the complex interface, while fluorine F cannot form effective halogen bond in the complex. In addition, the halogen substitution at different positions of peptide's aromatic ring would result in distinct effects on the halogen-bonding system. The computational findings were then verified by using fluorescence analysis; it is indicated that the halogen type and substitution position play critical role in the interaction strength of halogen bonds, and thus the PDZ5-peptide binding affinity can be improved considerably by optimizing their combination. Copyright © 2017 Elsevier Ltd. All rights reserved.

Atomic resolution ADF-STEM imaging of organic molecular crystal of halogenated copper phthalocyanine.

PubMed

Haruta, Mitsutaka; Yoshida, Kaname; Kurata, Hiroki; Isoda, Seiji

2008-05-01

Annular dark-field (ADF) scanning transmission electron microscopy (STEM) measurements are demonstrated for the first time to be applicable for acquiring Z-contrast images of organic molecules at atomic resolution. High-angle ADF imaging by STEM is a new technique that provides incoherent high-resolution Z-contrast images for organic molecules. In the present study, low-angle ADF-STEM is successfully employed to image the molecular crystal structure of hexadecachloro-Cu-phthalocyanine (Cl16-CuPc), an organic molecule. The structures of CuPc derivatives (polyhalogenated CuPc with Br and Cl) are determined quantitatively using the same technique to determine the occupancy of halogens at each chemical site. By comparing the image contrasts of atomic columns, the occupancy of Br is found to be ca. 56% at the inner position, slightly higher than that for random substitution and in good agreement with previous TEM results.

Supramolecular amplification of amyloid self-assembly by iodination

NASA Astrophysics Data System (ADS)

Bertolani, Arianna; Pirrie, Lisa; Stefan, Loic; Houbenov, Nikolay; Haataja, Johannes S.; Catalano, Luca; Terraneo, Giancarlo; Giancane, Gabriele; Valli, Ludovico; Milani, Roberto; Ikkala, Olli; Resnati, Giuseppe; Metrangolo, Pierangelo

2015-06-01

Amyloid supramolecular assemblies have found widespread exploitation as ordered nanomaterials in a range of applications from materials science to biotechnology. New strategies are, however, required for understanding and promoting mature fibril formation from simple monomer motifs through easy and scalable processes. Noncovalent interactions are key to forming and holding the amyloid structure together. On the other hand, the halogen bond has never been used purposefully to achieve control over amyloid self-assembly. Here we show that single atom replacement of hydrogen with iodine, a halogen-bond donor, in the human calcitonin-derived amyloidogenic fragment DFNKF results in a super-gelator peptide, which forms a strong and shape-persistent hydrogel at 30-fold lower concentration than the wild-type pentapeptide. This is remarkable for such a modest perturbation in structure. Iodination of aromatic amino acids may thus develop as a general strategy for the design of new hydrogels from unprotected peptides and without using organic solvents.

Molecular association via halogen bonding and other weak interactions in the crystal structures of 11-bromo-12-oxo-5β-cholan derivatives

NASA Astrophysics Data System (ADS)

Salunke, Deepak B.; Hazra, Braja G.; Gonnade, Rajesh G.; Pore, Vandana S.; Bhadbhade, Mohan M.

2008-12-01

Methyl 3α,7α-diacetoxy-12-oxo-5β-cholan-24-oate 2, methyl 11α-bromo-3α,7α-diacetoxy-12-oxo-5β-cholan-24-oate 3, methyl 11β-bromo-3α,7α-diacetoxy-12-oxo-5β-cholan-24-oate 4 and methyl 11,11-dibromo-3α,7α-diacetoxy-12-oxo-5β-cholan-24-oate 5 were synthesized. The crystal structures of these molecules were resolved to study the effect of bulky bromine atom in the steroid skeleton of cholic acid with different stereo-chemical orientations at C-11 on the two-dimensional arrangement of molecules and solid-state properties. All the molecules associate only via weak intermolecular interactions in their crystal structures, notable one being the Halogen Bonded assembly (C-Br…O) in 5.

Enantioselective decarboxylative chlorination of β-ketocarboxylic acids

PubMed Central

Shibatomi, Kazutaka; Kitahara, Kazumasa; Sasaki, Nozomi; Kawasaki, Yohei; Fujisawa, Ikuhide; Iwasa, Seiji

2017-01-01

Stereoselective halogenation is a highly useful organic transformation for multistep syntheses because the resulting chiral organohalides can serve as precursors for various medicinally relevant derivatives. Even though decarboxylative halogenation of aliphatic carboxylic acids is a useful and fundamental synthetic method for the preparation of a variety of organohalides, an enantioselective version of this reaction has not been reported. Here we report a highly enantioselective decarboxylative chlorination of β-ketocarboxylic acids to obtain α-chloroketones under mild organocatalytic conditions. The present method is also applicable for the enantioselective synthesis of tertiary α-chloroketones. The conversions of the resulting α-chloroketones into α-aminoketones and α-thio-substituted ketones via SN2 reactions at the tertiary carbon centres are also demonstrated. These results constitute an efficient approach for the synthesis of chiral organohalides and are expected to enhance the availability of enantiomerically enriched chiral compounds with heteroatom-substituted chiral stereogenic centres. PMID:28580951

Anaerobic biodegradation of halogenated and nonhalogenated N-, s-, and o-heterocyclic compounds in aquifer slurries

USGS Publications Warehouse

Adrian, Neal R.; Suflita, Joseph M.

1994-01-01

The fate of several halogenated and nonhalogenated heterocyclic compounds in anoxic aquifer slurries was investigated Substrate depletion and methane formation were monitored in serum bottle incubations by HPLC and GC, respectively Pyridine, pyrimidine, thiophene, and furan were not mineralized following an 11-month incubation, but the corresponding carboxylated or oxygenated compounds were That is, >74% of the theoretically expected amount of methane was recovered from nicotinic acid, uracil, or 2-furoic acid Chlorinated derivatives, like 2 chloro- or 6-chloronicotinic acid, as well as 4 chloro- and 5-chlorouracil resisted mineralization However, 5-bromouracil was reductively dehalogenated to stoichiometric amounts of uracil, whereas 2-chloropyrimidine was metabolized to a more polar unidentified compound that resisted further anaerobic biodegradation Microorganisms acclimated to 5-bromouracil were unable to transform 4 chloro or 5 chlorouracil These findings illustrate how the structure of heterocyclic contaminants influences their susceptibility to anaerobic decay

Enantioselective decarboxylative chlorination of β-ketocarboxylic acids

NASA Astrophysics Data System (ADS)

Shibatomi, Kazutaka; Kitahara, Kazumasa; Sasaki, Nozomi; Kawasaki, Yohei; Fujisawa, Ikuhide; Iwasa, Seiji

2017-06-01

Stereoselective halogenation is a highly useful organic transformation for multistep syntheses because the resulting chiral organohalides can serve as precursors for various medicinally relevant derivatives. Even though decarboxylative halogenation of aliphatic carboxylic acids is a useful and fundamental synthetic method for the preparation of a variety of organohalides, an enantioselective version of this reaction has not been reported. Here we report a highly enantioselective decarboxylative chlorination of β-ketocarboxylic acids to obtain α-chloroketones under mild organocatalytic conditions. The present method is also applicable for the enantioselective synthesis of tertiary α-chloroketones. The conversions of the resulting α-chloroketones into α-aminoketones and α-thio-substituted ketones via SN2 reactions at the tertiary carbon centres are also demonstrated. These results constitute an efficient approach for the synthesis of chiral organohalides and are expected to enhance the availability of enantiomerically enriched chiral compounds with heteroatom-substituted chiral stereogenic centres.

40 CFR 721.5452 - Alkali metal salt of halogenated organoborate (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Alkali metal salt of halogenated... Specific Chemical Substances § 721.5452 Alkali metal salt of halogenated organoborate (generic). (a... generically as alkali metal salt of halogenated organoborate (PMN P-00-0638) is subject to reporting under...

40 CFR 721.5452 - Alkali metal salt of halogenated organoborate (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alkali metal salt of halogenated... Specific Chemical Substances § 721.5452 Alkali metal salt of halogenated organoborate (generic). (a... generically as alkali metal salt of halogenated organoborate (PMN P-00-0638) is subject to reporting under...

Halogen bonding based recognition processes: a world parallel to hydrogen bonding.

PubMed

Metrangolo, Pierangelo; Neukirch, Hannes; Pilati, Tullio; Resnati, Giuseppe

2005-05-01

Halogen bonding is the noncovalent interaction between halogen atoms (Lewis acids) and neutral or anionic Lewis bases. The main features of the interaction are given, and the close similarity with the hydrogen bonding will become apparent. Some heuristic principles are presented to develop a rational crystal engineering based on halogen bonding. The focus is on halogen-bonded supramolecular architectures given by halocarbons. The potential of the interaction is shown by useful applications in the field of synthetic chemistry, material science, and bioorganic chemistry.

Systematic and Automated Development of Quantum Mechanically Derived Force Fields: The Challenging Case of Halogenated Hydrocarbons.

PubMed

Prampolini, Giacomo; Campetella, Marco; De Mitri, Nicola; Livotto, Paolo Roberto; Cacelli, Ivo

2016-11-08

A robust and automated protocol for the derivation of sound force field parameters, suitable for condensed-phase classical simulations, is here tested and validated on several halogenated hydrocarbons, a class of compounds for which standard force fields have often been reported to deliver rather inaccurate performances. The major strength of the proposed protocol is that all of the parameters are derived only from first principles because all of the information required is retrieved from quantum mechanical data, purposely computed for the investigated molecule. This a priori parametrization is carried out separately for the intra- and intermolecular contributions to the force fields, respectively exploiting the Joyce and Picky programs, previously developed in our group. To avoid high computational costs, all quantum mechanical calculations were performed exploiting the density functional theory. Because the choice of the functional is known to be crucial for the description of the intermolecular interactions, a specific procedure is proposed, which allows for a reliable benchmark of different functionals against higher-level data. The intramolecular and intermolecular contribution are eventually joined together, and the resulting quantum mechanically derived force field is thereafter employed in lengthy molecular dynamics simulations to compute several thermodynamic properties that characterize the resulting bulk phase. The accuracy of the proposed parametrization protocol is finally validated by comparing the computed macroscopic observables with the available experimental counterparts. It is found that, on average, the proposed approach is capable of yielding a consistent description of the investigated set, often outperforming the literature standard force fields, or at least delivering results of similar accuracy.

Pyrrolo isoquinolines

DOEpatents

Goodman, Mark M.; Shi, Bing Z.

2000-01-01

Compounds of the formula: ##STR1## wherein X, Y, and R, independently of one another, is each a H; halogen, wherein said halogen is selected from the group consisting of .sup.123 I, .sup.124 I, .sup.125 I, .sup.131 I, .sup.75 Br, .sup.76 Br, .sup.77 Br, .sup.82 Br, .sup.18 F, or .sup.210 At; small alkyl, small alkenyl, or small alkynyl, any of which contains from one to about six carbon atoms and optionally having a carbon atom replaced by an O or S; or halogen substituted-small alkyl, halogen substituted-small alkenyl, or halogen substituted-small alkynyl wherein said compound contains at least one radioacitve halogen. The compounds bind to the serotonin transporter. Depending upon the choice of halogen substituent, the compounds are useful for PET or SPECT imaging, diagnosis and treatment of psychiatric disorders such as depression, anxiety, obsessive-compulsive disorder, and other conditions associated with defects of serotonin transporter function.

40 CFR 721.275 - Halogenated-N-(2-propenyl)-N-(substituted phenyl) acetamide.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Halogenated-N-(2-propenyl)-N... New Uses for Specific Chemical Substances § 721.275 Halogenated-N-(2-propenyl)-N-(substituted phenyl... identified generically as halogenated-N-(2-propenyl)-N-(substituted phenyl) acetamide (P-83-1085) is subject...

40 CFR 721.275 - Halogenated-N-(2-propenyl)-N-(substituted phenyl) acetamide.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Halogenated-N-(2-propenyl)-N... New Uses for Specific Chemical Substances § 721.275 Halogenated-N-(2-propenyl)-N-(substituted phenyl... identified generically as halogenated-N-(2-propenyl)-N-(substituted phenyl) acetamide (P-83-1085) is subject...

Do Halogen–Hydrogen Bond Donor Interactions Dominate the Favorable Contribution of Halogens to Ligand–Protein Binding?

PubMed Central

2017-01-01

Halogens are present in a significant number of drugs, contributing favorably to ligand–protein binding. Currently, the contribution of halogens, most notably chlorine and bromine, is largely attributed to halogen bonds involving favorable interactions with hydrogen bond acceptors. However, we show that halogens acting as hydrogen bond acceptors potentially make a more favorable contribution to ligand binding than halogen bonds based on quantum mechanical calculations. In addition, bioinformatics analysis of ligand–protein crystal structures shows the presence of significant numbers of such interactions. It is shown that interactions between halogens and hydrogen bond donors (HBDs) are dominated by perpendicular C–X···HBD orientations. Notably, the orientation dependence of the halogen–HBD (X–HBD) interactions is minimal over greater than 100° with favorable interaction energies ranging from −2 to −14 kcal/mol. This contrasts halogen bonds in that X–HBD interactions are substantially more favorable, being comparable to canonical hydrogen bonds, with a smaller orientation dependence, such that they make significant, favorable contributions to ligand–protein binding and, therefore, should be actively considered during rational ligand design. PMID:28657759

Kinetics and mechanisms of some atomic oxygen reactions

NASA Technical Reports Server (NTRS)

Cvetanovic, R. J.

1987-01-01

Mechanisms and kinetics of some reactions of the ground state of oxygen atoms, O(3P), are briefly summarized. Attention is given to reactions of oxygen atoms with several different types of organic and inorganic compounds such as alkanes, alkenes, alkynes, aromatics, and some oxygen, nitrogen, halogen and sulfur derivatives of these compounds. References to some recent compilations and critical evaluations of reaction rate constants are given.

Likelihood of atom-atom contacts in crystal structures of halogenated organic compounds.

PubMed

Jelsch, Christian; Soudani, Sarra; Ben Nasr, Cherif

2015-05-01

The likelihood of occurrence of intermolecular contacts in crystals of halogenated organic compounds has been analysed statistically using tools based on the Hirshfeld surface. Several families of small halogenated molecules (containing organic F, Cl, Br or I atoms) were analysed, based on chemical composition and aromatic or aliphatic character. The behaviour of crystal contacts was also probed for molecules containing O or N. So-called halogen bonding (a halogen making short interactions with O or N, or a π interaction with C) is generally disfavoured, except when H is scarce on the molecular surface. Similarly, halogen⋯halogen contacts are more rare than expected, except for molecules that are poor in H. In general, the H atom is found to be the preferred partner of organic halogen atoms in crystal structures. On the other hand, C⋯C interactions in parallel π-stacking have a high propensity to occur in halogenated aromatic molecules. The behaviour of the four different halogen species (F, Cl, Br, I) is compared in several chemical composition contexts. The analysis tool can be refined by distinguishing several types for a given chemical species, such as H atoms bound to O or C. Such distinction shows, for instance, that C-H⋯Cl and O-H⋯O are the preferred interactions in compounds containing both O and Cl.

Hydrogen bond and halogen bond inside the carbon nanotube

NASA Astrophysics Data System (ADS)

Wang, Weizhou; Wang, Donglai; Zhang, Yu; Ji, Baoming; Tian, Anmin

2011-02-01

The hydrogen bond and halogen bond inside the open-ended single-walled carbon nanotubes have been investigated theoretically employing the newly developed density functional M06 with the suitable basis set and the natural bond orbital analysis. Comparing with the hydrogen or halogen bond in the gas phase, we find that the strength of the hydrogen or halogen bond inside the carbon nanotube will become weaker if there is a larger intramolecular electron-density transfer from the electron-rich region of the hydrogen or halogen atom donor to the antibonding orbital of the X-H or X-Hal bond involved in the formation of the hydrogen or halogen bond and will become stronger if there is a larger intermolecular electron-density transfer from the electron-rich region of the hydrogen or halogen atom acceptor to the antibonding orbital of the X-H or X-Hal bond. According to the analysis of the molecular electrostatic potential of the carbon nanotube, the driving force for the electron-density transfer is found to be the negative electric field formed in the carbon nanotube inner phase. Our results also show that the X-H bond involved in the formation of the hydrogen bond and the X-Hal bond involved in the formation of the halogen bond are all elongated when encapsulating the hydrogen bond and halogen bond within the carbon nanotube, so the carbon nanotube confinement may change the blue-shifting hydrogen bond and the blue-shifting halogen bond into the red-shifting hydrogen bond and the red-shifting halogen bond. The possibility to replace the all electron nanotube-confined calculation by the simple polarizable continuum model is also evaluated.

On the ultrafast charge migration and subsequent charge directed reactivity in Cl⋯N halogen-bonded clusters following vertical ionization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chandra, Sankhabrata; Bhattacharya, Atanu, E-mail: atanub@ipc.iisc.ernet.in; Periyasamy, Ganga

2015-06-28

In this article, we have presented ultrafast charge transfer dynamics through halogen bonds following vertical ionization of representative halogen bonded clusters. Subsequent hole directed reactivity of the radical cations of halogen bonded clusters is also discussed. Furthermore, we have examined effect of the halogen bond strength on the electron-electron correlation- and relaxation-driven charge migration in halogen bonded complexes. For this study, we have selected A-Cl (A represents F, OH, CN, NH{sub 2}, CF{sub 3}, and COOH substituents) molecules paired with NH{sub 3} (referred as ACl:NH{sub 3} complex): these complexes exhibit halogen bonds. To the best of our knowledge, this ismore » the first report on purely electron correlation- and relaxation-driven ultrafast (attosecond) charge migration dynamics through halogen bonds. Both density functional theory and complete active space self-consistent field theory with 6-31 + G(d, p) basis set are employed for this work. Upon vertical ionization of NCCl⋯NH{sub 3} complex, the hole is predicted to migrate from the NH{sub 3}-end to the ClCN-end of the NCCl⋯NH{sub 3} complex in approximately 0.5 fs on the D{sub 0} cationic surface. This hole migration leads to structural rearrangement of the halogen bonded complex, yielding hydrogen bonding interaction stronger than the halogen bonding interaction on the same cationic surface. Other halogen bonded complexes, such as H{sub 2}NCl:NH{sub 3}, F{sub 3}CCl:NH{sub 3}, and HOOCCl:NH{sub 3}, exhibit similar charge migration following vertical ionization. On the contrary, FCl:NH{sub 3} and HOCl:NH{sub 3} complexes do not exhibit any charge migration following vertical ionization to the D{sub 0} cation state, pointing to interesting halogen bond strength-dependent charge migration.« less

Cosmic-Ray Reaction and Greenhouse Effect of Halogenated Molecules: Culprits for Atmospheric Ozone Depletion and Global Climate Change

NASA Astrophysics Data System (ADS)

Lu, Q.-B.

2013-07-01

This study is focused on the effects of cosmic rays (solar activity) and halogen-containing molecules (mainly chlorofluorocarbons — CFCs) on atmospheric ozone depletion and global climate change. Brief reviews are first given on the cosmic-ray-driven electron-induced-reaction (CRE) theory for O3 depletion and the warming theory of halogenated molecules for climate change. Then natural and anthropogenic contributions to these phenomena are examined in detail and separated well through in-depth statistical analyses of comprehensive measured datasets of quantities, including cosmic rays (CRs), total solar irradiance, sunspot number, halogenated gases (CFCs, CCl4 and HCFCs), CO2, total O3, lower stratospheric temperatures and global surface temperatures. For O3 depletion, it is shown that an analytical equation derived from the CRE theory reproduces well 11-year cyclic variations of both polar O3 loss and stratospheric cooling, and new statistical analyses of the CRE equation with observed data of total O3 and stratospheric temperature give high linear correlation coefficients ≥ 0.92. After the removal of the CR effect, a pronounced recovery by 20 25 % of the Antarctic O3 hole is found, while no recovery of O3 loss in mid-latitudes has been observed. These results show both the correctness and dominance of the CRE mechanism and the success of the Montreal Protocol. For global climate change, in-depth analyses of the observed data clearly show that the solar effect and human-made halogenated gases played the dominant role in Earth's climate change prior to and after 1970, respectively. Remarkably, a statistical analysis gives a nearly zero correlation coefficient (R = -0.05) between corrected global surface temperature data by removing the solar effect and CO2 concentration during 1850-1970. In striking contrast, a nearly perfect linear correlation with coefficients as high as 0.96-0.97 is found between corrected or uncorrected global surface temperature and total amount of stratospheric halogenated gases during 1970-2012. Furthermore, a new theoretical calculation on the greenhouse effect of halogenated gases shows that they (mainly CFCs) could alone result in the global surface temperature rise of 0.6°C in 1970-2002. These results provide solid evidence that recent global warming was indeed caused by the greenhouse effect of anthropogenic halogenated gases. Thus, a slow reversal of global temperature to the 1950 value is predicted for coming 5 7 decades. It is also expected that the global sea level will continue to rise in coming 1 2 decades until the effect of the global temperature recovery dominates over that of the polar O3 hole recovery; after that, both will drop concurrently. All the observed, analytical and theoretical results presented lead to a convincing conclusion that both the CRE mechanism and the CFC-warming mechanism not only provide new fundamental understandings of the O3 hole and global climate change but have superior predictive capabilities, compared with the conventional models.

The unique role of halogen substituents in the design of modern agrochemicals.

PubMed

Jeschke, Peter

2010-01-01

The past 30 years have witnessed a period of significant expansion in the use of halogenated compounds in the field of agrochemical research and development. The introduction of halogens into active ingredients has become an important concept in the quest for a modern agrochemical with optimal efficacy, environmental safety, user friendliness and economic viability. Outstanding progress has been made, especially in synthetic methods for particular halogen-substituted key intermediates that were previously prohibitively expensive. Interestingly, there has been a rise in the number of commercial products containing 'mixed' halogens, e.g. one or more fluorine, chlorine, bromine or iodine atoms in addition to one or more further halogen atoms. Extrapolation of the current trend indicates that a definite growth is to be expected in fluorine-substituted agrochemicals throughout the twenty-first century. A number of these recently developed agrochemical candidates containing halogen substituents represent novel classes of chemical compounds with new modes of action. However, the complex structure-activity relationships associated with biologically active molecules mean that the introduction of halogens can lead to either an increase or a decrease in the efficacy of a compound, depending on its changed mode of action, physicochemical properties, target interaction or metabolic susceptibility and transformation. In spite of modern design concepts, it is still difficult to predict the sites in a molecule at which halogen substitution will result in optimal desired effects. This review describes comprehensively the successful utilisation of halogens and their unique role in the design of modern agrochemicals, exemplified by various commercial products from Bayer CropScience coming from different agrochemical areas.

Removal of Intermediate Aromatic Halogenated DBPs by Activated Carbon Adsorption: A New Approach to Controlling Halogenated DBPs in Chlorinated Drinking Water.

PubMed

Jiang, Jingyi; Zhang, Xiangru; Zhu, Xiaohu; Li, Yu

2017-03-21

During chlorine disinfection of drinking water, chlorine may react with natural organic matter (NOM) and bromide ion in raw water to generate halogenated disinfection byproducts (DBPs). To mitigate adverse effects from DBP exposure, granular activated carbon (GAC) adsorption has been considered as one of the best available technologies for removing NOM (DBP precursor) in drinking water treatment. Recently, we have found that many aromatic halogenated DBPs form in chlorination, and they act as intermediate DBPs to decompose and form commonly known DBPs including trihalomethanes and haloacetic acids. In this work, we proposed a new approach to controlling drinking water halogenated DBPs by GAC adsorption of intermediate aromatic halogenated DBPs during chlorination, rather than by GAC adsorption of NOM prior to chlorination (i.e., traditional approach). Rapid small-scale column tests were used to simulate GAC adsorption in the new and traditional approaches. Significant reductions of aromatic halogenated DBPs were observed in the effluents with the new approach; the removals of total organic halogen, trihalomethanes, and haloacetic acids by the new approach always exceeded those by the traditional approach; and the effluents with the new approach were considerably less developmentally toxic than those with the traditional approach. Our findings indicate that the new approach is substantially more effective in controlling halogenated DBPs than the traditional approach.

Halogenated solvent interactions with N,N-dimethyltryptamine: formation of quaternary ammonium salts and their artificially induced rearrangements during analysis.

PubMed

Brandt, Simon D; Martins, Cláudia P B; Freeman, Sally; Dempster, Nicola; Riby, Philip G; Gartz, Jochen; Alder, John F

2008-07-04

The psychoactive properties of N,N-dimethyltryptamine (DMT) 1a are known to induce altered states of consciousness in humans. This particular attribute attracts great interest from a variety of scientific and also clandestine communities. Our recent research has confirmed that DMT reacts with dichloromethane (DCM), either as a result of work-up or storage to give a quaternary N-chloromethyl ammonium salt 2a. Furthermore, this was observed to undergo rearrangement during analysis using gas chromatography-mass spectrometry (GC-MS) with products including 3-(2-chloroethyl)indole 3 and 2-methyltetrahydro-beta-carboline 4 (2-Me-THBC). This study further investigates this so far unexplored area of solvent interactions by the exposure of DMT to other halogenated solvents including dibromomethane and 1,2-dichloroethane (DCE). The N-bromomethyl- and N-chloroethyl quaternary ammonium derivatives were subsequently characterised by ion trap GC-MS in electron and chemical ionisation tandem MS mode and by NMR spectroscopy. The DCE-derived derivative formed at least six rearrangement products in the total ion chromatogram. Identification of mass spectrometry generated by-products was verified by conventional or microwave-accelerated synthesis. The use of deuterated DCM and deuterated DMT 1b provided insights into the mechanism of the rearrangements. The presence of potentially characteristic marker molecules may allow the identification of solvents used during the manufacture of controlled substances, which is often neglected since these are considered inert.

Boiling points of halogenated ethanes: an explanatory model implicating weak intermolecular hydrogen-halogen bonding.

PubMed

Beauchamp, Guy

2008-10-23

This study explores via structural clues the influence of weak intermolecular hydrogen-halogen bonds on the boiling point of halogenated ethanes. The plot of boiling points of 86 halogenated ethanes versus the molar refraction (linked to polarizability) reveals a series of straight lines, each corresponding to one of nine possible arrangements of hydrogen and halogen atoms on the two-carbon skeleton. A multiple linear regression model of the boiling points could be designed based on molar refraction and subgroup structure as independent variables (R(2) = 0.995, standard error of boiling point 4.2 degrees C). The model is discussed in view of the fact that molar refraction can account for approximately 83.0% of the observed variation in boiling point, while 16.5% could be ascribed to weak C-X...H-C intermolecular interactions. The difference in the observed boiling point of molecules having similar molar refraction values but differing in hydrogen-halogen intermolecular bonds can reach as much as 90 degrees C.

Halogen-free boron based electrolyte solution for rechargeable magnesium batteries

NASA Astrophysics Data System (ADS)

Zhu, Jinjie; Guo, Yongsheng; Yang, Jun; Nuli, Yanna; Zhang, Fan; Wang, Jiulin; Hirano, Shin-ichi

2014-02-01

All halogen containing electrolytes for Mg battery are apt to corrode conventional metal current collectors. In this paper, a new type of halogen-free boron based electrolyte (Mg[Mes3BPh]2/THF) is designed and prepared. Electrochemical tests show that this electrolyte system possesses high ion conductivity (1.5 × 10-3 S cm-1) and good Mg deposition-dissolution reversibility. More importantly, the same electrochemical window (2.6 V vs. Mg RE) of the electrolyte on Pt and stainless steel electrodes indicates that halogen-free electrolyte indeed lessens the corrosion to conventional metal current collectors. The surface morphologies of stainless steel, aluminum and copper are further observed after their anodic potentiostatic polarization in 0.25 mol L-1 Mg[Mes3BPh]2/THF electrolyte solution for 2 days. A comparison with halogen containing electrolytes proves that the presence of halogen in electrolyte is the reason for corrosion. This work provides a stepping stone for developing new halogen-free electrolyte systems for rechargeable Mg batteries.

Volatile (Li, B, F and Cl) mobility during amphibole breakdown in subduction zones

NASA Astrophysics Data System (ADS)

Debret, Baptiste; Koga, Kenneth T.; Cattani, Fanny; Nicollet, Christian; Van den Bleeken, Greg; Schwartz, Stephane

2016-02-01

Amphiboles are ubiquitous minerals in the altered oceanic crust. During subduction, their breakdown is governed by continuous reactions up to eclogitic facies conditions. Amphiboles thus contribute to slab-derived fluid throughout prograde metamorphism and continuously record information about volatile exchanges occurring between the slab and the mantle wedge. However, the fate of volatile elements and especially halogens, such as F and Cl, in amphibole during subduction is poorly constrained. We studied metagabbros from three different localities in the Western Alps: the Chenaillet ophiolite, the Queyras Schistes Lustrés and the Monviso meta-ophiolitic complexes. These samples record different metamorphic conditions, from greenschist to eclogite facies, and have interacted with different lithologies (e.g. sedimentary rocks, serpentinites) from their formation at mid-oceanic ridge, up to their devolatilization during subduction. In the oceanic crust, the initial halogen budget is mostly stored in magmatic amphibole (F = 300-7000 ppm; Cl = 20-1200 ppm) or in amphibole corona (F = 100-7000 ppm; Cl = 80-2000 ppm) and titanite (F = 200-1500 ppm; Cl < 200 ppm) formed during hydrothermal seafloor alteration. It is thus the fate of these phases that govern the halogen fluxes between the crust and the overlying mantle and/or the plate interface in subduction zones. Li and B are poorly stored in the oceanic crust (< 5 ppm). In subduction zones, prograde metamorphism of metagabbros is first marked by the crystallization of glaucophane at the expense of magmatic and amphibole coronas. This episode is accompanied with a decrease of halogen concentrations in amphiboles (< 200 ppm of F and Cl) suggesting that these elements can be transferred to the mantle wedge by fluids. In the Queyras Schistes Lustrés complex, the intense deformation and the abundant devolatilization of metasedimentary rocks produce large fluid flows that promote rock chemical hybridization (metasomatic mixing with hybrid composition between metasedimentary rock and metagabbro) at the metasedimentary rock/metagabbro contacts. Such fluid/rock interactions result in a strong addition of Li in glaucophane (up to 600 ppm) whereas halogen concentrations are unaffected. At eclogite facies conditions, metagabbros display low halogens concentrations (< 20 ppm of F and < 100 ppm of Cl) relative to altered oceanic crust (F = 40-650 ppm; Cl = 40-1400 ppm) suggesting that these elements are continuously released by fluids during the first 30-80 km of subduction whatever the tectonic environment (e.g. slab, plate interface) and the considered fluid/rock interactions.

The Halogen Bond

PubMed Central

2016-01-01

The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design. PMID:26812185

Adsorption of halogens on metal surfaces

NASA Astrophysics Data System (ADS)

Andryushechkin, B. V.; Pavlova, T. V.; Eltsov, K. N.

2018-06-01

This paper presents a review of the experimental and theoretical investigations of halogen interaction with metal surfaces. The emphasis was placed on the recent measurements performed with a scanning tunneling microscope in combination with density functional theory calculations. The surface structures formed on metal surface after halogen interaction are classified into three groups: chemisorbed monolayer, surface halide, bulk-like halide. Formation of monolayer structures is described in terms of surface phase transitions. Surface halide phases are considered to be intermediates between chemisorbed halogen and bulk halide. The modern theoretical approaches in studying the dynamics of metal halogenation reactions are also presented.

What’s New in Enzymatic Halogenations

PubMed Central

Fujimori, Danica Galoniæ; Walsh, Christopher T.

2007-01-01

Summary The halogenation of thousands of natural products occurs during biosynthesis and often confers important functional properties. While haloperoxidases had been the default paradigm for enzymatic incorporation of halogens, via X+ equivalents into organic scaffolds, a combination of microbial genome sequencing, enzymatic studies and structural biology have provided deep new insights into enzymatic transfer of halide equivalents in three oxidation states. These are: (1) the halide ions (X−) abundant in nature, (2) halogen atoms (X•), and (3) the X+ equivalents. The mechanism of halogen incorporation is tailored to the electronic demands of specific substrates and involves enzymes with distinct redox coenzyme requirements. PMID:17881282

Evaluation of carbon isotope fractionation during anaerobic reductive dehalogenation of chlorinated and brominated benzenes.

PubMed

Sohn, Seo Yean; Kuntze, Kevin; Nijenhuis, Ivonne; Häggblom, Max M

2018-02-01

Compound specific stable isotope analysis (CSIA) has been established as a useful tool to evaluate in situ biodegradation. Here, CSIA was used to determine microbial dehalogenation of chloro- and bromobenzenes in microcosms derived from Hackensack River sediments. Gas chromatography-isotope ratio mass spectrometry (GC-IRMS) was used to measure carbon isotope fractionation during reductive dehalogenation of hexachlorobenzene (HCB), pentachlorobenzene (PeCB), 1,2,3,5-tetrachlorobenzene (TeCB), 1,2,3,5-tetrabromobenzene (TeBB), and 1,3,5-tribromobenzene (TriBB). Strong evidence of isotope fractionation coupled to dehalogenation was not observed in the substrate, possibly due to the low solubilities of the highly halogenated benzene substrates and a dilution of the isotope signal. Nonetheless, we could measure a depletion of the δ 13 C value in the dichlorobenzene product during dechlorination of HCB, the sequential depletion and enrichment of δ 13 C value for trichlorobenzene in TeCB dechlorinating cultures, and the enrichment of δ 13 C during debromination of TriBB. This indicates that a measurable isotope fractionation occurred during reductive dehalogenation of highly halogenated chloro- and bromobenzenes in aquatic sediments. Thus, although more quantitative measurements will be needed, the data suggests that CSIA may have application for monitoring in situ microbial reductive dehalogenation of highly halogenated benzenes. Copyright © 2017. Published by Elsevier Ltd.

Effective binding of perhalogenated closo-borates to serum albumins revealed by spectroscopic and ITC studies

NASA Astrophysics Data System (ADS)

Kuperman, Marina V.; Losytskyy, Mykhaylo Yu.; Bykov, Alexander Yu.; Yarmoluk, Sergiy M.; Zhizhin, Konstantin Yu.; Kuznetsov, Nikolay T.; Varzatskii, Oleg A.; Gumienna-Kontecka, Elzbieta; Kovalska, Vladyslava B.

2017-08-01

The interactions of boron cluster compounds closo-borates with biomolecules are widely studied due to their efficiency as agents for boron neutron capture therapy of cancer. In present work the binding abilities of anionic halogen closo-borates [B10Hal10]2- (Hal = Cl, Br, I) and [B12Hal12]2- (Hal = Cl, I) towards bovine and human serum albumins were investigated by spectroscopic and isothermal titration calorimetry (ITC) methods. The protein fluorescence quenching method and ITC studies confirmed the complex formation. The degree of protein fluorescence quenching increased from chlorine to iodine boron derivatives that is attributed to external heavy atom effect. The ITC data point on the existence in the protein structure of two types of binding sites: with higher and lower affinity to closo-borates. Albumin-closo-borate complex binding ratio, n (4-5 anions per protein molecule) is higher than for the parent hydrogen closo-borates (2 anions per protein molecule). Binding constants estimated by fluorescent and ITC methods indicate higher affinity of halogen closo-borates to albumins (K in the range of 104-106 M-1) comparing to that of the hydrogen closo-borate (K about 103 M-1). Due to their high affinity and high binding ratio to albumins halogen closo-borates are proposed for further studies as agents for boron neutron capture therapy.

Hydrogen bonded C-H···Y (Y = O, S, Hal) molecular complexes: A natural bond orbital analysis

NASA Astrophysics Data System (ADS)

Isaev, A. N.

2016-03-01

Hydrogen bonded C-H···Y complexes formed by H2O, H2S molecules, hydrogen halides, and halogen-ions with methane, halogen substituted methane as well as with the C2H2 and NCH molecules were studied at the MP2/aug-cc-pVDZ level. The structure of NBOs corresponding to lone pair of acceptor Y, n Y, and vacant anti-σ-bond C-H of proton donor was analyzed and estimates of second order perturbation energy E(2) characterizing donor-acceptor n Y → σ C-H * charge-transfer interaction were obtained. Computational results for complexes of methane and its halogen substituted derivatives show that for each set of analogous structures, the EnY→σ*C-H (2) energy tends to grow with an increase in the s-component percentage in the lone pair NBO of acceptor Y. Calculations for different C···Y distances show that the equilibrium geometries of complexes lie in the region where the E(2) energy is highest and it changes symbatically with the length of the covalent E-H bond when the R(C···Y) distance is varied. The performed analysis allows us to divide the hydrogen bonded complexes into two groups, depending on the pattern of overlapping for NBOs of the hydrogen bridge.

Characterization of non-classical Csbnd Br⋯π interactions in (E)-1,3-dibromo-5-(2-(ferrocenyl)vinyl)benzene and related derivatives of ferrocene

NASA Astrophysics Data System (ADS)

Shukla, Rahul; Panini, Piyush; McAdam, C. John; Robinson, Brian H.; Simpson, Jim; Tagg, Tei; Chopra, Deepak

2017-03-01

Amongst the halogens, the involvement of bromine atoms in various types of intermolecular interactions is comparatively the least studied. In this manuscript, we report the formation of Csbnd Br⋯π interactions, with the π-rings being the cyclopentadienyl (Cp) rings of a ferrocene molecule in a newly synthesized compound (E)-1,3-dibromo-5-(2-(ferrocenyl)vinyl)benzene. We have also performed a detailed quantitative analysis on Csbnd Br⋯π interactions observed in the synthesized molecule and in several related molecules found in the Cambridge Structure Database (CSD) showing the presence of these interactions. A topological analysis based upon QTAIM theory and electrostatic potential ESP mapped on the Hirshfeld surface of these molecules confirm that these interactions are better described as "halogen bonds" wherein the electropositive region (σ-hole) on the Br-atom interacts with the electronegative region over the Cp-ring of the ferrocene. Further, the electronegative region on the bromine atom (perpendicular to the Csbnd Br bond) was observed to be involved in the formation of highly directional Csbnd H⋯Br interactions with the ∠Csbnd Br⋯H close to 90°. Thus the bromine atom is acting as both a "halogen bond donor" and "hydrogen bond acceptor" in the crystal packing with the two interactions being mutually orthogonal.

Metalloporphyrins and their uses as radiosensitizers for radiation therapy

DOEpatents

Miura, Michiko; Slatkin, Daniel N.

2004-07-06

The present invention covers radiosensitizers containing as an active ingredient halogenated derivatives of boronated porphyrins containing multiple carborane cages having the structure ##STR1## which selectively accumulate in neoplastic tissue within the irradiation volume and thus can be used in cancer therapies including, but not limited to, boron neutron--capture therapy and photodynamic therapy. The present invention also covers methods for using these radiosensitizers in tumor imaging and cancer treatment.

Arylthioindole inhibitors of tubulin polymerization. 3. Biological evaluation, structure-activity relationships and molecular modeling studies.

PubMed

La Regina, Giuseppe; Edler, Michael C; Brancale, Andrea; Kandil, Sahar; Coluccia, Antonio; Piscitelli, Francesco; Hamel, Ernest; De Martino, Gabriella; Matesanz, Ruth; Díaz, José Fernando; Scovassi, Anna Ivana; Prosperi, Ennio; Lavecchia, Antonio; Novellino, Ettore; Artico, Marino; Silvestri, Romano

2007-06-14

The new arylthioindole (ATI) derivatives 10, 14-18, and 21-24, which bear a halogen atom or a small size ether group at position 5 of the indole moiety, were compared with the reference compounds colchicine and combretastatin A-4 for biological activity. Derivatives 10, 11, 16, and 21-24 inhibited MCF-7 cell growth with IC50 values <50 nM. A halogen atom (14-17) at position 5 caused a significant reduction in the free energy of binding of compound to tubulin, with a concomitant reduction in cytotoxicity. In contrast, methyl (21) and methoxy (22) substituents at position 5 caused an increase in cytotoxicity. Compound 16, the most potent antitubulin agent, led to a large increase (56%) in HeLa cells in the G2/M phase at 24 h, and at 48 h, 26% of the cells were hyperploid. Molecular modeling studies showed that, despite the absence of the ester moiety present in the previously examined analogues, most of the compounds bind in the colchicine site in the same orientation as the previously studied ATIs. Binding to beta-tubulin involved formation of a hydrogen bond between the indole and Thr179 and positioning of the trimethoxy phenyl group in a hydrophobic pocket near Cys241.

40 CFR 63.2465 - What requirements must I meet for process vents that emit hydrogen halide and halogen HAP or HAP...

Code of Federal Regulations, 2014 CFR

2014-07-01

... process vents that emit hydrogen halide and halogen HAP or HAP metals? 63.2465 Section 63.2465 Protection... hydrogen halide and halogen HAP or HAP metals? (a) You must meet each emission limit in Table 3 to this...) of this section. (b) If any process vents within a process emit hydrogen halide and halogen HAP, you...

40 CFR 63.2465 - What requirements must I meet for process vents that emit hydrogen halide and halogen HAP or HAP...

Code of Federal Regulations, 2013 CFR

2013-07-01

... process vents that emit hydrogen halide and halogen HAP or HAP metals? 63.2465 Section 63.2465 Protection... hydrogen halide and halogen HAP or HAP metals? (a) You must meet each emission limit in Table 3 to this...) of this section. (b) If any process vents within a process emit hydrogen halide and halogen HAP, you...

40 CFR 63.2465 - What requirements must I meet for process vents that emit hydrogen halide and halogen HAP or HAP...

Code of Federal Regulations, 2012 CFR

2012-07-01

... process vents that emit hydrogen halide and halogen HAP or HAP metals? 63.2465 Section 63.2465 Protection... hydrogen halide and halogen HAP or HAP metals? (a) You must meet each emission limit in Table 3 to this...) of this section. (b) If any process vents within a process emit hydrogen halide and halogen HAP, you...

A metagenomic-based survey of microbial (de)halogenation potential in a German forest soil

PubMed Central

Weigold, Pascal; El-Hadidi, Mohamed; Ruecker, Alexander; Huson, Daniel H.; Scholten, Thomas; Jochmann, Maik; Kappler, Andreas; Behrens, Sebastian

2016-01-01

In soils halogens (fluorine, chlorine, bromine, iodine) are cycled through the transformation of inorganic halides into organohalogen compounds and vice versa. There is evidence that these reactions are microbially driven but the key enzymes and groups of microorganisms involved are largely unknown. Our aim was to uncover the diversity, abundance and distribution of genes encoding for halogenating and dehalogenating enzymes in a German forest soil by shotgun metagenomic sequencing. Metagenomic libraries of three soil horizons revealed the presence of genera known to be involved in halogenation and dehalogenation processes such as Bradyrhizobium or Pseudomonas. We detected a so far unknown diversity of genes encoding for (de)halogenating enzymes in the soil metagenome including specific and unspecific halogenases as well as metabolic and cometabolic dehalogenases. Genes for non-heme, no-metal chloroperoxidases and haloalkane dehalogenases were the most abundant halogenase and dehalogenase genes, respectively. The high diversity and abundance of (de)halogenating enzymes suggests a strong microbial contribution to natural halogen cycling. This was also confirmed in microcosm experiments in which we quantified the biotic formation of chloroform and bromoform. Knowledge on microorganisms and genes that catalyze (de)halogenation reactions is critical because they are highly relevant to industrial biotechnologies and bioremediation applications. PMID:27353292

Structures and electronic states of halogen-terminated graphene nano-flakes

NASA Astrophysics Data System (ADS)

Tachikawa, Hiroto; Iyama, Tetsuji

2015-12-01

Halogen-functionalized graphenes are utilized as electronic devices and energy materials. In the present paper, the effects of halogen-termination of graphene edge on the structures and electronic states of graphene flakes have been investigated by means of density functional theory (DFT) method. It was found that the ionization potential (Ip) and electron affinity of graphene (EA) are blue-shifted by the halogen termination, while the excitation energy is red-shifted. The drastic change showed a possibility as electronic devices such as field-effect transistors. The change of electronic states caused by the halogen termination of graphene edge was discussed on the basis of the theoretical results.

Deriving an atmospheric budget of total organic bromine using airborne in-situ measurements from the Western Pacific during SHIVA

NASA Astrophysics Data System (ADS)

Sala, S.; Bönisch, H.; Keber, T.; Oram, D. E.; Mills, G.; Engel, A.

2014-02-01

During the SHIVA (Stratospheric Ozone: Halogen Impacts in a Varying Atmosphere) project an extensive dataset of all halogen species relevant for the atmospheric budget of total organic bromine has been collected in the West Pacific region using the FALCON aircraft operated by the German Aerospace agency DLR (Deutsches Zentrum für Luft- und Raumfahrt) covering a vertical range from the planetary boundary layer up to the ceiling altitude of the aircraft of 13 km. In total, more than 700 measurements were performed with the newly developed fully-automated in-situ instrument GHOST-MS (Gas cHromatograph for the Observation of Tracers - coupled with a Mass Spectrometer) by the Goethe University of Frankfurt (GUF) and with the onboard whole-air sampler WASP with subsequent ground based state-of-the-art GC/MS analysis by the University of East Anglia (UEA). Both instruments yield good agreement for all major (CHBr3 and CH2Br2) and minor (CHBrCl, CHBrCl2 and CHBr2Cl) VSLS (very short-lived substances), at least at the level of their 2 σ measurement uncertainties. In contrast to the suggestion that the Western Pacific could be a major source region for VSLS (Pyle et al., 2011), we found only slightly enhanced mixing ratios of brominated halogen source gases relative to the levels reported in Montzka et al. (2011) for other tropical regions. A budget for total organic bromine, including all four halons,CH3Br and the VSLS, is derived for the upper troposphere, the input region for the TTL and thus also for the stratosphere, compiled from the SHIVA dataset. With exception of the two minor VSLS CHBrCl2 and CHBr2Cl, excellent agreement with the values reported in Montzka et al. (2011) is found, while being slightly higher than previous studies from our group based on balloon-borne measurements.

The relation between molecular structure and biological activity among mononitrophenols containing halogens

USGS Publications Warehouse

Applegate, Vernon C.; Johnson, B.G.H.; Smith, Manning A.

1966-01-01

The results of tests of the biological activity of certain nitrophenols containing halogen are reported. Some of these are shown to be significantly more toxic to larvae of the sea lamprey (Petromyzon marinus L.) than to fishes. It is proposed that the death of lamprey larvae exposed to these compounds results from an acute hypotension (shock) with concomitant circulatory and respiratory failure. Rainbow trout (Salmo gairdneri), on the other hand, appear to die, at higher concentrations of the toxin, due to a chemically-caused mechanical interference with respiration through the gills. A systematic series of studies of mononitrophenols containing halogens disclosed that those phenols having the nitro group in the para-position and a halogen atom or group in the meta-position are generally more toxic to lampreys than to fish. The halogens or halogen groups used in this study were fluorine, chlorine, bromine, and trifluormethyl. The same substituents in other positions only occasionally gave rise to selectively toxic compounds. The relationship between the selectively active class of nitrophenols containing halogens and other related structures is discussed.

Reversible capture and release of Cl 2 and Br 2 with a redox-active metal–organic framework

DOE PAGES

Tulchinsky, Yuri; Hendon, Christopher H.; Lomachenko, Kirill A.; ...

2017-03-28

Extreme toxicity, corrosiveness, and volatility pose serious challenges for the safe storage and transportation of elemental chlorine and bromine, which play critical roles in the chemical industry. Solid materials capable of forming stable nonvolatile compounds upon reaction with elemental halogens may partially mitigate these challenges by allowing safe halogen release on demand. Here we demonstrate that elemental halogens quantitatively oxidize coordinatively unsaturated Co(II) ions in a robust azolate metal-organic framework (MOF) to produce stable and safe-to-handle Co(III) materials featuring terminal Co(III)-halogen bonds. Thermal treatment of the oxidized MOF causes homolytic cleavage of the Co(III)-halogen bonds, reduction to Co(II), and concomitantmore » release of elemental halogens. The reversible chemical storage and thermal release of elemental halogens occur with no significant losses of structural integrity, as the parent cobaltous MOF retains its crystallinity and porosity even after three oxidation/reduction cycles. Finally, these results highlight a material operating via redox mechanism that may find utility in the storage and capture of other noxious and corrosive gases.« less

Model studies in cytochrome P-450-mediated toxicity of halogenated compounds: radical processes involving iron porphyrins.

PubMed Central

Brault, D

1985-01-01

Haloalkane toxicity originates from attack on biological targets by reactive intermediates derived from haloalkane metabolism by a hemoprotein, cytochrome P-450. Carbon-centered radicals and their peroxyl derivatives are most likely involved. The reactions of iron porphyrin--a model for cytochrome P-450--with various carbon-centered and peroxyl radicals generated by pulse radiolysis are examined. Competition between iron porphyrin and unsaturated fatty acids for attack by peroxyl radicals is pointed out. These kinetic data are used to derive a model for toxicity of haloalkanes with particular attention to carbon tetrachloride and halothane. The importance of local oxygen concentration and structural arrangement of fatty acids around cytochrome P-450 is emphasized. PMID:3007100

40 CFR 63.128 - Transfer operations provisions-test methods and procedures.

Code of Federal Regulations, 2013 CFR

2013-07-01

... using a scrubber or other halogen reduction device to reduce the vent stream halogen atom mass emission...)(2) shall determine the halogen atom mass emission rate prior to the combustor according to the...

40 CFR 63.128 - Transfer operations provisions-test methods and procedures.

Code of Federal Regulations, 2011 CFR

2011-07-01

... using a scrubber or other halogen reduction device to reduce the vent stream halogen atom mass emission...)(2) shall determine the halogen atom mass emission rate prior to the combustor according to the...

40 CFR 63.128 - Transfer operations provisions-test methods and procedures.

Code of Federal Regulations, 2010 CFR

2010-07-01

... using a scrubber or other halogen reduction device to reduce the vent stream halogen atom mass emission...)(2) shall determine the halogen atom mass emission rate prior to the combustor according to the...

40 CFR 63.128 - Transfer operations provisions-test methods and procedures.

Code of Federal Regulations, 2014 CFR

2014-07-01

... using a scrubber or other halogen reduction device to reduce the vent stream halogen atom mass emission...)(2) shall determine the halogen atom mass emission rate prior to the combustor according to the...

40 CFR 63.128 - Transfer operations provisions-test methods and procedures.

Code of Federal Regulations, 2012 CFR

2012-07-01

... using a scrubber or other halogen reduction device to reduce the vent stream halogen atom mass emission...)(2) shall determine the halogen atom mass emission rate prior to the combustor according to the...

Magnesium Bisamide-Mediated Halogen Dance of Bromothiophenes.

PubMed

Yamane, Yoshiki; Sunahara, Kazuhiro; Okano, Kentaro; Mori, Atsunori

2018-03-16

A magnesium bisamide-mediated halogen dance of bromothiophenes is described. The thienylmagnesium species generated in situ is more stable than the corresponding thienyllithium species, which was applied to trap the transient anion species with several electrophiles, such as allyl iodide, phenyl isocyanate, and tributylstannyl chloride. The utility of the magnesium bisamide-mediated halogen dance is useful in the concise synthesis of a medicinally advantageous compound via a one-pot, ester-directed halogen dance/Negishi cross coupling.

Degradation of halogenated aliphatic compounds by Xanthobacter autotrophicus GJ10.

PubMed Central

Janssen, D B; Scheper, A; Dijkhuizen, L; Witholt, B

1985-01-01

A bacterium that is able to utilize a number of halogenated short-chain hydrocarbons and halogenated carboxylic acids as sole carbon source for growth was identified as a strain of Xanthobacter autotrophicus. The organism constitutively produces two different dehalogenases. One enzyme is specific for halogenated alkanes, whereas the other, which is more heat stable and has a higher pH optimum, is specific for halogenated carboxylic acids. Haloalkanes were hydrolyzed in cell extracts to produce alcohols and halide ions, and a route for the metabolism of 1,2-dichlorethane is proposed. Both dehalogenases show a broad substrate specificity, allowing the degradation of bromine- and chlorine-substituted organic compounds. The results show that X. autotrophicus may play a role in the degradation of organochlorine compounds and that hydrolytic dehalogenases may be involved in the microbial metabolism of short-chain halogenated hydrocarbons in microorganisms. Images PMID:3994371

Evidence for Interfacial Halogen Bonding.

PubMed

Swords, Wesley B; Simon, Sarah J C; Parlane, Fraser G L; Dean, Rebecca K; Kellett, Cameron W; Hu, Ke; Meyer, Gerald J; Berlinguette, Curtis P

2016-05-10

A homologous series of donor-π-acceptor dyes was synthesized, differing only in the identity of the halogen substituents about the triphenylamine (TPA; donor) portion of each molecule. Each Dye-X (X=F, Cl, Br, and I) was immobilized on a TiO2 surface to investigate how the halogen substituents affect the reaction between the light-induced charge-separated state, TiO2 (e(-) )/Dye-X(+) , with iodide in solution. Transient absorption spectroscopy showed progressively faster reactivity towards nucleophilic iodide with more polarizable halogen substituents: Dye-F < Dye-Cl < Dye-Br < Dye-I. Given that all other structural and electronic properties for the series are held at parity, with the exception of an increasingly larger electropositive σ-hole on the heavier halogens, the differences in dye regeneration kinetics for Dye-Cl, Dye-Br, and Dye-I are ascribed to the extent of halogen bonding with the nucleophilic solution species. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Aerosol-halogen interaction: Change of physico-chemical properties of SOA by naturally released halogen species

NASA Astrophysics Data System (ADS)

Ofner, J.; Balzer, N.; Buxmann, J.; Grothe, H.; Krüger, H.; Platt, U.; Schmitt-Kopplin, P.; Zetzsch, C.

2011-12-01

Reactive halogen species are released by various sources like photo-activated sea-salt aerosol or salt pans and salt lakes. These heterogeneous release mechanisms have been overlooked so far, although their potential of interaction with organic aerosols like Secondary Organic Aerosol (SOA), Biomass Burning Organic Aerosol (BBOA) or Atmospheric Humic LIke Substances (HULIS) is completely unknown. Such reactions can constitute sources of gaseous organo-halogen compounds or halogenated organic particles in the atmospheric boundary layer. To study the interaction of organic aerosols with reactive halogen species (RHS), SOA was produced from α-pinene, catechol and guaiacol using an aerosol smog-chamber. The model SOAs were characterized in detail using a variety of physico-chemical methods (Ofner et al., 2011). Those aerosols were exposed to molecular halogens in the presence of UV/VIS irradiation and to halogens, released from simulated natural halogen sources like salt pans, in order to study the complex aerosol-halogen interaction. The heterogeneous reaction of RHS with those model aerosols leads to different gaseous species like CO2, CO and small reactive/toxic molecules like phosgene (COCl2). Hydrogen containing groups on the aerosol particles are destroyed to form HCl or HBr, and a significant formation of C-Br bonds could be verified in the particle phase. Carbonyl containing functional groups of the aerosol are strongly affected by the halogenation process. While changes of functional groups and gaseous species were visible using FTIR spectroscopy, optical properties were studied using Diffuse Reflectance UV/VIS spectroscopy. Overall, the optical properties of the processed organic aerosols are significantly changed. While chlorine causes a "bleaching" of the aerosol particles, bromine shifts the maximum of UV/VIS absorption to the red end of the UV/VIS spectrum. Further physico-chemical changes were recognized according to the aerosol size-distributions or the averaged carbon oxidation state (OSc). The heterogeneous reaction of SOA with molecular halogens released from the simulated salt-pan at different simulated environmental conditions leads to changes of several physico-chemical features of the aerosol. However, the halogen release mechanisms are also affected by the presence of organic aerosols. One order of magnitude less BrO was detected by an active Differential Optical Absorption Spectroscopy (DOAS) instrument in the presence of SOA compared to experiments without SOA. This work was supported by the German Research Foundation within the HALOPROC project. Ofner, J., Krüger, H.-U., Grothe, H., Schmitt-Kopplin, P., Whitmore, K., and Zetzsch, C. (2011), Atmos. Chem. Phys., 11, 1-15.

Organic Halogen and Related Trace Gases in the Tropical Atmosphere: Results from Recent Airborne Campaigns Over the Pacific

NASA Astrophysics Data System (ADS)

Atlas, E. L.; Navarro, M. A.; Donets, V.; Schauffler, S.; Lueb, R.; Hendershot, R.; Gabbard, S.; Hornbrook, R. S.; Apel, E. C.; Riemer, D. D.; Pan, L.; Salawitch, R. J.; Nicely, J. M.; Montzka, S. A.; Miller, B.; Moore, F. L.; Elkins, J. W.; Hintsa, E. J.; Campos, T. L.; Quack, B.; Zhu, X.; Pope, L.

2014-12-01

Organic halogen gases, especially containing bromine and iodine, play a significant role as precursors to active halogen chemistry and ozone catalytic loss. Much of the reactive organic halogen originates from biological processes in the surface ocean, which can be quite variable by season and location. The tropics and coastal margins are potentially important sources that are being examined. The recent coordinated CONTRAST/ATTREX/CAST missions were conducted in the Western Tropical Pacific, a region that is a major transport pathway for tropospheric air entering the stratosphere. One of the goals of the missions was to identify sources, distributions, and transport of organic halogens from the ocean surface into the tropical lower stratosphere. The missions were conducted during the NH winter season, Jan-Feb, 2014. In this presentation, we will discuss the distributions and variability of organic halogen gases in the study region and will examine the input of organic halogen species into the Tropical Tropopause Layer (TTL). Comparison with other tracers, such as methyl nitrate and NMHC, will help identify source regions for these gases. We will focus on the measurements obtained in the CONTRAST and ATTREX missions with data from in-situ GC/MS measurements and whole air samples collected on the NSF GV and NASA Global Hawk aircraft. Comparisons with other recent airborne campaigns, such as HIPPO and TC4, and with several ship-based studies will provide an additional context for evaluating the variability of organic halogen species in the tropical atmosphere and their role in transporting reactive halogen compounds into the UT/LS.

Angles between orthogonal spd bond orbitals with maximum strength.

PubMed

Pauling, L

1976-05-01

An equation is derived for values of bond angles for two equivalent best spd hybrid bond orbitals with given amounts of s, p, and d character, and is applied in the discussion of structures of transargononic compounds, including the xenon and halogen fluorides. Bond orbitals with a rather small amount of d character tend to lie at angles 90 degrees and 180 degrees , and those with a larger amount, at somewhat smaller angles.

Survey of less-inflammable hydraulic fluids for aircraft

NASA Technical Reports Server (NTRS)

Drake, Wray V; Drell, I L

1950-01-01

A survey of current information on civil and military development of less-inflammable hydraulic fluids for aircraft is presented. Types of less-inflammable fluid reported include: glycol derivative, water base, silicone, ester, and halogenated compound. Specification requirements, physical and chemical properties, hydraulic-system test results, and advantages and disadvantages of various hydraulic fluids are discussed. For completely satisfactory service, some modification of currently available fluids or of present hydraulic-system parts still appears necessary.

(2E)-3-[4-(Benz-yloxy)phen-yl]-1-(2,6-dichloro-3-fluoro-phen-yl)prop-2-en-1-one.

PubMed

Praveen, Aletti S; Yathirajan, Hemmige S; Gerber, Thomas; van Brecht, Benjamin; Betz, Richard

2012-12-01

In the title compound, C22H15Cl2FO2, a chalcone derivative featuring a threefold-halogenated aromatic substituent, the conformation about the C=C bond is E. In the crystal C-H⋯F and C-H⋯Cl contacts connect the mol-ecules into undulating sheets parallel to (101). In addition, C-H⋯π inter-actions are also present.

Asymmetric Synthesis of 1,2,9,9a-Tetrahydrocyclopropa[c]benzo[e]indol-4-one (CBI)

PubMed Central

Lajiness, James P.; Boger, Dale L.

2011-01-01

A short, asymmetric synthesis of the 1,2,9,9a-tetrahydrocyclopropa[c]benzo[e]indol-4-one (CBI) analogue of the CC-1065 and duocarmycin DNA alkylation subunits is described. Treatment of iodo-epoxide 5, prepared by late-stage alkylation of 4 with (S)-glycidal-3-nosylate, with EtMgBr at room temperature directly provides the optically pure alcohol 6 in 87% yield (99% ee) derived from selective metal–halogen exchange and subsequent regioselective intramolecular 6-endo-tet cyclization. The use of MeMgBr or i-PrMgBr also provides the product in high yields (82–87%), but requires larger amounts of the Grignard reagent to effect metal–halogen exchange and cyclization. Direct transannular spirocyclization of 7 following O-debenzylation of 6 provides N-Boc-CBI. This approach represents the most efficient (9-steps, 31% overall) and effective (99% ee) route to the optically pure CBI alkylation subunit yet described. PMID:21192653

Development of a flameproof elastic elastomeric fiber

NASA Technical Reports Server (NTRS)

Howarth, J. T.; Nilgrom, J.; Massucco, A.; Sheth, S. G.; Dawn, F. S.

1971-01-01

Various flexible polyurethane structures containing halogen were synthesized from polyesters derived from aliphatic or aromatic polyols and dibasic acids. Aliphatic halide structures could not be used because they are unstable at the required reaction temperatures, giving of hydrogen halide which hydrolyzes the ester linkages. In contract, halogen-containing aromatic polyols were stable and satisfactory products were made. The most promising composition, a brominated neopentyl glycol capped with toluene disocyanate, was used as a conventional diisocyanate, in conjunction with hydroxy-terminated polyethers or polyesters to form elastomeric urethanes containing about 10% bromine with weight. Products made in this manner will not burn in air, have an oxygen index value of about 25, and have tensile strength values of about 5,000 psi at 450% elongation. The most efficient additives for imparting flame retardancy to Spandex urethanes are aromatic halides and the most effective of these are the bromide compounds. Various levels of flame retardancy have been achieved depending on the levels of additives used.

Photocrystallographic observation of halide-bridged intermediates in halogen photoeliminations.

PubMed

Powers, David C; Anderson, Bryce L; Hwang, Seung Jun; Powers, Tamara M; Pérez, Lisa M; Hall, Michael B; Zheng, Shao-Liang; Chen, Yu-Sheng; Nocera, Daniel G

2014-10-29

Polynuclear transition metal complexes, which frequently constitute the active sites of both biological and chemical catalysts, provide access to unique chemical transformations that are derived from metal-metal cooperation. Reductive elimination via ligand-bridged binuclear intermediates from bimetallic cores is one mechanism by which metals may cooperate during catalysis. We have established families of Rh2 complexes that participate in HX-splitting photocatalysis in which metal-metal cooperation is credited with the ability to achieve multielectron photochemical reactions in preference to single-electron transformations. Nanosecond-resolved transient absorption spectroscopy, steady-state photocrystallography, and computational modeling have allowed direct observation and characterization of Cl-bridged intermediates (intramolecular analogues of classical ligand-bridged intermediates in binuclear eliminations) in halogen elimination reactions. On the basis of these observations, a new class of Rh2 complexes, supported by CO ligands, has been prepared, allowing for the isolation and independent characterization of the proposed halide-bridged intermediates. Direct observation of halide-bridged structures establishes binuclear reductive elimination as a viable mechanism for photogenerating energetic bonds.

Ultrafast Solvation Dynamics and Vibrational Coherences of Halogenated Boron-Dipyrromethene Derivatives Revealed through Two-Dimensional Electronic Spectroscopy.

PubMed

Lee, Yumin; Das, Saptaparna; Malamakal, Roy M; Meloni, Stephen; Chenoweth, David M; Anna, Jessica M

2017-10-18

Boron-dipyrromethene (BODIPY) chromophores have a wide range of applications, spanning areas from biological imaging to solar energy conversion. Understanding the ultrafast dynamics of electronically excited BODIPY chromophores could lead to further advances in these areas. In this work, we characterize and compare the ultrafast dynamics of halogenated BODIPY chromophores through applying two-dimensional electronic spectroscopy (2DES). Through our studies, we demonstrate a new data analysis procedure for extracting the dynamic Stokes shift from 2DES spectra revealing an ultrafast solvent relaxation. In addition, we extract the frequency of the vibrational modes that are strongly coupled to the electronic excitation, and compare the results of structurally different BODIPY chromophores. We interpret our results with the aid of DFT calculations, finding that structural modifications lead to changes in the frequency, identity, and magnitude of Franck-Condon active vibrational modes. We attribute these changes to differences in the electron density of the electronic states of the structurally different BODIPY chromophores.

Peptide selectivity between the PDZ domains of human pregnancy-related serine proteases (HtrA1, HtrA2, HtrA3, and HtrA4) can be reshaped by different halogen probes.

PubMed

Sun, Mei-Ling; Sun, Li-Mei; Wang, Yong-Qing

2018-06-01

The human HtrA family of serine proteases (HtrA1, HtrA2, HtrA3, and HtrA4) are the key enzymes associated with pregnancy and closely related to the development and progression of many pathological events. Previously, it was found that halogen substitution at the indole moiety of peptide Trp-1 residue can form a geometrically satisfactory halogen bond with the Drosophila discs large, zona occludens-1 (PDZ) domain of HtrA proteases. Here, we attempt to systematically investigate the effect of substitution with 4 halogen types and 2 indole positions on the binding affinity and specificity of peptide ligands to the 4 HtrA PDZ domains. The complex structures, interaction energies, halogen-bonding strength, and binding affinity of domain-peptide systems were modeled, analyzed, and measured via computational modeling and fluorescence-based assay. It is revealed that there is a compromise between the local rearrangement of halogen bond involving different halogen atoms and the global optimization of domain-peptide interaction; the substitution position is fundamentally important for peptide-binding affinity, while the halogen type can effectively shift peptide selectivity between the 4 domains. The HtrA1-PDZ and HtrA4-PDZ as well as HtrA2-PDZ and HtrA3-PDZ respond similarly to different halogen substitutions of peptide; -Br substitution at R2-position and -I substitution at R4-position are most effective in improving peptide selectivity for HtrA1-PDZ/HtrA4-PDZ and HtrA2-PDZ/HtrA3-PDZ, respectively; -F substitution would not address substantial effect on peptide selectivity for all the 4 domains. Consequently, the binding affinities of a native peptide ligand DSRIWWV -COOH as well as its 4 R2-halogenated counterparts were determined as 1.9, 1.4, 0.5, 0.27, and 0.92 μM, which are basically consistent with computational analysis. This study would help to rationally design selective peptide inhibitors of HtrA family members by using different halogen substitutions. Copyright © 2017 John Wiley & Sons, Ltd.

Derivatization in gas chromatographic determination of phenol and aniline traces in aqueous media

NASA Astrophysics Data System (ADS)

Gruzdev, I. V.; Zenkevich, I. G.; Kondratenok, B. M.

2015-06-01

Substituted anilines and phenols are the most common hydrophilic organic environmental toxicants. The principles of gas chromatographic determination of trace amounts of these compounds in aqueous media at concentrations <=0.1 μg litre-1 based on synthesis of their derivatives (derivatization) directly in the aqueous phase are considered. Conversion of relatively hydrophilic analytes into more hydrophobic derivatives makes it possible to achieve such low detection limits and optimize the protocols of extractive preconcentration and selective chromatographic detection. Among the known reactions, this condition is best met by electrophilic halogenation of compounds at the aromatic moiety. The bibliography includes 177 references.

Deriving an atmospheric budget of total organic bromine using airborne in-situ measurements of brominated hydrocarbons in the Western Pacific during SHIVA

NASA Astrophysics Data System (ADS)

Sala, Stephan; Bönisch, Harald; Keber, Timo; Oram, Dave; Mills, Graham; Engel, Andreas

2014-05-01

Halogenated hydrocarbons play a major role as precursors for stratospheric ozone depletion. Released from the surface in the troposphere, the halocarbons reach the stratosphere via transport through the tropical tropopause layer. The contribution of the so called very short lived species (VSLS), having atmospheric lifetimes of less than half a year as sources gases for stratospheric bromine is significant. Source gas observations of long-lived bromine compounds and VSLS have so far not been able to explain the amount of bromine derived in the stratosphere from observations of BrO and modeling of the ratio of BrO to total bromine. Due to the short lifetimes and the high atmospheric variability, the representativeness of the available observations of VSLS source gases remains unclear, as these may vary with region and display seasonal variability. During the SHIVA (Stratospheric Ozone: Halogen Impacts in a Varying Atmosphere) project an extensive dataset with over 700 samples of ambient air of all halogen species relevant for the atmospheric budget of total organic bromine (long lived halocarbons: H-1301, H-1211, H-1202, H-2402 and CH3Br, very short lived substances: CHBr3, CH2Br2, CHBr2Cl, CHBrCl2 and CHBrCl) have been collected from onboard the FALCON aircraft in the West Pacific region. Measurements were performed with the newly developed fully-automated in-situ instrument GHOST-MS (Gas chromatograph for the Observation of Tracers - coupled with a Mass Spectrometer) by the Goethe University of Frankfurt and with the onboard whole-air sampler WASP with subsequent ground based state-of-the-art GC/MS analysis by the University of East Anglia. We will present the datasets, compare these to other observation, derive a bromine budget for the West Pacific and derive an estimate of the amount of bromine from VSLS reaching the stratosphere. Using the mean mixing ratios in the upper troposphere of the halocarbons mentioned above, the calculated budget of the total organic bromine is (20.01 ± 1.77) ppt and the total amount from VSLS is (4.35 ± 0.59) ppt. Regarding the entry of bromine in the stratosphere, the estimation of the bromine content at the LZRH gives a value of (18.54 ± 1.78) ppt and a value of (2.88 ± 0.60) ppt from VSLS, reflecting a fraction of 16% of the total bromine budget.

Synthesis and evaluation of 2-halogenated-1,1-bis(4-hydroxyphenyl)-2-(3-hydroxyphenyl)-ethylenes as potential estrogen receptor-targeted radiodiagnostic and radiotherapeutic agents.

PubMed

Hanson, Robert N; Tongcharoensirikul, Pakamas; Barnsley, Kelton; Ondrechen, Mary Jo; Hughes, Alun; DeSombre, Eugene R

2015-04-01

A series of three 1,1-bis(4-hydroxyphenyl)-2-(3-hydroxyphenyl)-ethylene derivatives was prepared and evaluated as potential estrogen receptor imaging agents. The compounds display high binding affinity compared to estradiol, with the 2-iodo and 2-bromo-derivatives expressing higher affinity than the parent 2-nonhalogenated derivative. Evaluation in immature female rats also indicate that the compounds were all full estrogenic agonists with potencies in the same order of activity (I∼Br>H). Computational analysis of the interactions between the ligands and ERα-LBD demonstrated positive contribution of halide to binding properties. In preparation for studies using the radiohalogenated analogs, the corresponding protected 2-(tributylstannyl) derivative was prepared and converted to the corresponding 2-iodo-product. Copyright © 2015 Elsevier Inc. All rights reserved.

Shear bond strength of a bracket-bonding system cured with a light-emitting diode or halogen-based light-curing unit at various polymerization times

PubMed Central

Gupta, Sanjay Prasad; Shrestha, Basanta Kumar

2018-01-01

Purpose To determine and compare the shear bond strength (SBS) of bracket-bonding system cured with light-emitting diode (LED) and halogen-based light-curing unit at various polymerization times. Materials and methods Ninety six human maxillary premolar teeth extracted for orthodontic purpose were divided into four groups, according to the light-curing unit and exposure times used. In the halogen group, the specimens were light cured for 20 and 40 seconds. In the LED group, the specimens were light cured for 5 and 10 seconds. Stainless steel brackets were bonded with Enlight bonding system, stored in distilled water at 37°C for 24 hours and then submitted to SBS testing in a universal testing machine at a crosshead speed of 0.5 mm/minute. Adhesive remnant index (ARI) was used to evaluate the amount of adhesive remaining on the teeth determined by stereomicroscope at 10× magnification. Results The highest mean SBS was obtained with the halogen 40 seconds (18.27 MPa) followed by halogen 20 seconds (15.36 MPa), LED 10 seconds (14.60 MPa) and least with LED 5 seconds (12.49 MPa) group. According to analysis of variance (ANOVA) and Tukey’s multiple-comparison test, SBS of halogen 20 seconds group was not significantly different from halogen 40 seconds group, LED 5 seconds group and LED 10 seconds group, whereas halogen 40 seconds group was significantly different from LED 5 seconds and LED 10 seconds group. The method of light curing did not influence the ARI, with score 2 being predominant. Conclusion Polymerization with both halogen and LED resulted in SBS values that were clinically acceptable for orthodontic treatment in all groups. Hence, for bonding orthodontic brackets, photoactivation with halogen for 20 seconds and LED for 5 seconds is suggested. PMID:29692633

Treatment of halogen-containing waste and other waste materials

DOEpatents

Forsberg, Charles W.; Beahm, Edward C.; Parker, George W.

1997-01-01

A process for treating a halogen-containing waste material. The process provides a bath of molten glass containing a sacrificial metal oxide capable of reacting with a halogen in the waste material. The sacrificial metal oxide is present in the molten glass in at least a stoichiometric amount with respect to the halogen in the waste material. The waste material is introduced into the bath of molten glass to cause a reaction between the halogen in the waste material and the sacrificial metal oxide to yield a metal halide. The metal halide is a gas at the temperature of the molten glass. The gaseous metal halide is separated from the molten glass and contacted with an aqueous scrubber solution of an alkali metal hydroxide to yield a metal hydroxide or metal oxide-containing precipitate and a soluble alkali metal halide. The precipitate is then separated from the aqueous scrubber solution. The molten glass containing the treated waste material is removed from the bath as a waste glass. The process of the invention can be used to treat all types of waste material including radioactive wastes. The process is particularly suited for separating halogens from halogen-containing wastes.

Treatment of halogen-containing waste and other waste materials

DOEpatents

Forsberg, C.W.; Beahm, E.C.; Parker, G.W.

1997-03-18

A process is described for treating a halogen-containing waste material. The process provides a bath of molten glass containing a sacrificial metal oxide capable of reacting with a halogen in the waste material. The sacrificial metal oxide is present in the molten glass in at least a stoichiometric amount with respect to the halogen in the waste material. The waste material is introduced into the bath of molten glass to cause a reaction between the halogen in the waste material and the sacrificial metal oxide to yield a metal halide. The metal halide is a gas at the temperature of the molten glass. The gaseous metal halide is separated from the molten glass and contacted with an aqueous scrubber solution of an alkali metal hydroxide to yield a metal hydroxide or metal oxide-containing precipitate and a soluble alkali metal halide. The precipitate is then separated from the aqueous scrubber solution. The molten glass containing the treated waste material is removed from the bath as a waste glass. The process of the invention can be used to treat all types of waste material including radioactive wastes. The process is particularly suited for separating halogens from halogen-containing wastes. 3 figs.

Metal halogen battery system with multiple outlet nozzle for hydrate

DOEpatents

Bjorkman, Jr., Harry K.

1983-06-21

A metal halogen battery system, including at least one cell having a positive electrode and a negative electrode contacted by aqueous electrolyte containing the material of said metal and halogen, store means whereby halogen hydrate is formed and stored as part of an aqueous material, means for circulating electrolyte through the cell and to the store means, and conduit means for transmitting halogen gas formed in the cell to a hydrate former whereby the hydrate is formed in association with the store means, said store means being constructed in the form of a container which includes a filter means, said filter means being inoperative to separate the hydrate formed from the electrolyte, said system having, a hydrate former pump means associated with the store means and being operative to intermix halogen gas with aqueous electrolyte to form halogen hydrate, said hydrate former means including, multiple outlet nozzle means connected with the outlet side of said pump means and being operative to minimize plugging, said nozzle means being comprised of at least one divider means which is generally perpendicular to the rotational axes of gears within the pump means, said divider means acting to divide the flow from the pump means into multiple outlet flow paths.

Studies on complex π-π and T-stacking features of imidazole and phenyl/p-halophenyl units in series of 5-amino-1-(phenyl/p-halophenyl)imidazole-4-carboxamides and their carbonitrile derivatives: Role of halogens in tuning of conformation

NASA Astrophysics Data System (ADS)

Das, Aniruddha

2017-11-01

5-amino-1-(phenyl/p-halophenyl)imidazole-4-carboxamides (N-phenyl AICA) (2a-e) and 5-amino-1-(phenyl/p-halophenyl)imidazole-4-carbonitriles (N-phenyl AICN) (3a-e) had been synthesized. X-ray crystallographic studies of 2a-e and 3a-e had been performed to identify any distinct change in stacking patterns in their crystal lattice. Single crystal X-ray diffraction studies of 2a-e revealed π-π stack formations with both imidazole and phenyl/p-halophenyl units in anti and syn parallel-displaced (PD)-type dispositions. No π-π stacking of imidazole occurred when the halogen substituent is bromo or iodo; π-π stacking in these cases occurred involving phenyl rings only. The presence of an additional T-stacking had been observed in crystal lattices of 3a-e. Vertical π-π stacking distances in anti-parallel PD-type arrangements as well as T-stacking distances had shown stacking distances short enough to impart stabilization whereas syn-parallel stacking arrangements had got much larger π-π stacking distances to belie any syn-parallel stacking stabilization. DFT studies had been pursued for quantifying the π-π stacking and T-stacking stabilization. The plotted curves for anti-parallel and T-stacked moieties had similarities to the 'Morse potential energy curve for diatomic molecule'. The minima of the curves corresponded to the most stable stacking distances and related energy values indicated stacking stabilization. Similar DFT studies on syn-parallel systems of 2b corresponded to no π-π stacking stabilization at all. Halogen-halogen interactions had also been observed to stabilize the compounds 2d, 2e and 3d. Nano-structural behaviour of the series of compounds 2a-e and 3a-e were thoroughly investigated.

Method for halogenating or radiohalogenating a chemical compound

DOEpatents

Kabalka, George W.

2006-05-09

A method for obtaining a halogenated organic compound, whereby an organotrifluoroborate compound is reacted with a halide ion in the presence of an oxidizing agent to produce the corresponding halogenated organic compound. The method may be used for producing radiohalogenated organic compounds.

Double-chamber electrode for spectrochemical determination of chlorine and other halogens

USGS Publications Warehouse

de Paiva, Azevedo; Specht, A.W.; Harner, R.S.

1954-01-01

A double-chamber, graphite electrode, suitable for d.c. arc determination of halogens by means of the alkaline earth halide bands, is described. An upper chamber holds the alkaline earth compound and an interconnected, lower chamber holds the halogen compound. This arrangement assures that there will be an abundance of alkaline earths in the arc by the time the halogen is volatilized from the lower chamber, and thereby promotes maximum emission of the alkaline earth halide bands. ?? 1954.

Four groups of new aromatic halogenated disinfection byproducts: effect of bromide concentration on their formation and speciation in chlorinated drinking water.

PubMed

Pan, Yang; Zhang, Xiangru

2013-02-05

Bromide is naturally present in source waters worldwide. Chlorination of drinking water can generate a variety of chlorinated and brominated disinfection byproducts (DBPs). Although substantial efforts have been made to examine the effect of bromide concentration on the formation and speciation of halogenated DBPs, almost all previous studies have focused on trihalomethanes and haloacetic acids. Given that about 50% of total organic halogen formed in chlorination remains unknown, it is still unclear how bromide concentration affects the formation and speciation of the new/unknown halogenated DBPs. In this study, chlorinated drinking water samples with different bromide concentrations were prepared, and a novel approach-precursor ion scan using ultra performance liquid chromatography/electrospray ionization-triple quadrupole mass spectrometry-was adopted for the detection and identification of polar halogenated DBPs in these water samples. With this approach, 11 new putative aromatic halogenated DBPs were identified, and they were classified into four groups: dihalo-4-hydroxybenzaldehydes, dihalo-4-hydroxybenzoic acids, dihalo-salicylic acids, and trihalo-phenols. A mechanism for the formation of the four groups of new aromatic halogenated DBPs was proposed. It was found that increasing the bromide concentration shifted the entire polar halogenated DBPs as well as the four groups of new DBPs from being less brominated to being more brominated; these new aromatic halogenated DBPs might be important intermediate DBPs formed in drinking water chlorination. Moreover, the speciation of the four groups of new DBPs was modeled: the speciation patterns of the four groups of new DBPs well matched those determined from the model equations, and the reactivity differences between HOBr and HOCl in reactions forming the four groups of new DBPs were larger than those in reactions forming trihalomethanes and haloacetic acids.

Sedimentary halogens and noble gases within Western Antarctic xenoliths: Implications of extensive volatile recycling to the sub continental lithospheric mantle

NASA Astrophysics Data System (ADS)

Broadley, Michael W.; Ballentine, Chris J.; Chavrit, Déborah; Dallai, Luigi; Burgess, Ray

2016-03-01

Recycling of marine volatiles back into the mantle at subduction zones has a profound, yet poorly constrained impact on the geochemical evolution of the Earth's mantle. Here we present a combined noble gas and halogen study on mantle xenoliths from the Western Antarctic Rift System (WARS) to better understand the flux of subducted volatiles to the sub continental lithospheric mantle (SCLM) and assess the impact this has on mantle chemistry. The xenoliths are extremely enriched in the heavy halogens (Br and I), with I concentrations up to 1 ppm and maximum measured I/Cl ratios (85.2 × 10-3) being ∼2000 times greater than mid ocean ridge basalts (MORB). The Br/Cl and I/Cl ratios of the xenoliths span a range from MORB-like ratios to values similar to marine pore fluids and serpentinites, whilst the 84Kr/36Ar and 130Xe/36Ar ratios range from modern atmosphere to oceanic sediments. This indicates that marine derived volatiles have been incorporated into the SCLM during an episode of subduction related metasomatism. Helium isotopic analysis of the xenoliths show average 3He/4He ratios of 7.5 ± 0.5 RA (where RA is the 3He/4He ratio of air = 1.39 × 10-6), similar to that of MORB. The 3He/4He ratios within the xenoliths are higher than expected for the xenoliths originating from the SCLM which has been extensively modified by the addition of subducted volatiles, indicating that the SCLM beneath the WARS must have seen a secondary alteration from the infiltration and rise of asthenospheric fluids/melts as a consequence of rifting and lithospheric thinning. Noble gases and halogens within these xenoliths have recorded past episodes of volatile interaction within the SCLM and can be used to reconstruct a tectonic history of the WARS. Marine halogen and noble gas signatures within the SCLM xenoliths provide evidence for the introduction and retention of recycled volatiles within the SCLM by subduction related metasomatism, signifying that not all volatiles that survive subduction are mixed efficiently through the convecting mantle. The global SCLM therefore represents a potentially important reservoir for the long term residence of subducted volatiles.

Martian fluid and Martian weathering signatures identified in Nakhla, NWA 998 and MIL 03346 by halogen and noble gas analysis

NASA Astrophysics Data System (ADS)

Cartwright, J. A.; Gilmour, J. D.; Burgess, R.

2013-03-01

We report argon (Ar) noble gas, Ar-Ar ages and halogen abundances (Cl, Br, I) of Martian nakhlites Nakhla, NWA 998 and MIL 03346 to determine the presence of Martian hydrous fluids and weathering products. Neutron-irradiated samples were either crushed and step-heated (Nakhla only), or simply step-heated using a laser or furnace, and analysed for noble gases using an extension of the 40Ar-39Ar technique to determine halogen abundances. The data obtained provide the first isotopic evidence for a trapped fluid that is Cl-rich, has a strong correlation with 40ArXS (40ArXS = 40Armeasured - 40Arradiogenic) and displays 40ArXS/36Ar of ˜1000 - consistent with the Martian atmosphere. This component was released predominantly in the low temperature and crush experiments, which may suggest a fluid inclusion host. For the halogens, we observe similar Br/Cl and I/Cl ratios between the nakhlites and terrestrial reservoirs, which is surprising given the absence of crustal recycling, organic matter and frequent fluid activity on Mars. In particular, Br/Cl ratios in our Nakhla samples (especially olivine) are consistent with previously analysed Martian weathering products, and both low temperature and crush analyses show a similar trend to the evaporation of seawater. This may indicate that surface brines play an important role on Mars and on halogen assemblages within Martian meteorites and rocks. Elevated I/Cl ratios in the low temperature NWA 998 and MIL 03346 releases may relate to in situ terrestrial contamination, though we are unable to distinguish between low temperature terrestrial or Martian components. Whilst estimates of the amount of water present based on the 36Ar concentrations are too high to be explained by a fluid component alone, they are consistent with a mixed-phase inclusion (gas and fluid) or with shock-implanted Martian atmospheric argon. The observed fluid is dilute (low salinity, but high Br/Cl and I/Cl ratios), contains a Martian atmospheric component, and may represent a mixture of a shallow fluid with one derived from fluid circulation within the nakhlite cumulate pile - with heat for fluid circulation supplied by either the igneous intrusion or by an impact event.

Assembling supramolecular networks by halogen bonding in coordination polymers driven by 5-bromonicotinic acid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gu, Jin-Zhong, E-mail: gujzh@lzu.edu.cn; Wu, Jiang; Kirillov, Alexander M.

2014-05-01

A series of six coordination compounds ([Zn(5-Brnic){sub 2}]·1.5H{sub 2}O){sub n} (1), [Cd(5-Brnic){sub 2}]{sub n} (2), [Co(5-Brnic){sub 2}(H{sub 2}O){sub 2}]{sub n} (3), [Zn(5-Brnic){sub 2}(H{sub 2}biim)]{sub n} (4), ([Cd(5-Brnic){sub 2}(phen)]·H{sub 2}O){sub n} (5), and [Pb(5-Brnic){sub 2}(phen)] (6) have been generated by the hydrothermal method from the metal(II) nitrates, 5-bromonicotinic acid (5-BrnicH), and an optional ancillary 1,10-phenanthroline (phen) or 2,2′-biimidazole (H{sub 2}biim) ligand. All the products 1–6 have been characterized by IR spectroscopy, elemental, thermal, powder and single-crystal X-ray diffraction analyses. Their 5-bromonicotinate-driven structures vary from the 3D metal-organic framework with the seh-3,5-P21/c topology (in 2) and the 2D interdigitated layers with themore » sql topology (in 1 and 3), to the 1D chains (in 4 and 5) and the 0D discrete monomers (in 6). The 5-bromonicotinate moiety acts as a versatile building block and its tethered bromine atom plays a key role in reinforcing and extending the structures into diverse 3D supramolecular networks via the various halogen bonding Br⋯O, Br⋯Br, and Br⋯π interactions, as well as the N–H⋯O and C–H⋯O hydrogen bonds. The obtained results demonstrate a useful guideline toward engineering the supramolecular architectures in the coordination network assembly under the influence of various halogen bonding interactions. The luminescent (for 1, 2, 4, 5, and 6) and magnetic (for 3) properties have also been studied and discussed in detail. - Graphical abstract: Six coordination compounds driven by 5-bromonicotinic acid have been generated and structurally characterized, revealing diverse metal-organic networks that are further reinforced and extended via various halogen bonding interactions. - Highlights: • 5-Bromonicotinic acid is a versatile ligand for Zn, Cd, Co and Pb derivatives. • Careful selection of co-ligands and metals resulted in different network structures. • Halogen and hydrogen bonding interactions lead to various supramolecular networks. • Luminescent and magnetic properties were studied and discussed in detail.« less

Scientific conferences: A big hello to halogen bonding

NASA Astrophysics Data System (ADS)

Erdelyi, Mate

2014-09-01

Halogen bonding connects a wide range of subjects -- from materials science to structural biology, from computation to crystal engineering, and from synthesis to spectroscopy. The 1st International Symposium on Halogen Bonding explored the state of the art in this fast-growing field of research.

DESTRUCTION OF HALOGENATED HYDROCARBONS WITH SOLVATED ELECTRONS IN THE PRESENCE OF WATER. (R826180)

EPA Science Inventory

Model halogenated aromatic and aliphatic hydrocarbons and halogenated phenols were dehalogenated in seconds by solvated electrons generated from sodium in both anhydrous liquid ammonia and ammonia/water solutions. The minimum sodium required to completely dehalogenate these mo...

Halogen-bonding-triggered supramolecular gel formation

NASA Astrophysics Data System (ADS)

Meazza, Lorenzo; Foster, Jonathan A.; Fucke, Katharina; Metrangolo, Pierangelo; Resnati, Giuseppe; Steed, Jonathan W.

2013-01-01

Supramolecular gels are topical soft materials involving the reversible formation of fibrous aggregates using non-covalent interactions. There is significant interest in controlling the properties of such materials by the formation of multicomponent systems, which exhibit non-additive properties emerging from interaction of the components. The use of hydrogen bonding to assemble supramolecular gels in organic solvents is well established. In contrast, the use of halogen bonding to trigger supramolecular gel formation in a two-component gel (‘co-gel’) is essentially unexplored, and forms the basis for this study. Here, we show that halogen bonding between a pyridyl substituent in a bis(pyridyl urea) and 1,4-diiodotetrafluorobenzene brings about gelation, even in polar media such as aqueous methanol and aqueous dimethylsulfoxide. This demonstrates that halogen bonding is sufficiently strong to interfere with competing gel-inhibitory interactions and create a ‘tipping point’ in gel assembly. Using this concept, we have prepared a halogen bond donor bis(urea) gelator that forms co-gels with halogen bond acceptors.

79/81Br nuclear quadrupole resonance spectroscopic characterization of halogen bonds in supramolecular assemblies.

PubMed

Cerreia Vioglio, P; Szell, P M J; Chierotti, M R; Gobetto, R; Bryce, D L

2018-05-28

Despite the applicability of solid-state NMR to study the halogen bond, the direct NMR detection of 79/81 Br covalently bonded to carbon remains impractical due to extremely large spectral widths, even at ultra-high magnetic fields. In contrast, nuclear quadrupole resonance (NQR) offers comparatively sharp resonances. Here, we demonstrate the abilities of 79/81 Br NQR to characterize the electronic changes in the C-Br···N halogen bonding motifs found in supramolecular assemblies constructed from 1,4-dibromotetrafluorobenzene and nitrogen-containing heterocycles. An increase in the bromine quadrupolar coupling constant is observed, which correlates linearly with the halogen bond distance ( d Br···N ). Notably, 79/81 Br NQR is able to distinguish between two symmetry-independent halogen bonds in the same crystal structure. This approach offers a rapid and reliable indication for the occurrence of a halogen bond, with experimental times limited only by the observation of 79/81 Br NQR resonances.

Modulation of persistent organic pollutant toxicity through nutritional intervention: emerging opportunities in biomedicine and environmental remediation.

PubMed

Petriello, Michael C; Newsome, Bradley J; Dziubla, Thomas D; Hilt, J Zach; Bhattacharyya, Dibakar; Hennig, Bernhard

2014-09-01

Environmental pollution is increasing worldwide, and there is evidence that exposure to halogenated persistent organic pollutants (POPs) such as polychlorinated biphenyls can contribute to the pathology of inflammatory diseases such as atherosclerosis, diabetes, and cancer. Pollutant removal from contaminated sites and subsequent pollutant degradation are critical for reducing the long-term health risks associated with exposure. However, complete remediation of a toxicant from the environment is very difficult and cost-prohibitive. Furthermore, remediation technologies often result in the generation of secondary toxicants. Considering these circumstances, environmentally-friendly and sustainable remediation technologies and biomedical solutions to reduce vulnerability to environmental chemical insults need to be explored to reduce the overall health risks associated with exposure to environmental pollutants. We propose that positive lifestyle changes such as healthful nutrition and consumption of diets rich in fruits and vegetables or bioactive nutrients with antioxidant and/or anti-inflammatory properties will reduce the body's vulnerability to environmental stressors and thus reduce toxicant-mediated disease pathologies. Interestingly, emerging evidence now implicates the incorporation of bioactive nutrients, such as plant-derived polyphenols, in technologies focused on the capture, sensing and remediation of halogenated POPs. We propose that human nutritional intervention in concert with the use of natural polyphenol sensing and remediation platforms may provide a sensible means to develop primary and long-term prevention strategies of diseases associated with many environmental toxic insults including halogenated POPs. Copyright © 2014 Elsevier B.V. All rights reserved.

Modulation of persistent organic pollutant toxicity through nutritional intervention: emerging opportunities in biomedicine and environmental remediation

PubMed Central

Petriello, Michael C.; Newsome, Bradley J.; Dziubla, Thomas D.; Hilt, J. Zach; Bhattacharyya, Dibakar; Hennig, Bernhard

2014-01-01

Environmental pollution is increasing worldwide, and there is evidence that exposure to halogenated persistent organic pollutants (POPs) such as polychlorinated biphenyls can contribute to the pathology of inflammatory diseases such as atherosclerosis, diabetes, and cancer. Pollutant removal from contaminated sites and subsequent pollutant degradation are critical for reducing the long-term health risks associated with exposure. However, complete remediation of a toxicant from the environment is very difficult and cost-prohibitive. Furthermore, remediation technologies often result in the generation of secondary toxicants. Considering these circumstances, environmentally-friendly and sustainable remediation technologies and biomedical solutions to reduce vulnerability to environmental chemical insults need to be explored to reduce the overall health risks associate with exposure to environmental pollutants. We propose that positive lifestyle changes such as healthful nutrition and consumption of diets rich in fruits and vegetables or bioactive nutrients with antioxidant and/or anti-inflammatory properties will reduce the body’s vulnerability to environmental stressors and thus reduce toxicant-mediated disease pathologies. Interestingly, emerging evidence now implicates the incorporation of bioactive nutrients, such as plant-derived polyphenols, in technologies focused on the capture, sensing and remediation of halogenated POPs. We propose that human nutritional intervention in concert with the use of natural polyphenol sensing and remediation platforms may provide a sensible means to develop primary and long-term prevention strategies of diseases associated with many environmental toxic insults including halogenated POPs. PMID:24530186

Sources of volcanic aerosols: Petrologic and volcanological constraints

NASA Technical Reports Server (NTRS)

Sigurdsson, Haraldur

1991-01-01

Global climatic effects brought about by volcanism are related to the impact of volcanic gases and their derivative aerosols on the atmosphere, rather than the effects of volcanic ash. Evidence from both historic eruptions and polar ice cores indicate that volcanic sulfur gases are the dominant aerosol-forming component, resulting in produciton of a sulfuric acid-rich stratosphere aerosol that can have profound effects on the earth radiation budget over periods of a few years. Due to highly variable sulfur content of different magma types, the climatic effects do not relate simply to total erupted mass. There is a close relationship between volcanic sulfur yield to the atmospheric and hemispheric surface temperature decrease following an eruption, with up to 1 C surface temperature decrease indicated following a major volcanic event such as the 1815 Tambora eruption. While the erupted mass of HCl and HF is equal to or greater than that of sulfur gases in some volcanic events, the halogens do not form known aerosols nor are they abundant in ice core acidity layers. The early removal of halogens from eruption columns occurs by rain flushing and adsorption onto tephra particles, but the fate of halogens in the atmosphere following very large explosive eruptions is unknown. The CO2 flux to the atmosphere from volcanic eruptions is volumetrically one of the most important of the gas species, but owing to the huge size of the atmospheric reservoir of this gas, the volcanic contribution is likely to have negligible effects.

The contribution of hydrothermally altered ocean crust to the mantle halogen and noble gas cycles

NASA Astrophysics Data System (ADS)

Chavrit, Déborah; Burgess, Ray; Sumino, Hirochika; Teagle, Damon A. H.; Droop, Giles; Shimizu, Aya; Ballentine, Chris J.

2016-06-01

Recent studies suggest that seawater-derived noble gases and halogens are recycled into the deep mantle by the subduction of oceanic crust. To understand the processes controlling the availability of halogens and noble gases for subduction, we determined the noble gas elemental and isotopic ratios and halogen (Cl, Br, I) concentrations in 28 igneous samples from the altered oceanic crust (AOC) from 5 ODP sites in the Eastern and Western Pacific Ocean. Crushing followed by heating experiments enabled determination of noble gases and halogens in fluid inclusions and mineral phases respectively. Except for He and Ar, Ne, Kr and Xe isotopic ratios were all air-like suggesting that primary MORB signatures have been completely overprinted by air and/or seawater interaction. In contrast, 3He/4He ratios obtained by crushing indicate that a mantle helium component is still preserved, and 40Ar/36Ar values are affected by radiogenic decay in the mineral phases. The 130Xe/36Ar and 84Kr/36Ar ratios are respectively up to 15 times and 5 times higher than those of seawater and the highest ratios are found in samples affected by low temperature alteration (shallower than 800-900 m sub-basement). We consider three possible processes: (i) adsorption onto the clays present in the samples; (ii) fluid inclusions with a marine pore fluid composition; and (iii) fractionation of seawater through phase separation caused by boiling. Ninety percent of the Cl, Br and I were released during the heating experiments, showing that halogens are dominantly held in mineral phases prior to subduction. I/Cl ratios vary by 4 orders of magnitude, from 3 × 10-6 to 2 × 10-2. The mean Br/Cl ratio is 30% lower than in MORB and seawater. I/Cl ratios lower than MORB values are attributed to Cl-rich amphibole formation caused by hydrothermal alteration at depths greater than 800-900 m sub-basement together with different extents of I loss during low and high temperature alteration. At shallower depths, I/Cl ratios higher than MORB values can be explained by the addition of organic-rich sediments or the presence of organic detritus, both known to efficiently sequester I. Concentrations of 36Ar of the pre-subducting materials are sufficient to account for the 36Ar and composition of the mantle in the context of existing subduction-flux models. We find the Cl subduction flux of the oceanic crust to be about three times higher than the previous estimates and that sufficient Cl and Br can potentially be delivered by subduction over the last 3 Ga to account for mantle source compositions.

Angles between orthogonal spd bond orbitals with maximum strength*

PubMed Central

Pauling, Linus

1976-01-01

An equation is derived for values of bond angles for two equivalent best spd hybrid bond orbitals with given amounts of s, p, and d character, and is applied in the discussion of structures of transargononic compounds, including the xenon and halogen fluorides. Bond orbitals with a rather small amount of d character tend to lie at angles 90° and 180°, and those with a larger amount, at somewhat smaller angles. PMID:16592315

2-(4-aminophenyl) benzothiazole: a potent and selective pharmacophore with novel mechanistic action towards various tumour cell lines.

PubMed

Dubey, Raghvendra; Shrivastava, Prabhat K; Basniwal, Pawan K; Bhattacharya, Snehendu; Moorthy, Narayana S Hari Narayana

2006-06-01

2-(4-aminophenyl) benzothiazole (CJM -126) (Table 1 (1) and its analogues represent a potent and highly selective class of antitumor agents. These compounds in nanomolar range elicit potent growth inhibition in human-derived breast, colon, ovarian and renal tumour cell lines. Metabolism of benzothiazole plays a central role in its mode of action. Cytocrome P450 isoform, CYP1A1, biotransforms benzothiazoles, to active, as well as inactive metabolites. In vitro studies had confirmed that N-oxidation and N-acetylation (only 3' halogen congener) as main active metabolic transformation (generating cytotoxic electrophilic species), while C-6 oxidation and N-acetylation (except 3' halogen congener) as inactive metabolic transformation pathway. Generation of an inactive metabolite 2-(4-aminophenyl)-6-hydoxybenzothiazole [6-OH 126, (Table 1) (10)] is blocked by fluorinated analogue, substituted around benzothiazole nucleus, especially at 5-position. National Cancer Institute (NCI), USA, confirms this series as a unique mechanistic class distinct from clinically used chemotherapeutic agents. Benzothiazoles are potent aryl hydrocarbon receptor (AhR) agonists, binding to AhR results in induction of CYP1A1, causes generation of electrophilic reactive species which forms DNA adduct, ultimately resulting in cell death by activation of apoptotic machinery. To overcome the poor physiochemical and pharmaceutical properties (bioavailability problem) of this compounds, prodrug of benzothiazole derivatives were synthesized, which are introduced in clinical trails.

Impact of enhanced ozone deposition and halogen chemistry on tropospheric ozone over the Northern Hemisphere

EPA Science Inventory

Fate of ozone in marine environments has been receiving increased attention due to the tightening of ambient air quality standards. The role of deposition and halogen chemistry is examined through incorporation of an enhanced ozone deposition algorithm and inclusion of halogen ch...

40 CFR 721.10145 - Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino...

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Modified reaction products of alkyl... Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino compound... identified generically as modified reaction products of alkyl alcohol, halogenated alkane, substituted...

40 CFR 721.10145 - Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino...

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Modified reaction products of alkyl... Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino compound... identified generically as modified reaction products of alkyl alcohol, halogenated alkane, substituted...

Halogenated arsenenes as Dirac materials

NASA Astrophysics Data System (ADS)

Tang, Wencheng; Sun, Minglei; Ren, Qingqiang; Wang, Sake; Yu, Jin

2016-07-01

Arsenene is the graphene-like arsenic nanosheet, which has been predicted very recently [S. Zhang, Z. Yan, Y. Li, Z. Chen, and H. Zeng, Angewandte Chemie, 127 (2015) 3155-3158]. Using first-principles calculations, we systematically investigate the structures and electronic properties of fully-halogenated arsenenes. Formation energy analysis reveals that all the fully-halogenated arsenenes except iodinated arsenene are energetically favorable and could be synthesized. We have revealed the presence of Dirac cone in fully-halogenated arsenene compounds. They may have great potential applications in next generation of high-performance devices.

Density functional IR, Raman, and VCD spectra of halogen substituted β-lactams

NASA Astrophysics Data System (ADS)

Rode, Joanna E.; Dobrowolski, Jan Cz.

2003-06-01

Halogenoazetidinones are important as synthetic intermediates for preparation of halogen β-lactam (2-azetidinone) antibiotics and as building blocks for carbohydrates and amino acids. In this paper, we consider the influence of the halogen atom, substituted at the C4 position of the 2-azetidinone ring, on the geometry, IR, Raman, and vibrational circular dichroism spectra. The vibrational spectra were calculated for the chiral 4-( R)-X-2-azetidinone (X=F, Cl or Br) molecules at the B3PW91/aug-cc-pVTZ level. It was shown that the geometry of the molecules studied do not change much upon the change of the halogen atom. In case of the vibrational spectra, the position but even more the intensities depend strongly on the kind of halogen substituent.

Abnormal synergistic effects between Lewis acid-base interaction and halogen bond in F3B···NCX···NCM

NASA Astrophysics Data System (ADS)

Tang, Qingjie; Li, Qingzhong

2015-12-01

An abnormal synergistic effect was found between the Lewis acid-base interaction and halogen bond in triads F3B···NCX···NCM (X and M are halogen atoms), where the strong Lewis acid-base interaction between F3B and NCX has a larger enhancement than the weak halogen bond between NCX and NCM. This is in contrast with the traditional cooperative effect. It is interesting that the alkali-metal substituent as well as the heavier halogen atom play a more remarkable role in the enhancement of the interaction F3B···NCX than that of NCX···NCM, particularly, the alkali-metal substituent makes the abnormal synergistic effect be the traditional cooperative one.

Competition between Halogen, Hydrogen and Dihydrogen Bonding in Brominated Carboranes.

PubMed

Fanfrlík, Jindřich; Holub, Josef; Růžičková, Zdeňka; Řezáč, Jan; Lane, Paul D; Wann, Derek A; Hnyk, Drahomír; Růžička, Aleš; Hobza, Pavel

2016-11-04

Halogen bonds are a subset of noncovalent interactions with rapidly expanding applications in materials and medicinal chemistry. While halogen bonding is well known in organic compounds, it is new in the field of boron cluster chemistry. We have synthesized and crystallized carboranes containing Br atoms in two different positions, namely, bound to C- and B-vertices. The Br atoms bound to the C-vertices have been found to form halogen bonds in the crystal structures. In contrast, Br atoms bound to B-vertices formed hydrogen bonds. Quantum chemical calculations have revealed that halogen bonding in carboranes can be much stronger than in organic architectures. These findings open new possibilities for applications of carboranes, both in materials and medicinal chemistry. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigation of reactive halogens in the Arctic using a mobile instrumental laboratory

NASA Astrophysics Data System (ADS)

Custard, K.; Shepson, P. B.; Stephens, C. R.

2011-12-01

Custard, K kcustard@purdue.edu Chemistry Department, Purdue University, West Lafayette, IN, USA Shepson, P pshepson@purdue.edu Chemistry Department, Purdue University, West Lafayette, IN, USA Stephens, C thompscr@purdue.edu Chemistry Department, Purdue University, West Lafayette, IN, USA Investigation of the chemistry of reactive halogens in ice-covered regions is important because of its significant impact on atmospheric composition. Halogens in the Arctic react with ozone and gaseous elemental mercury to sometimes completely deplete them from the ambient atmosphere, at least during polar springtime. There is much uncertainty about the sources and concentrations of these atmospheric halogens in the Arctic, particularly with respect to chlorine. To gain a better understanding of them, we have developed a method to simultaneously measure the concentrations of BrOx and ClOx radicals using a flowtube method. The method involves reaction of the halogen atom with a halogenated alkene, to produce a multiply halogenated characteristic ketone product, which is then detected via GC/ECD. The system was deployed at Barrow, AK, using a mobile instrumental laboratory so that measurements could be made from multiple locations along the sea ice. In this paper we will discuss laboratory evaluation of the flowtube method, and present preliminary data from Barrow, AK, during the spring 2011 deployment.

Impact of Enhanced Ozone Deposition and Halogen Chemistry on Tropospheric Ozone over the Northern Hemisphere.

PubMed

Sarwar, Golam; Gantt, Brett; Schwede, Donna; Foley, Kristen; Mathur, Rohit; Saiz-Lopez, Alfonso

2015-08-04

Fate of ozone in marine environments has been receiving increased attention due to the tightening of ambient air quality standards. The role of deposition and halogen chemistry is examined through incorporation of an enhanced ozone deposition algorithm and inclusion of halogen chemistry in a comprehensive atmospheric modeling system. The enhanced ozone deposition treatment accounts for the interaction of iodide in seawater with ozone and increases deposition velocities by 1 order of magnitude. Halogen chemistry includes detailed chemical reactions of organic and inorganic bromine and iodine species. Two different simulations are completed with the halogen chemistry: without and with photochemical reactions of higher iodine oxides. Enhanced deposition reduces mean summer-time surface ozone by ∼3% over marine regions in the Northern Hemisphere. Halogen chemistry without the photochemical reactions of higher iodine oxides reduces surface ozone by ∼15% whereas simulations with the photochemical reactions of higher iodine oxides indicate ozone reductions of ∼48%. The model without these processes overpredicts ozone compared to observations whereas the inclusion of these processes improves predictions. The inclusion of photochemical reactions for higher iodine oxides leads to ozone predictions that are lower than observations, underscoring the need for further refinement of the halogen emissions and chemistry scheme in the model.

Characterization of halogenated DBPs and identification of new DBPs trihalomethanols in chlorine dioxide treated drinking water with multiple extractions.

PubMed

Han, Jiarui; Zhang, Xiangru; Liu, Jiaqi; Zhu, Xiaohu; Gong, Tingting

2017-08-01

Chlorine dioxide (ClO 2 ) is a widely used alternative disinfectant due to its high biocidal efficiency and low-level formation of trihalomethanes and haloacetic acids. A major portion of total organic halogen (TOX), a collective parameter for all halogenated DBPs, formed in ClO 2 -treated drinking water is still unknown. A commonly used pretreatment method for analyzing halogenated DBPs in drinking water is one-time liquid-liquid extraction (LLE), which may lead to a substantial loss of DBPs prior to analysis. In this study, characterization and identification of polar halogenated DBPs in a ClO 2 -treated drinking water sample were conducted by pretreating the sample with multiple extractions. Compared to one-time LLE, the combined four-time LLEs improved the recovery of TOX by 2.3 times. The developmental toxicity of the drinking water sample pretreated with the combined four-time LLEs was 1.67 times higher than that pretreated with one-time LLE. With the aid of ultra-performance liquid chromatography/electrospray ionization-triple quadrupole mass spectrometry, a new group of polar halogenated DBPs, trihalomethanols, were detected in the drinking water sample pretreated with multiple extractions; two of them, trichloromethanol and bromodichloromethanol, were identified with synthesized standard compounds. Moreover, these trihalomethanols were found to be the transformation products of trihalomethanes formed during ClO 2 disinfection. The results indicate that multiple LLEs can significantly improve extraction efficiencies of polar halogenated DBPs and is a better pretreatment method for characterizing and identifying new polar halogenated DBPs in drinking water. Copyright © 2017. Published by Elsevier B.V.

Singlet oxygen production by combining erythrosine and halogen light for photodynamic inactivation of Streptococcus mutans.

PubMed

Fracalossi, Camila; Nagata, Juliana Yuri; Pellosi, Diogo Silva; Terada, Raquel Sano Suga; Hioka, Noboru; Baesso, Mauro Luciano; Sato, Francielle; Rosalen, Pedro Luiz; Caetano, Wilker; Fujimaki, Mitsue

2016-09-01

Photodynamic inactivation of microorganisms is based on a photosensitizing substance which, in the presence of light and molecular oxygen, produces singlet oxygen, a toxic agent to microorganisms and tumor cells. This study aimed to evaluate singlet oxygen quantum yield of erythrosine solutions illuminated with a halogen light source in comparison to a LED array (control), and the photodynamic effect of erythrosine dye in association with the halogen light source on Streptococcus mutans. Singlet oxygen quantum yield of erythrosine solutions was quantified using uric acid as a chemical-probe in an aqueous solution. The in vitro effect of the photodynamic antimicrobial activity of erythrosine in association with the halogen photopolimerizing light on Streptococcus mutans (UA 159) was assessed during one minute. Bacterial cultures treated with erythrosine alone served as negative control. Singlet oxygen with 24% and 2.8% degradation of uric acid in one minute and a quantum yield of 0.59 and 0.63 was obtained for the erythrosine samples illuminated with the halogen light and the LED array, respectively. The bacterial cultures with erythrosine illuminated with the halogen light presented a decreased number of CFU mL(-1) in comparison with the negative control, with minimal inhibitory concentrations between 0.312 and 0.156mgmL(-1). The photodynamic response of erythrosine induced by the halogen light was capable of killing S. mutans. Clinical trials should be conducted to better ascertain the use of erythrosine in association with halogen light source for the treatment of dental caries. Copyright © 2016 Elsevier B.V. All rights reserved.

Role of halogen and hydrogen bonds for stabilization of antithyroid drugs with hypohalous acids (HOX, X = I, Br, and Cl) adducts

NASA Astrophysics Data System (ADS)

El-Sheshtawy, Hamdy S.; El-Mehasseb, Ibrahim

2017-11-01

The mechanism for the inhibition of thyroid hormones by the thioamide-like antithyroid drug is a key process in the thyroid gland function. Therefore, in this study theoretical investigation of the molecular interaction between two antithyroid drugs, namely methimazol (MMI) and thiazoline-2-thione (T2T), with the hypohalous acids (HOX, X = I, Br, and Cl), which act as heme-linked halogenated species to tyrosine residue was discussed. The calculations were performed by M06-2X and MP2 using aug-cc-pVDZ level of theory. In addition, wB97xd/6-31G* level of theory was used in order to account for the dispersion forces. The results show the possible formation of three adducts, which is stabilized by halogen bond (I), both halogen and hydrogen bonds (II), two hydrogen bonds (III). The binding energies of the complexes reveals stabilization in the order III > II > I. The binding energies of the complexes was increased with increasing the electron affinity and polarizability of halogen atom, the dipole moment of the complexes (I and II), the electrostatic potential on halogen atom (Vmax:i.e σ-hole), and the charge-transfer process through the halogen bond in I. On the other hand, the binding energies of the complexes decreased with increasing the halogen atom electronegativity and the dipole moment of complex III. Natural bond orbital (NBO) analysis was used to investigate the molecular orbital interactions and the charge transfer process upon complexation.

79/81Br nuclear quadrupole resonance spectroscopic characterization of halogen bonds in supramolecular assemblies† †Electronic supplementary information (ESI) available: 13C SSNMR spectra, powder X-ray diffractograms. See DOI: 10.1039/c8sc01094c

PubMed Central

Cerreia Vioglio, P.; Szell, P. M. J.; Chierotti, M. R.; Gobetto, R.

2018-01-01

Despite the applicability of solid-state NMR to study the halogen bond, the direct NMR detection of 79/81Br covalently bonded to carbon remains impractical due to extremely large spectral widths, even at ultra-high magnetic fields. In contrast, nuclear quadrupole resonance (NQR) offers comparatively sharp resonances. Here, we demonstrate the abilities of 79/81Br NQR to characterize the electronic changes in the C–Br···N halogen bonding motifs found in supramolecular assemblies constructed from 1,4-dibromotetrafluorobenzene and nitrogen-containing heterocycles. An increase in the bromine quadrupolar coupling constant is observed, which correlates linearly with the halogen bond distance (dBr···N). Notably, 79/81Br NQR is able to distinguish between two symmetry-independent halogen bonds in the same crystal structure. This approach offers a rapid and reliable indication for the occurrence of a halogen bond, with experimental times limited only by the observation of 79/81Br NQR resonances. PMID:29899948

Degree of conversion of two lingual retainer adhesives cured with different light sources.

PubMed

Usümez, Serdar; Büyükyilmaz, Tamer; Karaman, Ali Ihya; Gündüz, Beniz

2005-04-01

The aim of this study was to evaluate the degree of conversion (DC) of two lingual retainer adhesives, Transbond Lingual Retainer (TLR) and Light Cure Retainer (LCR), cured with a fast halogen light, a plasma arc light and a light-emitting diode (LED) at various curing times. A conventional halogen light served as the control. One hundred adhesive samples (five per group) were cured for 5, 10 or 15 seconds with an Optilux 501 (fast halogen light), for 3, 6 or 9 seconds with a Power Pac (plasma arc light), or for 10, 20 or 40 seconds with an Elipar Freelight (LED). Samples cured for 40 seconds with the conventional halogen lamp were used as the controls. Absorbance peaks were recorded using Fourier transform infrared (FT-IR) spectroscopy. DC values were calculated. Data were analysed using Kruskal-Wallis and Mann-Whitney U-tests. For the TLR, the highest DC values were achieved in 6 and 9 seconds with the plasma arc light. Curing with the fast halogen light for 15 seconds and with the LED for 40 seconds produced statistically similar DC values, but these were lower than those with the plasma arc light. All of these light exposures yielded a statistically significantly higher DC than 40 seconds of conventional halogen light curing. The highest DC value for the LCR was achieved in 15 seconds with the fast halogen light, then the plasma arc light curing for 6 seconds. These two combinations produced a statistically significantly higher DC when compared with the 40 seconds of conventional halogen light curing. The lowest DC for the LCR was achieved with 10 seconds of LED curing. The overall DC of the LCR was significantly higher than that of the TLR. The results suggest that a similar or higher DC than the control values could be achieved in 6-9 seconds by plasma arc curing, in 10-15 seconds by fast halogen curing or in 20 seconds by LED curing.

Halogens in chondritic meteorites and terrestrial accretion

NASA Astrophysics Data System (ADS)

Clay, Patricia L.; Burgess, Ray; Busemann, Henner; Ruzié-Hamilton, Lorraine; Joachim, Bastian; Day, James M. D.; Ballentine, Christopher J.

2017-11-01

Volatile element delivery and retention played a fundamental part in Earth’s formation and subsequent chemical differentiation. The heavy halogens—chlorine (Cl), bromine (Br) and iodine (I)—are key tracers of accretionary processes owing to their high volatility and incompatibility, but have low abundances in most geological and planetary materials. However, noble gas proxy isotopes produced during neutron irradiation provide a high-sensitivity tool for the determination of heavy halogen abundances. Using such isotopes, here we show that Cl, Br and I abundances in carbonaceous, enstatite, Rumuruti and primitive ordinary chondrites are about 6 times, 9 times and 15-37 times lower, respectively, than previously reported and usually accepted estimates. This is independent of the oxidation state or petrological type of the chondrites. The ratios Br/Cl and I/Cl in all studied chondrites show a limited range, indistinguishable from bulk silicate Earth estimates. Our results demonstrate that the halogen depletion of bulk silicate Earth relative to primitive meteorites is consistent with the depletion of lithophile elements of similar volatility. These results for carbonaceous chondrites reveal that late accretion, constrained to a maximum of 0.5 ± 0.2 per cent of Earth’s silicate mass, cannot solely account for present-day terrestrial halogen inventories. It is estimated that 80-90 per cent of heavy halogens are concentrated in Earth’s surface reservoirs and have not undergone the extreme early loss observed in atmosphere-forming elements. Therefore, in addition to late-stage terrestrial accretion of halogens and mantle degassing, which has removed less than half of Earth’s dissolved mantle gases, the efficient extraction of halogen-rich fluids from the solid Earth during the earliest stages of terrestrial differentiation is also required to explain the presence of these heavy halogens at the surface. The hydropilic nature of halogens, whereby they track with water, supports this requirement, and is consistent with volatile-rich or water-rich late-stage terrestrial accretion.

C-I···π Halogen Bonding Driven Supramolecular Helix of Bilateral N-Amidothioureas Bearing β-Turns.

PubMed

Cao, Jinlian; Yan, Xiaosheng; He, Wenbin; Li, Xiaorui; Li, Zhao; Mo, Yirong; Liu, Maili; Jiang, Yun-Bao

2017-05-17

We report the first example of C-I···π halogen bonding driven supramolecular helix in highly dilute solution of micromolar concentration, using alanine based bilateral I-substituted N-amidothioureas that contain helical fragments, the β-turn structures. The halogen bonding interactions afford head-to-tail linkages that help to propagate the helicity of the helical fragments. In support of this action of the halogen bonding, chiral amplification was observed in the supramolecular helix formed in acetonitrile solution. The present finding provides alternative tools in the design of self-assembling macromolecules.

Aromatic fluorine compounds. XI. Replacement of chlorine by fluorine in halopyridines

USGS Publications Warehouse

Finger, G.C.; Starr, L.D.; Dickerson, D.R.; Gutowsky, H.S.; Hamer, J.

1963-01-01

The ??-halogenated pyridines react with potassium fluoride in various solvents to give replacement of the ??-halogen by fluorine. A 50% yield of 2-fluoropyridine was obtained from 2-chloropyridine by heating with potassium fluoride in dimethyl sulfone or tetramethylene sulfone for twenty-one days; 2-bromopyridine gave a similar yield with a heating period of only seven days. The ??-halogens of the polyhalopyridines undergo the exchange reaction more readily than do the halogens of the ??-monohalopyridines. The proposed structures of the fluoropyridines are supported by alternate syntheses and by n.m.r. studies.

New halogenated phenylcoumarins as tyrosinase inhibitors.

PubMed

Matos, Maria João; Santana, Lourdes; Uriarte, Eugenio; Delogu, Giovanna; Corda, Marcella; Fadda, Maria Benedetta; Era, Benedetta; Fais, Antonella

2011-06-01

With the aim to find out structural features for the tyrosinase inhibitory activity, in the present communication we report the synthesis and pharmacological evaluation of a new series of phenylcoumarin derivatives with different number of hydroxyl or ether groups and bromo substituent in the scaffold. The synthesized compounds 5-12 were evaluated as mushroom tyrosinase inhibitors showing, two of them, lower IC(50) than the umbelliferone. Compound 12 (IC(50)=215 μM) is the best tyrosinase inhibitor of this series. Copyright © 2011 Elsevier Ltd. All rights reserved.

Electronic and Ionic Transport in Processable Conducting Polymers. Symmetry Effects on the Physical and Electrically Conducting, Substituted Poly(di-2-thienylphenylenes)

DTIC Science & Technology

1991-10-21

incorporated using a Grignard coupling reaction. 19 The derivatives with long alkoxy side groups were successfully halogenated with elemental bromine in CC14...transmetallation reaction of 2-thienyllithium with 7 anhydrous zinc chloride. This reagent was treated with the 1,4-dibromo-2,5- disubstitutedbenzene...were attributed to the steric effects in polymer 7c and the regiospecificity in the alkoxy substituted polymers. Experimental Section Reagents and

Palladium-catalyzed cross coupling reactions of 4-bromo-6H-1,2-oxazines

PubMed Central

Schmidt, Elmar; Andrä, Michal; Duhs, Marcel-Antoine; Linder, Igor

2009-01-01

Summary A number of 4-aryl- and 4-alkynyl-substituted 6H-1,2-oxazines 8 and 9 have been prepared in good yields via cross coupling reactions of halogenated precursors 2, which in turn are easily accessible by bromination of 6H-1,2-oxazines 1. Lewis-acid promoted reaction of 1,2-oxazine 9c with 1-hexyne provided alkynyl-substituted pyridine derivative 12 thus demonstrating the potential of this approach for the synthesis of pyridines. PMID:19936264

A Rapid, One-Pot Synthesis of β-Siloxy-α-Haloaldehydes

PubMed Central

Saadi, Jakub; Akakura, Matsujiro

2011-01-01

The Mukaiyama cross aldol reaction of α-fluoro-, α-chloro-, and α-bromoacetaldehyde-derived (Z)-tris(trimethylsilyl)- silyl enol ethers furnishing anti-β-siloxy-α-haloaldehydes is described. A highly diastereoselective, one-pot, sequential double aldol process, affording novel β,δ-bissiloxy-α,γ-bishaloaldehydes is developed. Reactions are catalyzed by C6F5CHTf2 and C6F5CTf2AlMe2 (0.5–1.5 mol%) and provide access to halogenated polyketide fragments. PMID:21815682

Halogen Bonding: A Powerful Tool for Modulation of Peptide Conformation

PubMed Central

2017-01-01

Halogen bonding is a weak chemical force that has so far mostly found applications in crystal engineering. Despite its potential for use in drug discovery, as a new molecular tool in the direction of molecular recognition events, it has rarely been assessed in biopolymers. Motivated by this fact, we have developed a peptide model system that permits the quantitative evaluation of weak forces in a biologically relevant proteinlike environment and have applied it for the assessment of a halogen bond formed between two amino acid side chains. The influence of a single weak force is measured by detection of the extent to which it modulates the conformation of a cooperatively folding system. We have optimized the amino acid sequence of the model peptide on analogues with a hydrogen bond-forming site as a model for the intramolecular halogen bond to be studied, demonstrating the ability of the technique to provide information about any type of weak secondary interaction. A combined solution nuclear magnetic resonance spectroscopic and computational investigation demonstrates that an interstrand halogen bond is capable of conformational stabilization of a β-hairpin foldamer comparable to an analogous hydrogen bond. This is the first report of incorporation of a conformation-stabilizing halogen bond into a peptide/protein system, and the first quantification of a chlorine-centered halogen bond in a biologically relevant system in solution. PMID:28581720

Tropospheric Halogen Chemistry

NASA Astrophysics Data System (ADS)

von Glasow, R.; Crutzen, P. J.

2003-12-01

Halogens are very reactive chemicals that are known to play an important role in anthropogenic stratospheric ozone depletion chemistry, first recognized by Molina and Rowland (1974). However, they also affect the chemistry of the troposphere. They are of special interest because they are involved in many reaction cycles that can affect the oxidation power of the atmosphere indirectly by influencing the main oxidants O3 and its photolysis product OH and directly, e.g., by reactions of the Cl radical with hydrocarbons (e.g., CH4).Already by the middle of the nineteenth century, Marchand (1852) reported the presence of bromine and iodine in rain and other natural waters. He also mentions the benefits of iodine in drinking water through the prevention of goitres and cretinism. In a prophetic monograph "Air and Rain: The Beginnings of a Chemical Climatology," Smith (1872) describes measurements of chloride in rain water, which he states to originate partly from the oceans by a process that he compares with the bursting of "soap bubbles" which produces "small vehicles" that transfer small spray droplets of seawater to the air. From deviations of the sulfate-to-chloride ratio in coastal rain compared to seawater, Smith concluded that chemical processes occur once the particles are airborne.For almost a century thereafter, however, atmospheric halogens received little attention. One exception was the work by Cauer (1939), who reported that iodine pollution has been significant in Western and Central Europe due to the inefficient burning of seaweed, causing mean gas phase atmospheric concentrations as high as or greater than 0.5 μg m-3. In his classical textbook Air Chemistry and Radioactivity, Junge (1963) devoted less than three pages to halogen gas phase chemistry, discussing chlorine and iodine. As reviewed by Eriksson (1959a, b), the main atmospheric source of halogens is sea salt, derived from the bursting of bubbles of air which are produced by ocean waves and other processes. Early work by Cauer (1951) had shown that Cl/Na and Cl/Mg ratios were lower in air than in seawater, indicating loss of chlorine by "acid displacement" from sea salt by the strong acids, H2SO4 (Eriksson (1959a, b) and HNO3 (Robbins et al., 1959). Already the first measurements of bromine in aerosols by Duce et al. (1963) showed that bromine, like chlorine, was lost from the sea salt particles, whereas iodine was strongly enriched ( Duce et al., 1965). Research since the early 1980s has shown that photochemical processes are actively involved.Interest in the chemistry of atmospheric halogens took a steep upward surge after it was postulated that the release of industrially produced halocarbons, in particular the chlorofluorocarbons (CFCs), CFCl3, and CF2Cl2, could cause severe depletions in stratospheric ozone (Molina and Rowland, 1974) by the reactions involving the CFC photolytic product radicals, Cl and ClO, as catalysts. The first stratospheric measurements of ClO did indeed show its presence in significant quantities in the stratosphere so that by the end of the 1970s USA, Canada, and the Scandinavian countries issued laws against the use of CFC gases as propellants in spray cans. In the mid-1980s the springtime stratospheric ozone hole over Antarctica was discovered by Farman et al. (1985), involving heterogeneous reactions on polar stratospheric clouds that lead to chlorine activation ( Solomon et al., 1986). Ten years later, in 1996, a complete phaseout ofthe production of the CFCs and a number of other chlorine- or bromine-containing chemicals came into effect for all nations in the developed world. In this contribution we will, however, concentrate on the impact of reactive chlorine, bromine, and iodine on tropospheric ozone chemistry.Halogens have the potential to be important in many facets of tropospheric chemistry. A multitude of gas phase reactions and gas-particle interactions occur that include coupling with the sulfur cycle and reactions with hydrocarbons. Loss of ozone by catalytic reactions involving halogen radicals lowers the concentrations of the hydroxyl radical OH and thus the oxidation power of the atmosphere. Figure 1 shows these and other relevant halogen-related processes schematically. The sum of particulate and gaseous halogen concentrations maximize in the marine troposphere. Important for our climate - via feedback with cloud microphysics mainly in the large regions of marine stratocumulus - are links between halogen chemistry and the sulfur cycle. HOBraq and HOClaq can increase the liquid phase oxidation of S(IV) to S(VI), while BrO can decrease the most important in situ source for SO2 in the marine troposphere, namely, the oxidation of DMS to SO2 by reaction with OH by providing an alternate pathway (BrO+DMS) that reduces the yield of SO2 from DMS oxidation. Thus, the presence of bromine and chlorine in the troposphere lowers gas phase SO2 concentrations and thus the formation of new sulfate particles via the reaction sequence SO2+OH→H2SO4. (17K)Figure 1. Schematic depiction of the most important halogen-related processes in the troposphere. High mixing ratios of iodine oxide at a coastal site indicate a potentially significant role of iodine for the destruction of O3 and new particle embryo formation (Alicke et al., 1999; O'Dowd et al., 1998). Almost 20 years earlier, Chameides and Davis (1980) suggested that open ocean iodine chemistry would be initiated by the photolysis of CH3I. This was based on the measurements of Lovelock et al. (1973) and Singh et al. (1979), who found volume mixing ratios of CH3I of 1-5 pmol mol-1 over the ocean.The potentially strong involvement of halogens in tropospheric chemistry was first observed in the Arctic, where strong ozone depletion events were found to coincide with high levels of bromine (Barrie et al., 1988).The first mid-latitude demonstration of reactive halogen chemistry in the troposphere was made downwind of salt pans in the Dead Sea area, where the so far highest atmospheric mixing ratios of BrO were measured (Hebestreit et al., 1999). Volcanoes are sources of halogens as well, mainly in the form of HCl. Biomass burning releases halogens as do industrial processes.So far we have only mentioned chlorine, bromine, and iodine. This is justified because chemistry of fluorine is of no consequence, as very unreactive HF is efficiently formed in the atmosphere, e.g., via the reaction F+H2O→HF+OH. However, several fluorine-containing gases of anthropogenic origin are potentially powerful greenhouse gases, because they absorb strongly in the infrared atmospheric window region near 10 μm. Fully fluorinated gases - such as SF6, CF4, and C2F6 - have atmospheric lifetimes of the order of thousands of years and thus possess very high global warming potential (GWP). Although their abundance in the atmosphere has not yet grown large enough to be of concern for Earth's climate, their production must ultimately be curtailed in the future. The most abundant fully fluorinated gas, CF4, had an atmospheric volume mixing ratio of ˜75 pmol mol-1 in 1995 (Warneck, 1999). Because of their higher concentrations in the atmosphere, about 270 pmol mol-1 and 530 pmol mol-1, respectively, the CFC gases, CFCl3 and CF2Cl2, already exert a significant radiative greenhouse forcing (Ramanathan, 1975) on Earth's climate. For further discussion about atmospheric fluorine, the reader is referred to a thorough review article by Harnisch (1999).Several overview articles have been published on tropospheric halogen chemistry since the early 1980s, starting with Cicerone (1981). Wayne et al. (1995) list in great detail reaction paths, laboratory data, and atmospheric implications of halogen oxides. A good overview on laboratory measurements was also given by de Haan et al. (1999). Reaction cycles involved in tropospheric halogen chemistry and measurements are also thoroughly discussed by Platt (2000) and Platt and Hönninger (2003). Important compilations of laboratory studies that were made to elucidate chemical reaction paths are given by, e.g., DeMore et al. (1997), Sander et al. (2000), and Atkinson et al. (1999, 2000). Emission inventories for chlorine were compiled by Graedel and Keene (1995) and Keene et al. (1999).In Section 4.02.2 of this overview we will first describe the main halogen reaction mechanisms and then discuss, in Section 4.02.3, the springtime surface ozone depletion events in high latitudes that were first observed in the Arctic. Another main part of this chapter is concerned with halogens in the marine boundary layer ( Section 4.02.4). In Section 4.02.5 we describe interactions of halogens with some other elements of atmospheric importance. A very recently discovered environment where halogen chemistry plays a large role are salt lakes ( Section 4.02.6). There the chemistry bears similarity to that of the high-latitude ozone depletion events. This is followed in Section 4.02.7 by a discussion of halogen chemistry in the free troposphere and in Section 4.02.8 by other sources of halogens such as industry and biomass burning.

The influence of ocean halogen and sulfur emissions in the air quality of a coastal megacity: The case of Los Angeles

EPA Science Inventory

The oceans are the main source of natural halogen and sulfur compounds, which have a significant influence on the oxidizing capacity of the marine atmosphere; however, their impact on the air quality of coastal cities is currently unknown. We explore the effect of marine halogens...

Halogen-free benzoxazine based curable compositions for high TG applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tietze, Roger; Nguyen, Yen-Loan

The present invention provides a halogen-free curable composition including a benzoxazine monomer, at least one epoxy resin, a catalyst, a toughening agent and a solvent. The halogen-free curable composition is especially suited for use in automobile and aerospace applications since the composition, upon curing, produces a composite having a high glass transition temperature.

Halogen free benzoxazine based curable compositions for high T.sub.g applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tietze, Roger; Nguyen, Yen-Loan

A method for forming a halogen-free curable composition containing a benzoxazine monomer, at least one epoxy resin, a catalyst, a toughening agent and a solvent. The halogen-free curable composition is especially suited for use in automobile and aerospace applications since the composition, upon curing, produces a composite having a high glass transition temperature.

Halogenated volatile organic compounds from the use of chlorine-bleach-containing household products.

PubMed

Odabasi, Mustafa

2008-03-01

Sodium hypochlorite (NaOCl) and many organic chemicals contained in household cleaning products may react to generate halogenated volatile organic compounds (VOCs). Halogenated VOC emissions from eight different chlorine bleach containing household products (pure and diluted) were investigated by headspace experiments. Chloroform and carbon tetrachloride were the leading compounds along with several halogenated compounds in the headspace of chlorine bleach products. One of the most surprising results was the presence of carbon tetrachloride (a probable human carcinogen and a powerful greenhouse gas that was banned for household use by the U.S. Food and Drug Administration) in very high concentrations (up to 101 mg m(-3)). By mixing surfactants or soap with NaOCl, it was shown that the formation of carbon tetrachloride and several other halogenated VOCs is possible. In addition to quantitatively determined halogenated VOCs (n = 15), several nitrogen-containing (n = 4), chlorinated (n = 10), oxygenated compounds (n = 22), and hydrocarbons (n = 14) were identified in the headspace of bleach products. Among these, 1,1-dichlorobutane and 2-chloro-2-nitropropane were the most abundant chlorinated VOCs, whereas trichloronitromethane and hexachloroethane were the most frequently detected ones. Indoor air halogenated VOC concentrations resulting from the use of four selected household products were also measured before, during, and 30 min after bathroom, kitchen, and floor cleaning applications. Chloroform (2.9-24.6 microg m(-3)) and carbon tetrachloride (0.25-459 microg m(-3)) concentrations significantly increased during the use of bleach containing products. During/ before concentration ratios ranged between 8 and 52 (25 +/- 14, average +/- SD) for chloroform and 1-1170 (146 +/- 367, average +/- SD) for carbon tetrachloride, respectively. These results indicated that the bleach use can be important in terms of inhalation exposure to carbon tetrachloride, chloroform and several other halogenated VOCs.

Quantum Chemical Examination of the Sequential Halogen Incorporation Scheme for the Modeling of Speciation of I/Br/Cl-Containing Trihalomethanes.

PubMed

Zhang, Chenyang; Li, Maodong; Han, Xuze; Yan, Mingquan

2018-02-20

The recently developed three-step ternary halogenation model interprets the incorporation of chlorine, bromine, and iodine ions into natural organic matter (NOM) and formation of iodine-, bromine-, and chlorine-containing trihalomethanes (THMs) based on the competition of iodine, bromine, and chlorine species at each node of the halogenation sequence. This competition is accounted for using the dimensionless ratios (denoted as γ) of kinetic rates of reactions of the initial attack sites or halogenated intermediates with chlorine, bromine, and iodine ions. However, correlations between the model predictions made and mechanistic aspects of the incorporation of halogen species need to be ascertained in more detail. In this study, quantum chemistry calculations were first used to probe the formation mechanism of 10 species of Cl-/Br-/I- THMs. The HOMO energy (E HOMO ) of each mono-, bi-, or trihalomethanes were calculated by B3LYP method in Gaussian 09 software. Linear correlations were found to exist between the logarithms of experimentally determined kinetic preference coefficients γ reported in prior research and, on the other hand, differences of E HOMO values between brominated/iodinated and chlorinated halomethanes. One notable exception from this trend was that observed for the incorporation of iodine into mono- and di-iodinated intermediates. These observations confirm the three-step halogen incorporation sequence and the factor γ in the statistical model. The combined use of quantum chemistry calculations and the ternary sequential halogenation model provides a new insight into the microscopic nature of NOM-halogen interactions and the trends seen in the behavior of γ factors incorporated in the THM speciation models.

The halogen bond: Nature and applications

NASA Astrophysics Data System (ADS)

Costa, Paulo J.

2017-10-01

The halogen bond, corresponding to an attractive interaction between an electrophilic region in a halogen (X) and a nucleophile (B) yielding a R-X⋯B contact, found applications in many fields such as supramolecular chemistry, crystal engineering, medicinal chemistry, and chemical biology. Their large range of applications also led to an increased interest in their study using computational methods aiming not only at understanding the phenomena at a fundamental level, but also to help in the interpretation of results and guide the experimental work. Herein, a succinct overview of the recent theoretical and experimental developments is given starting by discussing the nature of the halogen bond and the latest theoretical insights on this topic. Then, the effects of the surrounding environment on halogen bonds are presented followed by a presentation of the available method benchmarks. Finally, recent experimental applications where the contribution of computational chemistry was fundamental are discussed, thus highlighting the synergy between the lab and modeling techniques.

Global Observations of Inorganic Gases in the Remote Atmosphere - First Observations from the Atmospheric Tomography Mission (ATom)

NASA Astrophysics Data System (ADS)

Veres, P. R.; Neuman, J. A.

2017-12-01

The Atmospheric Tomography Mission (ATom) is a NASA field program that investigates the impact of human emissions on air quality and climate in remote regions of the atmosphere. NASA DC-8 flights during the ATom sampled the atmosphere over the Pacific and Atlantic Oceans, up to 12 km altitude and nearly from pole to pole. New observations of key species (e.g. N2O5, reactive halogens, nitrous acid) in these regions are provided during the third deployment of the NASA DC-8 research aircraft (October, 2017) by the NOAA iodide ion time-of-flight chemical ionization mass spectrometer (iCIMS). In this study, we will present the first observations of inorganic gas-phase species using iCIMS from the ATom 3 deployment. Laboratory results detailing the instrument performance including inlet response times, background characterization and sensitivity will be presented. We will show vertical profiles of newly measured trace gases derived from in-situ observations, and discuss the potential impact on the NOx, NOy and reactive halogen budgets.

Quantum descriptors for predictive toxicology of halogenated aliphatic hydrocarbons.

PubMed

Trohalaki, S; Pachter, R

2003-04-01

In order to improve Quantitative Structure-Activity Relationships (QSARs) for halogenated aliphatics (HA) and to better understand the biophysical mechanism of toxic response to these ubiquitous chemicals, we employ improved quantum-mechanical descriptors to account for HA electrophilicity. We demonstrate that, unlike the lowest unoccupied molecular orbital energy, ELUMO, which was previously used as a descriptor, the electron affinity can be systematically improved by application of higher levels of theory. We also show that employing the reciprocal of ELUMO, which is more consistent with frontier molecular orbital (FMO) theory, improves the correlations with in vitro toxicity data. We offer explanations based on FMO theory for a result from our previous work, in which the LUMO energies of HA anions correlated surprisingly well with in vitro toxicity data. Additional descriptors are also suggested and interpreted in terms of the accepted biophysical mechanism of toxic response to HAs and new QSARs are derived for various chemical categories that compose the data set employed. These alternate descriptors provide important insight and could benefit other classes of compounds where the biophysical mechanism of toxic response involves dissociative attachment.

Cytotoxic Halogenated Macrolides and Modified Peptides from the Apratoxin-Producing Marine Cyanobacterium Lyngbya bouillonii from Guam

PubMed Central

Matthew, Susan; Salvador, Lilibeth A.; Schupp, Peter J.; Paul, Valerie J.; Luesch, Hendrik

2010-01-01

Collections of the marine cyanobacterium Lyngbya bouillonii from shallow patch reefs in Apra Harbor, Guam, afforded three hitherto undescribed analogues of the glycosidic macrolide lyngbyaloside, namely 2-epi-lyngbyaloside (1) and the regioisomeric 18E- and 18Z–lyngbyalosides C (2 and 3). Concurrently we discovered two new analogues of the cytoskeletal actin-disrupting lyngbyabellins, 27-deoxylyngbyabellin A (4) and lyngbyabellin J (5), a novel macrolide of the laingolide family, laingolide B (6), and a linear modified peptide, lyngbyapeptin D (7), along with known lyngbyabellins A and B, lyngbyapeptin A, and lyngbyaloside. The structures of 1–7 were elucidated by a combination of NMR spectroscopic and mass spectrometric analysis. Compounds 1–6 were either brominated (1–3) or chlorinated (4–6), consistent with halogenation being a hallmark of many marine natural products. All extracts derived from these L. bouillonii collections were highly cytotoxic due to the presence of apratoxin A or also apratoxin C. Compounds 1–5 showed weak to moderate cytotoxicity to HT29 colorectal adenocarcinoma and HeLa cervical carcinoma cells. PMID:20704304

Is nucleophilic cleavage chemistry practical for 4-membered heterocycles?

PubMed

Banks, Harold D

2009-11-07

A computational study at the MP2(Full)/6-311++G(d,p)//MP2(Full)/6-31+G(d) level of the ammonolysis of halogen substituted azetidines, oxetanes and thietanes was performed in the gas phase and in the commonly used solvent, acetonitrile. Using the free energy of activation of a benchmark reaction for evaluation of synthetic viability, several haloazetidines and oxetanes that possessed the required reactivity were identified; however, no substituted thietane investigated herein was determined to be synthetically useful under the mild conditions selected for this study. In the case of the azetidines, the side reaction of displacement of halide ion was determined to be the preferred reaction course in acetonitrile; however, the amino product of the reactions of the 2-haloazetidines cleaved at an acceptable rate under mild conditions. For the oxetane derivatives investigated, 2-fluorooxetane proved to be a direct source of ring cleavage product. Nucleophilic cleavage of halogen-substituted azetidines and oxetanes is predicted to be a viable source of functionalized three-carbon moieties under mild conditions in organic synthesis.

Emissions of Bromine and Iodine from the Marine Environment in New Zealand

NASA Astrophysics Data System (ADS)

Martinez-Aviles, M.; Kreher, K.; Johnston, P. V.; Hay, T.; Thomas, A.; Schofield, R.

2009-12-01

As noted in the WMO/UNEP Scientific Assessment of Ozone Depletion: 2006, halogenated very short-lived substances (VSLS) contribute to the atmospheric budget of halogens and thereby lead to substantial decreases in ozone and increases in surface UV radiation in the tropics and mid-latitudes. Halogenated VSLS are primarily of natural origin; oceanic emissions constitute the largest source providing 90-95% of the total global flux to the atmosphere. Macro algae in the ocean appear to be an important source of polyhalogenated VSLS. Oxidation of halogenated VSLS in the atmosphere (i.e. photolysis and reactions with OH) produces halogen oxide radicals (e.g. ClO, BrO, IO) which have been suggested as the main component of gas-phase halogens. Countries with long coastlines and little land suitable for forestation are investigating the possibility of industrial scale marine kelp farming as a means of carbon sequestration. This marine analogy of the Kyoto Protocol forest has been thought as a means to contribute to climate change mitigation. Knowledge of how natural emissions of VSLS will respond to both the drivers of climate change (e.g. changes in CO2 and land use) and to the consequences of climate change (e.g. changes in sea surface temperature and wind stress) is very limited. As a result, it is imperative that observational studies are performed to quantify the contributions of these natural VSLS to halogen loading in the troposphere and, subsequently, in the stratosphere. For this, transport and degradation processes of the source gases and product gases need to be studied and quantified. A key question surfacing from the WMO Assessment is to what extent halogenated VSLS contribute to atmospheric Bry and Iy. During a field campaign conducted during the spring of 2009, measurements of BrO and IO were made along the coastline of the South Island of New Zealand using a portable Multi Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) spectrometer with the aim of determining coastal sites where high active halogen release could be observed. The selected sites had high biomass concentration of marine algae that would be exposed by low tides. Local macro algae type, tidal height, sunlight, temperature, and wind speed were recorded and correlated to the resulting data in order to better understand the environmental factors that modulate the emissions of halogen oxides from the marine environment to the troposphere. Results of this multi-disciplinary approach to studying brominated VSLS and their atmospheric implications are presented. As well, the chemical processes taking place and producing these halogen oxides are discussed in a thorough manner. This study contributes to a better understanding of the origin of bromine and iodine in the lowermost atmosphere (i.e. marine boundary layer). Particularly, the role that natural emissions of halogenated VSLS from the ocean may play in the halogen budget of the lower atmosphere is addressed by quantitatively understanding key links in this chain so that its potential future impacts on atmospheric chemistry, surface UV radiation, and the biosphere can be thoroughly assessed.

Enzymatic synthesis of long double-stranded DNA labeled with haloderivatives of nucleobases in a precisely pre-determined sequence

PubMed Central

2011-01-01

Background Restriction endonucleases are widely applied in recombinant DNA technology. Among them, enzymes of class IIS, which cleave DNA beyond recognition sites, are especially useful. We use BsaI enzyme for the pinpoint introduction of halogen nucleobases into DNA. This has been done for the purpose of anticancer radio- and phototherapy that is our long-term objective. Results An enzymatic method for synthesizing long double-stranded DNA labeled with the halogen derivatives of nucleobases (Hal-NBs) with 1-bp accuracy has been put forward and successfully tested on three different DNA fragments containing the 5-bromouracil (5-BrU) residue. The protocol assumes enzymatic cleavage of two Polymerase-Chain-Reaction (PCR) fragments containing two recognition sequences for the same or different class IIS restriction endonucleases, where each PCR fragment has a partially complementary cleavage site. These sites are introduced using synthetic DNA primers or are naturally present in the sequence used. The cleavage sites are not compatible, and therefore not susceptible to ligation until they are partially filled with a Hal-NB or original nucleobase, resulting in complementary cohesive end formation. Ligation of these fragments ultimately leads to the required Hal-NB-labeled DNA duplex. With this approach, a synthetic, extremely long DNA fragment can be obtained by means of a multiple assembly reaction (n × maximum PCR product length: n × app. 50 kb). Conclusions The long, precisely labeled DNA duplexes obtained behave in very much the same manner as natural DNA and are beyond the range of chemical synthesis. Moreover, the conditions of synthesis closely resemble the natural ones, and all the artifacts accompanying the chemical synthesis of DNA are thus eliminated. The approach proposed seems to be completely general and could be used to label DNA at multiple pre-determined sites and with halogen derivatives of any nucleobase. Access to DNAs labeled with Hal-NBs at specific position is an indispensable condition for the understanding and optimization of DNA photo- and radio-degradation, which are prerequisites for clinical trials of Hal-NBs in anticancer therapy. PMID:21864341

Enzymatic synthesis of long double-stranded DNA labeled with haloderivatives of nucleobases in a precisely pre-determined sequence.

PubMed

Sobolewski, Ireneusz; Polska, Katarzyna; Zylicz-Stachula, Agnieszka; Jeżewska-Frąckowiak, Joanna; Rak, Janusz; Skowron, Piotr

2011-08-24

Restriction endonucleases are widely applied in recombinant DNA technology. Among them, enzymes of class IIS, which cleave DNA beyond recognition sites, are especially useful. We use BsaI enzyme for the pinpoint introduction of halogen nucleobases into DNA. This has been done for the purpose of anticancer radio- and phototherapy that is our long-term objective. An enzymatic method for synthesizing long double-stranded DNA labeled with the halogen derivatives of nucleobases (Hal-NBs) with 1-bp accuracy has been put forward and successfully tested on three different DNA fragments containing the 5-bromouracil (5-BrU) residue. The protocol assumes enzymatic cleavage of two Polymerase-Chain-Reaction (PCR) fragments containing two recognition sequences for the same or different class IIS restriction endonucleases, where each PCR fragment has a partially complementary cleavage site. These sites are introduced using synthetic DNA primers or are naturally present in the sequence used. The cleavage sites are not compatible, and therefore not susceptible to ligation until they are partially filled with a Hal-NB or original nucleobase, resulting in complementary cohesive end formation. Ligation of these fragments ultimately leads to the required Hal-NB-labeled DNA duplex. With this approach, a synthetic, extremely long DNA fragment can be obtained by means of a multiple assembly reaction (n × maximum PCR product length: n × app. 50 kb). The long, precisely labeled DNA duplexes obtained behave in very much the same manner as natural DNA and are beyond the range of chemical synthesis. Moreover, the conditions of synthesis closely resemble the natural ones, and all the artifacts accompanying the chemical synthesis of DNA are thus eliminated. The approach proposed seems to be completely general and could be used to label DNA at multiple pre-determined sites and with halogen derivatives of any nucleobase. Access to DNAs labeled with Hal-NBs at specific position is an indispensable condition for the understanding and optimization of DNA photo- and radio-degradation, which are prerequisites for clinical trials of Hal-NBs in anticancer therapy.

Effect of the 3-halo substitution of the 2'-deoxy aminopyridinyl-pseudocytidine derivatives on the selectivity and stability of antiparallel triplex DNA with a CG inversion site.

PubMed

Wang, Lei; Taniguchi, Yosuke; Okamura, Hidenori; Sasaki, Shigeki

2017-07-15

Triplex formation against a target duplex DNA has the potential to become a tool for the genome research. However, there is an intrinsic restriction on the duplex DNA sequences capable of forming the triplex DNA. Recently, we demonstrated the selective formation of the stable antiparallel triplexes containing the CG inversion sites using the 2'-deoxy-1-methylpseudocytidine derivative (ΨdC), whose amino group was conjugated with the 2-aminopyridine at its 5-position as an additional hydrogen bonding unit (AP-ΨdC). The 1-N of 2-aminopyridine was supposed to be protonated to form the hydrogen bond with the guanine of the CG inversion site. In this study, to test the effect of the 3-substitution of the 2-aminopyridine unit of AP-ΨdC on the triplex stability, we synthesized the 3-halogenated 2-aminopyridine derivatives of AP-ΨdC. The pKa values 1-N of the 2-aminopyridine unit of AP-ΨdC as the monomer nucleoside were determined to be 6.3 for 3-CH 3 ( Me AP-ΨdC), 6.1 for 3-H (AP-ΨdC), 4.3 for 3-Cl ( Cl AP-ΨdC), 4.4 for 3-Br ( Br AP-ΨdC), and 4.7 for 3-I ( I AP-ΨdC), suggesting that all the halogenated AP-ΨdCs are not protonated under neutral conditions. Interestingly, although the recognition selectivity depends on the sequence context, the TFO having the sequence of the 3'-G-( I AP-ΨdC)-A-5' context showed the selective triplex formation with the CG inversion site. These results suggest that the protonation at the 1-N position plays an important role in the stable and selective triplex formation of AP-ΨdC derivatives in any sequences. Copyright © 2017 Elsevier Ltd. All rights reserved.

Halogenated naphthyl methoxy piperidines for mapping serotonin transporter sites

DOEpatents

Goodman, Mark M.; Faraj, Bahjat

1999-01-01

Halogenated naphthyl methoxy piperidines having a strong affinity for the serotonin transporter are disclosed. Those compounds can be labeled with positron-emitting and/or gamma emitting halogen isotopes by a late step synthesis that maximizes the useable lifeterm of the label. The labeled compounds are useful for localizing serotonin transporter sites by positron emission tomography and/or single photon emission computed tomography.

Halogenated naphthyl methoxy piperidines for mapping serotonin transporter sites

DOEpatents

Goodman, M.M.; Faraj, B.

1999-07-06

Halogenated naphthyl methoxy piperidines having a strong affinity for the serotonin transporter are disclosed. Those compounds can be labeled with positron-emitting and/or gamma emitting halogen isotopes by a late step synthesis that maximizes the useable lifeterm of the label. The labeled compounds are useful for localizing serotonin transporter sites by positron emission tomography and/or single photon emission computed tomography.

Effects of halogenated aromatics/aliphatics and nitrogen(N)-heterocyclic aromatics on estimating the persistence of future pharmaceutical compounds using a modified QSAR model.

PubMed

Lim, Seung Joo; Fox, Peter

2014-02-01

The effects of halogenated aromatics/aliphatics and nitrogen(N)-heterocyclic aromatics on estimating the persistence of future pharmaceutical compounds were investigated using a modified half life equation. The potential future pharmaceutical compounds investigated were approximately 2000 pharmaceutical drugs currently undergoing the United States Food and Drug Administration (US FDA) testing. EPI Suite (BIOWIN) model estimates the fates of compounds based on the biodegradability under aerobic conditions. While BIOWIN considered the biodegradability of a compound only, the half life equation used in this study was modified by biodegradability, sorption and cometabolic oxidation. It was possible that the potential future pharmaceutical compounds were more accurately estimated using the modified half life equation. The modified half life equation considered sorption and cometabolic oxidation of halogenated aromatic/aliphatics and nitrogen(N)-heterocyclic aromatics in the sub-surface, while EPI Suite (BIOWIN) did not. Halogenated aliphatics in chemicals were more persistent than halogenated aromatics in the sub-surface. In addition, in the sub-surface environment, the fates of organic chemicals were much more affected by halogenation in chemicals than by nitrogen(N)-heterocyclic aromatics. © 2013.

Halogenated compounds from marine algae.

PubMed

Cabrita, Maria Teresa; Vale, Carlos; Rauter, Amélia Pilar

2010-08-09

Marine algae produce a cocktail of halogenated metabolites with potential commercial value. Structures exhibited by these compounds go from acyclic entities with a linear chain to complex polycyclic molecules. Their medical and pharmaceutical application has been investigated for a few decades, however other properties, such as antifouling, are not to be discarded. Many compounds were discovered in the last years, although the need for new drugs keeps this field open as many algal species are poorly screened. The ecological role of marine algal halogenated metabolites has somehow been overlooked. This new research field will provide valuable and novel insight into the marine ecosystem dynamics as well as a new approach to comprehending biodiversity. Furthermore, understanding interactions between halogenated compound production by algae and the environment, including anthropogenic or global climate changes, is a challenging target for the coming years. Research of halogenated metabolites has been more focused on macroalgae than on phytoplankton. However, phytoplankton could be a very promising material since it is the base of the marine food chain with quick adaptation to environmental changes, which undoubtedly has consequences on secondary metabolism. This paper reviews recent progress on this field and presents trends on the role of marine algae as producers of halogenated compounds.

Halogenated Compounds from Marine Algae

PubMed Central

Cabrita, Maria Teresa; Vale, Carlos; Rauter, Amélia Pilar

2010-01-01

Marine algae produce a cocktail of halogenated metabolites with potential commercial value. Structures exhibited by these compounds go from acyclic entities with a linear chain to complex polycyclic molecules. Their medical and pharmaceutical application has been investigated for a few decades, however other properties, such as antifouling, are not to be discarded. Many compounds were discovered in the last years, although the need for new drugs keeps this field open as many algal species are poorly screened. The ecological role of marine algal halogenated metabolites has somehow been overlooked. This new research field will provide valuable and novel insight into the marine ecosystem dynamics as well as a new approach to comprehending biodiversity. Furthermore, understanding interactions between halogenated compound production by algae and the environment, including anthropogenic or global climate changes, is a challenging target for the coming years. Research of halogenated metabolites has been more focused on macroalgae than on phytoplankton. However, phytoplankton could be a very promising material since it is the base of the marine food chain with quick adaptation to environmental changes, which undoubtedly has consequences on secondary metabolism. This paper reviews recent progress on this field and presents trends on the role of marine algae as producers of halogenated compounds. PMID:20948909

Role of growth media and chemical enhancers in secondary metabolites production from Aspergillus carbonarius (NRL-369) and their pharmaceutical potentials.

PubMed

Khan, Abid Ali; Bacha, Nafess; Ahmad, Bashir; Cox, R J; Bakht, Jehan

2016-07-01

The present study investigates the effect of different growth media and chemical enhancer on silent genes in Aspergillus carbonarius (NRL-369) for secondary metabolites production and its in vitro biological activities. Results revealed that Aspergillus carbonarius (NRL-369) grown in Czapeak yeast extract broth medium produced more metabolites compared with other media. Chemical epigenetic modifiers (suberoyl-anilide hydroxamic acid (SAHA) and 5-azacytidine (5-AZA) at concentration of 15mM were effective for the expression of silent genes resulting in increased secondary metabolites production. Secondary metabolites extracted in ethyl acetate and fractionized in n-Hexane showed variable degree of growth inhibitions of the tested microorganisms. Similarly, these samples were also active against brine shrimps and Lemna.

Halogen radicals contribute to photooxidation in coastal and estuarine waters

PubMed Central

Parker, Kimberly M.; Mitch, William A.

2016-01-01

Although halogen radicals are recognized to form as products of hydroxyl radical (•OH) scavenging by halides, their contribution to the phototransformation of marine organic compounds has received little attention. We demonstrate that, relative to freshwater conditions, seawater halides can increase photodegradation rates of domoic acid, a marine algal toxin, and dimethyl sulfide, a volatile precursor to cloud condensation nuclei, up to fivefold. Using synthetic seawater solutions, we show that the increased photodegradation is specific to dissolved organic matter (DOM) and halides, rather than other seawater salt constituents (e.g., carbonates) or photoactive species (e.g., iron and nitrate). Experiments in synthetic and natural coastal and estuarine water samples demonstrate that the halide-specific increase in photodegradation could be attributed to photochemically generated halogen radicals rather than other photoproduced reactive intermediates [e.g., excited-state triplet DOM (3DOM*), reactive oxygen species]. Computational kinetic modeling indicates that seawater halogen radical concentrations are two to three orders of magnitude greater than freshwater •OH concentrations and sufficient to account for the observed halide-specific increase in photodegradation. Dark •OH generation by gamma radiolysis demonstrates that halogen radical production via •OH scavenging by halides is insufficient to explain the observed effect. Using sensitizer models for DOM chromophores, we show that halogen radicals are formed predominantly by direct oxidation of Cl− and Br− by 3DOM*, an •OH-independent pathway. Our results indicate that halogen radicals significantly contribute to the phototransformation of algal products in coastal or estuarine surface waters. PMID:27162335

Halogen Chemistry at North American Coastal Sites

NASA Astrophysics Data System (ADS)

Stutz, J.; Pikelnaya, O.; Laskin, A.; Sumner, A.; Jobson, B. T.; Finley, B.; Lawler, M.; Saltzman, E. S.; Pszenny, A. A.; Deegan, B.

2007-12-01

In recent years observational evidence has emerged that reactive halogen species (RHS), such as chlorine atoms, and bromine and iodine oxides, are present in coastal areas. Their chemistry can be significant as they catalytically destroy O3; oxidize hydrocarbons, dimethylsulfide, and S(IV); and modify NOx and HOx cycling. Despite their potential importance our observational database on RHS is still very limited. Most observations of RHS thus far have been made in clean areas and very few observations along the North American coast have been made. Here we will review our current understanding of RHS chemistry in both clean and polluted environments. Recent observations at coastal areas around the world will be discussed. We will also give an overview of an experiment performed by our group in Malibu, CA in October 2006 and present initial results. A suite of trace gases and environmental parameters, including halogen molecules, halogen oxides, Cl + VOC reaction products, aerosol composition, O3, NOx, CO, VOCs, meteorology, and radiation, were measured during a three week period. In addition, Cl + VOC reaction products were measured at two locations in urban Los Angeles. Clear evidence for the presence of various halogen species on the California coast was found. Observations during periods with relatively clean marine air and during times where our site was in the outflow of Los Angeles show the impact of pollution on coastal atmospheric chemistry. Our observations will be compared to earlier studies of halogen chemistry at coastal areas to further advance our understanding of halogen chemistry.

Sorption of halogenated phenols and pharmaceuticals to biochar: affecting factors and mechanisms.

PubMed

Oh, Seok-Young; Seo, Yong-Deuk

2016-01-01

The feasibility of using biochar as a sorbent to remove nine halogenated phenols (2,4-dichlorophenol, 2,4-dibromophenol, 2,4-difluorophenol, 2-chlorophenol, 4-chlorophenol, 2-bromophenol, 4-bromophenol, 2-fluorophenol, and 4-fluorophenol) and two pharmaceuticals (triclosan and ibuprofen) from water was examined through a series of batch experiments. Types of biochar, synthesized using various biomasses including fallen leaves, rice straw, corn stalk, used coffee grounds, and biosolids, were evaluated. Compared to granular activated carbon (GAC), most of the biochar samples did not effectively remove halogenated phenols or pharmaceuticals from water. The increase in pH and deprotonation of phenols in biochar systems may be responsible for its ineffectiveness at this task. When pH was maintained at 4 or 7, the sorption capacity of biochar was markedly increased. Considering maximum sorption capacity and properties of sorbents and sorbates, it appears that the sorption capacity of biochar for halogenated phenols is related to the surface area and carbon content of the biochar and the hydrophobicity of halogenated phenols. In the cases of triclosan and ibuprofen, the sorptive capacities of GAC, graphite, and biochars were also significantly affected by pH, according to the point of zero charge (PZC) of sorbents and deprotonation of the pharmaceuticals. Pyrolysis temperature did not affect the sorption capacity of halogenated phenols or pharmaceuticals. Based on the experimental observations, some biochars are good candidates for removal of halogenated phenols, triclosan, and ibuprofen from water and soil.

Hydrophobic Organic Compounds in Hydraulic Fracturing Flowback Waters: Identification and Source Apportionment

NASA Astrophysics Data System (ADS)

Plata, D.; Shregglman, K.; Elsner, M.; Getzinger, G.; Ferguson, L.; Drollette, B.; Karatum, O.; Nelson, R. K.; Reddy, C. M.

2014-12-01

Current hydraulic fracturing technologies rely on organic chemicals to serve multiple critical functions, including corrosion inhibition, in situ gel formation, and friction reduction. While industrial users have disclosed several hundreds of compound and mixture identities, it is unclear which of these are used and where, in what proportion, and with what frequency. Furthermore, while flowback and production waters contain both fracturing additive and geogenic compounds, they may contain potential reaction byproducts as well. Here, we identified several hundred organic compounds present in six hydraulic fracturing flowback waters over the Fayetteville shale. Identifications were made via non-target analysis using two-dimensional gas chromatography with time of flight mass spectrometry for hydrophobic organic compounds and liquid chromatography- orbitrap mass spectrometry. Compound identities were confirmed using purchased standards when available. Using the SkyTruth database and the Waxman list of disclosed compounds, we assigned compounds as either fracturing-fluid-derived or geogenic (or both), or a putative transformation products thereof. Several unreported halogenated compounds were detected, including chlorinated, brominated, and iodated species that have no known natural sources. Control studies indicated that these could not be formed under typical laboratory or field storage conditions, suggesting that halogenation reactions may give rise to novel compounds in the subsurface, presumably via reaction between fracturing fluid additives and shale-derived brines. Further, the six samples were strikingly heterogeneous, reflecting the diversity in fracturing fluid composition and flowback handling procedures at the time of the study.

40 CFR Table 3 to Subpart Ffff of... - Emission Limits for Hydrogen Halide and Halogen HAP Emissions or HAP Metals Emissions From...

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 12 2011-07-01 2009-07-01 true Emission Limits for Hydrogen Halide and... to Subpart FFFF of Part 63—Emission Limits for Hydrogen Halide and Halogen HAP Emissions or HAP... following table that applies to your process vents that contain hydrogen halide and halogen HAP emissions or...

40 CFR Table 3 to Subpart Ffff of... - Emission Limits for Hydrogen Halide and Halogen HAP Emissions or HAP Metals Emissions From...

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 12 2010-07-01 2010-07-01 true Emission Limits for Hydrogen Halide and... to Subpart FFFF of Part 63—Emission Limits for Hydrogen Halide and Halogen HAP Emissions or HAP... following table that applies to your process vents that contain hydrogen halide and halogen HAP emissions or...

40 CFR 63.2465 - What requirements must I meet for process vents that emit hydrogen halide and halogen HAP or HAP...

Code of Federal Regulations, 2011 CFR

2011-07-01

... process vents that emit hydrogen halide and halogen HAP or HAP metals? 63.2465 Section 63.2465 Protection... Compliance Requirements § 63.2465 What requirements must I meet for process vents that emit hydrogen halide... section. (b) If any process vents within a process emit hydrogen halide and halogen HAP, you must...

Novel urea and bis-urea primaquine derivatives with hydroxyphenyl or halogenphenyl substituents: Synthesis and biological evaluation.

PubMed

Perković, I; Antunović, M; Marijanović, I; Pavić, K; Ester, K; Kralj, M; Vlainić, J; Kosalec, I; Schols, D; Hadjipavlou-Litina, D; Pontiki, E; Zorc, B

2016-11-29

A series of novel compounds 3a-j and 6a-j with primaquine and hydroxyl or halogen substituted benzene moieties bridged by urea or bis-urea functionalities were designed, synthesized and evaluated for biological activity. The title compounds were prepared using benzotriazole as the synthon, through several synthetic steps. 3-[3,5-Bis(trifluoromethyl)phenyl]-1-{4-[(6-methoxyquinolin-8-yl)amino]pentyl}urea (3j) was the most active urea and 1-[({4-[(6-methoxyquinolin-8-yl)amino]pentyl}carbamoyl)amino]-3-[3-(trifluoromethyl)phenyl]urea (6h) the most active bis-urea derivative in antiproliferative screening in vitro against eight tested cancer cell lines. Urea derivatives 3a-g with hydroxy group or one halogen atom showed moderate antiproliferative effects against all the tested cell lines, but stronger activity against breast carcinoma MCF-7 cell line, while trifluoromethyl derivatives 3h-j showed antiproliferative effects against all the tested cell lines in low micromolar range. Finally, bis-ureas with hydroxy and fluoro substituents 6a-d showed extreme selectivity and chloro or bromo derivatives 6e-g high selectivity against MCF-7 cells (IC 50 0.1-2.6 μM). p-Fluoro derivative 6d, namely 3-(4-fluorophenyl)-1-[({4-[(6-methoxyquinolin-8-yl)amino]pentyl}carbamoyl)amino]urea, is the most promising compound. Further biological experiments showed that 6d affected cell cycle and induced cell death of MCF-7 cell line. Due to its high activity against MCF-7 cell line (IC 50 0.31 μM), extreme selectivity and full agreement with the Lipinski's and Gelovani's rules for prospective small molecular drugs, 6d may be considered as a lead compound in development of breast carcinoma drugs. Urea 3b and almost all bis-ureas showed high antioxidant activity in DPPH assay, but urea derivatives were more active in lipid peroxidation test. Only few compounds exhibited weak inhibition of soybean lipoxygenase. Compound 3j exhibited the strongest antimicrobial activity in susceptibility assay in vitro (MIC = 1.6-12.5 μg ml -1 ). Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Nontypical iodine–halogen bonds in the crystal structure of (3 E )-8-chloro-3-iodomethylidene-2,3-dihydro-1,4-oxazino[2,3,4- ij ]quinolin-4-ium triiodide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bartashevich, E. V.; Batalov, V. I.; Yushina, I. D.

2016-03-23

Two kinds of iodine–iodine halogen bonds are the focus of our attention in the crystal structure of the title salt, C 12H 8ClINO +·I 3 -, described by X-ray diffraction. The first kind is a halogen bond, reinforced by charges, between the I atom of the heterocyclic cation and the triiodide anion. The second kind is the rare case of a halogen bond between the terminal atoms of neighbouring triiodide anions. The influence of relatively weakly bound iodine inside an asymmetric triiodide anion on the thermal and Raman spectroscopic properties has been demonstrated.

Biodegradation of Trihalomethanes and Other Halogenated Aliphatic Compounds

NASA Technical Reports Server (NTRS)

Smith, G. B.

1996-01-01

The biological dehalogenation of common water pollutants such as trichloromethane (chloroform) and other halogenated aliphatic compounds was the subject of this project. Samples from diverse water environments such as from groundwater contaminated with halogenated compounds and wastewaters from regional treatment plants were studied to identify conditions that favor certain dehalogenation reactions over others. Gene probe analyses of DNA extracted from the dichlormethane-degrading wastewater indicated the presence of the gene coding for dichloromethane dehalogenase, indicating the genetic basis for the dechlorination activity observed. These studies indicate that methanogenic bacteria are the organisms responsible for the chloroform dechlorination. Dechlorination of a common chlorofluorocarbon (CFC-11) was identified in samples taken from a regional aquifer contaminated with halogenated aliphatic compounds.

Hypochlorous Acid Reacts with the N-Terminal Methionines of Proteins to Give Dehydromethionine, a Potential Biomarker for Neutrophil-Induced Oxidative Stress†

PubMed Central

Beal, Jennifer L.; Foster, Steven B.; Ashby, Michael T.

2009-01-01

Electrophilic halogenating agents, including hypohalous acids and haloamines, oxidize free methionine and the N-terminal methionines of peptides and proteins (e.g., Met-1 of anti-inflammatory peptide 1 and ubiquitin) to produce dehydromethionine (a five-membered isothiazolidinium heterocycle). Amide derivatives of methionine are oxidized to the corresponding sulfoxide derivatives under the same reaction conditions (e.g., Met-3 of anti-inflammatory peptide 1). Other biological oxidants, including hydrogen peroxide and peroxynitrite, also only produce the corresponding sulfoxides. Hypothiocyanite does not react with methionine residues. It is suggested that dehydromethionine may be a useful biomarker for the myeloperoxidase-induced oxidative stress associated with many inflammatory diseases. PMID:19839600

Photoluminescence of epoxy resin modified by carbazole and its halogen derivative at 82 K

NASA Astrophysics Data System (ADS)

Mandowska, E.; Mandowski, A.; Tsvirko, M.

2009-10-01

The spectra and relative quantum yield of fluorescence and phosphorescence were measured for 9-(2,3-epoxypropyl)carbazole (EPK) added to epoxy resin (R) (R 5EPK - 5% weight content of the carbazole group in a polymer) and its mono and dihalogen derivative (Cl and Br). The materials under study have excellent mechanical properties. At 82 K photoluminescence (PL) spectra of these materials are composed of fluorescence (FL) and phosphorescence (PH) components while at 280 K, PH component is not observed. The vibrational frequencies of fluorescence and phosphorescence for R 5EPK were determined using Gaussian deconvolution. A decrease in the fluorescence and an increase in the phosphorescence quantum efficiency were observed after chemical bonding of heavy atoms Cl and Br.

5-(Halomethyl)uridine derivatives as potential antitumor radiosensitizers: A DFT study

NASA Astrophysics Data System (ADS)

Wang, Shoushan; Zhang, Min; Liu, Peng; Xie, Shilei; Cheng, Faliang; Wang, Lishi

2018-01-01

Considering the fact that the efficiency of the uridine-5-methyl radical in producing cytotoxic DNA intrastrand cross-link lesions is greatly higher than that of the uridine-5-yl radical, the radiosensitizing action of 5-(halomethyl)uridines (5-XCH2U, X = F, Cl, or Br) is studied in the present work. It is found that 5-XCH2U has sufficient electron affinity to capture a pre-hydrated or a hydrated electron, and electron attachment leads to significantly facile X- elimination forming the uridine-5-methyl radical. All these three halogenated uridine derivatives are shown to be potential radiosensitizers, with their radiosensitizing abilities increased in an order 5-FCH2U < 5-ClCH2U ≈ 5-BrCH2U.

Fluoride-containing podophyllum derivatives exhibit antitumor activities through enhancing mitochondrial apoptosis pathway by increasing the expression of caspase-9 in HeLa cells

PubMed Central

Zhao, Wei; Yang, Yong; Zhang, Ya-Xuan; Zhou, Chen; Li, Hong-Mei; Tang, Ya-Ling; Liang, Xin-Hua; Chen, Tao; Tang, Ya-Jie

2015-01-01

This work aims to provide sampling of halogen-containing aniline podophyllum derivatives and their mode of action with an in-depth comparison among fluorine, chloride and bromide for clarifying the important role and impact of fluorine substitution on enhancing antitumor activity, with an emphasis on the development of drug rational design for antitumor drug. The tumor cytotoxicity of fluoride-containing aniline podophyllum derivatives were in general improved by 10–100 times than those of the chloride and bromide-containing aniline podophyllum derivatives since fluoride could not only strongly solvated in protic solvents but also forms tight ion pairs in most aprotic solvents. When compared with chloride and bromide, the higher electronegativity fluoride substituted derivatives significantly enhanced mitochondrial apoptosis pathway by remarkably increasing the expression of caspase-9 in HeLa cells. The current findings would stimulate an enormous amount of research directed toward exploiting novel leading compounds based on podophyllum derivatives, especially for the fluoride-substituted structures with promising antitumor activity. PMID:26608216

Photochemically and Thermally Driven Full-Color Reflection in a Self-Organized Helical Superstructure Enabled by a Halogen-Bonded Chiral Molecular Switch.

PubMed

Wang, Hao; Bisoyi, Hari Krishna; Wang, Ling; Urbas, Augustine M; Bunning, Timothy J; Li, Quan

2018-02-05

Supramolecular approaches toward the fabrication of functional materials and systems have been an enabling endeavor. Recently, halogen bonding has been harnessed as a promising supramolecular tool. Herein we report the synthesis and characterization of a novel halogen-bonded light-driven axially chiral molecular switch. The photoactive halogen-bonded chiral switch is able to induce a self-organized, tunable helical superstructure, that is, cholesteric liquid crystal (CLC), when doped into an achiral liquid crystal (LC) host. The halogen-bonded switch as a chiral dopant has a high helical twisting power (HTP) and shows a large change of its HTP upon photoisomerization. This light-driven dynamic modulation enables reversible selective reflection color tuning across the entire visible spectrum. The chiral switch also displays a temperature-dependent HTP change that enables thermally driven red, green, and blue (RGB) reflection colors in the self-organized helical superstructure. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Selective Nitrate Recognition by a Halogen-Bonding Four-Station [3]Rotaxane Molecular Shuttle.

PubMed

Barendt, Timothy A; Docker, Andrew; Marques, Igor; Félix, Vítor; Beer, Paul D

2016-09-05

The synthesis of the first halogen bonding [3]rotaxane host system containing a bis-iodo triazolium-bis-naphthalene diimide four station axle component is reported. Proton NMR anion binding titration experiments revealed the halogen bonding rotaxane is selective for nitrate over the more basic acetate, hydrogen carbonate and dihydrogen phosphate oxoanions and chloride, and exhibits enhanced recognition of anions relative to a hydrogen bonding analogue. This elaborate interlocked anion receptor functions via a novel dynamic pincer mechanism where upon nitrate anion binding, both macrocycles shuttle from the naphthalene diimide stations at the periphery of the axle to the central halogen bonding iodo-triazolium station anion recognition sites to form a unique 1:1 stoichiometric nitrate anion-rotaxane sandwich complex. Molecular dynamics simulations carried out on the nitrate and chloride halogen bonding [3]rotaxane complexes corroborate the (1) H NMR anion binding results. © 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Two-dimensional networks of brominated Y-shaped molecules on Au(111)

NASA Astrophysics Data System (ADS)

Jeon, Un Seung; Chang, Min Hui; Jang, Won-Jun; Lee, Soon-Hyung; Han, Seungwu; Kahng, Se-Jong

2018-02-01

In the design of supramolecular structures, Y-shaped molecules are useful to expand the structures in three different directions. The supramolecular structures of Y-shaped molecules with three halogen-ligands on surfaces have been extensively studied, but much less are done for those with six halogen-ligands. Here, we report on the intermolecular interactions of a Y-shaped molecule, 1,3,5-Tris(3,5-dibromophenyl)benzene, with six Br-ligands studied using scanning tunneling microscopy (STM). Honeycomb-like structures were observed on Au(111), and could be explained with chiral triple-nodes made of three Br···Br halogen bonds. Molecular models were proposed based on STM images and reproduced with density-functional theory calculations. Although the molecule has six Br-ligands, only three of them form Br···Br halogen bonds because of geometrical restrictions. Our study shows that halogenated Y-shaped molecules will be useful components for building supramolecular structures.

Halogen-Mediated Conversion of Hydrocarbons to Commodities.

PubMed

Lin, Ronghe; Amrute, Amol P; Pérez-Ramírez, Javier

2017-03-08

Halogen chemistry plays a central role in the industrial manufacture of various important chemicals, pharmaceuticals, and polymers. It involves the reaction of halogens or halides with hydrocarbons, leading to intermediate compounds which are readily converted to valuable commodities. These transformations, predominantly mediated by heterogeneous catalysts, have long been successfully applied in the production of polymers. Recent discoveries of abundant conventional and unconventional natural gas reserves have revitalized strong interest in these processes as the most cost-effective gas-to-liquid technologies. This review provides an in-depth analysis of the fundamental understanding and applied relevance of halogen chemistry in polymer industries (polyvinyl chloride, polyurethanes, and polycarbonates) and in the activation of light hydrocarbons. The reactions of particular interest include halogenation and oxyhalogenation of alkanes and alkenes, dehydrogenation of alkanes, conversion of alkyl halides, and oxidation of hydrogen halides, with emphasis on the catalyst, reactor, and process design. Perspectives on the challenges and directions for future development in this exciting field are provided.

Metal halogen battery construction with improved technique for producing halogen hydrate

DOEpatents

Fong, Walter L.; Catherino, Henry A.; Kotch, Richard J.

1983-01-01

An improved electrical energy storage system comprising, at least one cell having a positive electrode and a negative electrode separated by aqueous electrolyte, a store means wherein halogen hydrate is formed and stored as part of an aqueous material having a liquid level near the upper part of the store, means for circulating electrolyte through the cell, conduit means for transmitting halogen gas formed in the cell to a hydrate forming apparatus associated with the store, said hydrate forming apparatus including, a pump to which there is introduced quantities of the halogen gas and chilled water, said pump being located in the store and an outlet conduit leading from the pump and being substantially straight and generally vertically disposed and having an exit discharge into the gas space above the liquid level in the store, and wherein said hydrate forming apparatus is highly efficient and very resistant to plugging or jamming. The disclosure also relates to an improved method for producing chlorine hydrate in zinc chlorine batteries.

40 CFR Table 3 to Subpart Ffff of... - Emission Limits for Hydrogen Halide and Halogen HAP Emissions or HAP Metals Emissions From...

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 13 2013-07-01 2012-07-01 true Emission Limits for Hydrogen Halide and..., Table 3 Table 3 to Subpart FFFF of Part 63—Emission Limits for Hydrogen Halide and Halogen HAP Emissions... limit in the following table that applies to your process vents that contain hydrogen halide and halogen...

40 CFR Table 3 to Subpart Ffff of... - Emission Limits for Hydrogen Halide and Halogen HAP Emissions or HAP Metals Emissions From...

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 13 2014-07-01 2014-07-01 false Emission Limits for Hydrogen Halide.... FFFF, Table 3 Table 3 to Subpart FFFF of Part 63—Emission Limits for Hydrogen Halide and Halogen HAP... limit in the following table that applies to your process vents that contain hydrogen halide and halogen...

40 CFR Table 3 to Subpart Ffff of... - Emission Limits for Hydrogen Halide and Halogen HAP Emissions or HAP Metals Emissions From...

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 13 2012-07-01 2012-07-01 false Emission Limits for Hydrogen Halide.... FFFF, Table 3 Table 3 to Subpart FFFF of Part 63—Emission Limits for Hydrogen Halide and Halogen HAP... limit in the following table that applies to your process vents that contain hydrogen halide and halogen...

Source identification and apportionment of halogenated compounds observed at a remote site in East Asia.

PubMed

Li, Shanlan; Kim, Jooil; Park, Sunyoung; Kim, Seung-Kyu; Park, Mi-Kyung; Mühle, Jens; Lee, Gangwoong; Lee, Meehye; Jo, Chun Ok; Kim, Kyung-Ryul

2014-01-01

The sources of halogenated compounds in East Asia associated with stratospheric ozone depletion and climate change are relatively poorly understood. High-precision in situ measurements of 18 halogenated compounds and carbonyl sulfide (COS) made at Gosan, Jeju Island, Korea, from November 2007 to December 2011 were analyzed by a positive matrix factorization (PMF). Seven major industrial sources were identified from the enhanced concentrations of halogenated compounds observed at Gosan and corresponding concentration-based source contributions were also suggested: primary aluminum production explaining 37% of total concentration enhancements, solvent usage of which source apportionment is 25%, fugitive emissions from HCFC/HFC production with 11%, refrigerant replacements (9%), semiconductor/electronics industry (9%), foam blowing agents (6%), and fumigation (3%). Statistical trajectory analysis was applied to specify the potential emission regions for seven sources using back trajectories. Primary aluminum production, solvent usage and fugitive emission sources were mainly contributed by China. Semiconductor/electronics sources were dominantly located in Korea. Refrigerant replacement, fumigation and foam blowing agent sources were spread throughout East Asian countries. The specified potential source regions are consistent with country-based consumptions and emission patterns, verifying the PMF analysis results. The industry-based emission sources of halogenated compounds identified in this study help improve our understanding of the East Asian countries' industrial contributions to halogenated compound emissions.

Stratospheric Ozone destruction by the Bronze-Age Minoan eruption (Santorini Volcano, Greece)

PubMed Central

Cadoux, Anita; Scaillet, Bruno; Bekki, Slimane; Oppenheimer, Clive; Druitt, Timothy H.

2015-01-01

The role of volcanogenic halogen-bearing (i.e. chlorine and bromine) compounds in stratospheric ozone chemistry and climate forcing is poorly constrained. While the 1991 eruption of Pinatubo resulted in stratospheric ozone loss, it was due to heterogeneous chemistry on volcanic sulfate aerosols involving chlorine of anthropogenic rather than volcanogenic origin, since co-erupted chlorine was scavenged within the plume. Therefore, it is not known what effect volcanism had on ozone in pre-industrial times, nor what will be its role on future atmospheres with reduced anthropogenic halogens present. By combining petrologic constraints on eruption volatile yields with a global atmospheric chemistry-transport model, we show here that the Bronze-Age ‘Minoan’ eruption of Santorini Volcano released far more halogens than sulfur and that, even if only 2% of these halogens reached the stratosphere, it would have resulted in strong global ozone depletion. The model predicts reductions in ozone columns of 20 to >90% at Northern high latitudes and an ozone recovery taking up to a decade. Our findings emphasise the significance of volcanic halogens for stratosphere chemistry and suggest that modelling of past and future volcanic impacts on Earth’s ozone, climate and ecosystems should systematically consider volcanic halogen emissions in addition to sulfur emissions. PMID:26206616

Stratospheric Ozone destruction by the Bronze-Age Minoan eruption (Santorini Volcano, Greece).

PubMed

Cadoux, Anita; Scaillet, Bruno; Bekki, Slimane; Oppenheimer, Clive; Druitt, Timothy H

2015-07-24

The role of volcanogenic halogen-bearing (i.e. chlorine and bromine) compounds in stratospheric ozone chemistry and climate forcing is poorly constrained. While the 1991 eruption of Pinatubo resulted in stratospheric ozone loss, it was due to heterogeneous chemistry on volcanic sulfate aerosols involving chlorine of anthropogenic rather than volcanogenic origin, since co-erupted chlorine was scavenged within the plume. Therefore, it is not known what effect volcanism had on ozone in pre-industrial times, nor what will be its role on future atmospheres with reduced anthropogenic halogens present. By combining petrologic constraints on eruption volatile yields with a global atmospheric chemistry-transport model, we show here that the Bronze-Age 'Minoan' eruption of Santorini Volcano released far more halogens than sulfur and that, even if only 2% of these halogens reached the stratosphere, it would have resulted in strong global ozone depletion. The model predicts reductions in ozone columns of 20 to >90% at Northern high latitudes and an ozone recovery taking up to a decade. Our findings emphasise the significance of volcanic halogens for stratosphere chemistry and suggest that modelling of past and future volcanic impacts on Earth's ozone, climate and ecosystems should systematically consider volcanic halogen emissions in addition to sulfur emissions.

Application of high hydrostatic pressure for increasing activity and stability of enzymes.

PubMed

Mozhaev, V V; Lange, R; Kudryashova, E V; Balny, C

1996-10-20

Elevated hydrostatic pressure has been used to increase catalytic activity and thermal stability of alpha-chymotrypsin (CT). For an anilide substrate, characterized by a negative value of the reaction activation volume (DeltaV( not equal)), an increase in pressure at 20 degrees C results in an exponential acceleration of the hydrolysis rate catalyzed by CT reaching a 6.5-fold increase in activity at 4700 atm (4.7 kbar). Due to a strong temperature dependence of DeltaV( not equal), the acceleration effect of high pressure becomes more pronounced at high temperatures. For example, at 50 degrees C, under a pressure of 3.6 kbar, CT shows activity which is more than 30 times higher than the activity at normal conditions (20 degrees C, 1 atm). At pressures of higher than 3.6 kbar, the enzymatic activity is decreased due to a pressure-induced denaturation.Elevated hydrostatic pressure is also efficient for increasing stability of CT against thermal denaturation. For example, at 55 degrees C, CT is almost instantaneously inactivated at atmospheric pressure, whereas under a pressure of 1.8 kbar CT retains its anilide-hydrolyzing activity during several dozen minutes. Additional stabilization can be achieved in the presence of glycerol, which is most effective for protection of CT at an intermediate concentration of 40% (v/v). There has been observed an additivity in stabilization effects of high pressure and glycerol: thermal inactivation of pressure-stabilized CT can be decelerated in a supplementary manner by addition of 40% (v/v) glycerol. The protection effect of glycerol on the catalytic activity and stability of CT becomes especially pronounced when both extreme factors of temperature and pressure reach critical values. For example, at approximately 55 degrees C and 4.7 kbar, enzymatic activity of CT in the presence of 40% (v/v) glycerol is severalfold higher than in aqueous buffer.The results of this study are discussed in terms of the hypotheses which explain the action of external and medium effects on protein structure, such as preferential hydration and osmotic pressure.

Carcinogenicity of by-products of disinfection in mouse and rat liver

DOE Office of Scientific and Technical Information (OSTI.GOV)

Herren-Freund, S.L.; Pereira, M.A.

1986-11-01

By-products of disinfection were tested for initiating and/or promoting activity in rat liver by using the rat liver foci bioassay. The assay uses an increased incidence of ..gamma..-glutamyltranspeptidase-positive foci (GGT foci) as an indicator of carcinogenicity. The by-products of disinfection, including chloramine, halogenated humic acids, halogenated ethanes, halogenated acetonitriles, halogenated methanes, halogenated ethylene, and N-Cl piperidine, did not initiate GGT foci, which would indicate that they are not capable of initiating carcinogenesis. Chloroform and halogenated benzenes were tested in this assay for their ability to promote the occurrence of GGT foci and tumors initiated by diethylnitrosamine (DENA). Chloroform either hadmore » no effect or inhibited the occurrence of GGT foci when administered subsequent to a single dose of DENA. However, when the chloroform was administered in drinking water concurrently with weekly doses of DENA, it enhanced the formation of liver tumors. Of 20 halogenated benzenes tested, only 1,2,4,5-tetrachlorobenzene and hexachlorobenzene promoted the occurrence of DENA-initiated GGT foci. Thus in rat liver, the tested by-products of drinking water disinfection did not demonstrate tumor-initiating activity, although a few appeared to possess tumor-promoting activity. Chloroform was also tested for tumor-promoting activity in 15-days-old Swiss mice initiated with ethylnitrosourea (ENU). ENU at 5 and 20 ..mu..g/g caused a dose-dependent increase in liver tumors. In male mice, chloroform inhibited both spontaneous and ENU-induced liver tumors. When administered in the drinking water, chloroform inhibited, whereas phenobarbital promoted, hepatocarcinogenesis in mice.« less

13C and 19F solid-state NMR and X-ray crystallographic study of halogen-bonded frameworks featuring nitrogen-containing heterocycles.

PubMed

Szell, Patrick M J; Gabriel, Shaina A; Gill, Russell D D; Wan, Shirley Y H; Gabidullin, Bulat; Bryce, David L

2017-03-01

Halogen bonding is a noncovalent interaction between the electrophilic region of a halogen (σ-hole) and an electron donor. We report a crystallographic and structural analysis of halogen-bonded compounds by applying a combined X-ray diffraction (XRD) and solid-state nuclear magnetic resonance (SSNMR) approach. Single-crystal XRD was first used to characterize the halogen-bonded cocrystals formed between two fluorinated halogen-bond donors (1,4-diiodotetrafluorobenzene and 1,3,5-trifluoro-2,4,6-triiodobenzene) and several nitrogen-containing heterocycles (acridine, 1,10-phenanthroline, 2,3,5,6-tetramethylpyrazine, and hexamethylenetetramine). New structures are reported for the following three cocrystals, all in the P2 1 /c space group: acridine-1,3,5-trifluoro-2,4,6-triiodobenzene (1/1), C 6 F 3 I 3 ·C 13 H 9 N, 1,10-phenanthroline-1,3,5-trifluoro-2,4,6-triiodobenzene (1/1), C 6 F 3 I 3 ·C 12 H 8 N 2 , and 2,3,5,6-tetramethylpyrazine-1,3,5-trifluoro-2,4,6-triiodobenzene (1/1), C 6 F 3 I 3 ·C 8 H 12 N 2 . 13 C and 19 F solid-state magic-angle spinning (MAS) NMR is shown to be a convenient method to characterize the structural features of the halogen-bond donor and acceptor, with chemical shifts attributable to cocrystal formation observed in the spectra of both nuclides. Cross polarization (CP) from 19 F to 13 C results in improved spectral sensitivity in characterizing the perfluorinated halogen-bond donor when compared to conventional 1 H CP. Gauge-including projector-augmented wave density functional theory (GIPAW DFT) calculations of magnetic shielding constants, along with optimization of the XRD structures, provide a final set of structures in best agreement with the experimental 13 C and 19 F chemical shifts. Data for carbons bonded to iodine remain outliers due to well-known relativistic effects.

Structural Perspective on Enzymatic Halogenation

PubMed Central

2008-01-01

Simple halogen substituents frequently afford key structural features that account for the potency and selectivity of natural products, including antibiotics and hormones. For example, when a single chlorine atom on the antibiotic vancomycin is replaced by hydrogen, the resulting antibacterial activity decreases by up to 70% (HarrisC. M.; KannanR.; KopeckaH.; HarrisT. M.J. Am. Chem. Soc.1985, 107, 6652−6658). This Account analyzes how structure underlies mechanism in halogenases, the molecular machines designed by nature to incorporate halogens into diverse substrates. Traditional synthetic methods of integrating halogens into complex molecules are often complicated by a lack of specificity and regioselectivity. Nature, however, has developed a variety of elegant mechanisms for halogenating specific substrates with both regio- and stereoselectivity. An improved understanding of the biological routes toward halogenation could lead to the development of novel synthetic methods for the creation of new compounds with enhanced functions. Already, researchers have co-opted a fluorinase from the microorganism Streptomyces cattleya to produce 18F-labeled molecules for use in positron emission tomography (PET) (DengH.; CobbS. L.; GeeA. D.; LockhartA.; MartarelloL.; McGlincheyR. P.; O’HaganD.; OnegaM.Chem. Commun.2006, 652−654). Therefore, the discovery and characterization of naturally occurring enzymatic halogenation mechanisms has become an active area of research. The catalogue of known halogenating enzymes has expanded from the familiar haloperoxidases to include oxygen-dependent enzymes and fluorinases. Recently, the discovery of a nucleophilic halogenase that catalyzes chlorinations has expanded the repertoire of biological halogenation chemistry (DongC.; HuangF.; DengH.; SchaffrathC.; SpencerJ. B.; O’HaganD.; NaismithJ. H.Nature2004, 427, 561−56514765200). Structural characterization has provided a basis toward a mechanistic understanding of the specificity and chemistry of these enzymes. In particular, the latest crystallographic snapshots of active site architecture and halide binding sites have provided key insights into enzyme catalysis. Herein is a summary of the five classes of halogenases, focusing on the three most recently discovered: flavin-dependent halogenases, non-heme iron-dependent halogenases, and nucleophilic halogenases. Further, the potential roles of halide-binding sites in determining halide selectivity are discussed, as well as whether or not binding-site composition is always a seminal factor for selectivity. Expanding our understanding of the basic chemical principles that dictate the activity of the halogenases will advance both biology and chemistry. A thorough mechanistic analysis will elucidate the biological principles that dictate specificity, and the application of those principles to new synthetic techniques will expand the utility of halogenations in small-molecule development. PMID:18774824

Synthesis of indolizidinone analogues of cytotoxic alkaloids: monocyclic precursors are also active.

PubMed

Boto, Alicia; Miguélez, Javier; Marín, Raquel; Díaz, Mario

2012-05-15

Readily available proline derivatives can be transformed in just two steps into analogues of cytotoxic phenanthroindolizidine alkaloids. The key step uses a sequential radical scission-oxidation-alkylation process, which yields 2-substituted pyrrolidine amides. A second process effects the cyclization to give the desired alkaloid analogues, which possess an indolizidine core. The major and minor isomers (dr 3:2 to 3:1) can be easily separated, allowing their use to study structure-activity relationships (SAR). The process is versatile and allows the introduction of aryl and heteroaryl groups (including biphenyl, halogenated phenyl, and pyrrole rings). Some of these alkaloid analogues displayed a selective cytotoxic activity against tumorogenic human neuronal and mammary cancer cells, and one derivative caused around 80% cell death in both tumor lines at micromolar doses. The cytotoxicity of some monocyclic precursors was also studied, being comparable or superior to the bicyclic derivatives. Copyright © 2012 Elsevier Ltd. All rights reserved.

Crystal structures of two bis-(iodo-meth-yl)benzene derivatives: similarities and differences in the crystal packing.

PubMed

McAdam, C John; Hanton, Lyall R; Moratti, Stephen C; Simpson, Jim

2015-12-01

The isomeric derivatives 1,2-bis-(iodo-meth-yl)benzene, (I), and 1,3-bis-(iodo-meth-yl)benzene (II), both C8H8I2, were prepared by metathesis from their di-bromo analogues. The ortho-derivative, (I), lies about a crystallographic twofold axis that bis-ects the C-C bond between the two iodo-methyl substituents. The packing in (I) relies solely on C-H⋯I hydrogen bonds supported by weak parallel slipped π-π stacking inter-actions [inter-centroid distance = 4.0569 (11) Å, inter-planar distance = 3.3789 (8) Å and slippage = 2.245 Å]. While C-H⋯I hydrogen bonds are also found in the packing of (II), type II, I⋯I halogen bonds [I⋯I = 3.8662 (2) Å] and C-H⋯π contacts feature prominently in stabilizing the three-dimensional structure.

Syntheses of cytotoxic novel arctigenin derivatives bearing halogen and alkyl groups on aromatic rings.

PubMed

Yamauchi, Satoshi; Wukirsari, Tuti; Ochi, Yoshiaki; Nishiwaki, Hisashi; Nishi, Kosuke; Sugahara, Takuya; Akiyama, Koichi; Kishida, Taro

2017-09-01

The new lignano-9,9'-lactones (α,β-dibenzyl-γ-butyrolactone lignans), which showed the higher cytotoxicity than arctigenin, were synthesized. The well-known cytotoxic arctigenin showed activity against HL-60 cells (EC 50 =12μM), however, it was inactive against HeLa cells (EC 50 >100μM). The synthesized (3,4-dichloro, 2'-butoxy)-derivative 55 and (3,4-dichloro, 4'-butyl)-derivative 66 bearing the lignano-9,9'-lactone structures showed the EC 50 values of 10μM and 9.4μM against HL-60 cells, respectively. Against HeLa cells, the EC 50 value of the derivative 66 was 27μM. By comparing the activities with the corresponding 9,9'-epoxy structure (tetrahydrofuran compounds), the importance of the lactone structure of 55 and 66 for the higher activities was shown. The substituents on the aromatic ring of the lignano-9,9'-lactones affected the cytotoxicity level, observing more than 10-fold difference. Copyright © 2017. Published by Elsevier Ltd.

Nontypical iodine–halogen bonds in the crystal structure of (3 E )-8-chloro-3-iodomethylidene-2,3-dihydro-1,4-oxazino[2,3,4- ij ]quinolin-4-ium triiodide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bartashevich, E. V.; Batalov, V. I.; Yushina, I. D.

2016-04-29

Two kinds of iodine–iodine halogen bonds are the focus of our attention in the crystal structure of the title salt, C 12H 8ClINO +·I 3 -, described by X-ray diffraction. The first kind is a halogen bond, reinforced by charges, between the I atom of the heterocyclic cation and the triiodide anion. The second kind is the rare case of a halogen bond between the terminal atoms of neighbouring triiodide anions. Lastly, the influence of relatively weakly bound iodine inside an asymmetric triiodide anion on the thermal and Raman spectroscopic properties has been demonstrated.

Auger analysis of films formed on metals in sliding contact with halogenated polymers

NASA Technical Reports Server (NTRS)

Pepper, S. V.

1974-01-01

The use of Auger electron spectroscopy (AES) to search for transferred polymer must contend with the fact that there has been no published work on Auger analysis of polymers. Since this is a new area for AES, the Auger spectra of polymers and of halogenated polymers in particular is discussed. It is shown that the Auger spectra of halogenated polymers have certain characteristics that permit an assessment of whether a polymeric transfer film has been established by sliding contact. The discussion is general and the concepts should be useful in considering the Auger analysis of any polymer. The polymers chosen for this study are the halogenated polymers polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), and polychlorotrifluorethylene (PCTFE).

Halogenated solvent remediation

DOEpatents

Sorenson, Jr., Kent S.

2008-11-11

Methods for enhancing bioremediation of ground water contaminated with nonaqueous halogenated solvents are disclosed. An illustrative method includes adding an electron donor for microbe-mediated anaerobic reductive dehalogenation of the halogenated solvents, which electron donor enhances mass transfer of the halogenated solvents from residual source areas into the aqueous phase of the ground water. Illustrative electron donors include C.sub.2-C.sub.4 carboxylic acids and hydroxy acids, salts thereof, esters of C.sub.2-C.sub.4 carboxylic acids and hydroxy acids, and mixtures thereof, of which lactic acid, salts of lactic acid--such as sodium lactate, lactate esters, and mixtures thereof are particularly illustrative. The microbes are either indigenous to the ground water, or such microbes can be added to the ground water in addition to the electron donor.

Interactions between volatile organic compounds and reactive halogen in the tropical marine atmosphere using WRF-Chem

NASA Astrophysics Data System (ADS)

Badia, Alba; Reeves, Claire E.; Baker, Alex; Volkamer, Rainer; von Glasow, Roland

2016-04-01

Halogen species (chlorine, bromine and iodine) are known to play an important role in the chemistry and oxidizing capacity of the troposphere, particularly in the marine boundary layer (MBL). Reactive halogens cause ozone (O3) destruction, change the HOx and NOX partitioning, affect the oxidation of volatile organic compounds (VOCs) and mercury, reduce the lifetime of methane, and take part in new particle formation. Numerical models predicted that reactive halogen compounds account for 30% of O3 destruction in the MBL and 5-20% globally. There are indications that the chemistry of reactive halogens and oxygenated VOCs (OVOCs) in the tropics are inter-related. Moreover, the presence of aldehydes, such as glyoxal (CHOCHO), has a potential impact on radical cycling and secondary organic aerosol (SOA) formation in the MBL and free troposphere (FT). Model calculations suggest aldehydes to be an important sink for bromine atoms and hence competition for their reaction with O3 forming BrO and so illustrating a link between the cycles of halogens and OVOCs in the marine atmosphere. The main objective of this contribution is to investigate the atmospheric chemistry in the tropical East Pacific with a focus on reactive halogens and OVOCs and their links using the latest version of the Weather Research and Forecasting (WRF) model coupled with Chemistry (WRF-Chem) and field data from the TORERO campaign. WRF-Chem is a highly flexible community model for atmospheric research where aerosol-radiation-cloud feedback processes are taken into account. Our current reaction mechanism in WRF-Chem is based on the MOZART mechanism and has been extended to include bromine, chlorine and iodine chemistry. The MOZART mechanism includes detailed gas-phase chemistry of CHOCHO formation as well as state-of-the-science pathways to form SOA. Oceanic emissions of aldehydes, including CHOCHO, and of organic halogens based on measurements from the TORERO campaign have been added into the model. Sea surface emissions of inorganic iodine are calculated using the parameterisation of Carpenter et al., 2013. Focusing on TORERO observations from the ships and a selected number of flights we present an evaluation of the relevant tropospheric gas-phase chemistry (O3, H2O), inorganic halogen species (BrO, IO), aldehydes (CH3CHO, CHOCHO) and Very Short Lived Halocarbons (VSLH).

The effect of varying halogen substituent patterns on the cytochrome P450 catalysed dehalogenation of 4-halogenated anilines to 4-aminophenol metabolites.

PubMed

Cnubben, N H; Vervoort, J; Boersma, M G; Rietjens, I M

1995-05-11

The cytochrome P450 catalysed biotransformation of 4-halogenated anilines was studied in vitro with special emphasis on the dehalogenation to 4-aminophenol metabolites. The results demonstrated that a fluorine substituent at the C4 position was more easily eliminated from the aromatic ring than a chloro-, bromo- or iodo-substituent. HPLC analysis of in vitro biotransformation patterns revealed that the dehalogenation of the C4-position was accompanied by formation of non-halogenated 4-aminophenol, without formation of NIH-shifted metabolites. Changes in the apparent Vmax for the microsomal oxidative dehalogenation appeared to correlate with the electronegativity of the halogen substituent at C4, the fluorine substituent being the one most easily eliminated. A similar decrease in the rate of dehalogenation from a fluoro- to a chloro- to a bromo- to an iodo-substituent was observed in a system with purified reconstituted cytochrome P450 IIB1, in a tertiair butyl hydroperoxide supported microsomal cytochrome P450 system as well as in a system with microperoxidase 8. This microperoxidase 8 is a haem-based mini-enzyme without a substrate binding site, capable of catalysing cytochrome P450-like reaction chemistry. Together, these results excluded the possibility that the difference in the rate of dehalogenation with a varying C4-halogen substituent arose from a change in the contribution of cytochrome P450 enzymes involved in oxidative dehalogenation with a change in the halogen substituent. Rather, they strongly suggested that the difference was indeed due to an intrinsic electronic parameter of the various C4 halogenated anilines dependent on the type of halogen substituent. Additional in vitro experiments with polyfluorinated anilines demonstrated that elimination of the C4-fluorine substituent became more difficult upon the introduction of additional electron withdrawing fluorine substituents in the aniline-ring. 19F-NMR analysis of the metabolite patterns showed that the observed decrease in 4-aminophenol formation was accompanied by a metabolic switch to 2-aminophenols and N-hydroxyanilines, while products resulting from NIH-type mechanisms were not observed. For a C4-chloro-, bromo-, or iodo-substituted 2-fluoroaniline the Vmax for the oxidative dehalogenation was reduced by the additional electron withdrawing fluorine substituent at the C2 position in a similar way.(ABSTRACT TRUNCATED AT 400 WORDS)

A box model study on photochemical interactions between VOCs and reactive halogen species in the marine boundary layer

NASA Astrophysics Data System (ADS)

Toyota, K.; Kanaya, Y.; Takahashi, M.; Akimoto, H.

2003-09-01

A new chemical scheme is developed for the multiphase photochemical box model SEAMAC (size-SEgregated Aerosol model for Marine Air Chemistry) to investigate photochemical interactions between volatile organic compounds (VOCs) and reactive halogen species in the marine boundary layer (MBL). Based primarily on critically evaluated kinetic and photochemical rate parameters as well as a protocol for chemical mechanism development, the new scheme has achieved a near-explicit treatment of oxidative degradation of up to C3-hydrocarbons CH4, C2H6, C3H8, C2H4, C3H6, and C2H2) initiated by reactions with OH radicals, Cl- and Br-atoms, and O3. Rate constants and product yields for reactions involving halogen species are taken from the literature where available, but the majority of them need to be estimated. In particular, addition reactions of halogen atoms with alkenes will result in the formation of halogenated organic intermediates, whose photochemical loss rates are carefully evaluated in the present work. Model calculations with the new chemical scheme reveal that the oceanic emissions of acetaldehyde (CH3CHO) and alkenes (especially C3H6) are important factors for regulating reactive halogen chemistry in the MBL by promoting the conversion of Br atoms into HBr or more stable brominated intermediates in the organic form. The latter include brominated hydroperoxides, bromoacetaldehyde, and bromoacetone, which sequester bromine from reactive inorganic pool. The total mixing ratio of brominated organic species thus produced is likely to reach 10-20% or more of that of inorganic gaseous bromine species over wide regions over the ocean. On the other hand, the reaction between Br atoms and C2H2 is unimportant for determining the degree of bromine activation in the remote MBL. It is suggested that peroxyacetic acid formed via CH3CHO oxidation is one of the important chemical agents for triggering autocatalytic halogen release from sea-salt aerosols. These results imply that reactive halogen chemistry can mediate a link between the oceanic emissions of VOCs and the behaviors of compounds that are sensitive to halogen chemistry such as dimethyl sulfide, NOx, and O3 in the MBL.

Palladium- and Copper-Catalyzed Arylation of Carbon-Hydrogen Bonds

PubMed Central

Daugulis, Olafs; Do, Hien-Quang; Shabashov, Dmitry

2010-01-01

The transition-metal-catalyzed functionalization of C-H bonds is a powerful method for generating carbon-carbon bonds. Although significant advances to this field have been reported during the last decade, many challenges remain. First, most of the methods are substrate-specific and thus cannot be generalized. Second, conversions of unactivated (i.e. not benzylic or alpha to heteroatom) sp3 C–H bonds to C–C bonds are rare, with most examples limited to t-butyl groups—a conversion that is inherently simple because there are no β-hydrogens that can be eliminated. Finally, the palladium, rhodium, and ruthenium catalysts routinely used for the conversion of C–H bonds to C–C bonds are expensive. Catalytically active metals that are cheaper and less exotic (e.g. copper, iron, and manganese) are rarely used. This Account describes our attempts to provide solutions to these three problems. We have developed a general method for directing-group-containing arene arylation by aryl iodides. Using palladium acetate as the catalyst, we arylated anilides, benzamides, benzoic acids, benzylamines, and 2-substituted pyridine derivatives under nearly identical conditions. We have also developed a method for the palladium-catalyzed auxiliary-assisted arylation of unactivated sp3 C–H bonds. This procedure allows for the β-arylation of carboxylic acid derivatives and the γ-arylation of amine derivatives. Furthermore, copper catalysis can be used to mediate the arylation of acidic arene C–H bonds (i.e. those with pKa values <35 in DMSO). Using a copper iodide catalyst in combination with a base and a phenanthroline ligand, we successfully arylated electron-rich and electron-deficient heterocycles and electron-poor arenes possessing at least two electron-withdrawing groups. The reaction exhibits unusual regioselectivity: arylation occurs at the most hindered position. This copper-catalyzed method supplements the well-known C–H activation/borylation methodology, in which functionalization usually occurs at the least hindered position. We also describe preliminary investigations to determine the mechanisms of these transformations. We anticipate that other transition metals, including iron, nickel, cobalt, and silver, will also be able to facilitate deprotonation/arylation reaction sequences. PMID:19552413

Palladium- and copper-catalyzed arylation of carbon-hydrogen bonds.

PubMed

Daugulis, Olafs; Do, Hien-Quang; Shabashov, Dmitry

2009-08-18

The transition-metal-catalyzed functionalization of C-H bonds is a powerful method for generating carbon-carbon bonds. Although significant advances to this field have been reported during the past decade, many challenges remain. First, most of the methods are substrate-specific and thus cannot be generalized. Second, conversions of unactivated (i.e., not benzylic or alpha to heteroatom) sp(3) C-H bonds to C-C bonds are rare, with most examples limited to t-butyl groups, a conversion that is inherently simple because there are no beta-hydrogens that can be eliminated. Finally, the palladium, rhodium, and ruthenium catalysts routinely used for the conversion of C-H bonds to C-C bonds are expensive. Catalytically active metals that are cheaper and less exotic (e.g., copper, iron, and manganese) are rarely used. This Account describes our attempts to provide solutions to these three problems. We have developed a general method for directing-group-containing arene arylation by aryl iodides. Using palladium acetate as the catalyst, we arylated anilides, benzamides, benzoic acids, benzylamines, and 2-substituted pyridine derivatives under nearly identical conditions. We have also developed a method for the palladium-catalyzed auxiliary-assisted arylation of unactivated sp(3) C-H bonds. This procedure allows for the beta-arylation of carboxylic acid derivatives and the gamma-arylation of amine derivatives. Furthermore, copper catalysis can be used to mediate the arylation of acidic arene C-H bonds (i.e., those with pK(a) values <35 in DMSO). Using a copper iodide catalyst in combination with a base and a phenanthroline ligand, we successfully arylated electron-rich and electron-deficient heterocycles and electron-poor arenes possessing at least two electron-withdrawing groups. The reaction exhibits unusual regioselectivity: arylation occurs at the most hindered position. This copper-catalyzed method supplements the well-known C-H activation/borylation methodology, in which functionalization usually occurs at the least hindered position. We also describe preliminary investigations to determine the mechanisms of these transformations. We anticipate that other transition metals, including iron, nickel, cobalt, and silver, will also be able to facilitate deprotonation/arylation reaction sequences.

Substituent Effects on the [N-I-N](+) Halogen Bond.

PubMed

Carlsson, Anna-Carin C; Mehmeti, Krenare; Uhrbom, Martin; Karim, Alavi; Bedin, Michele; Puttreddy, Rakesh; Kleinmaier, Roland; Neverov, Alexei A; Nekoueishahraki, Bijan; Gräfenstein, Jürgen; Rissanen, Kari; Erdélyi, Máté

2016-08-10

We have investigated the influence of electron density on the three-center [N-I-N](+) halogen bond. A series of [bis(pyridine)iodine](+) and [1,2-bis((pyridine-2-ylethynyl)benzene)iodine](+) BF4(-) complexes substituted with electron withdrawing and donating functionalities in the para-position of their pyridine nitrogen were synthesized and studied by spectroscopic and computational methods. The systematic change of electron density of the pyridine nitrogens upon alteration of the para-substituent (NO2, CF3, H, F, Me, OMe, NMe2) was confirmed by (15)N NMR and by computation of the natural atomic population and the π electron population of the nitrogen atoms. Formation of the [N-I-N](+) halogen bond resulted in >100 ppm (15)N NMR coordination shifts. Substituent effects on the (15)N NMR chemical shift are governed by the π population rather than the total electron population at the nitrogens. Isotopic perturbation of equilibrium NMR studies along with computation on the DFT level indicate that all studied systems possess static, symmetric [N-I-N](+) halogen bonds, independent of their electron density. This was further confirmed by single crystal X-ray diffraction data of 4-substituted [bis(pyridine)iodine](+) complexes. An increased electron density of the halogen bond acceptor stabilizes the [N···I···N](+) bond, whereas electron deficiency reduces the stability of the complexes, as demonstrated by UV-kinetics and computation. In contrast, the N-I bond length is virtually unaffected by changes of the electron density. The understanding of electronic effects on the [N-X-N](+) halogen bond is expected to provide a useful handle for the modulation of the reactivity of [bis(pyridine)halogen](+)-type synthetic reagents.

Substituent Effects on the [N–I–N]+ Halogen Bond

PubMed Central

2016-01-01

We have investigated the influence of electron density on the three-center [N–I–N]+ halogen bond. A series of [bis(pyridine)iodine]+ and [1,2-bis((pyridine-2-ylethynyl)benzene)iodine]+ BF4– complexes substituted with electron withdrawing and donating functionalities in the para-position of their pyridine nitrogen were synthesized and studied by spectroscopic and computational methods. The systematic change of electron density of the pyridine nitrogens upon alteration of the para-substituent (NO2, CF3, H, F, Me, OMe, NMe2) was confirmed by 15N NMR and by computation of the natural atomic population and the π electron population of the nitrogen atoms. Formation of the [N–I–N]+ halogen bond resulted in >100 ppm 15N NMR coordination shifts. Substituent effects on the 15N NMR chemical shift are governed by the π population rather than the total electron population at the nitrogens. Isotopic perturbation of equilibrium NMR studies along with computation on the DFT level indicate that all studied systems possess static, symmetric [N–I–N]+ halogen bonds, independent of their electron density. This was further confirmed by single crystal X-ray diffraction data of 4-substituted [bis(pyridine)iodine]+ complexes. An increased electron density of the halogen bond acceptor stabilizes the [N···I···N]+ bond, whereas electron deficiency reduces the stability of the complexes, as demonstrated by UV-kinetics and computation. In contrast, the N–I bond length is virtually unaffected by changes of the electron density. The understanding of electronic effects on the [N–X–N]+ halogen bond is expected to provide a useful handle for the modulation of the reactivity of [bis(pyridine)halogen]+-type synthetic reagents. PMID:27265247

Chalcogen- and halogen-bonds involving SX2 (X = F, Cl, and Br) with formaldehyde.

PubMed

Mo, Lixin; Zeng, Yanli; Li, Xiaoyan; Zhang, Xueying; Meng, Lingpeng

2016-07-01

The capacity of SX2 (X = F, Cl, and Br) to engage in different kinds of noncovalent bonds was investigated by ab initio calculations. SCl2 (SBr2) has two σ-holes upon extension of Cl (Br)-S bonds, and two σ-holes upon extension of S-Cl (Br) bonds. SF2 contains only two σ-holes upon extension of the F-S bond. Consequently, SCl2 and SBr2 form chalcogen and halogen bonds with the electron donor H2CO while SF2 forms only a chalcogen bond, i.e., no F···O halogen bond was found in the SF2:H2CO complex. The S···O chalcogen bond between SF2 and H2CO is the strongest, while the strongest halogen bond is Br···O between SBr2 and H2CO. The nature of these two types of noncovalent interaction was probed by a variety of methods, including molecular electrostatic potentials, QTAIM, energy decomposition, and electron density shift maps. Termolecular complexes X2S···H2CO···SX'2 (X = F, Cl, Br, and X' = Cl, Br) were constructed to study the interplay between chalcogen bonds and halogen bonds. All these complexes contained S···O and Cl (Br)···O bonds, with longer intermolecular distances, smaller values of electron density, and more positive three-body interaction energies, indicating negative cooperativity between the chalcogen bond and the halogen bond. In addition, for all complexes studied, interactions involving chalcogen bonds were more favorable than those involving halogen bonds. Graphical Abstract Molecular electrostatic potential and contour map of the Laplacian of the electron density in Cl2S···H2CO···SCl2 complex.

Gas discharge headlights and visibility of coloured road signs.

PubMed

Venkatachalam, Kannan; Smith, George

2000-01-01

BACKGROUND: Automotive headlamps mostly use the tungsten halogen bulb but several years ago a new type of headlamp, the gas discharge bulb, was introduced. Because of the different spectral output of this type of lamp, there has been a suggestion that it may affect the colour recognition and sign conspicuity under night-time conditions. In this study, the visibility of the road signs is used to examine the effect of the gas discharge lamp's spectrum compared with that of the conventional halogen headlamp. METHODS: The spectral output of the lamps and the spectral reflectance of common-coloured road signs were measured using a Spectra-Pritchard spectroradiometer. Using luminous reflectance data, chromaticity co-ordinates and the colorimetric shift of the road signs, when illuminated by gas discharge lamps, were plotted using CIE x,y co-ordinate system. Colour rendering indices of the lamp were calculated using Munsell samples and road signs as proscribed by the CIE Publication. In addition, the visibility index of the road signs was calculated using Adrian's 'Visibility of Target' model. RESULTS: The gas discharge headlamp has more energy in the blue region and less energy in the red region of the spectrum than the halogen headlamp. The general colour rendering index of the gas discharge lamp is higher than that of the halogen lamp. When compared with daylight, all coloured road signs used in this study have less colorimetric shift when illuminated by the gas discharge headlamp than by the halogen headlamp. CONCLUSION: The result indicates that the gas discharge lamp, while having a very different spectrum from daylight or tungsten halogen lamps, should not have a deleterious effect on sign detection or recognition, when compared to daylight or tungsten halogen lamps.

Residual HEMA and TEGDMA Release and Cytotoxicity Evaluation of Resin-Modified Glass Ionomer Cement and Compomers Cured with Different Light Sources

PubMed Central

Botsali, Murat Selim; Kuşgöz, Adem; Altintaş, Subutay Han; Ülker, Hayriye Esra; Kiliç, Serdar; Başak, Feridun; Ülker, Mustafa

2014-01-01

The purpose of this study was first to evaluate the elution of 2-hydroxyethyl methacrylate (HEMA) and triethylene glycol dimethacrylate (TEGDMA) monomers from resin-modified glass ionomer cement (RMGIC) and compomers cured with halogen and light-emitting diode (LED) light-curing units (LCUs). The effect of cured materials on the viability of L929 fibroblast cells was also evaluated. One RMGIC (Ketac N100) and two compomers (Dyract Extra and Twinkystar) were tested. Materials were prepared in teflon disks and light-cured with LED or halogen LCUs. The residual monomers of resin materials in solution were identified using high-performance liquid chromatography. The fibroblast cells' viability was analyzed using MTT assay. The type of LCU did not have a significant effect on the elution of HEMA and TEGDMA. A greater amount of HEMA than TEGMDA was eluted. The amount of TEGDMA eluted from Twinkystar was greater than Dyract Extra (P < 0.05) when cured with a halogen LCU. All material-LCU combinations decreased the fibroblast cells' viability more than the control group (P < 0.01), except for Dyract Extra cured with a halogen LCU (P > 0.05). Curing with the LED LCU decreased the cells' viability more than curing with the halogen LCU for compomers. For Ketac N100, the halogen LCU decreased the cells' viability more than the LED LCU. PMID:24592149

Process for removing halogenated aliphatic and aromatic compounds from petroleum products

DOEpatents

Googin, J.M.; Napier, J.M.; Travaglini, M.A.

1983-09-20

A process is described for removing halogenated aliphatic and aromatic compounds, e.g., polychlorinated biphenyls, from petroleum products by solvent extraction. The halogenated aliphatic and aromatic compounds are extracted from a petroleum product into a polar solvent by contacting the petroleum product with the polar solvent. The polar solvent is characterized by a high solubility for the extracted halogenated aliphatic and aromatic compounds, a low solubility for the petroleum product and considerable solvent power for polyhydroxy compound. The preferred polar solvent is dimethylformamide. A miscible compound, such as, water or a polyhydroxy compound, is added to the polar extraction solvent to increase the polarity of the polar extraction solvent. The halogenated aliphatic and aromatic compounds are extracted from the highly-polarized mixture of water or polyhydroxy compound and polar extraction solvent into a low polar or nonpolar solvent by contacting the water or polyhydroxy compound-polar solvent mixture with the low polar or nonpolar solvent. The halogenated aliphatic and aromatic compounds and the low polar or nonpolar solvent are separated by physical means, e.g., vacuum evaporation. The polar and nonpolar solvents are recovered from recycling. The process can easily be designed for continuous operation. Advantages of the process include that the polar solvent and a major portion of the nonpolar solvent can be recycled, the petroleum products are reclaimable and the cost for disposing of waste containing polychlorinated biphenyls is significantly reduced. 1 fig.

Process for removing halogenated aliphatic and aromatic compounds from petroleum products

DOEpatents

Googin, John M.; Napier, John M.; Travaglini, Michael A.

1983-01-01

A process for removing halogenated aliphatic and aromatic compounds, e.g., polychlorinated biphenyls, from petroleum products by solvent extraction. The halogenated aliphatic and aromatic compounds are extracted from a petroleum product into a polar solvent by contacting the petroleum product with the polar solvent. The polar solvent is characterized by a high solubility for the extracted halogenated aliphatic and aromatic compounds, a low solubility for the petroleum product and considerable solvent power for polyhydroxy compound. The preferred polar solvent is dimethylformamide. A miscible compound, such as, water or a polyhydroxy compound, is added to the polar extraction solvent to increase the polarity of the polar extraction solvent. The halogenated aliphatic and aromatic compounds are extracted from the highly-polarized mixture of water or polyhydroxy compound and polar extraction solvent into a low polar or nonpolar solvent by contacting the water or polyhydroxy compound-polar solvent mixture with the low polar or nonpolar solvent. The halogenated aliphatic and aromatic compounds and the low polar or nonpolar solvent are separated by physical means, e.g., vacuum evaporation. The polar and nonpolar solvents are recovered from recycling. The process can easily be designed for continuous operation. Advantages of the process include that the polar solvent and a major portion of the nonpolar solvent can be recycled, the petroleum products are reclaimable and the cost for disposing of waste containing polychlorinated biphenyls is significantly reduced.

Process for removing halogenated aliphatic and aromatic compounds from petroleum products. [Polychlorinated biphenyls; methylene chloride; perchloroethylene; trichlorofluoroethane; trichloroethylene; chlorobenzene

DOEpatents

Googin, J.M.; Napier, J.M.; Travaglini, M.A.

1982-03-31

A process for removing halogenated aliphatic and aromatic compounds, e.g., polychlorinated biphenyls, from petroleum products by solvent extraction. The halogenated aliphatic and aromatic compounds are extracted from a petroleum product into a polar solvent by contracting the petroleum product with the polar solvent. The polar solvent is characterized by a high solubility for the extracted halogenated aliphatic and aromatic compounds, a low solubility for the petroleum product and considerable solvent power for polyhydroxy compound. The preferred polar solvent is dimethylformamide. A miscible polyhydroxy compound, such as, water, is added to the polar extraction solvent to increase the polarity of the polar extraction solvent. The halogenated aliphatic and aromatic compounds are extracted from the highly-polarized mixture of polyhydroxy compound and polar extraction solvent into a low polar or nonpolar solvent by contacting the polyhydroxy compound-polar solvent mixture with the low polar or nonpolar solvent. The halogenated aliphatic and aromatic compounds in the low polar or nonpolar solvent by physical means, e.g., vacuum evaporation. The polar and nonpolar solvents are recovered for recycling. The process can easily be designed for continuous operation. Advantages of the process include that the polar solvent and a major portion of the nonpolar solvent can be recycled, the petroleum products are reclaimable and the cost for disposing of waste containing polychlorinated biphenyls is significantly reduced. 2 tables.

Temporal dynamics of halogenated organic compounds in Marcellus Shale flowback.

PubMed

Luek, Jenna L; Harir, Mourad; Schmitt-Kopplin, Philippe; Mouser, Paula J; Gonsior, Michael

2018-06-01

The chemistry of hydraulic fracturing fluids and wastewaters is complex and is known to vary by operator, geologic formation, and fluid age. A time series of hydraulic fracturing fluids, flowback fluids, and produced waters was collected from two adjacent Marcellus Shale gas wells for organic chemical composition analyses using ultrahigh resolution mass spectrometry. Hierarchical clustering was used to compare and extract ions related to different fluid ages and many halogenated organic molecular ions were identified in flowback fluids and early produced waters based on exact mass. Iodinated organic compounds were the dominant halogen class in these clusters and were nearly undetectable in hydraulic fracturing fluid prior to injection. The iodinated ions increased in flowback and remained elevated after ten months of well production. We suggest that these trends are mainly driven by dissolved organic matter reacting with reactive halogen species formed abiotically through oxidizing chemical additives applied to the well and biotically via iodide-oxidizing bacteria. Understanding the implications of these identified halogenated organic compounds will require future investigation in to their structures and environmental fate. Copyright © 2018 Elsevier Ltd. All rights reserved.

Cocrystal assembled by 1,4-diiodotetrafluorobenzene and phenothiazine based on C-I...π/N/S halogen bond and other assisting interactions.

PubMed

Wang, Hui; Jin, Wei Jun

2017-04-01

The halogen-bonded cocrystal of 1,4-diiodotetrafluorobenzene (1,4-DITFB) with the butterfly-shape non-planar heterocyclic compound phenothiazine (PHT) was successfully assembled by the conventional solution-based method. X-ray single-crystal diffraction analysis reveals a 3:2 stoichiometric ratio for the cocrystal (1,4-DITFB/PHT), and the cocrystal structure is constructed via C-I...π, C-I...N and C-I...S halogen bonds as well as other assisting interactions (e.g. C-H...F/S hydrogen bond, C-H...H-C and C-F...F-C bonds). The small shift of the 1,4-DITFB vibrational band to lower frequencies in FT-IR and Raman spectroscopies provide evidence to confirm the existence of the halogen bond. In addition, the non-planarity of the PHT molecule in the cocrystal results in PHT emitting weak phosphorescence and relatively strong delayed fluorescence. Thus, a wide range of delayed fluorescence and weak phosphorescence could play a significant role in selecting a proper π-conjugated system to engineer functional cocrystal and luminescent materials by halogen bonds.

Induction and prevention of micronuclei and chromosomal aberrations in cultured human lymphocytes exposed to the light of halogen tungsten lamps.

PubMed

D'Agostini, F; Caimo, A; De Filippi, S; De Flora, S

1999-07-01

Previous studies have shown that the light emitted by halogen tungsten lamps contains UV radiation in the UV-A, UV-B and UV-C regions, induces mutations and irreparable DNA damage in bacteria, enhances the frequency of micronuclei in cultured human lymphocytes and is potently carcinogenic to the skin of hairless mice. The present study showed that the light emitted by an uncovered, traditional halogen lamp induces a significant, dose-related and time-related increase not only in micronuclei but also in chromosome-type aberrations, such as breaks, and even more in chromatid-type aberrations, such as isochromatid breaks, exchanges and isochromatid/chromatid interchanges, all including gaps or not, in cultured human lymphocytes. All these genotoxic effects were completely prevented by shielding the same lamp with a silica glass cover, blocking UV radiation. A new model of halogen lamp, having the quartz bulb treated in order to reduce the output of UV radiation, was considerably less genotoxic than the uncovered halogen lamp, yet induction of chromosomal alterations was observed at high illuminance levels.

Selenium-Mediated Dehalogenation of Halogenated Nucleosides and its Relevance to the DNA Repair Pathway.

PubMed

Mondal, Santanu; Manna, Debasish; Mugesh, Govindasamy

2015-08-03

Halogenated nucleosides can be incorporated into the newly synthesized DNA of replicating cells and therefore are commonly used in the detection of proliferating cells in living tissues. Dehalogenation of these modified nucleosides is one of the key pathways involved in DNA repair mediated by the uracil-DNA glycosylase. Herein, we report the first example of a selenium-mediated dehalogenation of halogenated nucleosides. We also show that the mechanism for the debromination is remarkably different from that of deiodination and that the presence of a ribose or deoxyribose moiety in the nucleosides facilitates the deiodination. The results described herein should help in understanding the metabolism of halogenated nucleosides in DNA and RNA. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Volatile Halogenated Organic Compounds Released to Seawater from Temperate Marine Macroalgae

NASA Astrophysics Data System (ADS)

Gschwend, Philip M.; Macfarlane, John K.; Newman, Kathleen A.

1985-03-01

Volatile halogenated organic compounds synthesized by various industrial processes are troublesome pollutants because they are persistent in terrestrial ecosystems and because they may be present in sufficient quantities to alter the natural atmospheric cycles of the halogens. Certain of these compounds, including polybromomethanes and several previously unobserved alkyl monohalides and dihalides, appear to be natural products of the marine environment. A variety of temperate marine macroalgae (the brown algae Ascophyllum nodosum and Fucus vesiculosis, the green algae Enteromorpha linza and Ulva lacta, and the red alga Gigartina stellata) not only contain volatile halogenated organic compounds but also release them to seawater at rates of nanograms to micrograms of each compound per gram of dry algae per day. The macroalgae may be an important source of bromine-containing material released to the atmosphere.

Loss of halogens from crystallized and glassy silicic volcanic rocks

USGS Publications Warehouse

Noble, D.C.; Smith, V.C.; Peck, L.C.

1967-01-01

One hundred and sixty-four F and Cl analyses of silicic welded tuffs and lavas and glass separates are presented. Comparison of the F and Cl contents of crystallized rocks with those of nonhydrated glass and hydrated glassy rocks from the same rock units shows that most of the halogens originally present were lost on crystallization. An average of about half of the F and four-fifths of the Cl originally present was lost. Analyses of hydrated natural glasses and of glassy rocks indicate that in some cases significant amounts of halogens may be removed from or added to hydrated glass through prolonged contact with ground water. The data show that the original halogen contents of the groundmass of a silicic volcanic rock can be reliably determined only from nonhydrated glass. ?? 1967.

Tropospheric impacts of volcanic halogen emissions: first simulations of reactive halogen chemistry in the Eyjafjallajökull eruption plume

NASA Astrophysics Data System (ADS)

Roberts, Tjarda

2013-04-01

Volcanic plumes are regions of high chemical reactivity. Instrumented research aircraft that probed the 2010 Icelandic Eyjafjallajökull eruption plume identified in-plume ozone depletion and reactive halogens (Cl, BrO), the latter also detected by satellite. These measurements add to growing evidence that volcanic plumes support rapid reactive halogen chemistry, with predicted impacts including depletion of atmospheric oxidants and mercury deposition. However, attempts to simulate volcanic plume halogen chemistry and predict impacts are subject to considerable uncertainties. e.g. in rate constants for HOBr reactive uptake (see this session: EGU2013-6076), or in the high-temperature initialisation. Model studies attempting to replicate volcanic plume halogen chemistry are restricted by a paucity of field data that is required both for model tuning and verification, hence reported model 'solutions' are not necessarily unique. To this end, the aircraft, ground-based and satellite studies of the Eyjafjallajökull eruption provide a valuable combination of datasets for improving our understanding of plume chemistry and impacts. Here, PlumeChem simulations of Eyjafjallajökull plume reactive halogen chemistry and impacts are presented and verified by observations for the first time. Observed ozone loss, a function of plume strength and age, is quantitatively reproduced by the model. Magnitudinal agreement to reported downwind BrO and Cl is also shown. The model predicts multi-day impacts, with reactive bromine mainly as BrO, HOBr and BrONO2 during daytime, and Br2 and BrCl at night. BrO/SO2 is reduced in more dispersed plumes due to enhanced partitioning to HOBr, of potential interest to satellite studies of BrO downwind of volcanoes. Additional predicted impacts of Eyjafjallajökull volcanic plume halogen chemistry include BrO-mediated depletion of HOx that reduces the rate of SO2 oxidation to H2SO4, hence the formation of sulphate aerosol. The model predicts NOx is rapidly converted into nitric acid (via BrONO2). Such HNO3-formation might contribute towards new particle formation, noting reported very high in-plume particle nucleation rates in Eyjafjallajökull plume. Thus, plume halogen chemistry influences on aerosol formation and growth are emphasized regarding studies of climatic and health impacts of volcanic aerosol. As the plume disperses, in-plume ozone concentrations partially recover due to entrainment of O3-rich background air. However, the cumulative net impact on ozone depletion continues. Whilst the global tropospheric impact of Eyjafjallajokull is small, up-scaling of the model findings in the context of present day global volcanic degassing and recent historic eruptions indicates potential for significant impacts of global volcanic halogen emissions on tropospheric ozone, particularly during periods of enhanced volcanic activity. Notably, this model-observation study of Eyjafjallajökull plume exhibits contrasts to a related model-observation study that quantified ozone loss in Redoubt volcano eruption plume (Kelly et al., JVGR in press). Meteorological and volcanological causes for these differences in plume halogen evolution (hence impacts) are discussed. This has implications for wider atmospheric modelling efforts to quantify global impacts from volcanic halogen emissions and highlights the useful role of fully-flexible and computationally inexpensive models such as PlumeChem to inform larger (regional or global) model studies regarding model initialisation and particularly near-source plume chemistry.

The halosol process for water disinfection and dehalogenation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Acra, A.; Jurdi, M.; Mu'allem, H.

Substitution of chlorine and its derivatives as agents to disinfect water and wastewater effluents because of concern for the formation of the mutagenic and carcinogenic trihalomethanes (THM) may be a protracted endeavor. Excess chlorine residuals need to be controlled by dechlorinated agents, e.g., SO{sub 2}, to avoid esthetic objections voiced by consumers and the risk to aquatic environments. We focused on the phenomenon of photodecomposition and aqueons halogen solutions by sunlight. The halosol process, a batch system for solar dehalogenation, was developed into a flow-through system for the halosol disinfection of water. A prototype facility incorporated a solar reactor, throughmore » which chlorinated water flowed, made of borosilicate glass tube with a serpentine shape supported by a frame. Disinfection is induced by two cooperative biocidal agents (a halogen and sunlight) with sequential solar dehalogenation. An overall mean photodechlorination rate, K, of 0.238 m{sup 2}/W-h was obtained. The calculated solar UV-A fluence required to reduce the initial chlorine residuals by 90% and 99% was 9.65 and 19.30 W-h/m{sup 2}. The most effective photodechlorination components of sunlight were in the UV-A region of the spectrum: effectiveness decreased exponentially with wavelength.« less

Ultrafast nuclear dynamics in halomethanes studied with time-resolved Coulomb explosion imaging and channel-selective Fourier spectroscopy

NASA Astrophysics Data System (ADS)

Malakar, Y.; Kaderiya, B.; Pearson, W. L.; Ziaee, F.; Kanaka Raju, P.; Zohrabi, M.; Jensen, K.; Rajput, J.; Ben-Itzhak, I.; Rolles, D.; Rudenko, A.

2016-05-01

Halomethanes have recently attracted considerable attention since they often serve as prototype systems for laser-controlled chemistry (e.g., selective bond breaking or concerted elimination reactions), and are important molecules in atmospheric chemistry. Here we combine a femtosecond laser pump-probe setup with coincident 3D ion momentum imaging apparatus to study strong-field induced nuclear dynamics in methane and several of its halogenated derivatives (CH3 I, CH2 I2, CH2 ICl). We apply a time-resolved Coulomb explosion imaging technique to map the nuclear motion on both, bound and continuum potential surfaces, disentangle different fragmentation pathways and, for halogenated molecules, observe clear signatures of vibrational wave packets in neutral or ionized states. Channel-selective and kinetic-energy resolved Fourier analysis of these data allows for unique identification of different electronic states and vibrational modes responsible for a particular structure. Supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U. S. DOE. K. R. P. and W. L. P. supported by NSF Award No. IIA-143049. K.J. supported by the NSF-REU Grant No. PHYS-1461251.

Transformation of halogen-, alkyl-, and alkoxy-substituted anilines by a lactase of Trametes versicolor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoff, T.; Liu, S.Y.; Bollag, J.M.

1985-05-01

The lactase of the fungus Trametes versicolor was able to polymerize various halogen-, alkyl-, and alkoxy-substituted anilines, showing substrate specificity similar to that of horseradish peroxidase, whereas the lactase of Rhizoctonia praticola was active only with p-methoxyaniline. The substrate specificities of the enzymes were determined by using gas chromatography to measure the decrease in substrate concentration during incubation. With p-chloroaniline as the substrate, the peroxidase and the Trametes lactase showed maximum activity near pH 4.2. The transformation of this substrate gave rise to a number of oligomers, ranging from dimers to pentamers, as determined by mass spectrometry. The product profilesmore » obtained by high-pressure liquid chromatography were similar for the two enzymes. A chemical reaction was observed between p-chloroaniline and an enzymatically formed dimer, resulting in the formation of a trimer. All three enzymes oxidized p-methoxyaniline to 2-amino-5-p-anisidinobenzoquinone di-p-methoxyphenylimine, but only the T. versicolor lactase and the peroxidase caused the formation of a pentamer (2,5-di-p-anisidinobenzoquinone di-p-methoxyphenylimine). These results demonstrate that in addition to horseradish peroxidase, a T. versicolor lactase can also polymerize aniline derivatives.« less

Halogenated Solvent Cleaning: National Emission Standards for Hazardous Air Pollutants (NESHAP)

EPA Pesticide Factsheets

Learn about the Maximum Achievable Control Technology (MACT) standards for halogenated solvent cleaner. Find the rule history information, federal register citations, legal authority, and additional resources.

Second-order optical effects in several pyrazolo-quinoline derivatives

NASA Astrophysics Data System (ADS)

Makowska-Janusik, M.; Gondek, E.; Kityk, I. V.; Wisła, J.; Sanetra, J.; Danel, A.

2004-11-01

Using optical poling of several pyazolo-quinoline (PAQ) derivatives we have found an existence of sufficiently high second order optical susceptibility at wavelength 1.76 μm varying in the range 0.9-2.8 pm/V. The performed quantum chemical simulations of the UV-absorption for isolated, solvated and incorporated into the polymethacrylate (PMMA) polymer films have shown that the PM3 method is the best among the semi-empirical ones to simulate the optical properties. The calculations of the hyperpolarizabilites have shown a good correlation with experimentally measured susceptibilities obtained from the optical poling. We have found that experimental susceptibility depends on linear molecular polarizability and photoinducing changes of the molecular dipole moment. It is clearly seen for the PAQ4-PAQ6 molecules possessing halogen atoms with relatively large polarizabilities.

A Simple Base-Mediated Halogenation of Acidic sp2 C-H Bonds under Non-Cryogenic Conditions

PubMed Central

Do, Hien-Quang; Daugulis, Olafs

2009-01-01

A new method has been developed for in situ halogenation of acidic sp2 carbon-hydrogen bonds in heterocycles and electron-deficient arenes. Either selective monohalogenation or one-step exhaustive polyhalogenation is possible for substrates possessing several C-H bonds that are flanked by electron-withdrawing groups. For the most acidic arenes, such as pentafluorobenzene, K3PO4 base can be employed instead of BuLi for metalation/halogenation sequences. PMID:19102661

Dissociative Photoionization of 1-Halogenated Silacyclohexanes: Silicon Traps the Halogen.

PubMed

Bodi, Andras; Sigurdardottir, Katrin Lilja; Kvaran, Ágúst; Bjornsson, Ragnar; Arnason, Ingvar

2016-11-23

The threshold photoelectron spectra and threshold photoionization mass spectra of 1-halogenated-1-silacyclohexanes, for the halogens X = F, Cl, Br, and I, have been obtained using synchrotron vacuum ultraviolet radiation and photoelectron photoion coincidence spectroscopy. As confirmed by a similar ionization onset and density functional theory molecular orbitals, the ionization to the ground state is dominated by electron removal from the silacyclohexane ring for X = F, Cl, and Br, and from the halogen lone pair for X = I. The breakdown diagrams show that the dissociative photoionization mechanism is also different for X = I. Whereas the parent ions decay by ethylene loss for X = F to Br in the low-energy regime, the iodine atom is lost for X = I. The first step is followed by a sequential ethylene loss at higher internal energies in each of the compounds. It is argued that the tendency of silicon to lower bond angles stabilizes the complex cation in which C 2 H 4 is η 2 -coordinated to it, and which precedes ethylene loss. Together with the relatively strong silicon-halogen bonds and the increased inductive effect of the silacyclohexane ring in stabilizing the cation, this explains the main differences observed in the fragmentation of the halogenated silacyclohexane and halogenated cyclohexane ions. The breakdown diagrams have been modeled taking into account slow dissociations at threshold and the resulting kinetic shift. The 0 K appearance energies have been obtained to within 0.08 eV for the ethylene loss for X = F to Br (10.56, 10.51, and 10.51 eV, respectively), the iodine atom loss for X = I (10.11 eV), the sequential ethylene loss for X = F to I (12.29, 12.01, 11.94, and 11.86 eV, respectively), and the minor channels of H loss for X = F (10.56 eV) and propylene loss in X = Cl (also at 10.56 eV). The appearance energies for the major channels likely correspond to the dissociative photoionization reaction energy.

A box model study on photochemical interactions between VOCs and reactive halogen species in the marine boundary layer

NASA Astrophysics Data System (ADS)

Toyota, K.; Kanaya, Y.; Takahashi, M.; Akimoto, H.

2004-09-01

A new chemical scheme is developed for the multiphase photochemical box model SEAMAC (size-SEgregated Aerosol model for Marine Air Chemistry) to investigate photochemical interactions between volatile organic compounds (VOCs) and reactive halogen species in the marine boundary layer (MBL). Based primarily on critically evaluated kinetic and photochemical rate parameters as well as a protocol for chemical mechanism development, the new scheme has achieved a near-explicit description of oxidative degradation of up to C3-hydrocarbons (CH4, C2H6, C3H8, C2H4, C3H6, and C2H2) initiated by reactions with OH radicals, Cl- and Br-atoms, and O3. Rate constants and product yields for reactions involving halogen species are taken from the literature where available, but the majority of them need to be estimated. In particular, addition reactions of halogen atoms with alkenes will result in forming halogenated organic intermediates, whose photochemical loss rates are carefully evaluated in the present work. Model calculations with the new chemical scheme reveal that the oceanic emissions of acetaldehyde (CH3CHO) and alkenes (especially C3H6) are important factors for regulating reactive halogen chemistry in the MBL by promoting the conversion of Br atoms into HBr or more stable brominated intermediates in the organic form. The latter include brominated hydroperoxides, bromoacetaldehyde, and bromoacetone, which sequester bromine from a reactive inorganic pool. The total mixing ratio of brominated organic species thus produced is likely to reach 10-20% or more of that of inorganic gaseous bromine species over wide regions over the ocean. The reaction between Br atoms and C2H2 is shown to be unimportant for determining the degree of bromine activation in the remote MBL. These results imply that reactive halogen chemistry can mediate a link between the oceanic emissions of VOCs and the behaviors of compounds that are sensitive to halogen chemistry such as dimethyl sulfide, NOx, and O3 in the MBL.

Sensitivity of Tropospheric Chemical Composition to Halogen-Radical Chemistry Using a Fully Coupled Size-Resolved Multiphase Chemistry-Global Climate System: Halogen Distributions, Aerosol Composition, and Sensitivity of Climate-Relevant Gases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Long, M.; Keene, W. C.; Easter, Richard C.

Observations and model studies suggest a significant but highly non-linear role for halogens, primarily Cl and Br, in multiphase atmospheric processes relevant to tropospheric chemistry and composition, aerosol evolution, radiative transfer, weather, and climate. The sensitivity of global atmospheric chemistry to the production of marine aerosol and the associated activation and cycling of inorganic Cl and Br was tested using a size-resolved multiphase coupled chemistry/global climate model (National Center for Atmospheric Research’s Community Atmosphere Model (CAM); v3.6.33). Simulation results showed strong meridional and vertical gradients in Cl and Br species. The simulation reproduced most available observations with reasonable confidence permittingmore » the formulation of potential mechanisms for several previously unexplained halogen phenomena including the enrichment of Br- in submicron aerosol, and the presence of a BrO maximum in the polar free troposphere. However, simulated total volatile Br mixing ratios were generally high in the troposphere. Br in the stratosphere was lower than observed due to the lack of long-lived organobromine species in the simulation. Comparing simulations using chemical mechanisms with and without reactive Cl and Br species demonstrated a significant temporal and spatial sensitivity of primary atmospheric oxidants (O3, HOx, NOx), CH4, and non-methane hydrocarbons (NMHC’s) to halogen cycling. Simulated O3 and NOx were globally lower (65% and 35%, respectively, less in the planetary boundary layer based on median values) in simulations that included halogens. Globally, little impact was seen in SO2 and non-sea-salt SO42- processing due to halogens. Significant regional differences were evident: The lifetime of nss-SO42- was extended downwind of large sources of SO2. The burden and lifetime of DMS (and its oxidation products) were lower by a factor of 5 in simulations that included halogens, versus those without, leading to a 20% reduction in nss-SO42- in the southern hemisphere planetary boundary layer based on median values.« less

Detection of halogenated flame retardants in polyurethane foam by particle induced X-ray emission

NASA Astrophysics Data System (ADS)

Maley, Adam M.; Falk, Kyle A.; Hoover, Luke; Earlywine, Elly B.; Seymour, Michael D.; DeYoung, Paul A.; Blum, Arlene; Stapleton, Heather M.; Peaslee, Graham F.

2015-09-01

A novel application of particle-induced X-ray emission (PIXE) has been developed to detect the presence of chlorinated and brominated flame retardant chemicals in polyurethane foams. Traditional Gas Chromatography-Mass Spectrometry (GC-MS) methods for the detection and identification of halogenated flame retardants in foams require extensive sample preparation and data acquisition time. The elemental analysis of the halogens in polyurethane foam performed by PIXE offers the opportunity to identify the presence of halogenated flame retardants in a fraction of the time and sample preparation cost. Through comparative GC-MS and PIXE analysis of 215 foam samples, excellent agreement between the two methods was obtained. These results suggest that PIXE could be an ideal rapid screening method for the presence of chlorinated and brominated flame retardants in polyurethane foams.

Development of nonflammable cellulosic foams

NASA Technical Reports Server (NTRS)

Luttinger, M.

1972-01-01

The development of a moldable cellulosic foam for use in Skylab instrument storage cushions is considered. Requirements include density of 10 lb cu ft or less, minimal friability with normal handling, and nonflammability in an atmosphere of 70 percent oxygen and 30 percent nitrogen at 6.2 psia. A study of halogenated foam components was made, including more highly chlorinated binders, halogen-containing additives, and halogenation of the cellulose. The immediate objective was to reduce the density of the foam through reduction in inorganic phosphate without sacrificing flame-retarding properties of the foams. The use of frothing techniques was investigated, with particular emphasis on a urea-formaldehyde foam. Halogen-containing flame retardants were deemphasized in favor of inorganic salts and the preparation of phosphate and sulphate esters of cellulose. Utilization of foam products for civilian applications was also considered.

Halogenated solvent remediation

DOEpatents

Sorenson, Kent S.

2004-08-31

Methods for enhancing bioremediation of ground water contaminated with nonaqueous halogenated solvents are disclosed. A preferred method includes adding a composition to the ground water wherein the composition is an electron donor for microbe-mediated reductive dehalogenation of the halogenated solvents and enhances mass transfer of the halogenated solvents from residual source areas into the aqueous phase of the ground water. Illustrative compositions effective in these methods include surfactants such as C.sub.2 -C.sub.4 carboxylic acids and hydroxy acids, salts thereof, esters of C.sub.2 -C.sub.4 carboxylic acids and hydroxy acids, and mixtures thereof. Especially preferred compositions for use in these methods include lactic acid, salts of lactic acid, such as sodium lactate, lactate esters, and mixtures thereof. The microbes are either indigenous to the ground water, or such microbes can be added to the ground water in addition to the composition.

Synthesis and biological evaluation of novel N-phenyl ureidobenzenesulfonate derivatives as potential anticancer agents. Part 2. Modulation of the ring B.

PubMed

Gagné-Boulet, Mathieu; Moussa, Hanane; Lacroix, Jacques; Côté, Marie-France; Masson, Jean-Yves; Fortin, Sébastien

2015-10-20

DNA double strand-breaks (DSBs) are the most deleterious lesions that can affect the genome of living beings and are lethal if not quickly and properly repaired. Recently, we discovered a new family of anticancer agents designated as N-phenyl ureidobenzenesulfonates (PUB-SOs) that are blocking the cells cycle progression in S-phase and inducing DNA DSBs. Previously, we have studied the effect of several modifications on the molecular scaffold of PUB-SOs on their cytocidal properties. However, the effect of the nature and the position of substituents on the aromatic ring B is still poorly studied. In this study, we report the preparation and the biological evaluation of 45 new PUB-SO derivatives substituted by alkyl, alkoxy, halogen and nitro groups at different positions on the aromatic ring B. All PUB-SOs were active in the submicromolar to low micromolar range (0.24-20 μM). The cell cycle progression analysis showed that PUB-SOs substituted at position 2 by alkyl, halogen or nitro groups or substituted at position 4 by a hydroxyl group arrest the cell cycle progression in S-phase. Interestingly, all others PUB-SOs substituted at positions 3 and 4 arrested the cell cycle in G2/M-phase. PUB-SOs arresting the cell cycle progression in S-phase also induced the phosphorylation of H2AX (γH2AX) which is indicating the generation of DNA DSBs. We evidenced that few modifications on the ring B of PUB-SOs scaffold lead to cytocidal derivatives arresting the cell cycle in S-phase and inducing γH2AX and DSBs. In addition, this study shows that these new anticancer agents are promising and could be used as alternative to circumvent some of the biopharmaceutical complications that might be encountered during the development of PUB-SOs. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Rate constants and temperature dependences for the reactions of hydroxyl radical with several halogenated methanes, ethanes, and propanes by relative rate measurements

NASA Technical Reports Server (NTRS)

Hsu, K.-J.; DeMore, W. B.

1995-01-01

Rate constants of 15 OH reactions with halogen-substituted alkanes, C1 to C3, were studied using a relative rate technique in the temperature range 283-403 K. Compounds studied were CHF2Cl (22), CHF2Br (22B), CH3F (41), CH2F2 (32), CHF3 (23), CHClFCCl2F (122a), CHCl2CF3 (123), CHClFCF3 (124), CH3CF3 (143a), CH3CH2F (161), CF3CHFCF3 (227ea), CF3CH2CF3 (236fa), CF3CHFCHF2 (236ea), and CHF2CF2CH2F (245ca). Using CH4, CH3CCl3, CF3CF2H, and C2H6 as primary reference standards (JPL 92-20 rate constants), absolute rate constants are derived. Results are in good agreement with previous experimental results for six of the compounds studied, including CHF2Cl, CHF2Br, CH2F2, CH3CF3, CHFClCFCl2, and CF3CHFCF3. For the remainder the relative rate constants are lower than those derived from experiments in which OH loss was used to measure the reaction rate. Comparisons of the derived Arrhenius A factors with previous literature transition-state calculations show order of magnitude agreement in most cases. However, the experimental A factors show a much closer proportionality to the number of H atoms in the molecule than is evident from the transition state calculations. For most of the compounds studied, an A factor of (8 +/- 3)E-13 cm(exp 3)/(molecule s) per C-H bond is observed. A new measurement of the ratio k(CH3CCl3)/k(CH4) is reported that is in good agreement with previous data.

Comparing colour discrimination and proofreading performance under compact fluorescent and halogen lamp lighting.

PubMed

Mayr, Susanne; Köpper, Maja; Buchner, Axel

2013-01-01

Legislation in many countries has banned inefficient household lighting. Consequently, classic incandescent lamps have to be replaced by more efficient alternatives such as halogen and compact fluorescent lamps (CFL). Alternatives differ in their spectral power distributions, implying colour-rendering differences. Participants performed a colour discrimination task - the Farnsworth-Munsell 100 Hue Test--and a proofreading task under CFL or halogen lighting of comparable correlated colour temperatures at low (70 lx) or high (800 lx) illuminance. Illuminance positively affected colour discrimination and proofreading performance, whereas the light source was only relevant for colour discrimination. Discrimination was impaired with CFL lighting. There were no differences between light sources in terms of self-reported physical discomfort and mood state, but the majority of the participants correctly judged halogen lighting to be more appropriate for discriminating colours. The findings hint at the colour-rendering deficiencies associated with energy-efficient CFLs. In order to compare performance under energy-efficient alternatives of classic incandescent lighting, colour discrimination and proofreading performance was compared under CFL and halogen lighting. Colour discrimination was impaired under CFLs, which hints at the practical drawbacks associated with the reduced colour-rendering properties of energy-efficient CFLs.

Process for oxidation of hydrogen halides to elemental halogens

DOEpatents

Lyke, Stephen E.

1992-01-01

An improved process for generating an elemental halogen selected from chlorine, bromine or iodine, from a corresponding hydrogen halide by absorbing a molten salt mixture, which includes sulfur, alkali metals and oxygen with a sulfur to metal molar ratio between 0.9 and 1.1 and includes a dissolved oxygen compound capable of reacting with hydrogen halide to produce elemental halogen, into a porous, relatively inert substrate to produce a substrate-supported salt mixture. Thereafter, the substrate-supported salt mixture is contacted (stage 1) with a hydrogen halide while maintaining the substrate-supported salt mixture during the contacting at an elevated temperature sufficient to sustain a reaction between the oxygen compound and the hydrogen halide to produce a gaseous elemental halogen product. This is followed by purging the substrate-supported salt mixture with steam (stage 2) thereby recovering any unreacted hydrogen halide and additional elemental halogen for recycle to stage 1. The dissolved oxygen compound is regenerated in a high temperature (stage 3) and an optical intermediate temperature stage (stage 4) by contacting the substrate-supported salt mixture with a gas containing oxygen whereby the dissolved oxygen compound in the substrate-supported salt mixture is regenerated by being oxidized to a higher valence state.

When Will the Antarctic Ozone Hole Recover?

NASA Technical Reports Server (NTRS)

Newman, Paul A.; Nash, Eric R.; Kawa, S. Randolph; Montzka, Steve

2005-01-01

The Antarctic ozone hole develops each year and culminates by early Spring. Antarctic ozone values have been monitored since 1979 using satellite observations from the TOMS instrument. The severity of the hole has been assessed from TOMS using the minimum total ozone value from the October monthly mean (depth of the hole) and by calculating the average size during the September-October period. Ozone is mainly destroyed by halogen catalytic cycles, and these losses are modulated by temperature variations in the collar of the polar lower stratospheric vortex. In this presentation, we show the relationships of halogens and temperature to both the size and depth of the hole. Because atmospheric halogen levels are responding to international agreements that limit or phase out production, the amount of halogens in the stratosphere should decrease over the next few decades. Using projections of halogen levels combined with age-of-air estimates, we find that the ozone hole is recovering at an extremely slow rate and that large ozone holes will regularly recur over the next 2 decades. We will show estimates of both when the ozone hole will begin to show first signs of recovery, and when the hole will fully recover to pre-1980 levels.

Detecting the Recovery of the Antarctic Ozone Hole

NASA Technical Reports Server (NTRS)

Newman, Paul A.; Nash, Eric R.; Kawa, S. Randolph; Montzka, Steve

2004-01-01

The Antarctic ozone hole develops each year and culminates by early Spring. Antarctic ozone values have been monitored since 1979 using satellite observations from the TOMS instrument. The severity of the hole has been assessed from TOMS using the minimum total ozone value from the October monthly mean (depth of the hole) and by calculating the average size during the September-October period. Ozone is mainly destroyed by halogen catalytic cycles, and these losses are modulated by temperature variations in the collar of the polar lower stratospheric vortex. In this presentation, we show the relationships of halogens and temperature to both the size and depth of the hole. Because atmospheric halogen levels are responding to international agreements that limit or phase out production, the amount of halogens in the stratosphere should decrease over the next few decades. Using projections of halogen levels combined with age-of-air estimates, we find that the ozone hole is recovering at an extremely slow rate and that large ozone holes will regularly recur over the next 2 decades. We will show estimates of both when the ozone hole will begin to show first signs of recovery, and when the hole will fully recover to pre-1980 levels.

Comparison of microleakages of photo-cured composites using three different light sources: halogen lamp, LED and argon laser: an in vitro study.

PubMed

Tielemans, M; Compere, Ph; Geerts, S O; Lamy, M; Limme, M; De Moor, R J G; Delmé, K I M; Bertrand, M F; Rompen, E; Nammour, S

2009-01-01

In this study, we compared the microleakage of composite fillings cured with halogen bulb, LED and argon ion laser (488 nm). Twenty-four extracted human molars were divided randomly in three groups. Six cavities were prepared on the coronal part of each tooth. Standard cavities (1.7 x 2 mm) were prepared. Cavities were acid etched, sealed with Scotch Bond 1 and filled by a hybrid composite. Cavities were exposed to one light source, thermocycled and immersed in a 2% methylene blue dye solution. Dye penetration in the leakage of cavities was recorded using a digital optical microscope. Mean values of percentage of dye penetrations in microleakages of cavities were 49.303 +/- 5.178% for cavities cured with LED, 44.486 +/- 6.075% with halogen bulb and 36.647 +/- 5.936% for those cured by argon laser. Statistically significant difference exists between cavities cured by halogen vs LED (P < 0.01), halogen vs laser (P < 0.001) and LED vs laser (P < 0.001). The lowest microleakage was observed in the cavities and composites cured with argon ion laser.

Halogenation of Hydraulic Fracturing Additives in the Shale Well Parameter Space

NASA Astrophysics Data System (ADS)

Sumner, A. J.; Plata, D.

2017-12-01

Horizontal Drilling and Hydraulic fracturing (HDHF) involves the deep-well injection of a `fracking fluid' composed of diverse and numerous chemical additives designed to facilitate the release and collection of natural gas from shale plays. The potential impacts of HDHF operations on water resources and ecosystems are numerous, and analyses of flowback samples revealed organic compounds from both geogenic and anthropogenic sources. Furthermore, halogenated chemicals were also detected, and these compounds are rarely disclosed, suggesting the in situ halogenation of reactive additives. To test this transformation hypothesis, we designed and operated a novel high pressure and temperature reactor system to simulate the shale well parameter space and investigate the chemical reactivity of twelve commonly disclosed and functionally diverse HDHF additives. Early results revealed an unanticipated halogenation pathway of α-β unsaturated aldehyde, Cinnamaldehyde, in the presence of oxidant and concentrated brine. Ongoing experiments over a range of parameters informed a proposed mechanism, demonstrating the role of various shale-well specific parameters in enabling the demonstrated halogenation pathway. Ultimately, these results will inform a host of potentially unintended interactions of HDHF additives during the extreme conditions down-bore of a shale well during HDHF activities.

The effects of titanium dioxide coatings on light-derived heating and transdermal heat transfer in bovine skin

NASA Astrophysics Data System (ADS)

Bartle, S. J.; Thomson, D. U.; Gehring, R.; van der Merwe, D.

2017-11-01

The effects of titanium dioxide coatings of bovine hides on light absorption and transdermal transfer of light-derived heat were investigated. Four hair-on rug hides from Holstein cattle were purchased. Twelve samples about 20 cm on a side were cut from each hide; nine from the black-colored areas, and three from the white areas. Samples were randomized and assigned to four coating treatments: (1) white hide with no coating (White), (2) black hide with no coating (Black), (3) black hide with 50% coating (Mid), and (4) black hide with 100% coating (High). Coatings were applied to the black hide samples using a hand sprayer. Lux measurements were taken using a modified lux meter at three light intensities generated with a broad spectrum, cold halogen light source. Reflectance over a wavelength range of 380 to 900 nm was measured using a spectroradiometer. The transdermal transfer of heat derived from absorbed light was measured by applying a broad spectrum, cold halogen light source to the stratum corneum (coated) side of the sample and recording the temperature of the dermis-side using a thermal camera for 10 min at 30-s intervals. At the high light level, the White, Black, Mid, and High coating treatments had different ( P < 0.001) lux values of 64,945, 1741, 15,978, and 40,730 lx, respectively. In the visible wavelength range (400 to 750 nm), Black hides reflected 10 to 15% of the light energy, hides with the Mid coating treatment reflected 35 to 40%, and hides with the High coating treatment reflected 70 to 80% of the light energy. The natural White hide samples reflected 60 to 80% of the light energy. The average maximum temperatures at the dermis-side of the hides due to transferred heat were 34.5, 70.1, 55.0, and 31.7, for the White, Black, Mid, and High treatments, respectively. Reflective coatings containing titanium dioxide on cattle hides were effective in reducing light energy absorption and reduced light-derived heat transfer from the skin surface to deeper skin layers.

MEMBRANES FOR DRINKING WATER TREATMENT

EPA Science Inventory

Various treatment technologies have proven effective in controlling halogenated disinfection by-products such as precursor removal and the use of alternative disinfectants. One of the most promising methods for halogenated by-product control includes removal of precursors before ...

40 CFR 65.83 - Performance requirements.

Code of Federal Regulations, 2012 CFR

2012-07-01

... stream nonhalogenated by reducing the vent stream halogen atom mass emission rate to less than 0.45... requirements of paragraph (a)(1) or (2) of this section. The mass emission rate of halogen atoms contained in...

40 CFR 65.83 - Performance requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... stream nonhalogenated by reducing the vent stream halogen atom mass emission rate to less than 0.45... requirements of paragraph (a)(1) or (2) of this section. The mass emission rate of halogen atoms contained in...

40 CFR 65.83 - Performance requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... stream nonhalogenated by reducing the vent stream halogen atom mass emission rate to less than 0.45... requirements of paragraph (a)(1) or (2) of this section. The mass emission rate of halogen atoms contained in...

40 CFR 65.83 - Performance requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

... stream nonhalogenated by reducing the vent stream halogen atom mass emission rate to less than 0.45... requirements of paragraph (a)(1) or (2) of this section. The mass emission rate of halogen atoms contained in...

40 CFR 65.83 - Performance requirements.

Code of Federal Regulations, 2014 CFR

2014-07-01

... stream nonhalogenated by reducing the vent stream halogen atom mass emission rate to less than 0.45... requirements of paragraph (a)(1) or (2) of this section. The mass emission rate of halogen atoms contained in...

POSSIBLE MOLECULAR TARGETS OF HALOGENATED ARMOATIC HYDROCARBONS IN NEURONAL CELLS.

EPA Science Inventory

Halogenated aromatic hydrocarbons including polychlorinated biphenyls (PCBs) are persistent bioaccumulative toxicants. Due to these characteristics, there is considerable regulatory concern over the potential adverse health affects, especially to children, associated with exposur...

Monoclonal antibodies for the separate detection of halodeoxyuridines and method for their use

DOEpatents

Vanderlaan, M.; Watkins, B.E.; Stanker, L.H.

1991-10-01

Monoclonal antibodies are described which have specific affinities for halogenated nucleoside analogs and are preferentially selective for one particular halogen. Such antibodies, when incorporated into immunochemical reagents, may be used to identify and independently quantify the cell division character of more than one population or subpopulation in flow cytometric measurements. Independent assessment of division activity in cell sub-populations facilitates selection of appropriate time and dose for administration of anti-proliferative agents. The hybridomas which secrete halogen selective antibodies and the method of making them are described. 14 figures.

Monoclonal antibodies for the separate detection of halodeoxyuridines and method for their use

DOEpatents

Vanderlaan, Martin; Watkins, Bruce E.; Stanker, Larry H.

1991-01-01

Monoclonal antibodies are described which have specific affinities for halogenated nucleoside analogs and are preferentially selective for one particular halogen. Such antibodies, when incorporated into immunochemical reagents, may be used to identify and independently quantify the cell division character of more than one population or subpopulation in flow cytometric measurements. Independent assessment of division activity in cell sub-populations facilitates selection of appropriate time and dose for administration of anti-proliferative agents. The hybridomas which secrete halogen selective antibodies and the method of making them are described.

Mysterious iodine-overabundance in Antarctic meteorites

NASA Technical Reports Server (NTRS)

Dreibus, G.; Waenke, H.; Schultz, L.

1986-01-01

Halogen as well as other trace element concentrations in meteorite finds can be influenced by alteration processes on the Earth's surface. The discovery of Antarctic meteorites offered the opportunity to study meteorites which were kept in one of the most sterile environment of the Earth. Halogen determination in Antartic meteorites was compared with non-Antarctic meteorites. No correlation was found between iodine concentration and the weathering index, or terrestrial age. The halogen measurements indicate a contaminating phase rich in iodine and also containing chlorine. Possible sources for this contamination are discussed.

Methods for producing single crystal mixed halide perovskites

DOEpatents

Zhu, Kai; Zhao, Yixin

2017-07-11

An aspect of the present invention is a method that includes contacting a metal halide and a first alkylammonium halide in a solvent to form a solution and maintaining the solution at a first temperature, resulting in the formation of at least one alkylammonium halide perovskite crystal, where the metal halide includes a first halogen and a metal, the first alkylammonium halide includes the first halogen, the at least one alkylammonium halide perovskite crystal includes the metal and the first halogen, and the first temperature is above about 21.degree. C.

Phenolic aminocarboxylate chelates of 99mTc as hepatobiliary agents.

PubMed

Hunt, F C; Maddalena, D J; Wilson, J G; Bautovich, G J

1986-01-01

A series of alkyl- and halogen-substituted derivatives of ethylenediamine di[o-hydroxyphenylacetic acid] (EDDHA) and N,N'-bis[2-hydroxybenzyl] ethylenediamine N,N'-diacetic acid (HBED) were complexed with 99mTc and their biodistribution was determined in rats. All complexes displayed substantial hepatobiliary excretion; of each series, 99mTc-Br-EDDHA and 99mTc-di-Cl-HBED had the maximum amount in the gastrointestinal tract. Scintigraphic studies of 99mTc-Cl-EDDHA in dogs revealed prompt imaging of the liver followed by imaging of the gall bladder as the complex was excreted into the bile.

Core-dependent and ligand-dependent relativistic corrections to the nuclear magnetic shieldings in MH4-n Y n (n = 0-4; M = Si, Ge, Sn, and Y = H, F, Cl, Br, I) model compounds.

PubMed

Maldonado, Alejandro F; Aucar, Gustavo A; Melo, Juan I

2014-09-01

The nuclear magnetic shieldings of Si, Ge, and Sn in MH(4-n) Y(n) (M = Si, Ge, Sn; Y = F, Cl, Br, I and n = 1-4) molecular systems are highly influenced by the substitution of one or more hydrogens by heavy-halogen atoms. We applied the linear response elimination of small components (LRESC) formalism to calculate those shieldings and learn whether including only a few of the leading relativistic correction terms is sufficient to be able to quantitatively reproduce the full relativistic value. It was observed that the nuclear magnetic shieldings change as the number of heavy halogen substituents and their weights vary, and the pattern of σ(M) generally does not exhibit the normal halogen dependence (NHD) behavior that can be seen in similar molecular systems containing carbon atoms. We also analyzed each relativistic correction afforded by the LRESC method and split them in two: core-dependent and ligand-dependent contributions; we then looked for the electronic mechanisms involved in the different relativistic effects and in the total relativistic value. Based on this analysis, we were able to study the electronic mechanism involved in a recently proposed relativistic effect, the "heavy atom effect on vicinal heavy atom" (HAVHA), in more detail. We found that the main electronic mechanism is the spin-orbit or σ p (T(3)) correction, although other corrections such as σ p (S(1)) and σ p (S(3)) are also important. Finally, we analyzed proton magnetic shieldings and found that, for molecules containing Sn as the central atom, σ(H) decreases as the number of heavy halogen substituents (of the same type: either F, Cl, or Br) increases, albeit at different rates for different halogens. σ(H) only increase as the number of halogen substituents increases if the halogen is iodine.

Halogen degassing during ascent and eruption of water-poor basaltic magma

USGS Publications Warehouse

Edmonds, M.; Gerlach, T.M.; Herd, Richard A.

2009-01-01

A study of volcanic gas composition and matrix glass volatile concentrations has allowed a model for halogen degassing to be formulated for K??lauea Volcano, Hawai'i. Volcanic gases emitted during 2004-2005 were characterised by a molar SO2/HCl of 10-64, with a mean of 33; and a molar HF/HCl of 0-5, with a mean of 1.0 (from approximately 2500 measurements). The HF/HCl ratio was more variable than the SO2/HCl ratio, and the two correlate weakly. Variations in ratio took place over rapid timescales (seconds). Matrix glasses of Pele's tears erupted in 2006 have a mean S, Cl and F content of 67, 85 and 173??ppm respectively, but are associated with a large range in S/F. A model is developed that describes the open system degassing of halogens from parental magmas, using the glass data from this study, previously published results and parameterisation of sulphur degassing from previous work. The results illustrate that halogen degassing takes place at pressures of < 1??MPa, equivalent to < ~ 35??m in the conduit. Fluid-melt partition coefficients for Cl and F are low (< 1.5); F only degasses appreciably at < 0.1??MPa above atmospheric pressure, virtually at the top of the magma column. This model reproduces the volcanic gas data and other observations of volcanic activity well and is consistent with other studies of halogen degassing from basaltic magmas. The model suggests that variation in volcanic gas halogen ratios is caused by exsolution and gas-melt separation at low pressures in the conduit. There is no evidence that either diffusive fractionation or near-vent chemical reactions involving halogens is important in the system, although these processes cannot be ruled out. The fluxes of HCl and HF from K??lauea during 2004-5 were ~ 25 and 12??t/d respectively. ?? 2008 Elsevier B.V.

Iron Mineral Catalyzed C-H Activation As a Potential Pathway for Halogenation Processes

NASA Astrophysics Data System (ADS)

Tubbesing, C.; Schoeler, H. F.; Benzing, K.; Krause, T.; Lippe, S.; Rudloff, M.

2014-12-01

Due to increasing drinking water demand of mankind and an expected climate change the impact of salt lakes and salt deserts will increase within the next decades. Furthermore, a rising sea level influences coastal areas like salt marshes and abets processes which will lead to elevated organohalogen formation. An additional increase of the global warming potential, of particle formation and stratospheric ozone depletion is expected. Understanding these multifaceted processes is essential for mankind to be prepared for these alterations of the atmosphere. For example, Keppler et al. (2000) described the production of volatile halogenated organic compounds via oxidation of organic matter driven by ferric iron. However, the formation of long-chained alkyl halides in salt lakes is yet undisclosed. Despite the relative "inertness" of alkanes a direct halogenation of these compounds might be envisaged. In 2005 Vaillancourt et al. discovered a nonheme iron enzyme which is able to halogenate organic compounds via generating the high valent ferryl cation as reaction center. Based on various publications about C-H activation (Bergman, 2007) we postulate a halogenation process in which an iron containing minerals catalyse the C-H bond cleavage of organic compounds in soils. The generated organic radicals are highly reactive towards halides connected to the iron complex. We suggest that next to diagenetically altered iron containing enzymes, minerals such as oxides, hydroxides and sulfides are involved in abiotic halogenation processes. We applied the amino acid methionine as organic model compound and soluble iron species as reactants. All samples were incubated in aqueous phases containing various NaCl concentrations. As a result various halogenated ethanes and ethenes were identified as reaction products. References Bergman, R. G. (2007) Nature, 446(7134) 391-393 Keppler, F., et al. (2000) Nature, 403(6767) 298-301 Vaillancourt, F. H., et al. (2005) Nature, 436(7054) 1191-1194

40 CFR 65.154 - Halogen scrubbers and other halogen reduction devices.

Code of Federal Regulations, 2010 CFR

2010-07-01

... which it is part, as specified in 40 CFR 63.100(k) (if the referencing subpart is 40 CFR part 63... anticipated in the scrubber during representative operating conditions other than startups, shutdowns, or...

RESIDUAL RISK ASSESSMENT: HALOGENATED SOLVENTS

EPA Science Inventory

This source category previously subjected to a technology-based standard will be examined to determine if health or ecological risks are significant enough to warrant further regulation for Halogenated Solvent Degreasing Facilities. These assessments utilize existing models and d...

Cross-reactivity of Halogenated Platinum Salts

EPA Science Inventory

Halogenated platinum (Pt) salts are well-known respiratory sensitizers associated with the development of asthma. People may be exposed to a variety of platinum compounds in different contexts (e.g. occupationally, automobile exhaust). Published reports suggest that sensitizati...

Halogen bonding, chalcogen bonding, pnictogen bonding, tetrel bonding: origins, current status and discussion.

PubMed

Brammer, Lee

2017-10-13

The role of the closing lecture in a Faraday Discussion is to summarise the contributions made to the Discussion over the course of the meeting and in so doing capture the main themes that have arisen. This article is based upon my Closing Remarks Lecture at the 203 rd Faraday Discussion meeting on Halogen Bonding in Supramolecular and Solid State Chemistry, held in Ottawa, Canada, on 10-12 th July, 2017. The Discussion included papers on fundamentals and applications of halogen bonding in the solid state and solution phase. Analogous interactions involving main group elements outside group 17 were also examined. In the closing lecture and in this article these contributions have been grouped into the four themes: (a) fundamentals, (b) beyond the halogen bond, (c) characterisation, and (d) applications. The lecture and paper also include a short reflection on past work that has a bearing on the Discussion.

Selective Nitrate Recognition by a Halogen‐Bonding Four‐Station [3]Rotaxane Molecular Shuttle

PubMed Central

Barendt, Timothy A.; Docker, Andrew; Marques, Igor; Félix, Vítor

2016-01-01

Abstract The synthesis of the first halogen bonding [3]rotaxane host system containing a bis‐iodo triazolium‐bis‐naphthalene diimide four station axle component is reported. Proton NMR anion binding titration experiments revealed the halogen bonding rotaxane is selective for nitrate over the more basic acetate, hydrogen carbonate and dihydrogen phosphate oxoanions and chloride, and exhibits enhanced recognition of anions relative to a hydrogen bonding analogue. This elaborate interlocked anion receptor functions via a novel dynamic pincer mechanism where upon nitrate anion binding, both macrocycles shuttle from the naphthalene diimide stations at the periphery of the axle to the central halogen bonding iodo‐triazolium station anion recognition sites to form a unique 1:1 stoichiometric nitrate anion–rotaxane sandwich complex. Molecular dynamics simulations carried out on the nitrate and chloride halogen bonding [3]rotaxane complexes corroborate the 1H NMR anion binding results. PMID:27436297

Analysis of Organohalogen Products From Chlorination of Natural Waters Under Simulated Biofouling Control Conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bean, R. M.; Mann, D. C.; Riley, R. G.

1980-06-01

The products of low-level chlorination of natural waters from ten locations across the continental United States have been studied, with emphasis on volatile and lipophilic organohalogen components. A specially designed apparatus permitted continuous sampling and chlorination of water in a manner analogous to some types of cooling water treatments. Volatile components were analyzed using headspace, purge-and-trap, and resin adsorption methods. The less-volatile components were collected by passing large volumes of the chlorinated water over XAD-2 columns. Total organic halogen collected on XAD resins was compared with the halogen contribution of haloform compounds. The XAD samples were further separated into fractionsmore » according to molecular weight and polarity using liquid chrOmatography. These studies indicate that haloforms are the most abundant lipophilic halogenated products formed from low-level chlorination of natural waters, but that other halogenated lipophilic material is also formed.« less

Origin of the X-Hal (Hal = Cl, Br) bond-length change in the halogen-bonded complexes.

PubMed

Wang, Weizhou; Hobza, Pavel

2008-05-01

The origin of the X-Hal bond-length change in the halogen bond of the X-Hal...Y type has been investigated at the MP2(full)/6-311++G(d,p) level of theory using a natural bond orbital analysis, atoms in molecules procedure, and electrostatic potential fitting methods. Our results have clearly shown that various theories explaining the nature of the hydrogen bond cannot be applied to explain the origin of the X-Hal bond-length change in the halogen bond. We provide a new explanation for this change. The elongation of the X-Hal bond length is caused by the electron-density transfer to the X-Hal sigma* antibonding orbital. For the blue-shifting halogen bond, the electron-density transfer to the X-Hal sigma* antibonding orbital is only of minor importance; it is the electrostatic attractive interaction that causes the X-Hal bond contraction.

SYNTHESIS AND STUDY OF HALOGENATED BENZYLAMIDES OF SOME ISOCYCLIC AND HETEROCYCLIC ACIDS AS POTENTIAL ANTICONVULSANTS.

PubMed

Strupińska, Marzanna; Rostafińska-Suchar, Grażyna; Pirianowicz-Chaber, Elżbieta; Grabczuk, Mateusz; Józwenko, Magdalena; Kowalczyk, Hubert; Szuba, Joanna; Wójcicka, Monika; Chen, Tracy; Mazurek, Aleksander P

2015-01-01

A series of potential anticonvulsants have been synthesized. There are eight fluorobenzylamides and three chlorobenzylamides of isocyclic or heterocyclic acids. Two not halogenated benzylamides were also synthesized to compare the effect of halogenation. The aim of the research performed was to evaluate whether halogenation of the mother structure is able to improve its anticonvulsant activity. The compounds were tested in Anticonvulsant Screening Project (ASP) of Antiepileptic Drug Development Program (ADDP) of NIH. Compound 1 showed MES ED50 = 80.32 mg/kg, PI = 3.16. Compound 7 showed CKM ED50 = 56.72 mg/kg. Compound 8 showed MES ED50 = 34.23 mg/kg and scPTZ ED50 > 300 mg/kg, PI = 8.53.Compound 13 showed 6Hz ED50 = 78.96, PI = 3.37. The results indicate that fluorination does not improve activity, whereas chlorination in our experiment even reduces it.

Hospital hydrotherapy pools treated with ultra violet light: bad bacteriological quality and presence of thermophilic Naegleria.

PubMed Central

De Jonckheere, J. F.

1982-01-01

The microbiological quality of eight halogenated and two u.v.-treated hydrotherapy pools in hospitals was investigated. The microbiological quality of halogenated hydrotherapy pools was comparable to halogenated public swimming pools, although in some Pseudomonas aeruginosa and faecal pollution indicators were more frequent due to bad management. On the other hand u.v.-treated hydrotherapy pools had very bad microbiological quality. Apart from faecal pollution indicators, P. aeruginosa was present in very high numbers. Halogenated hydrotherapy pools were not highly contaminated with amoebae, and Naegleria spp. were never detected. On the other hand u.v.-treated pools contained very high numbers of thermophilic Naegleria. The Naegleria isolated were identified as N. lovaniensis, a species commonly found in association with N. fowleri. Isoenzyme analysis showed a different type of N. lovaniensis was present in each of two u.v.-treated pools. Images Plate 1 PMID:7061835

Occurrence and behavior of natural and anthropogenic (emerging and historical) halogenated compounds in marine biota from the Coast of Concepcion (Chile).

PubMed

Barón, Enrique; Rudolph, Ignacio; Chiang, Gustavo; Barra, Ricardo; Eljarrat, Ethel; Barceló, Damià

2013-09-01

Fifty-five biota samples from the Coast of Concepcion (Chile) were analyzed for PBDEs, emerging brominated FRs, halogenated norbornenes and naturally-occurring MeO-PBDEs. PBDEs, MeO-PBDEs and halogenated norbornenes were detected at concentration levels ranging from 11 to 170, nd to 118 and nd to 5.8 ng/g lw, respectively. However, emerging brominated FRs such as decabromodiphenylethane (DBDPE), hexabromobenzene (HBB) and pentabromoethylbenzene (PBEB) were not detected in any sample. Bioaccumulation and bioconcentration processes were evaluated for the different families of compounds. Biomagnification factors (BMFs) were calculated, and some PBDE congeners (BDE-28, BDE-183 and BDE-209) as well as MeO-PBDEs presented BMF>1, being values of the naturally occurring MeO-PBDEs higher than those obtained for PBDEs. As regards halogenated norbornenes, BMF<1 were found. Copyright © 2013 Elsevier B.V. All rights reserved.

Halogen-Enriched Fragment Libraries as Leads for Drug Rescue of Mutant p53

PubMed Central

2012-01-01

The destabilizing p53 cancer mutation Y220C creates a druggable surface crevice. We developed a strategy exploiting halogen bonding for lead discovery to stabilize the mutant with small molecules. We designed halogen-enriched fragment libraries (HEFLibs) as starting points to complement classical approaches. From screening of HEFLibs and subsequent structure-guided design, we developed substituted 2-(aminomethyl)-4-ethynyl-6-iodophenols as p53-Y220C stabilizers. Crystal structures of their complexes highlight two key features: (i) a central scaffold with a robust binding mode anchored by halogen bonding of an iodine with a main-chain carbonyl and (ii) an acetylene linker, enabling the targeting of an additional subsite in the crevice. The best binders showed induction of apoptosis in a human cancer cell line with homozygous Y220C mutation. Our structural and biophysical data suggest a more widespread applicability of HEFLibs in drug discovery. PMID:22439615

An expert system for prediction of chemical toxicity

USGS Publications Warehouse

Hickey, James P.; Aldridge, Andrew J.; Passino-Reader, Dora R.; Frank, Anthony M.

1992-01-01

The National Fisheries Research Center- Great Lakes has developed an interactive computer program that uses the structure of an organic molecule to predict its acute toxicity to four aquatic species. The expert system software, written in the muLISP language, identifies the skeletal structures and substituent groups of an organic molecule from a user-supplied standard chemical notation known as a SMILES string, and then generates values for four solvatochromic parameters. Multiple regression equations relate these parameters to the toxicities (expressed as log10LC50s and log10EC50s, along with 95% confidence intervals) for four species. The system is demonstrated by prediction of toxicity for anilide-type pesticides to the fathead minnow (Pimephales promelas). This software is designed for use on an IBM-compatible personal computer by personnel with minimal toxicology background for rapid estimation of chemical toxicity. The system has numerous applications, with much potential for use in the pharmaceutical industry

Multistep divergent synthesis of benzimidazole linked benzoxazole/benzothiazole via copper catalyzed domino annulation.

PubMed

Liao, Jen-Yu; Selvaraju, Manikandan; Chen, Chih-Hau; Sun, Chung-Ming

2013-04-21

An efficient, facile synthesis of structurally diverse benzimidazole integrated benzoxazole and benzothiazoles has been developed. In a multi-step synthetic sequence, 4-fluoro-3-nitrobenzoic acid was converted into benzimidazole bis-heterocycles, via the intermediacy of benzimidazole linked ortho-chloro amines. The amphiphilic reactivity of this intermediate was designed to achieve the title compounds by the reaction of various acid chlorides and isothiocyanates in a single step through the in situ formation of ortho-chloro anilides and thioureas under microwave irradiation. A versatile one pot domino annulation reaction was developed to involve the reaction of benzimidazole linked ortho-chloro amines with acid chlorides and isothiocyanates. The initial acylation and urea formation followed by copper catalyzed intramolecular C-O and C-S cross coupling reactions furnished the angularly oriented bis-heterocycles which bear a close resemblance to the streptomyces antibiotic UK-1.

Chromatographic resolution of closely related species in pharmaceutical chemistry: dehalogenation impurities and mixtures of halogen isomers.

PubMed

Regalado, Erik L; Zhuang, Ping; Chen, Yadan; Makarov, Alexey A; Schafer, Wes A; McGachy, Neil; Welch, Christopher J

2014-01-07

In recent years, the use of halogen-containing molecules has proliferated in the pharmaceutical industry, where the incorporation of halogens, especially fluorine, has become vitally important for blocking metabolism and enhancing the biological activity of pharmaceuticals. The chromatographic separation of halogen-containing pharmaceuticals from associated isomers or dehalogenation impurities can sometimes be quite difficult. In an attempt to identify the best current tools available for addressing this important problem, a survey of the suitability of four chromatographic method development platforms (ultra high-performance liquid chromatography (UHPLC), core shell HPLC, achiral supercritical fluid chromatography (SFC) and chiral SFC) for separating closely related mixtures of halogen-containing pharmaceuticals and their dehalogenated isosteres is described. Of the 132 column and mobile phase combinations examined for each mixture, a small subset of conditions were found to afford the best overall performance, with a single UHPLC method (2.1 × 50 mm, 1.9 μm Hypersil Gold PFP, acetonitrile/methanol based aqueous eluents containing either phosphoric or perchloric acid with 150 mM sodium perchlorate) affording excellent separation for all samples. Similarly, a survey of several families of closely related halogen-containing small molecules representing the diversity of impurities that can sometimes be found in purchased starting materials for synthesis revealed chiral SFC (Chiralcel OJ-3 and Chiralpak IB, isopropanol or ethanol with 25 mM isobutylamine/carbon dioxide) as well as the UHPLC (2.1 × 50 mm, 1.8 μm ZORBAX RRHD Eclipse Plus C18 and the Gold PFP, acetonitrile/methanol based aqueous eluents containing phosphoric acid) as preferred methods.

Reconciliation of Halogen-Induced Ozone Loss with the Total-Column Ozone Record

NASA Technical Reports Server (NTRS)

Shepherd, T. G.; Plummer, D. A.; Scinocca, J. F.; Hegglin, M. I.; Fioletov, V. E.; Reader, M. C.; Remsberg, E.; von Clarmann, T.; Wang, H. J.

2014-01-01

The observed depletion of the ozone layer from the 1980s onwards is attributed to halogen source gases emitted by human activities. However, the precision of this attribution is complicated by year-to-year variations in meteorology, that is, dynamical variability, and by changes in tropospheric ozone concentrations. As such, key aspects of the total-column ozone record, which combines changes in both tropospheric and stratospheric ozone, remain unexplained, such as the apparent absence of a decline in total-column ozone levels before 1980, and of any long-term decline in total-column ozone levels in the tropics. Here we use a chemistry-climate model to estimate changes in halogen-induced ozone loss between 1960 and 2010; the model is constrained by observed meteorology to remove the eects of dynamical variability, and driven by emissions of tropospheric ozone precursors to separate out changes in tropospheric ozone. We show that halogen-induced ozone loss closely followed stratospheric halogen loading over the studied period. Pronounced enhancements in ozone loss were apparent in both hemispheres following the volcanic eruptions of El Chichon and, in particular, Mount Pinatubo, which significantly enhanced stratospheric aerosol loads. We further show that approximately 40% of the long-term non-volcanic ozone loss occurred before 1980, and that long-term ozone loss also occurred in the tropical stratosphere. Finally, we show that halogeninduced ozone loss has declined by over 10% since stratospheric halogen loading peaked in the late 1990s, indicating that the recovery of the ozone layer is well underway.

Skin Sensitizing Potency of Halogenated Platinum Salts.

EPA Science Inventory

The relationship between occupational exposure to halogenated platinum (Pt) salts and Pt-specific allergic sensitization is well-established. Although human case reports and clinical studies demonstrate that Pt salts are potent skin sensitizers, no studies have been published tha...

Absorption spectroscopy setup for determination of whole human blood and blood-derived materials spectral characteristics

NASA Astrophysics Data System (ADS)

Wróbel, M. S.; Gnyba, M.; Milewska, D.; Mitura, K.; Karpienko, K.

2015-09-01

A dedicated absorption spectroscopy system was set up using tungsten-halogen broadband source, optical fibers, sample holder, and a commercial spectrometer with CCD array. Analysis of noise present in the setup was carried out. Data processing was applied to the absorption spectra to reduce spectral noise, and improve the quality of the spectra and to remove the baseline level. The absorption spectra were measured for whole blood samples, separated components: plasma, saline, washed erythrocytes in saline and human whole blood with biomarkers - biocompatible nanodiamonds (ND). Blood samples had been derived from a number of healthy donors. The results prove a correct setup arrangement, with adequate preprocessing of the data. The results of blood-ND mixtures measurements show no toxic effect on blood cells, which proves the NDs as a potential biocompatible biomarkers.

Novel Carbon Films for Next Generation Rotating Equipment Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michael McNallan; Ali Erdemir; Yury Gogotsi

2006-02-20

This report describes the results of research performed on a new generation of low friction, wear resistant carbon coatings for seals and bearings in high speed rotating equipment. The low friction coatings, Near Frictionless Carbon (NFC), a high hydrogen content diamondlike carbon, and Carbide Derived Carbon (CDC), a conversion coating produced on the surfaces of metal carbides by halogenation, can be applied together or separately to improve the performance of seals and bearings, with benefits to energy efficiency and environmental protection. Because hard carbide ceramics, such as silicon carbide, are widely used in the seals industry, this coating is particularlymore » attractive as a low cost method to improve performance. The technology of CDC has been licensed to an Illinois company, Carbide Derivative Technologies, Inc. (CDTI) to implement the commercialization of this material.« less

Synthesis and receptor binding studies of novel 4,4-disubstituted arylalkyl/arylalkylsulfonyl piperazine and piperidine-based derivatives as a new class of σ1 ligands.

PubMed

Sadeghzadeh, Masoud; Sheibani, Shahab; Ghandi, Mehdi; Daha, Fariba Johari; Amanlou, Massoud; Arjmand, Mohammad; Hasani Bozcheloie, Abolfazl

2013-06-01

This study presents the synthesis and biological evaluation of a new series of arylalkyl/arylalkylsulfonyl piperazine and piperidine-based derivatives as sigma receptor ligands. It was found that a number of halogen substituted sulfonamides display relatively high and low affinities to σ1 and σ2 receptors, respectively. The σ1 affinities and subtype selectivities of four piperidine derivatives were also found to be generally comparable to those of piperazine analogues. Compared to σ1-Rs compounds with n = 0 and 2, those with n = 1 proved to have optimal length of carbon chain by exhibiting higher affinities. Within this series, the 4-benzyl-1-(3-iodobenzylsulfonyl)piperidine sigma ligand was identified with 96-fold σ1/σ2 selectivity ratio (Kiσ1 = 0.96 ± 0.05 nM and Kiσ2 = 91.8 ± 8.1 nM). Copyright © 2013 Elsevier Masson SAS. All rights reserved.

40 CFR 721.535 - Halogenated alkane (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... Section 721.535 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.535 Halogenated alkane (generic). (a) Chemical substance and significant new uses subject to...

40 CFR 65.63 - Performance and group status change requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

... halogen atom mass emission rate to less than 0.45 kilogram per hour (0.99 pound per hour) prior to any... the requirements of paragraph (a)(1) or (2) of this section. The mass emission rate of halogen atoms...

40 CFR 65.63 - Performance and group status change requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... halogen atom mass emission rate to less than 0.45 kilogram per hour (0.99 pound per hour) prior to any... the requirements of paragraph (a)(1) or (2) of this section. The mass emission rate of halogen atoms...

40 CFR 65.63 - Performance and group status change requirements.

Code of Federal Regulations, 2014 CFR

2014-07-01

... halogen atom mass emission rate to less than 0.45 kilogram per hour (0.99 pound per hour) prior to any... the requirements of paragraph (a)(1) or (2) of this section. The mass emission rate of halogen atoms...

40 CFR 65.63 - Performance and group status change requirements.

Code of Federal Regulations, 2012 CFR

2012-07-01

... halogen atom mass emission rate to less than 0.45 kilogram per hour (0.99 pound per hour) prior to any... the requirements of paragraph (a)(1) or (2) of this section. The mass emission rate of halogen atoms...

An Apparatus for Photochemical Studies.

ERIC Educational Resources Information Center

Winter, M. J.; Winter, P. V.

1984-01-01

Describes an apparatus developed for photochemical studies, particularly those involving the fluorescence of halogenated acetones. The apparatus is constructed from equipment normally found in a moderately sized physical chemical laboratory. Also provides background information on some aspects of the photophysics of halogenated propanones. (JN)

Halogen dependent symmetry change in two series of wheel cluster organic frameworks built from La18 tertiary building units.

PubMed

Fang, Wei-Hui; Zhang, Lei; Zhang, Jian; Yang, Guo-Yu

2016-01-25

Two series of wheel cluster organic frameworks (WCOFs) built from La18 tertiary building units are hydrothermally made, which show halogen-dependent structural symmetry, and demonstrate different chiral performances.

SUBSTITUTION REACTIONS FOR THE DETOXIFICATION OF HAZARDOUS CHEMICALS

EPA Science Inventory

Chemical Treatment is one of several treatment techniques used for the remediation of toxic and hazardous chemicals. Chemical treatment in this report is defined as substitution of halogens by hydrogens for the conversion of halogenated organic toxicant into its native hydrocarb...

Incombustible resin composition

NASA Technical Reports Server (NTRS)

Akima, T.

1982-01-01

Incombustible resin compositions composed of aromatic compounds were obtained through (1) combustion polymer material and (2) bisphenol A or halogenated bisphenol A and bisphenol A diglycidl ether or halogenated bisphenol A diglycidyl ether. The aromatic compound is an adduct of bifunctional phenols and bifunctional epoxy resins.

State-of-the art of selective detection and identification of I-, Br-, Cl-, and F-containing compounds in gas chromatography and liquid chromatography.

PubMed

Brede, Cato; Pedersen-Bjergaard, Stig

2004-09-24

This review article presents an overview of halogen-specific detection in gas chromatography (GC) and liquid chromatography (LC). Attention is primarily focused on the use of plasma emission spectroscopy and plasma mass spectrometry as detectors, but other halogen-selective detection principles are also mentioned. Different instrumental configurations are discussed both with respect to technical set-up and performance, the principal reasons for halogen-selective detection are highlighted, and recent applications are reviewed from areas such as environmental chemistry, petroleum characterization, and drug analysis.

Simulation of the transport of halogen species from the equatorial and mid-latitude stratosphere to the polar stratosphere in a two-dimensional model

NASA Technical Reports Server (NTRS)

Yung, Yuk L.; Shia, R. L.; Allen, M.; Zurek, R. W.; Crisp, D.; Wen, J. S.

1988-01-01

The bulk of O sub 3 destruction in the Antarctic stratosphere takes place in the lower stratosphere between 15 and 25 km. Both O sub 3 and the halogen reservoir species have their origins in the higher altitude region (20 to 30 km) in the equatorial and mid-latitude stratosphere. Using the Caltech-JPL two-dimensional residual circulation model, researchers investigate the growth of stratospheric halogen due to the increase of CFCl sub 3 and CF sub 2 Cl sub 2.

Symmetric and asymmetric halogen-containing metallocarboranylporphyrins and uses thereof

DOEpatents

Miura, Michiko; Wu, Haitao

2013-05-21

The present invention is directed to low toxicity boronated compounds and methods for their use in the treatment, visualization, and diagnosis of tumors. More specifically, the present invention is directed to low toxicity halogenated, carborane-containing 5,10,15,20-tetraphenylporphyrin compounds and methods for their use particularly in boron neutron capture therapy (BNCT) and photodynamic therapy (PDT) for the treatment of tumors of the brain, head and neck, and surrounding tissue. The invention is also directed to using these halogenated, carborane-containing tetraphenylporphyrin compounds in methods of tumor imaging and/or diagnosis such as MRI, SPECT, or PET.

Combined Diffraction and Density Functional Theory Calculations of Halogen-Bonded Cocrystal Monolayers

PubMed Central

2013-01-01

This work describes the combined use of synchrotron X-ray diffraction and density functional theory (DFT) calculations to understand the cocrystal formation or phase separation in 2D monolayers capable of halogen bonding. The solid monolayer structure of 1,4-diiodobenzene (DIB) has been determined by X-ray synchrotron diffraction. The mixing behavior of DIB with 4,4′-bipyridyl (BPY) has also been studied and interestingly is found to phase-separate rather than form a cocrystal, as observed in the bulk. DFT calculations are used to establish the underlying origin of this interesting behavior. The DFT calculations are demonstrated to agree well with the recently proposed monolayer structure for the cocrystal of BPY and 1,4-diiodotetrafluorobenzene (DITFB) (the perfluorinated analogue of DIB), where halogen bonding has also been identified by diffraction. Here we have calculated an estimate of the halogen bond strength by DFT calculations for the DITFB/BPY cocrystal monolayer, which is found to be ∼20 kJ/mol. Computationally, we find that the nonfluorinated DIB and BPY are not expected to form a halogen-bonded cocrystal in a 2D layer; for this pair of species, phase separation of the components is calculated to be lower energy, in good agreement with the diffraction results. PMID:24215390

Combined diffraction and density functional theory calculations of halogen-bonded cocrystal monolayers.

PubMed

Sacchi, Marco; Brewer, Adam Y; Jenkins, Stephen J; Parker, Julia E; Friščić, Tomislav; Clarke, Stuart M

2013-12-03

This work describes the combined use of synchrotron X-ray diffraction and density functional theory (DFT) calculations to understand the cocrystal formation or phase separation in 2D monolayers capable of halogen bonding. The solid monolayer structure of 1,4-diiodobenzene (DIB) has been determined by X-ray synchrotron diffraction. The mixing behavior of DIB with 4,4'-bipyridyl (BPY) has also been studied and interestingly is found to phase-separate rather than form a cocrystal, as observed in the bulk. DFT calculations are used to establish the underlying origin of this interesting behavior. The DFT calculations are demonstrated to agree well with the recently proposed monolayer structure for the cocrystal of BPY and 1,4-diiodotetrafluorobenzene (DITFB) (the perfluorinated analogue of DIB), where halogen bonding has also been identified by diffraction. Here we have calculated an estimate of the halogen bond strength by DFT calculations for the DITFB/BPY cocrystal monolayer, which is found to be ∼20 kJ/mol. Computationally, we find that the nonfluorinated DIB and BPY are not expected to form a halogen-bonded cocrystal in a 2D layer; for this pair of species, phase separation of the components is calculated to be lower energy, in good agreement with the diffraction results.

When will the Antarctic Ozone Hole Recover?

NASA Technical Reports Server (NTRS)

Newman, Paul A.; Nash, Eric R.; Kawa, S. Randolph; Montzka, Steve

2006-01-01

The Antarctic ozone hole develops each year and culminates by early Spring. Antarctic ozone values have been monitored since 1979 using satellite observations from the .TOMS instrument. The severity of the hole has been assessed from TOMS using the minimum total ozone value from the October monthly mean (depth of the hole) and by calculating the average size during the September-October period. Ozone is mainly destroyed by halogen catalytic cycles, and these losses are modulated by temperature variations in the collar of the polar lower stratospheric vortex. In this presentation, we show the relationships of halogens and temperature to, both the size and depth of the hole. Because atmospheric halogen levels are responding to international agreements that limit or phase out production, the amount of halogens in the stratosphere should decrease over the next few decades. Using projections of halogen levels combined with age-of-air estimates, we find that the ozone hole is recovering at an extremely slow rate and that large ozone holes will regularly recur over the next 2 decades. The ozone hole will begin to show first signs of recovery in about 2023, and the hole will fully recover to pre-1980 levels in approximately 2070. This 2070 recovery is 20 years later than recent projections.

Amyloid-like aggregates formation by bovine apo-carbonic anhydrase in various alcohols: A comparative study.

PubMed

Es-Haghi, Ali; Ebrahim-Habibi, Azadeh; Sabbaghian, Marjan; Nemat-Gorgani, Mohsen

2016-11-01

Peptides and proteins convert from their native states to amyloid fibrillar aggregates in a number of pathological conditions. Characterizing these species could provide useful information on their pathogenicity and the key factors involved in their generation. In this study, we have observed the ability of the model protein apo-bovine carbonic anhydrase (apo-BCA) to form amyloid-like aggregates in the presence of halogenated and non-halogenated alcohols. Far-UV circular dichroism, ThT fluorescence, atomic force microscopy and dynamic light scattering were used to characterize these structures. The concentration required for effective protein aggregation varied between the solvents, with non-halogenated alcohols acting in a wider range. These aggregates show amyloid-like structures as determined by specific techniques used for characterizing amyloid structures. Oligomers were obtained with various size distributions, but fibrillar structures were not observed. Use of halogenated alcohols resulted into smaller hydrodynamic radii, and most stable oligomers were formed in hexafluoropropan-2-ol (HFIP). At optimal concentrations used to generate these structures, the non-halogenated alcohols showed higher hydrophobicity, which may be related to the lower stability of the generated oligomers. These oligomers have the potential to be used as models in the search for effective treatments in proteinopathies. Copyright © 2016 Elsevier B.V. All rights reserved.

Performance analysis of photoresistor and phototransistor for automotive’s halogen and xenon bulbs light output

NASA Astrophysics Data System (ADS)

Rammohan, A.; Kumar, C. Ramesh

2017-11-01

Illumination of any light is measured using a different kind of calibrated equipment’s available in the market such as a goniometer, spectral radiometer, photometer, Lux meter and camera based systems which directly display the illumination of automotive headlights light distribution in the unit of lux, foot-candles, lumens/sq. ft. and Lambert etc., In this research, we dealt with evaluating the photo resistor or Light Dependent Resistor (LDR) and phototransistor whether it is useful for sensing light patterns of Automotive Halogen and Xenon bulbs. The experiments are conducted during night hours under complete dark space. We have used the headlamp setup available in TATA SUMO VICTA vehicle in the Indian market and conducted the experiments separately for Halogen and Xenon bulbs under low and high beam operations at various degrees and test points within ten meters of distance. Also, we have compared the light intensity of halogen and xenon bulbs to prove the highest light intensity between halogen and Xenon bulbs. After doing a rigorous test with these two sensors it is understood both are good to sensing beam pattern of automotive bulbs and even it is good if we use an array of sensors or a mixed combination of sensors for measuring illumination purposes under perfect calibrations.

Characterization of anthropogenic impacts in a large urban center by examining the spatial distribution of halogenated flame retardants.

PubMed

Wei, Yan-Li; Bao, Lian-Jun; Wu, Chen-Chou; Zeng, Eddy Y

2016-08-01

Anthropogenic impacts have continuously intensified in mega urban centers with increasing urbanization and growing population. The spatial distribution pattern of such impacts can be assessed with soil halogenated flame retardants (HFRs) as HFRs are mostly derived from the production and use of various consumer products. In the present study, soil samples were collected from the Pearl River Delta (PRD), a large urbanized region in southern China, and its surrounding areas and analyzed for a group of HFRs, i.e., polybrominated diphenyl ethers (PBDEs), decabromodiphenyl ethane, bis(hexachlorocyclopentadieno)cyclooctane (DP) and hexabromobenzene. The sum concentrations of HFRs and PBDEs were in the ranges of 0.66-6500 and 0.37-5700 (mean: 290 and 250) ng g(-1) dry weight, respectively, around the middle level of the global range. BDE-209 was the predominant compound likely due to the huge amounts of usage and its persistence. The concentrations of HFRs were greater in the land-use types of residency, industry and landfill than in agriculture, forestry and drinking water source, and were also greater in the central PRD than in its surrounding areas. The concentrations of HFRs were moderately significantly (r(2) = 0.32-0.57; p < 0.05) correlated with urbanization levels, population densities and gross domestic productions in fifteen administrative districts. The spatial distribution of DP isomers appeared to be stereoselective as indicated by the similarity in the spatial patterns for the ratio of anti-DP versus the sum of DP isomers (fanti-DP) and DP concentrations. Finally, the concentrations of HFRs sharply decreased with increasing distance from an e-waste recycling site, indicating that e-waste derived HFRs largely remained in local soil. Copyright © 2016 Elsevier Ltd. All rights reserved.

Synthetic cannabinoid JWH-018 and its halogenated derivatives JWH-018-Cl and JWH-018-Br impair Novel Object Recognition in mice: Behavioral, electrophysiological and neurochemical evidence.

PubMed

Barbieri, M; Ossato, A; Canazza, I; Trapella, C; Borelli, A C; Beggiato, S; Rimondo, C; Serpelloni, G; Ferraro, L; Marti, M

2016-10-01

It is well known that an impairment of learning and memory function is one of the major physiological effects caused by natural or synthetic cannabinoid consumption in rodents, nonhuman primates and in humans. JWH-018 and its halogenated derivatives (JWH-018-Cl and JWH-018-Br) are synthetic CB1/CB2 cannabinoid agonists, illegally marketed as "Spice" and "herbal blend" for their Cannabis-like psychoactive effects. In the present study the effects of acute exposure to JWH-018, JWH-018-Cl, JWH-018-Br (JWH-018-R compounds) and Δ(9)-THC (for comparison) on Novel Object Recognition test (NOR) has been investigated in mice. Moreover, to better characterize the effects of JWH-018-R compounds on memory function, in vitro electrophysiological and neurochemical studies in hippocampal preparations have been performed. JWH-018, JWH-018-Cl and JWH-018-Br dose-dependently impaired both short- and long-memory retention in mice (respectively 2 and 24 h after training session). Their effects resulted more potent respect to that evoked by Δ(9)-THC. Moreover, in vitro studies showed as JWH-018-R compounds negatively affected electrically evoked synaptic transmission, LTP and aminoacid (glutamate and GABA) release in hippocampal slices. Behavioral, electrophysiological and neurochemical effects were fully prevented by CB1 receptor antagonist AM251 pretreatment, suggesting a CB1 receptor involvement. These data support the hypothesis that synthetic JWH-018-R compounds, as Δ(9)-THC, impair cognitive function in mice by interfering with hippocampal synaptic transmission and memory mechanisms. This data outline the danger that the use and/or abuse of these synthetic cannabinoids may represent for the cognitive process in human consumer. Copyright © 2016 Elsevier Ltd. All rights reserved.

Studies toward the oxidative and reductive activation of C-S bonds in 2'-S-aryl-2'-thiouridine derivatives.

PubMed

Rayala, Ramanjaneyulu; Giuglio-Tonolo, Alain; Broggi, Julie; Terme, Thierry; Vanelle, Patrice; Theard, Patricia; Médebielle, Maurice; Wnuk, Stanislaw F

2016-04-21

Studies directed toward the oxidative and reductive desulfurization of readily available 2'- S -aryl-2'-thiouridine derivatives were investigated with the prospect to functionalize the C2'-position of nucleosides. The oxidative desulfurization-difluorination strategy was successful on 2-(arylthio)alkanoate surrogates, while extension of the combination of oxidants and fluoride sources was not an efficient fluorination protocol when applied to 2'- S -aryl-2'-thiouridine derivatives, resulting mainly in C5-halogenation of the pyrimidine ring and C2'-monofluorination without desulfurization. Cyclic voltammetry of 2'-arylsulfonyl-2'-deoxyuridines and their 2'-fluorinated analogues showed that cleavage of the arylsulfone moiety could occur, although at relatively high cathodic potentials. While reductive-desulfonylation of 2'-arylsulfonyl-2'-deoxyuridines with organic electron donors (OEDs) gave predominantly base-induced furan type products, chemical (OED) and electrochemical reductive-desulfonylation of the α-fluorosulfone derivatives yielded the 2'-deoxy-2'-fluorouridine and 2',3'-didehydro-2',3'-dideoxy-2'-fluorouridine derivatives. These results provided good evidence of the generation of a C2'-anion through carbon-sulfur bond cleavage, opening new horizons for the reductive-functionalization approaches in nucleosides.

Studies toward the oxidative and reductive activation of C-S bonds in 2'-S-aryl-2'-thiouridine derivatives

PubMed Central

Rayala, Ramanjaneyulu; Giuglio-Tonolo, Alain; Broggi, Julie; Terme, Thierry; Vanelle, Patrice; Theard, Patricia; Médebielle, Maurice; Wnuk, Stanislaw F.

2016-01-01

Studies directed toward the oxidative and reductive desulfurization of readily available 2'-S-aryl-2'-thiouridine derivatives were investigated with the prospect to functionalize the C2'-position of nucleosides. The oxidative desulfurization-difluorination strategy was successful on 2-(arylthio)alkanoate surrogates, while extension of the combination of oxidants and fluoride sources was not an efficient fluorination protocol when applied to 2'-S-aryl-2'-thiouridine derivatives, resulting mainly in C5-halogenation of the pyrimidine ring and C2'-monofluorination without desulfurization. Cyclic voltammetry of 2'-arylsulfonyl-2'-deoxyuridines and their 2'-fluorinated analogues showed that cleavage of the arylsulfone moiety could occur, although at relatively high cathodic potentials. While reductive-desulfonylation of 2'-arylsulfonyl-2'-deoxyuridines with organic electron donors (OEDs) gave predominantly base-induced furan type products, chemical (OED) and electrochemical reductive-desulfonylation of the α-fluorosulfone derivatives yielded the 2'-deoxy-2'-fluorouridine and 2',3'-didehydro-2',3'-dideoxy-2'-fluorouridine derivatives. These results provided good evidence of the generation of a C2'-anion through carbon-sulfur bond cleavage, opening new horizons for the reductive-functionalization approaches in nucleosides. PMID:27019535

Trigonal Mn3 and Co3 Clusters Supported by Weak-Field Ligands: A Structural, Spectroscopic, Magnetic, and Computational Investigation into the Correlation of Molecular and Electronic Structure

PubMed Central

Fout, Alison R.; Xiao, Dianne J.; Zhao, Qinliang; Harris, T. David; King, Evan R.; Eames, Emily V.; Zheng, Shao-Liang; Betley, Theodore A.

2012-01-01

Transamination of divalent transition metal starting materials (M2(N(SiMe3)2)4, M = Mn, Co) with hexadentate ligand platforms RLH6 (RLH6 = MeC(CH2NPh-o-NR)3 where R = H, Ph, Mes (Mes = Mesityl)) or H,CyLH6 = 1,3,5-C6H9(NHPh-o-NH2)3 with added pyridine or tertiary phosphine co-ligands afforded trinuclear complexes of the type (RL)Mn3(py)3 and (RL)Co3(PMe2R’)3 (R’ = Me, Ph). While the sterically less encumbered ligand varieties, HL or PhL, give rise to local square-pyramidal geometries at each of the bound metal atoms, with four anilides forming an equatorial plane and an exogenous pyridine or phosphine in the apical site, the mesityl-substituted ligand (MesL) engenders local tetrahedral coordination. Both the neutral Mn3 and Co3 clusters feature S = 1/2 ground states, as determined by dc magnetometry, 1H NMR spectroscopy, and low-temperature EPR spectroscopy. Within the Mn3 clusters, the long internuclear Mn–Mn separations suggest minimal direct metal-metal orbital overlap. Accordingly, fits to variable-temperature magnetic susceptibility data reveal the presence of weak antiferromagnetic superexchange interactions through the bridging anilide ligands with exchange couplings ranging from J = −16.8 to −42 cm−1. Conversely, the short Co–Co interatomic distances suggest a significant degree of direct metal-metal orbital overlap, akin to the related Fe3 clusters. With the Co3 series, the S = 1/2 ground state can be attributed to population of a single molecular orbital manifold that arises from mixing of the metal- and o-phenylenediamide (OPDA) ligand-based frontier orbitals. Chemical oxidation of the neutral Co3 clusters affords diamagnetic cationic clusters of the type [(RL)Co3(PMe2R)3]+. DFT calculations on the neutral (S = ½) and cationic (S = 0) Co3 clusters reveal that oxidation occurs at an oribital with contributions from both the Co3 core and OPDA subunits. The predicted bond elongations within the ligand OPDA units are corroborated by the ligand bond perturbations observed by X-ray crystallography. PMID:22991939

40 CFR 372.3 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-07-01

..., roasters, and foundry furnaces). (8) Titanium dioxide chloride process oxidation reactors. (9) Methane... sulfur values from spent sulfuric acid. (12) Halogen acid furnaces (HAFs) for the production of acid from halogenated hazardous waste generated by chemical production facilities where the furnace is located on the...

40 CFR 372.3 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-07-01

..., roasters, and foundry furnaces). (8) Titanium dioxide chloride process oxidation reactors. (9) Methane... sulfur values from spent sulfuric acid. (12) Halogen acid furnaces (HAFs) for the production of acid from halogenated hazardous waste generated by chemical production facilities where the furnace is located on the...

40 CFR 372.3 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-07-01

.... (9) Methane reforming furnaces. (10) Pulping liquor recovery furnaces. (11) Combustion devices used... production of acid from halogenated hazardous waste generated by chemical production facilities where the furnace is located on the site of a chemical production facility, the acid product has a halogen acid...

Mouse Model of Halogenated Platinum Salt Hypersensitivity

EPA Science Inventory

Occupational exposure to halogenated platinum salts can trigger the development of asthma. Concern for increased asthma risk exists for the general population due to the use of platinum (Pt) in catalytic converters and its emerging use as a diesel fuel additive. To investigate a...

40 CFR 63.11496 - What are the standards and compliance requirements for process vents?

Code of Federal Regulations, 2014 CFR

2014-07-01

... of halogen atoms in accordance with § 63.115(d)(2)(v). Alternatively, you may elect to designate the... 20 parts per million by volume (ppmv). (2) Reduce the halogen atom mass emission rate before the...

40 CFR 63.2450 - What are my general requirements for complying with this subpart?

Code of Federal Regulations, 2012 CFR

2012-07-01

..., as defined in § 63.2550, by calculating the mass emission rate of halogen atoms in accordance with... determine the halogen atom emission rate prior to the combustion device according to the procedures in § 63...

40 CFR 63.11496 - What are the standards and compliance requirements for process vents?

Code of Federal Regulations, 2013 CFR

2013-07-01

... of halogen atoms in accordance with § 63.115(d)(2)(v). Alternatively, you may elect to designate the... 20 parts per million by volume (ppmv). (2) Reduce the halogen atom mass emission rate before the...

Biological Activity of Recently Discovered Halogenated Marine Natural Products

PubMed Central

Gribble, Gordon W.

2015-01-01

This review presents the biological activity—antibacterial, antifungal, anti-parasitic, antiviral, antitumor, antiinflammatory, antioxidant, and enzymatic activity—of halogenated marine natural products discovered in the past five years. Newly discovered examples that do not report biological activity are not included. PMID:26133553

Organic halogenated contaminants in mother-fetus pairs of harbor seals (Phoca vitulina richardii) from Alaska, 2000-2002

USDA-ARS?s Scientific Manuscript database

Environmental stressors may interfere with foraging, survival and reproduction of marine mammals resulting in marine mammal population decline. In this study, organic halogenated pollutants [OHs, including organochlorine pesticides, polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCN...

Halogenated Solvent Cleaning Compliance Assistance Memoranda for the National Emission Standards for Hazardous Air Pollutants (NESHAP)

EPA Pesticide Factsheets

This page contains three documents, one from 1997, one from 1999, and one from 2001, that provide further clarification on complying with the National Emission Standards for Hazardous Air Pollutants (NESHAP) for Halogenated Solvent Cleaning.

In silico validation and structure activity relationship study of a series of pyridine-3-carbohydrazide derivatives as potential anticonvulsants in generalized and partial seizures.

PubMed

Sinha, Reema; Sara, Udai Vir Singh; Khosa, Ratan Lal; Stables, James; Jain, Jainendra

2013-06-01

A series of twelve compounds (Compounds RNH1-RNH12) of acid hydrazones of pyridine-3-carbohydrazide or nicotinic acid hydrazide was synthesized and evaluated for anticonvulsant activity by MES, scPTZ, minimal clonic seizure and corneal kindling seizure test. Neurotoxicity was also determined for these compounds by rotarod test. Results showed that halogen substitution at meta and para position of phenyl ring exhibited better protection than ortho substitution. Compounds RNH4 and RNH12, were found to be the active analogs displaying 6Hz ED50 of 75.4 and 14.77 mg/kg while the corresponding MES ED50 values were 113.4 and 29.3 mg/kg respectively. In addition, compound RNH12 also showed scPTZ ED50 of 54.2 mg/kg. In the series, compound RNH12 with trifluoromethoxy substituted phenyl ring was the most potent analog exhibiting protection in all four animal models of epilepsy. Molecular docking study has also shown significant binding interactions of these two compounds with 1OHV, 2A1H and 1PBQ receptors. Thus, N-[(meta or para halogen substituted) benzylidene] pyridine-3-carbohydrazides could be used as lead compounds in anticonvulsant drug design and discovery.

Photonics and application of dipyrrinates in the optical devices

NASA Astrophysics Data System (ADS)

Aksenova, Iu; Bashkirtsev, D.; Prokopenko, A.; Kuznetsova, R.; Dudina, N.; Berezin, M.

2016-08-01

In this paper spectral-luminescent, lasing, photochemical, and sensory characteristics of a number of Zn(II) and B(III) coordination complexes with dipyrrinates with different structures are presented. We have discussed relations of the structure of investigated compounds and formed solvates with their optical characteristics. The results showed that alkyl substituted dipyrrinates derivatives have excellent luminescent characteristics and demonstrated effective lasing upon excitation of Nd:YAG-laser. They can be used as active media for liquid tunable lasers. Zinc and boron fluoride complexes of dipyrrinates with heavy atoms in structure don't have fluorescence but have long-lived emission due to increased nonradiative intersystem processes in the excited state by the mechanism of a heavy atom. For solid samples based on halogenated complexes was found dependency of the long-lived emission intensity of the oxygen concentration in gas flow. The presence of line segment indicates the possibility of the use of these complexes as a basis for creation of optical sensors for oxygen. Moreover, results of a study of halogen-substituted aza-complexes under irradiation are presented. Such complexes are promising for the creating media for generation of singlet oxygen (1O2), which is important for photodynamic therapy in medicine and photocatalytic reactions in the industry.

Dissolved organic matter composition drives the marine production of brominated very short-lived substances.

PubMed

Liu, Yina; Thornton, Daniel C O; Bianchi, Thomas S; Arnold, William A; Shields, Michael R; Chen, Jie; Yvon-Lewis, Shari A

2015-03-17

Brominated very short-lived substances (BrVSLS), such as bromoform, are important trace gases for stratospheric ozone chemistry. These naturally derived trace gases are formed via bromoperoxidase-mediated halogenation of dissolved organic matter (DOM) in seawater. Information on DOM type in relation to the observed BrVSLS concentrations in seawater, however, is scarce. We examined the sensitivity of BrVSLS production in relation to the presence of specific DOM moieties. A total of 28 model DOM compounds in artificial seawater were treated with vanadium bromoperoxidase (V-BrPO). Our results show a clear dependence of BrVSLS production on DOM type. In general, molecules that comprise a large fraction of the bulk DOM pool did not noticeably affect BrVSLS production. Only specific cell metabolites and humic acid appeared to significantly enhance BrVSLS production. Amino acids and lignin phenols suppressed enzyme-mediated BrVSLS production and may instead have formed halogenated nonvolatile molecules. Dibromomethane production was not observed in any experiments, suggesting it is not produced by the same pathway as the other BrVSLS. Our results suggest that regional differences in DOM composition may explain the observed BrVSLS concentration variability in the global ocean. Ultimately, BrVSLS production and concentrations are likely affected by DOM composition, reactivity, and cycling in the ocean.

Perspective on the Role of Negative Ions and Ion-Ion Plasmas in Heavy Ion Fusion Science, Magnetic Fusion Energy,and Related Fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grisham, L. R.; Kwan, J. W.

2008-08-01

Some years ago it was suggested that halogen negative ions could offer a feasible alternative path to positive ions as a heavy ion fusion driver beam which would not suffer degradation due to electron accumulation in the accelerator and beam transport system, and which could be converted to a neutral beam by photodetachment near the chamber entrance if desired. Since then, experiments have demonstrated that negative halogen beams can be extracted and accelerated away from the gas plume near the source with a surviving current density close to what could be achieved with a positive ion of similar mass, andmore » with comparable optical quality. In demonstrating the feasibility of halogen negative ions as heavy ion driver beams, ion - ion plasmas, an interesting and somewhat novel state of matter, were produced. These plasmas, produced near the extractor plane of the sources, appear, based upon many lines of experimental evidence, to consist of almost equal densities of positive and negative chlorine ions, with only a small component of free electrons. Serendipitously, the need to extract beams from this plasma for driver development provides a unique diagnostic tool to investigate the plasma, since each component - positive ions, negative ions, and electrons - can be extracted and measured separately. We discuss the relevance of these observations to understanding negative ion beam extraction from electronegative plasmas such as halogens, or the more familiar hydrogen of magnetic fusion ion sources. We suggest a concept which might improve negative hydrogen extraction by the addition of a halogen. The possibility and challenges of producing ion - ion plasmas with thin targets of halogens or, perhaps, salt, is briefly addressed.« less

Chiral halogenated Schiff base compounds: green synthesis, anticancer activity and DNA-binding study

NASA Astrophysics Data System (ADS)

Ariyaeifar, Mahnaz; Amiri Rudbari, Hadi; Sahihi, Mehdi; Kazemi, Zahra; Kajani, Abolghasem Abbasi; Zali-Boeini, Hassan; Kordestani, Nazanin; Bruno, Giuseppe; Gharaghani, Sajjad

2018-06-01

Eight enantiomerically pure halogenated Schiff base compounds were synthesized by reaction of halogenated salicylaldehydes with 3-Amino-1,2-propanediol (R or S) in water as green solvent at ambient temperature. All compounds were characterized by elemental analyses, NMR (1H and 13C), circular dichroism (CD) and FT-IR spectroscopy. FS-DNA binding studies of these compounds carried out by fluorescence quenching and UV-vis spectroscopy. The obtained results revealed that the ligands bind to DNA as: (Rsbnd ClBr) > (Rsbnd Cl2) > (Rsbnd Br2) > (Rsbnd I2) and (Ssbnd ClBr) > (Ssbnd Cl2) > (Ssbnd Br2) > (Ssbnd I2), indicating the effect of halogen on binding constant. In addition, DNA-binding constant of the Ssbnd and R-enantiomers are different from each other. The ligands can form halogen bonds with DNA that were confirmed by molecular docking. This method was also measured the bond distances and bond angles. The study of obtained data can have concluded that binding affinity of the ligands to DNA depends on strength of halogen bonds. The potential anticancer activity of ligands were also evaluated on MCF-7 and HeLa cancer cell lines by using MTT assay. The results showed that the anticancer activity and FS-DNA interaction is significantly dependent on the stereoisomers of Schiff base compounds as R-enantiomers displayed significantly higher activity than S-enantiomers. The molecular docking was also used to illustrate the specific DNA-binding of synthesized compounds and groove binding mode of DNA interaction was proposed for them. In addition, molecular docking results indicated that there are three types of bonds (Hsbnd and X-bond and hX-bond) between synthesized compounds and base pairs of DNA.

Transformation of bisphenol A in water distribution systems: a pilot-scale study.

PubMed

Li, Cong; Wang, Zilong; Yang, Y Jeffrey; Liu, Jingqing; Mao, Xinwei; Zhang, Yan

2015-04-01

Halogenations of bisphenol A (BPA) in a pilot-scale water distribution system (WDS) of a cement-lined ductile cast iron pipe were investigated. The water in the pilot-scale WDS was chlorinated with a free chlorine concentration of 0.7 mg L(-1) using sodium hypochlorite, and with an initial BPA concentration of 100 μg L(-1) was spiked in the WDS. Halogenated compounds in the BPA experiments were identified using EI/GC/MS and GC. Several BPA congeners, including 2-chlorobisphenol A (MCBPA), dichlorobisphenol A (D2-CBPA), 2,2',6-trichlorobisphenol A (T3CBPA), 2,2',6,6'-tetrachlorobisphenol A (T4CBPA), 2-bromobisphenol A (MBBPA), and bromochlorobisphenol A (MBMCBPA) were found. Moreover, further halogenation yielded other reaction intermediates, including 2,4,6-trichlorophenol (T3CP), dichlorobisphenol A, bromodichlorophenol, and dibromochlorophenol. After halogenation for 120min, most of the abovementioned reaction intermediates disappeared and were replaced by trihalomethanes (THMs). Based on these experimental findings, the halogenation process of BPA oxidation in a WDS includes three stages: (1) halogenation on the aromatic ring; (2) chlorine or bromine substitution followed by cleavage of the α-C bond on the isopropyl moiety with a positive partial charge and a β'-C bond on the benzene moiety with a negative partial charge; and (3) THMs and a minor HAA formation from phenolic intermediates through the benzene ring opening with a chlorine and bromine substitution of the hydrogen on the carbon atoms. The oxidation mechanisms of the entire transformation from BPA to THM/HAA in the WDS were proposed. Copyright © 2014 Elsevier Ltd. All rights reserved.

Observations and modeling of bromine induced mercury oxidation in the tropical free troposphere during TORERO

NASA Astrophysics Data System (ADS)

Coburn, Sean; Wang, Siyuan; terSchure, Arnout; Evans, Matt; Volkamer, Rainer

2013-04-01

The Tropical Ocean tRoposphere Exchange experiment TORERO (Jan/Feb 2012) probed air-sea exchange of very short lived halogens and organic carbon species over the full tropospheric air column above the eastern tropical Pacific Ocean. It is well known that halogens influence the oxidative capacity in the marine boundary layer, but their distribution and abundance is less clear in the tropical free troposphere, where most of tropospheric ozone mass resides, and about 80% of the global methane destruction occurs. The oxidation of elemental mercury (GEM) by halogens (i.e., bromine) further forms gaseous oxidized mercury (GOM), and this oxidation is accelerated at the low temperatures in the free troposphere compared to the boundary layer. Free tropospheric halogen radical abundances are thus of particular importance to understand the entry pathways for GOM deposition from the free troposphere to ecosystem, and the subsequent bio-accumulation of this neurotoxin. This presentation summarizes new observational evidence for halogen vertical distributions over the full tropospheric air column, and their abundance in the tropical troposphere, at mid-latitudes in the Northern and Southern hemisphere. BrO and IO were measured simultaneously by the CU Airborne MAX-DOAS instrument, and organic halogen precursors were measured by online GC-MS (TOGA) during 22 research flights aboard the NSF/NCAR GV aircraft. We employ atmospheric box modeling constrained by observations of gas-phase hydrocarbons, aerosols, photolysis frequencies, and meterological parameters measured aboard the plane to test the observed BrO and IO abundances, and evaluate the rate of GEM oxidation in light of recent updates about the stability of the Hg-Br adduct, and it's fate (Goodsite et al., 2012; Dibble et al., 2012). Finally, we compare our measurements with output from the GEOS-Chem model for selected case studies.

The anomalous halogen bonding interactions between chlorine and bromine with water in clathrate hydrates.

PubMed

Dureckova, Hana; Woo, Tom K; Udachin, Konstantin A; Ripmeester, John A; Alavi, Saman

2017-10-13

Clathrate hydrate phases of Cl 2 and Br 2 guest molecules have been known for about 200 years. The crystal structure of these phases was recently re-determined with high accuracy by single crystal X-ray diffraction. In these structures, the water oxygen-halogen atom distances are determined to be shorter than the sum of the van der Waals radii, which indicates the action of some type of non-covalent interaction between the dihalogens and water molecules. Given that in the hydrate phases both lone pairs of each water oxygen atom are engaged in hydrogen bonding with other water molecules of the lattice, the nature of the oxygen-halogen interactions may not be the standard halogen bonds characterized recently in the solid state materials and enzyme-substrate compounds. The nature of the halogen-water interactions for the Cl 2 and Br 2 molecules in two isolated clathrate hydrate cages has recently been studied with ab initio calculations and Natural Bond Order analysis (Ochoa-Resendiz et al. J. Chem. Phys. 2016, 145, 161104). Here we present the results of ab initio calculations and natural localized molecular orbital analysis for Cl 2 and Br 2 guests in all cage types observed in the cubic structure I and tetragonal structure I clathrate hydrates to characterize the orbital interactions between the dihalogen guests and water. Calculations with isolated cages and cages with one shell of coordinating molecules are considered. The computational analysis is used to understand the nature of the halogen bonding in these materials and to interpret the guest positions in the hydrate cages obtained from the X-ray crystal structures.

Extending Halogen-based Medicinal Chemistry to Proteins

PubMed Central

El Hage, Krystel; Pandyarajan, Vijay; Phillips, Nelson B.; Smith, Brian J.; Menting, John G.; Whittaker, Jonathan; Lawrence, Michael C.; Meuwly, Markus; Weiss, Michael A.

2016-01-01

Insulin, a protein critical for metabolic homeostasis, provides a classical model for protein design with application to human health. Recent efforts to improve its pharmaceutical formulation demonstrated that iodination of a conserved tyrosine (TyrB26) enhances key properties of a rapid-acting clinical analog. Moreover, the broad utility of halogens in medicinal chemistry has motivated the use of hybrid quantum- and molecular-mechanical methods to study proteins. Here, we (i) undertook quantitative atomistic simulations of 3-[iodo-TyrB26]insulin to predict its structural features, and (ii) tested these predictions by X-ray crystallography. Using an electrostatic model of the modified aromatic ring based on quantum chemistry, the calculations suggested that the analog, as a dimer and hexamer, exhibits subtle differences in aromatic-aromatic interactions at the dimer interface. Aromatic rings (TyrB16, PheB24, PheB25, 3-I-TyrB26, and their symmetry-related mates) at this interface adjust to enable packing of the hydrophobic iodine atoms within the core of each monomer. Strikingly, these features were observed in the crystal structure of a 3-[iodo-TyrB26]insulin analog (determined as an R6 zinc hexamer). Given that residues B24–B30 detach from the core on receptor binding, the environment of 3-I-TyrB26 in a receptor complex must differ from that in the free hormone. Based on the recent structure of a “micro-receptor” complex, we predict that 3-I-TyrB26 engages the receptor via directional halogen bonding and halogen-directed hydrogen bonding as follows: favorable electrostatic interactions exploiting, respectively, the halogen's electron-deficient σ-hole and electronegative equatorial band. Inspired by quantum chemistry and molecular dynamics, such “halogen engineering” promises to extend principles of medicinal chemistry to proteins. PMID:27875310

Temperature analysis during bonding of brackets using LED or halogen light base units.

PubMed

Silva, Paulo César Gomes; De Fátima Zanirato Lizarelli, Rosane; Moriyama, Lílian Tan; De Toledo Porto Neto, Sizenando; Bagnato, Vanderlei Salvador

2005-02-01

The purpose of our investigation is to compare the intrapulpal temperature changes following blue LED system and halogen lamp irradiation at the enamel surface of permanent teeth. The fixation of brackets using composite resin is more comfortable and faster when using a photo-curable composite. Several light sources can be used: halogens, arc plasma, lasers, and recently blue LED systems. An important aspect to be observed during such a procedures is the temperature change. In this study, we have used nine human extracted permanent teeth: three central incisors, three lateral incisors, and three canines. Teeth were exposed to two light sources: blue LED system (preliminary commercial model LEC 470-II) and halogen lamp (conventional photo-cure equipment). The surface of teeth was exposed for 20, 40, and 60 sec at the buccal and lingual enamel surface with an angle of 45 degrees. Temperature values measured by a thermistor placed at pulpar chamber were read in time intervals of 1 sec. We obtained plots showing the temperature evolution as a function of time for each experiment. There is a correlation between heating quantity and exposition time of light source: with increasing exposition time, heating increases into the pulpal chamber. The halogen lamp showed higher heating than the LED system, which showed a shorter time of cooling than halogen lamp. The blue LED system seems like the indicated light source for photo-cure of composite resin during the bonding of brackets. The fixation of brackets using composite resin is more comfortable and faster when using a photo-curable composite. Blue LED equipment did not heat during its use. This could permit a shorter clinical time of operation and better performance.

METABOLIC FATE OF HALOGENATED DISINFECTION BY-PRODUCTS IN VIVO, AND RELATION TO BIOLOGICAL ACTIVITY

EPA Science Inventory

Objectives/Hypotheses: Halogenated by-products of drinking water disinfection are of concern because of uncertainty over their health effects, particularly an increased risk of kidney and bladder cancer and widespread consumption. Due to their abundance relative to other h...

40 CFR 721.8675 - Halogenated pyridines.

Code of Federal Regulations, 2013 CFR

2013-07-01

... CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8675 Halogenated pyridines. (a) Chemical substances and significant new uses subject to... subject to reporting under this section for the significant new uses described in paragraph (a)(1)(i) of...

40 CFR 721.8675 - Halogenated pyridines.

Code of Federal Regulations, 2014 CFR

2014-07-01

... CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8675 Halogenated pyridines. (a) Chemical substances and significant new uses subject to... subject to reporting under this section for the significant new uses described in paragraph (a)(1)(i) of...

40 CFR 721.8675 - Halogenated pyridines.

Code of Federal Regulations, 2012 CFR

2012-07-01

... CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8675 Halogenated pyridines. (a) Chemical substances and significant new uses subject to... subject to reporting under this section for the significant new uses described in paragraph (a)(1)(i) of...

Impact of enhanced ozone deposition and halogen chemistry on model performance

EPA Science Inventory

In this study, an enhanced ozone deposition scheme due to the interaction of iodide in sea-water and atmospheric ozone and the detailed chemical reactions of organic and inorganic halogen species are incorporated into the hemispheric Community Multiscale Air Quality model. Prelim...

The Impact of New Estimates of Mixing Ratio and Flux-based Halogen Scenarios on Ozone Evolution

NASA Technical Reports Server (NTRS)

Oman, Luke D.; Douglass, Anne R.; Liang, Qing; Strahan, Susan E.

2014-01-01

The evolution of ozone in the 21st century has been shown to be mainly impacted by the halogen emissions scenario and predicted changes in the circulation of the stratosphere. New estimates of mixing ratio and flux-based emission scenarios have been produced from the SPARC Lifetime Assessment 2013. Simulations using the Goddard Earth Observing System Chemistry-Climate Model (GEOSCCM) are conducted using this new A1 2014 halogen scenario and compared to ones using the A1 2010 scenario. This updated version of GEOSCCM includes a realistic representation of the Quasi-Biennial Oscillation and improvements related to the break up of the Antarctic polar vortex. We will present results of the ozone evolution over the recent past and 21st century to the A1 2010, A1 2014 mixing ratio, and an A1 2014 flux-based halogen scenario. Implications of the uncertainties in these estimates as well as those from possible circulation changes will be discussed.

Optrode for sensing hydrocarbons

DOEpatents

Miller, Holly; Milanovich, Fred P.; Hirschfeld, Tomas B.; Miller, Fred S.

1987-01-01

A two-phase system employing the Fujiwara reaction is provided for the fluorometric detection of halogenated hydrocarbons. A fiber optic is utilized to illuminate a column of pyridine trapped in a capillary tube coaxially attached at one end to the illuminating end of the fiber optic. A strongly alkaline condition necessary for the reaction is maintained by providing a reservoir of alkali in contact with the column of pyridine, the surface of contact being adjacent to the illuminating end of the fiber optic. A semipermeable membrane caps the other end of the capillary tube, the membrane being preferentially permeable to the halogenated hydrocarbon and but preferentially impermeable to water and pyridine. As the halogenated hydrocarbon diffuses through the membrane and into the column of pyridine, fluorescent reaction products are formed. Light propagated by the fiber optic from a light source, excites the fluorescent products. Light from the fluorescence emission is also collected by the same fiber optic and transmitted to a detector. The intensity of the fluorescence gives a measure of the concentration of the halogenated hydrocarbons.

Optrode for sensing hydrocarbons

DOEpatents

Miller, H.; Milanovich, F.P.; Hirschfeld, T.B.; Miller, F.S.

1987-05-19

A two-phase system employing the Fujiwara reaction is provided for the fluorometric detection of halogenated hydrocarbons. A fiber optic is utilized to illuminate a column of pyridine trapped in a capillary tube coaxially attached at one end to the illuminating end of the fiber optic. A strongly alkaline condition necessary for the reaction is maintained by providing a reservoir of alkali in contact with the column of pyridine, the surface of contact being adjacent to the illuminating end of the fiber optic. A semipermeable membrane caps the other end of the capillary tube, the membrane being preferentially permeable to the halogenated hydrocarbon but preferentially impermeable to water and pyridine. As the halogenated hydrocarbon diffuses through the membrane and into the column of pyridine, fluorescent reaction products are formed. Light propagated by the fiber optic from a light source, excites the fluorescent products. Light from the fluorescence emission is also collected by the same fiber optic and transmitted to a detector. The intensity of the fluorescence gives a measure of the concentration of the halogenated hydrocarbons. 6 figs.

Optrode for sensing hydrocarbons

DOEpatents

Miller, H.; Milanovich, F.P.; Hirschfeld, T.B.; Miller, F.S.

1988-09-13

A two-phase system employing the Fujiwara reaction is provided for the fluorometric detection of halogenated hydrocarbons. A fiber optic is utilized to illuminate a column of pyridine trapped in a capillary tube coaxially attached at one end to the illuminating end of the fiber optic. A strongly alkaline condition necessary for the reaction is maintained by providing a reservoir of alkali in contact with the column of pyridine, the surface of contact being adjacent to the illuminating end of the fiber optic. A semipermeable membrane caps the other end of the capillary tube, the membrane being preferentially permeable to the halogenated hydrocarbon and but preferentially impermeable to water and pyridine. As the halogenated hydrocarbon diffuses through the membrane and into the column of pyridine, fluorescent reaction products are formed. Light propagated by the fiber optic from a light source, excites the fluorescent products. Light from the fluorescence emission is also collected by the same fiber optic and transmitted to a detector. The intensity of the fluorescence gives a measure of the concentration of the halogenated hydrocarbons. 5 figs.

Optrode for sensing hydrocarbons

DOEpatents

Miller, Holly; Milanovich, Fred P.; Hirschfeld, Tomas B.; Miller, Fred S.

1988-01-01

A two-phase system employing the Fujiwara reaction is provided for the fluorometric detection of halogenated hydrocarbons. A fiber optic is utilized to illuminate a column of pyridine trapped in a capillary tube coaxially attached at one end to the illuminating end of the fiber optic. A strongly alkaline condition necessary for the reaction is maintained by providing a reservoir of alkali in contact with the column of pyridine, the surface of contact being adjacent to the illuminating end of the fiber optic. A semipermeable membrane caps the other end of the capillary tube, the membrane being preferentially permeable to the halogenated hydrocarbon and but preferentially impermeable to water and pyridine. As the halogenated hydrocarbon diffuses through the membrane and into the column of pyridine, fluorescent reaction products are formed. Light propagated by the fiber optic from a light source, excites the fluorescent products. Light from the fluorescence emission is also collected by the same fiber optic and transmitted to a detector. The intensity of the fluorescence gives a measure of the concentration of the halogenated hydrocarbons.

A quantum chemical study of the structures, stability, and spectroscopy of halogen- and hydrogen-boned complexes between cyanoacetaldehyde and hypochlorous acids

NASA Astrophysics Data System (ADS)

Tang, Qingjie; Guo, Zhenfu; Li, Qingzhong

2014-03-01

The complexes of cyanoacetaldehyde and hypohalous acid (HOX, X = Cl, Br, and I) have been investigated. They can form six different structures (A, B, C, D, E, and F), the former three structures are mainly combined through a N(O)⋯X halogen bond and the latter three structures are maintained mainly by a N(O)⋯H hydrogen bond, although other weaker interactions are also present in most structures. The hydrogen-bonded structures are more stable than the respective halogen-bonded structures. The Osbnd H and Osbnd X bonds in the halogen- and hydrogen-bonded complexes are lengthened and show an observed red shift, while those in the weaker secondary interactions are contracted and display a small blue shift. The orbital interactions in NBO analysis and the electron densities in AIM analysis provide useful and reliable information for the strength of each type of interaction in different structures.

Chemical Loss of Polar Ozone: Present Understanding and Remaining Uncertainties

NASA Technical Reports Server (NTRS)

Salawitch, Ross; Canty, Tim; Cunnold, Derek; Dorf, Marcel; Frieler, Katja; Godin-Beekman, Sophie; Newchurch, Michael; Pfeilsticker, Klaus; Rex, Markus; Stimpfle, Rick;

Spectroscopic detection of halogen bonding resolves dye regeneration in the dye-sensitized solar cell.

PubMed

Parlane, Fraser G L; Mustoe, Chantal; Kellett, Cameron W; Simon, Sarah J; Swords, Wesley B; Meyer, Gerald J; Kennepohl, Pierre; Berlinguette, Curtis P

2017-11-24

The interactions between a surface-adsorbed dye and a soluble redox-active electrolyte species in the dye-sensitized solar cell has a significant impact on the rate of regeneration of photo-oxidized dye molecules and open-circuit voltage of the device. Dyes must therefore be designed to encourage these interfacial interactions, but experimentally resolving how such weak interactions affect electron transfer is challenging. Herein, we use X-ray absorption spectroscopy to confirm halogen bonding can exist at the dye-electrolyte interface. Using a known series of triphenylamine-based dyes bearing halogen substituents geometrically positioned for reaction with halides in solution, halogen bonding was detected only in cases where brominated and iodinated dyes were photo-oxidized. This result implies that weak intermolecular interactions between photo-oxidized dyes and the electrolyte can impact device photovoltages. This result was unexpected considering the low concentration of oxidized dyes (less than 1 in 100,000) under full solar illumination.

Measurements of IO in the Tropical Marine Boundary Layer using Laser-Induced Fluorescence Spectroscopy

NASA Astrophysics Data System (ADS)

Walker, H.; Ingham, T.; Heard, D. E.

2012-12-01

Halogenated short-lived substances (VSLS) are emitted from the oceans by marine species such as macroalgae and phytoplankton and contribute to halogen loading in the troposphere and lower stratosphere. Transport of halogenated VSLS into the stratosphere occurs mainly in the tropics, where ascending warm air carries them aloft, and leads to catalytic depletion of stratospheric ozone on a global scale and formation of the Antarctic ozone hole. The tropical marine environment is therefore an important region in which to study the effects of these short-lived halogen species on ozone depletion. The SHIVA (Stratospheric Ozone: Halogen Impacts in a Varying Atmosphere) project combines ship-borne, aircraft-based and ground-based measurements in and over the South China Sea and the Sulu Sea, and around the coast of Malaysian Borneo, to reduce uncertainties in the amount of halogenated VSLS reaching the stratosphere, the associated ozone depletion, and the effects of a changing climate on these processes. In this work we present measurements of IO radicals made onboard the German research vessel Sonne during SHIVA, between Singapore and Manila. IO is formed via photolysis of iodine-containing source gases (e.g. I2, CH3I) to produce I atoms, which react with ozone. It is therefore an important species to consider when assessing the impacts of halogen chemistry on ozone depletion. Measurements of IO were made over a two-week period by the University of Leeds Laser-Induced Fluorescence (LIF) instrument, which excites IO radicals at λ ~ 445 nm and detects the resultant fluorescence at λ ~ 512 nm. A suite of supporting gas- and aqueous-phase measurements were also made, including concentrations of halocarbons (e.g. CHBr3, CH3I), trace pollutant gases (e.g. CO, O3, NOx), and biological parameters (e.g. abundance and speciation of phytoplankton). Preliminary data analysis indicates that IO was detected above the instrumental limit of detection (0.3 pptv for a 30 minute averaging period) on 9 days during the cruise, with a maximum mixing ratio of ~ 2.5 pptv. The results are analysed with a photochemical box model using concurrent measurements of source gases (I2, CH3I).

A Comparative Evaluation of the Influence of Command Set Methods on Microleakage of Glass Ionomer Cement: An In Vitro Study.

PubMed

Punnathara, Sairaj; Krishnakumar, Ramalingam; Govindarajan, Mohan; Kanaran, Momeka; Philip, Sunil Thomas; Nair, Aswin Saseendran; Peter, Joby

2017-06-01

A major challenge when using glass ionomer cement in clinical situation particularly in paediatric dentistry is to overcome the problem of microleakage. Fast or command setting of Type IX glass ionomer cement using external energy source enhances the setting reaction and results in improved initial physical and mechanical properties. To compare and evaluate the influence of ultrasonic activation, halogen light irradiation and combined effect of both on microleakage of enamel adjacent to Type IX glass ionomer restorations. For forty premolar teeth, standard Class V cavities prepared were restored with GC Gold Label Type IX glass ionomer cement in vitro. The specimens were randomly divided into four groups: 1) Control group; 2) halogen group; 3) ultrasonic group; 4) ultrasonic with halogen group. The teeth were kept in distilled water for 24 hours. Teeth were exposed to 1500 thermocycles at temperature of 12°C ±2 and 60°C ±2 with alternate immersion in hot and cold water for one minute. First teeth were immersed in dye solution for four hours and then in developing solution for four hours. The samples were sectioned buccolingually through centre of the restorations and degree of dye penetration was assessed under stereomicroscope and scored. One-Way ANOVA model was constructed followed by post-hoc Tukey's test for multiple pair wise comparison of mean values. Statistically significant differences were found in microleakage among the four groups (p<0.001) with respect to dye penetration. Halogen group showed least microleakage followed by control but differences between them were statistically not significant (p>0.05). Similarly the differences between Ultrasonic plus halogen group and ultrasonic group were not significant (p>0.05). The differences between ultrasonic and halogen group were statistically significant (p<0.05). Halogen light decreases the microleakage of enamel adjacent to GC Type IX glass ionomer restorations, when used to accelerate the setting reaction of glass ionomers and can be used as command set method in paediatric dentistry.

Linking precious metal enrichment and halogen cycling in mafic magmatic systems: insights from the Rum layered intrusion, NW Scotland

NASA Astrophysics Data System (ADS)

Kelly, A. P.; O'Driscoll, B.; Clay, P. L.; Burgess, R.

2017-12-01

Layered intrusions host the world's largest known concentrations of the platinum-group elements (PGE). Emphasis has been attached to the role of halogen-bearing fluids in concentrating the precious metals, but whether this occurs at the magmatic stage, or via subsequent metasomatism, is actively debated. One obstacle to progress has been the analytical difficulty of measuring low abundances of the halogens in the cumulate products of layered intrusions. To elucidate the importance of the halogens in facilitating PGE-mineralisation, as well as fingerprint halogen provenance and assess the importance of halogen cycling in mafic magma systems more generally, a suite of samples encompassing different stages of activity of the Palaeogene Rum layered intrusion was investigated. Halogen abundances were measured by neutron irradiation noble gas mass spectrometric analysis, permitting the detection of relatively low (ppm-ppb) abundances of Cl, Br and I in mg-sized samples. The samples include PGE-enriched chromite seams, various cumulates (e.g., peridotites), picrites (approximating the Rum parental magma), and pegmatites representing volatile-rich melts that circulated the intrusion at a late-stage in its solidification history. The new data reveal that PGE-bearing chromite seams contain relatively low Cl concentrations (2-3 ppm), with high molar ratios of Br/Cl and I/Cl (0.005 and 0.009, respectively). The picrites and cumulates have Br/Cl and I/Cl ratios close to sub-continental lithospheric mantle values of approximately 0.0013 and 0.00002, respectively, and thus likely reflect the Rum magma source region. A positive correlation between Cl and Br signifies comparable partitioning behaviour in all samples. However, I is more variable, displaying a positive correlation with Cl for more primitive samples (e.g. picrite and peridotite), and seemingly decoupling from Br and Cl in chromite seams and pegmatites. The relative enrichment of I over Cl in the chromite seams points to the local involvement of an organic-rich sedimentary assimilant and potentially represents an important trigger for PGE-mineralisation. Similarly high I/Cl signatures in some of the late-stage pegmatites suggest that fluids with this distinctive composition circulated the cooling Rum intrusion for a protracted period of time.

Unexpected autumnal halogen activity in the lower troposphere at Neumayer III/Antarctica

NASA Astrophysics Data System (ADS)

Nasse, Jan-Marcus; Frieß, Udo; Pöhler, Denis; Schmitt, Stefan; Weller, Rolf; Schaefer, Thomas; Platt, Ulrich

2017-04-01

The influence of Reactive Halogen Species (RHS, like IO, BrO, ClO, etc.) on the lower polar troposphere has been subject of intense research for several decades. Ozone Depletion Events (ODEs) caused by the catalytic reaction of tropospheric ozone with inorganic halogen species or the oxidation of gaseous elemental mercury are well observed phenomena that occur during the respective springtime in both Arctic and Antarctica. Chlorine atoms also react more efficiently with hydrocarbons than e.g. OH radicals and all reactive halogen species can furthermore influence the atmospheric sulphur or nitrate cycles. While an autocatalytic release mechanism from salty surfaces, the so called bromine explosion, has been identified to rapidly increase inorganic bromine mixing ratios many aspects of atmospheric halogen chemistry in polar regions remains unclear. Since January 2016, we are operating an active Long Path DOAS instrument at Neumayer III on the Antarctic Ekström shelf ice designed for autonomous measurements. This instrument is able to detect a wide range of trace gases absorbing in the UV/Vis including ClO, BrO, OClO, IO, I2, OIO, ozone, NO2, H2O, O4, and SO2 at a temporal resolution of 5-30 minutes. The analysis of the first year of observations shows several surprising findings which give new insights into polar halogen chemistry. E.g. we observe surprisingly strong bromine activity in late summer and autumn (in addition to well-known springtime events) with mixing ratios often higher than 20 pptv. We could even observe peak mixing ratios of 110 pptv. The observed BrO levels could be the result of local/regional chemistry rather than long-range transport and modulated by the stability of the boundary layer. Also, there are hints for NOx - driven halogen activation. Furthermore, chlorine monoxide (ClO) and OClO mixing ratios of several ten pptv could be detected on a number of days, however the source mechanism for reactive chlorine remains unclear. We will give an overview of the entire time series and discuss interesting case studies with regard to chemistry, atmospheric conditions and transport.

Sources of halogens in the environment, influences on human and animal health.

PubMed

Fuge, R

1988-06-01

Of the halogens, fluorine has the highest crustal abundance (544 mg/kg) while iodine has the lowest (0.25 mg/kg), however, chlorine is by far the most abundant halogen in the cosmos. The geochemistries of the four naturally occurring halogens have some similarities with fluorine, chlorine and bromine being classified as lithophile elements while iodine is more chalcophile in nature. Bromine and iodine behave in a similar fashion in the secondary environment and could be classified as biophile elements being concentrated in organic matter. Chlorine, bromine and iodine are strongly enriched in the sea while iodine and to a lesser extent bromine are further concentrated in the marine algae.Apart from the occurrence of fluorine in fluorite (CaF2) there are few commonly occurring minerals which contain the halogens as essential constituents. In the igneous environment fluorine and chlorine tend to occupy hydroxyl lattice sites in micas, amphiboles, apatites etc., while in sediments clays can contain appreciable quantities of these elements. Bromine and iodine, however, would be unlikely to fit into the lattice sites of common rock-forming minerals.Bromine, like iodine, is probably volatilised from the marine environment and is carried on to land surfaces. This behaviour of iodine and bromine is reflected in the increased I/CI and Br/CI ratios of surface run-off in continental compared with near coastal environments.Limited information on the soil geochemistry of the halogens suggests that the soil contents of chlorine, bromine and iodine are influenced by proximity to the sea. Soil fluorine, however, is generally dependent on its content in the parent material. In some areas pollutant sources of the halogens contribute appreciably to their concentration in the environment.Iodine and chlorine are essential elements for mammals and fluorine has been shown to have beneficial effects on bone and tooth formation. However, excess quantities of dietary fluorine can be harmful. It is possible, in view of its ubiquitous occurrence in the biosphere, that bromine has a hitherto unknown function in human and animal health.

The Role of Halogens in High-Grade Metamorphism and Anatexis

NASA Astrophysics Data System (ADS)

Aranovich, L.; Safonov, O.

2016-12-01

We review factors controlling the distribution of the two major halogens, F and Cl, in high-grade metamorphic rocks; their compositional correlations and partitioning between minerals; experimental data on stability and phase equilibria of the halogen-bearing minerals; the influence of halogens on Fe-Mg exchange reactions; and the means of estimating concentrations/activity of halogen species concentration/ activity in the fluid phase ("chlorimetry and fluorimetry") via calculation of equilibrium conditions for mineral assemblages containing halogen-bearing phases. Clear negative correlation between the F content and XFe=Fe/(Fe+Mg) suggests that natural biotite and amphibole obey the Fe-F avoidance rule. A strong positive correlation exists between K and Cl in amphibole. A scattering of points on the XFe -Cl and TiO2- Cl diagrams indicate the possible involvement of an exotic Cl-rich phase (fluid or melt) during the formation of Cl-bearing biotite and amphibole. Fluorine and Cl substituting for OH-groups substantially stabilize minerals relative to dehydration and melting. They should also strongly affect partitioning of Fe and Mg between biotite, amphibole and anhydrous minerals. This effect is quantified for Fe-Mg exchange reactions involving biotite (Zhu and Sverjensky, 1992), but remains to be evaluated for amphibole. Calculations based on recent thermodynamic systematics show that the relatively Mg-rich, Cl-poor biotite (for example, XFe = 0.4 and about 0.2 wt.% Cl) may coexist with a fairly Cl-rich fluid, i.e. total Cl/(Cl+H2O) from 0.1-0.3, depending on the assemblage, under granulite facies P-T conditions. Alkali (and Ca) metasomatism caused by interaction of high grade rocks with halogen-bearing fluids has major impact on the subsolidus phase transformations and melting processes during high-grade metamorphism and anatexis. For example, an increase in sodium content in plagioclase (Pl) by 20 mol% due to infiltration of Na- fluid into the quartz (Qtz)-bearing rocks decreases melting temperature by about 50o. Similar effect may occur in the originally Qtz-absent rocks due to interaction with Ca-rich fluids. Acknowledgements: This work was supported by RFBR grant 15-05-01053.

Three-year observations of halocarbons at the Nepal Climate Observatory at Pyramid (NCO-P, 5079 m a.s.l.) on the Himalayan range

NASA Astrophysics Data System (ADS)

Maione, M.; Giostra, U.; Arduini, J.; Furlani, F.; Bonasoni, P.; Cristofanelli, P.; Laj, P.; Vuillermoz, E.

2011-04-01

A monitoring programme for halogenated climate-altering gases has been established in the frame of the SHARE EV-K2-CNR project at the Nepal Climate Laboratory - Pyramid in the Himalayan range at the altitude of 5079 m a.s.l. The site is very well located to provide important insights on changes in atmospheric composition in a region that is of great significance for emissions of both anthropogenic and biogenic halogenated compounds. Measurements are performed since March 2006, with grab samples collected on a weekly basis. The first three years of data have been analysed. After the identification of the atmospheric background values for fourteen halocarbons, the frequency of occurrence of pollution events have been compared with the same kind of analysis for data collected at other global background stations. The analysis showed the fully halogenated species, whose production and consumption are regulated under the Montreal Protocol, show a significant occurrence of "above the baseline" values, as a consequence of their current use in the developing countries surrounding the region, meanwhile the hydrogenated gases, more recently introduced into the market, show less frequent spikes. Atmospheric concentration trends have been calculated as well, and they showed a fast increase, ranging from 5.7 to 12.6%, of all the hydrogenated species, and a clear decrease of methyl chloroform (-17.7%). The comparison with time series from other stations has also allowed to derive Meridional gradients, which are absent for long living well mixed species, while for the more reactive species, the gradient increases inversely with respect to their atmospheric lifetime. The effect of long range transport and of local events on the atmospheric composition at the station has been analysed as well, allowing the identification of relevant source regions the Northern half of the Indian sub-continent. Also, at finer spatial scales, a smaller, local contribution of forest fires from the Khumbu valley has been detected.

Ion yields in UV-MALDI mass spectrometry as a function of excitation laser wavelength and optical and physico-chemical properties of classical and halogen-substituted MALDI matrixes.

PubMed

Soltwisch, Jens; Jaskolla, Thorsten W; Hillenkamp, Franz; Karas, Michael; Dreisewerd, Klaus

2012-08-07

The laser wavelength constitutes a key parameter in ultraviolet-matrix-assisted laser desorption ionization-mass spectrometry (UV-MALDI-MS). Optimal analytical results are only achieved at laser wavelengths that correspond to a high optical absorption of the matrix. In the presented work, the wavelength dependence and the contribution of matrix proton affinity to the MALDI process were investigated. A tunable dye laser was used to examine the wavelength range between 280 and 355 nm. The peptide and matrix ion signals recorded as a function of these irradiation parameters are displayed in the form of heat maps, a data representation that furnishes multidimensional data interpretation. Matrixes with a range of proton affinities from 809 to 866 kJ/mol were investigated. Among those selected are the standard matrixes 2,5-dihydroxybenzoic acid (DHB) and α-cyano-4-hydroxycinnamic acid (HCCA) as well as five halogen-substituted cinnamic acid derivatives, including the recently introduced 4-chloro-α-cyanocinnamic acid (ClCCA) and α-cyano-2,4-difluorocinnamic acid (DiFCCA) matrixes. With the exception of DHB, the highest analyte ion signals were obtained toward the red side of the peak optical absorption in the solid state. A stronger decline of the molecular analyte ion signals generated from the matrixes was consistently observed at the low wavelength side of the peak absorption. This effect is mainly the result of increased fragmentation of both analyte and matrix ions. Optimal use of multiply halogenated matrixes requires adjustment of the excitation wavelength to values below that of the standard MALDI lasers emitting at 355 (Nd:YAG) or 337 nm (N(2) laser). The combined data provide new insights into the UV-MALDI desorption/ionization processes and indicate ways to improve the analytical sensitivity.

Germylenes: structures, electron affinities, and singlet-triplet gaps of the conventional XGeCY(3) (X = H, F, Cl, Br, and I; Y = F and Cl) species and the unexpected cyclic XGeCY(3) (Y = Br and I) systems.

PubMed

Bundhun, Ashwini; Abdallah, Hassan H; Ramasami, Ponnadurai; Schaefer, Henry F

2010-12-23

A systematic investigation of the X-Ge-CY(3) (X = H, F, Cl, Br, and I; Y = F, Cl, Br, and I) species is carried out using density functional theory. The basis sets used for all atoms (except iodine) in this work are of double-ζ plus polarization quality with additional s- and p-type diffuse functions, and denoted DZP++. Vibrational frequency analyses are performed to evaluate zero-point energy corrections and to determine the nature of the stationary points located. Predicted are four different forms of neutral-anion separations: adiabatic electron affinity (EA(ad)), zero-point vibrational energy corrected EA(ad(ZPVE)), vertical electron affinity (EA(vert)), and vertical detachment energy (VDE). The electronegativity (χ) reactivity descriptor for the halogens (X = F, Cl, Br, and I) is used as a tool to assess the interrelated properties of these germylenes. The topological position of the halogen atom bound to the divalent germanium center is well correlated with the trend in the electron affinities and singlet-triplet gaps. For the expected XGeCY(3) structures (X = H, F, Cl, Br, and I; Y = F and Cl), the predicted trend in the electron affinities is well correlated with simpler germylene derivatives (J. Phys. Chem. A 2009, 113, 8080). The predicted EA(ad(ZPVE)) values with the BHLYP functional range from 1.66 eV (FGeCCl(3)) to 2.20 eV (IGeCF(3)), while the singlet-triplet splittings range from 1.28 eV (HGeCF(3)) to 2.22 eV (FGeCCl(3)). The XGeCY(3) (Y = Br and I) species are most often characterized by three-membered cyclic systems involving the divalent germanium atom, the carbon atom, and a halogen atom.

Process for the solvent extraction for the radiolysis and dehalogenation of halogenated organic compounds in soils, sludges, sediments and slurries

DOEpatents

Golden, Jeffry

2007-02-13

A process of extracting halogenated organic compounds, and particularly PCBs, from soil, sediment, slurry, sludge and dehalogenating the compounds contacts a contaminated soil sample with an extraction medium of a mixture of an alkane and a water miscible alcohol. The organic compounds dissolve in the extraction medium which is separated from the soil by passing water upwardly through the soil. The extraction medium floats to the surface of the water and is separated. Thereafter, the extraction medium containing the halogenated organic contaminants is subjected to ionizing radiation to radiolytically dehalogenate the compounds.

Process for the solvent extraction for the radiolysis and dehalogenation of halogenated organic compounds in soils, sludges, sediments and slurries

DOEpatents

Mincher, Bruce J.; Curry, Randy Dale; Clevenger, Thomas E.; Golden, Jeffry

2003-05-27

A process of extracting halogenated organic compounds, and particularly PCBs, from soil, sediment, slurry, sludge and dehalogenating the compounds contacts a contaminated soil sample with an extraction medium of a mixture of an alkane and a water miscible alcohol. The organic compounds dissolve in the extraction medium which is separated from the soil by passing water upwardly through the soil. The extraction medium floats to the surface of the water and is separated. Thereafter, the extraction medium containing the halogenated organic contaminants is subjected to ionizing radiation to radiolytically dehalogenate the compounds.

Process for the solvent extraction for the radiolysis and dehalogenation of halogenated organic compounds in soils, sludges, sediments and slurries

DOEpatents

Mincher, Bruce J.; Curry, Randy Dale; Clevenger, Thomas E.; Golden, Jeffry

2000-01-01

A process of extracting halogenated organic compounds, and particularly PCBs, from soil, sediment, slurry, sludge and dehalogenating the compounds contacting a contaminated soil sample with an extraction medium of a mixture of an alkane and a water miscible alcohol. The organic compounds dissolve in the extraction medium which is separated from the soil by passing water upwardly through the soil. The extraction medium floats to the surface of the water and is separated. Thereafter, the extraction medium containing the halogenated organic contaminants is subjected to ionizing radiation to radiolytically dehalogenate the compounds.

Nuclear Analysis and Technology Assessment of Radar Concepts. Volume II. Radiation Vulnerability Assessment of Radar Components.

DTIC Science & Technology

1981-05-20

broken and the material outgasses hydrogen. Halogenated polymers (e.g., Teflon or polyvinyl chloride) outgas the halogen or even yield the acid (e.g...the etching of the glass by HF. In other words, halogenated polymers when they are irradiated outgas acid vapors which are quite corrosive to any...Si~o S n 4~-1 -zi s -ic!et a:-:r su’i~ K :rs :c 3 xS I, :-aat, :.e ef-:n2 -n tc’ : "s-iacz on. a’ Iv-?g im :y’-,q st~c! y nay ze I :,.;es:*r:m I

Halogen effect for improving high temperature oxidation resistance of Ti-50Al by anodization

NASA Astrophysics Data System (ADS)

Mo, Min-Hua; Wu, Lian-Kui; Cao, Hua-Zhen; Lin, Jun-Pin; Zheng, Guo-Qu

2017-06-01

The high temperature oxidation resistance of Ti-50Al was significantly improved via halogen effect which was achieved by anodizing in an ethylene glycol solution containing with fluorine ion. The anodized Ti-50Al with holes and micro-cracks could be self-repaired during oxidation at 1000 °C. The thickness of the oxide scale increases with the prolonging of oxidation time. On the basis of halogen effect for improving the high temperature oxidation resistance of Ti-50Al by anodization, only fluorine addition into the electrolyte can effectively improve the high temperature oxidation resistance of Ti-50Al.

METHOD AND MEANS FOR RADIATION DOSIMETRY

DOEpatents

Shulte, J.W.; Suttle, J.F.

1958-02-18

This patent relates to a method and device for determining quantities of gamma radiation and x radiation by exposing to such radiation a mature of a purified halogenated hydrocarbon chosen from the class consisting of chloroform, bromoform, tetrachloroethane and 1,1,2trichloroethane, and a minor quantity of a sensitizer chosen from the class consisting of oxygen, benzoyl peroxide, sodium peroxide, and nitrobenzene, the proportion of the sensitizer being at least about 10/sup -5/ moles per cubic centimeter of halogenated hydrocarbon, the total amount of sensitizer depending upon the range of radiation to be measured, and chemically measuring the amount of decomposition generated by the irradiation of the sensitized halogenated hydrocarbon.

Halogenase engineering and its utility in medicinal chemistry.

PubMed

Fraley, Amy E; Sherman, David H

2018-06-15

Halogenation is commonly used in medicinal chemistry to improve the potency of pharmaceutical leads. While synthetic methods for halogenation present selectivity and reactivity challenges, halogenases have evolved over time to perform selective reactions under benign conditions. The optimization of halogenation biocatalysts has utilized enzyme evolution and structure-based engineering alongside biotransformation in a variety of systems to generate stable site-selective variants. The recent improvements in halogenase-catalyzed reactions has demonstrated the utility of these biocatalysts for industrial purposes, and their ability to achieve a broad substrate scope implies a synthetic tractability with increasing relevance in medicinal chemistry. Copyright © 2018 Elsevier Ltd. All rights reserved.

40 CFR 721.8875 - Substituted halogenated pyridinol.

Code of Federal Regulations, 2012 CFR

2012-07-01

... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8875 Substituted halogenated pyridinol. (a) Chemical substances and significant new uses... pyridinol (PMN P-88-1273) is subject to reporting under this section for the significant new uses described...

40 CFR 721.8750 - Halogenated substituted pyridine.

Code of Federal Regulations, 2010 CFR

2010-07-01

... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8750 Halogenated substituted pyridine. (a) Chemical substances and significant new uses... pyridine (PMN P-86-838) is subject to reporting under this section for the significant new uses described...

40 CFR 721.8875 - Substituted halogenated pyridinol.

Code of Federal Regulations, 2013 CFR

2013-07-01

... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8875 Substituted halogenated pyridinol. (a) Chemical substances and significant new uses... pyridinol (PMN P-88-1273) is subject to reporting under this section for the significant new uses described...

40 CFR 721.8850 - Disubstituted halogenated pyridinol.

Code of Federal Regulations, 2011 CFR

2011-07-01

... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8850 Disubstituted halogenated pyridinol. (a) Chemical substances and significant new uses... pyridinol (PMN P-88-1274) is subject to reporting under this section for the significant new uses described...

40 CFR 721.8850 - Disubstituted halogenated pyridinol.

Code of Federal Regulations, 2012 CFR

2012-07-01

... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8850 Disubstituted halogenated pyridinol. (a) Chemical substances and significant new uses... pyridinol (PMN P-88-1274) is subject to reporting under this section for the significant new uses described...

40 CFR 721.8750 - Halogenated substituted pyridine.

Code of Federal Regulations, 2012 CFR

2012-07-01

... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8750 Halogenated substituted pyridine. (a) Chemical substances and significant new uses... pyridine (PMN P-86-838) is subject to reporting under this section for the significant new uses described...

40 CFR 721.8850 - Disubstituted halogenated pyridinol.

Code of Federal Regulations, 2013 CFR

2013-07-01

... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8850 Disubstituted halogenated pyridinol. (a) Chemical substances and significant new uses... pyridinol (PMN P-88-1274) is subject to reporting under this section for the significant new uses described...

40 CFR 721.8875 - Substituted halogenated pyridinol.

Code of Federal Regulations, 2014 CFR

2014-07-01

... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8875 Substituted halogenated pyridinol. (a) Chemical substances and significant new uses... pyridinol (PMN P-88-1273) is subject to reporting under this section for the significant new uses described...

40 CFR 721.8750 - Halogenated substituted pyridine.

Code of Federal Regulations, 2011 CFR

2011-07-01

... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8750 Halogenated substituted pyridine. (a) Chemical substances and significant new uses... pyridine (PMN P-86-838) is subject to reporting under this section for the significant new uses described...

40 CFR 721.8700 - Halogenated alkyl pyridine.

Code of Federal Regulations, 2013 CFR

2013-07-01

... CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8700 Halogenated alkyl pyridine. (a) Chemical substances and significant new uses subject to... subject to reporting under this section for the significant new uses described in paragraph (a)(1)(i) of...

40 CFR 721.8875 - Substituted halogenated pyridinol.

Code of Federal Regulations, 2010 CFR

2010-07-01

... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8875 Substituted halogenated pyridinol. (a) Chemical substances and significant new uses... pyridinol (PMN P-88-1273) is subject to reporting under this section for the significant new uses described...

40 CFR 721.8750 - Halogenated substituted pyridine.

Code of Federal Regulations, 2013 CFR

2013-07-01

... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8750 Halogenated substituted pyridine. (a) Chemical substances and significant new uses... pyridine (PMN P-86-838) is subject to reporting under this section for the significant new uses described...

40 CFR 721.8875 - Substituted halogenated pyridinol.

Code of Federal Regulations, 2011 CFR

2011-07-01

... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8875 Substituted halogenated pyridinol. (a) Chemical substances and significant new uses... pyridinol (PMN P-88-1273) is subject to reporting under this section for the significant new uses described...

40 CFR 721.8850 - Disubstituted halogenated pyridinol.

Code of Federal Regulations, 2014 CFR

2014-07-01

... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8850 Disubstituted halogenated pyridinol. (a) Chemical substances and significant new uses... pyridinol (PMN P-88-1274) is subject to reporting under this section for the significant new uses described...

40 CFR 721.8750 - Halogenated substituted pyridine.

Code of Federal Regulations, 2014 CFR

2014-07-01

... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8750 Halogenated substituted pyridine. (a) Chemical substances and significant new uses... pyridine (PMN P-86-838) is subject to reporting under this section for the significant new uses described...

40 CFR 721.8850 - Disubstituted halogenated pyridinol.

Code of Federal Regulations, 2010 CFR

2010-07-01

... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8850 Disubstituted halogenated pyridinol. (a) Chemical substances and significant new uses... pyridinol (PMN P-88-1274) is subject to reporting under this section for the significant new uses described...

40 CFR 721.8700 - Halogenated alkyl pyridine.

Code of Federal Regulations, 2012 CFR

2012-07-01

... CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8700 Halogenated alkyl pyridine. (a) Chemical substances and significant new uses subject to... subject to reporting under this section for the significant new uses described in paragraph (a)(1)(i) of...

EVOLUTION OF AN ANALYTICAL METHOD FOR HALOGENATED FURANONES IN DRINKING WATER

EPA Science Inventory

A unified method of detection for seven halogenated furanones present in drinking waters at the ng/L level has been developed. The use of GC/ECD makes this method amenable to manyenvironmental laboratories and water treatment plants in the United States. Detection limits observe...

Cofacial Assembly of Metallomacrocycles. A Molecular Engineering Approach to Electrically Conductive Polymers.

DTIC Science & Technology

1981-05-13

34molecular metals." THE COFACIAL ASSEMBLY STRATEGY Although the above molecular macrocycle, halogen cocrystalli - zation approach to the synthesis of...substitute various oxidizing quinones for halogens in the cocrystallization synthesis have failed because integrated stacK (Figure 2C,D) insulators are

40 CFR 63.116 - Process vent provisions-performance test methods and procedures to determine compliance.

Code of Federal Regulations, 2014 CFR

2014-07-01

... reduce the vent stream halogen atom mass emission rate to less than 0.45 kilogram per hour prior to a combustion control device in compliance with § 63.113(c)(2) of this subpart shall determine the halogen atom...

40 CFR 63.116 - Process vent provisions-performance test methods and procedures to determine compliance.

Code of Federal Regulations, 2011 CFR

2011-07-01

... reduce the vent stream halogen atom mass emission rate to less than 0.45 kilogram per hour prior to a combustion control device in compliance with § 63.113(c)(2) of this subpart shall determine the halogen atom...

40 CFR 63.116 - Process vent provisions-performance test methods and procedures to determine compliance.

Code of Federal Regulations, 2013 CFR

2013-07-01

... reduce the vent stream halogen atom mass emission rate to less than 0.45 kilogram per hour prior to a combustion control device in compliance with § 63.113(c)(2) of this subpart shall determine the halogen atom...

40 CFR 63.116 - Process vent provisions-performance test methods and procedures to determine compliance.

Code of Federal Regulations, 2012 CFR

2012-07-01

... reduce the vent stream halogen atom mass emission rate to less than 0.45 kilogram per hour prior to a combustion control device in compliance with § 63.113(c)(2) of this subpart shall determine the halogen atom...

Request for Correction 11001 Toxicological Review of Halogenated Platinum Salts and Platinum Compounds

EPA Pesticide Factsheets

Request for Correction by the International Platinum Group Metals Association seeking the correction of information disseminated in the draft EPA document Toxicological Review of Halogenated Platinum Salts and Platinum Compounds: In Support of Summary Information on the Integrated Risk Information System (IRIS).

40 CFR 721.4484 - Halogenated indane (generic name).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Halogenated indane (generic name). 721.4484 Section 721.4484 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) TOXIC... into a plastic, resin matrix, or pelletized so humans are not reasonally likely to be exposed. (2) The...

40 CFR 721.4484 - Halogenated indane (generic name).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Halogenated indane (generic name). 721.4484 Section 721.4484 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) TOXIC... into a plastic, resin matrix, or pelletized so humans are not reasonally likely to be exposed. (2) The...

A Comparison of Ionic and Covalent Iodine Dihalides: An Integrated Experiment.

ERIC Educational Resources Information Center

Woolf, Alfred A.

1978-01-01

Compares the preparation and decomposition of potassium dibromoiodate and of phenyl iodine dichloride in a flexible experiment which accustoms the student to handle halogens, to test for halogens in mixtures, and to appreciate the difference between thermodynamic and kinetic control of reactions. (Author/MA)

40 CFR 721.2140 - Carbo-poly-cycli-col azo-alkyl-aminoalkyl-carbo-mono-cyclic ester, halogen acid salt.

Code of Federal Regulations, 2012 CFR

2012-07-01

... subject to reporting. (1) The chemical substance generically identified as carbopolycyclicol azo-al-kyl-a-mino-al-kyl-car-bo-mon-o-cyc-lic ester, halogen acid salt (PMN P-88-1682) is subject to reporting under...

40 CFR 721.2140 - Carbo-poly-cycli-col azo-alkyl-aminoalkyl-carbo-mono-cyclic ester, halogen acid salt.

Code of Federal Regulations, 2013 CFR

2013-07-01

... subject to reporting. (1) The chemical substance generically identified as carbopolycyclicol azo-al-kyl-a-mino-al-kyl-car-bo-mon-o-cyc-lic ester, halogen acid salt (PMN P-88-1682) is subject to reporting under...

40 CFR 721.2140 - Carbo-poly-cycli-col azo-alkyl-aminoalkyl-carbo-mono-cyclic ester, halogen acid salt.

Code of Federal Regulations, 2014 CFR

2014-07-01

... subject to reporting. (1) The chemical substance generically identified as carbopolycyclicol azo-al-kyl-a-mino-al-kyl-car-bo-mon-o-cyc-lic ester, halogen acid salt (PMN P-88-1682) is subject to reporting under...

40 CFR 721.2140 - Carbo-poly-cycli-col azo-alkyl-aminoalkyl-carbo-mono-cyclic ester, halogen acid salt.

Code of Federal Regulations, 2011 CFR

2011-07-01

... subject to reporting. (1) The chemical substance generically identified as carbopolycyclicol azo-al-kyl-a-mino-al-kyl-car-bo-mon-o-cyc-lic ester, halogen acid salt (PMN P-88-1682) is subject to reporting under...

Semiconductor cooling apparatus

NASA Technical Reports Server (NTRS)

Banks, Bruce A. (Inventor); Gaier, James R. (Inventor)

1993-01-01

Gas derived graphite fibers generated by the decomposition of an organic gas are joined with a suitable binder. This produces a high thermal conductivity composite material which passively conducts heat from a source, such as a semiconductor, to a heat sink. The fibers may be intercalated. The intercalate can be halogen or halide salt, alkaline metal, or any other species which contributes to the electrical conductivity improvement of the graphite fiber. The fibers are bundled and joined with a suitable binder to form a high thermal conductivity composite material device. The heat transfer device may also be made of intercalated highly oriented pyrolytic graphite and machined, rather than made of fibers.

A computational study on the strength and nature of bifurcated aerogen bonds

NASA Astrophysics Data System (ADS)

Esrafili, Mehdi D.; Sadr-Mousavi, Asma

2018-04-01

A quantum chemical study is performed to unveil the strength and bonding properties of bifurcated aerogen-bonding (BAB) interactions in complexes formed between ZO3 molecules (Z = Ar, Kr and Xe) and 1,2-dihydroxybenzene derivatives. The interaction energies of the resulting complexes are between -7.70 and -15.59 kcal/mol. The nature of BAB interactions is identified by the molecular electrostatic potential, quantum theory of atoms in molecules, noncovalent interaction index and natural bond orbital analyses. The mutual influence between the BAB and a halogen, chalcogen, pnicogen or tetrel bonding interaction is also studied in systems where these interactions coexist.

Antimicrobial activity of allylic thiocyanates derived from the Morita-Baylis-Hillman reaction

PubMed Central

Sá, Marcus Mandolesi; Ferreira, Misael; Lima, Emerson Silva; dos Santos, Ivanildes; Orlandi, Patrícia Puccinelli; Fernandes, Luciano

2014-01-01

Bacterial resistance to commonly used antibiotics has been recognized as a significant global health issue. In this study, we carried out the screening of a family of allylic thiocyanates for their action against a diversity of bacteria and fungi with a view to developing new antimicrobial agents. Allylic thiocyanates bearing halogenated aryl groups, which were readily obtained in two steps from the Morita-Baylis-Hillman adducts, showed moderate-to-high activity against selective pathogens, including a methicillin-resistant S. aureus (MRSA) strain. In particular cases, methyl (Z)-3-(2,4-dichlorophenyl)-2-(thiocyanomethyl)-2-propenoate exhibited antimicrobial activity comparable to the reference antibiotic Imipenem. PMID:25477911

Conference on Deep Earth and Planetary Volatiles

NASA Technical Reports Server (NTRS)

1994-01-01

The following topics are covered in the presented papers: (1) rare gases systematics and mantle structure; (2) volatiles in the earth; (3) impact degassing of water and noble gases from silicates; (4) D/H ratios and H2O contents of mantle-derived amphibole megacrysts; (5) thermochemistry of dense hydrous magnesium silicates; (6) modeling of the effect of water on mantle rheology; (7) noble gas isotopes and halogens in volatile-rich inclusions in diamonds; (8) origin and loss of the volatiles of the terrestrial planets; (9) structure and the stability of hydrous minerals at high pressure; (10) recycling of volatiles at subduction zones and various other topics.

Refined potentials for rare gas atom adsorption on rare gas and alkali-halide surfaces

NASA Technical Reports Server (NTRS)

Wilson, J. W.; Heinbockel, J. H.; Outlaw, R. A.

1985-01-01

The utilization of models of interatomic potential for physical interaction to estimate the long range attractive potential for rare gases and ions is discussed. The long range attractive force is calculated in terms of the atomic dispersion properties. A data base of atomic dispersion parameters for rare gas atoms, alkali ion, and halogen ions is applied to the study of the repulsive core; the procedure for evaluating the repulsive core of ion interactions is described. The interaction of rare gas atoms on ideal rare gas solid and alkali-halide surfaces is analyzed; zero coverage absorption potentials are derived.

Enhanced surface modification engineering (H, F, Cl, Br, and NO{sub 2}) of CdS nanowires with and without surface dangling bonds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zeng, Yijie; Xing, Huaizhong, E-mail: xinghz@dhu.edu.cn; Lu, Aijiang

2015-08-07

Semiconductor nanowires (NWs) can be applied in gas sensing and cell detection, but the sensing mechanism is not clearly understood. In this study, surface modification effect on the electronic properties of CdS NWs for different diameters with several species (H, F, Cl, Br, and NO{sub 2}) is investigated by first principles calculations. The surface dangling bonds and halogen elements are chosen to represent the environment of the surface. Halogen passivation drastically changes the band gaps due to the strong electronegativity and the energy level of halogen atoms. Density of states analysis indicates that valence band maximum (VBM) of halogen-passivated NWsmore » is formed by the p states of halogen atoms, while VBM of H-passivated NWs is originated from Cd 4d and S 3p orbitals. To illustrate that surface modification can be applied in gas sensing, NO{sub 2}-absorbed NWs with different coverage are calculated. Low coverage of NO{sub 2} introduces a deep p-type dopant-like level, while high coverage introduces a shallow n-type dopant-like level into the band structure. The transformation is due to that at low coverage the adsorption is chemical while at high coverage is physical. These findings might promote the understanding of surface modification effect and the sensing mechanism of NWs as gas sensors.« less

Recovery of the Antarctic Ozone Hole

NASA Technical Reports Server (NTRS)

Newman, Paul A.; Nash, Eric R.; Kawa, S. Randolph; Montzka, Steve; Schauffler, Sue; Stolarski, Richard S.; Douglass, Anne R.; Pawson, Steven; Nielsen, J. Eric

2006-01-01

The Antarctic ozone hole develops each year and culminates by early Spring. Antarctic ozone values have been monitored since 1979 using satellite observations from the TOMS and OMI instruments. The severity of the hole has been assessed using the minimum total ozone value from the October monthly mean (depth of the hole), the average size during the September-October period, and the ozone mass deficit. Ozone is mainly destroyed by halogen catalytic cycles, and these losses are modulated by temperature variations in the collar of the polar lower stratospheric vortex. In this presentation, we show the relationships of halogens and temperature to both the size and depth of the hole. Because atmospheric halogen levels are responding to international agreements that limit or phase out production, the amount of halogens in the stratosphere should decrease over the next few decades. We use two methods to estimate ozone hole recovery. First, we use projections of halogen levels combined with age-of-air estimates in a parametric model. Second, we use a coupled chemistry climate model to assess recovery. We find that the ozone hole is recovering at an extremely slow rate and that large ozone holes will regularly recur over the next 2 decades. Furthermore, full recovery to 1980 levels will not occur until approximately 2068. We will also show some error estimates of these dates and the impact of climate change on the recovery.

Molecular mechanism of metal-independent decomposition of lipid hydroperoxide 13-HPODE by halogenated quinoid carcinogens.

PubMed

Qin, Hao; Huang, Chun-Hua; Mao, Li; Xia, Hai-Ying; Kalyanaraman, Balaraman; Shao, Jie; Shan, Guo-Qiang; Zhu, Ben-Zhan

2013-10-01

Halogenated quinones are a class of carcinogenic intermediates and newly identified chlorination disinfection by-products in drinking water. 13-Hydroperoxy-9,11-octadecadienoic acid (13-HPODE) is the most extensively studied endogenous lipid hydroperoxide. Although it is well known that the decomposition of 13-HPODE can be catalyzed by transition metal ions, it is not clear whether halogenated quinones could enhance its decomposition independent of metal ions and, if so, what the unique characteristics and similarities are. Here we show that 2,5-dichloro-1,4-benzoquinone (DCBQ) could markedly enhance the decomposition of 13-HPODE and formation of reactive lipid alkyl radicals such as pentyl and 7-carboxyheptyl radicals, and the genotoxic 4-hydroxy-2-nonenal (HNE), through the complementary application of ESR spin trapping, HPLC-MS, and GC-MS methods. Interestingly, two chloroquinone-lipid alkoxyl conjugates were also detected and identified from the reaction between DCBQ and 13-HPODE. Analogous results were observed with other halogenated quinones. This represents the first report that halogenated quinoid carcinogens can enhance the decomposition of the endogenous lipid hydroperoxide 13-HPODE and formation of reactive lipid alkyl radicals and genotoxic HNE via a novel metal-independent nucleophilic substitution coupled with homolytic decomposition mechanism, which may partly explain their potential genotoxicity and carcinogenicity. Copyright © 2013 Elsevier Inc. All rights reserved.

Converting a conventional wired-halogen illuminated indirect ophthalmoscope to a wireless-light emitting diode illuminated indirect ophthalmoscope in less than 1000/- rupees.

PubMed

Kothari, Mihir; Kothari, Kedar; Kadam, Sanjay; Mota, Poonam; Chipade, Snehal

2015-01-01

To report the "do it yourself" method of converting an existing wired-halogen indirect ophthalmoscope (IO) to a wireless-light emitting diode (LED) IO and report the preferences of the patients and the ophthalmologists. In this prospective observational study, a conventional IO was converted to wireless-LED IO using easily available, affordable electrical components. Conventional and the converted IO were then used to perform photo-stress test and take the feedback of subjects and the ophthalmologists regarding its handling and illumination characteristics. The cost of conversion to wireless-LED was 815/- rupees. Twenty-nine subjects, mean age 34.3 [formula in text] 10 years with normal eyes were recruited in the study. Between the two illumination systems, there was no statistical difference in the magnitude of the visual acuity loss and the time to recovery of acuity and the bleached vision on photo-stress test, although the visual recovery was clinically faster with LED illumination. The heat sensation was more with halogen illumination than the LED (P = 0.009). The ophthalmologists rated wireless-LED IO higher than wired-halogen IO on the handling, examination comfort, patient's visual comfort and quality of the image. Twenty-two (81%) ophthalmologists wanted to change over to wireless-LED IO. Converting to wireless-LED IO is easy, cost-effective and preferred over a wired-halogen indirect ophthalmoscope.

Are superhalogens without halogen ligand capable of transcending traditional halogen-based superhalogens? Ab initio case study of binuclear anions based on pseudohalogen ligand

NASA Astrophysics Data System (ADS)

Li, Jin-Feng; Sun, Yin-Yin; Bai, Hongcun; Li, Miao-Miao; Li, Jian-Li; Yin, Bing

2015-06-01

The superhalogen properties of polynuclear structures without halogen ligand are theoretically explored here for several [M2(CN)5]-1 (M = Ca, Be) clusters. At CCSD(T) level, these clusters have been confirmed to be superhalogens due to their high vertical electron detachment energies (VDE). The largest one is 9.70 eV for [Ca2(CN)5]-1 which is even higher than those of corresponding traditional structures based on fluorine or chlorine ligands. Therefore the superhalogens stronger than the traditional halogen-based structures could be realized by ligands other than halogen atoms. Compared with CCSD(T), outer valence Green's function (OVGF) method either overestimates or underestimates the VDEs for different structures while MP2 results are generally consistent in the aspect of relative values. The extra electrons of the highest VDE anions here aggregate on the bridging CN units with non-negligible distribution occurring on other CN units too. These two features lower both the potential and kinetic energies of the extra electron respectively and thus lead to high VDE. Besides superhalogen properties, the structures, relative stabilities and thermodynamic stabilities with respect to the detachment of cyanide ligand were also investigated. The sum of these results identifies the potential of polynuclear structures with pseudohalogen ligand as suitable candidates with enhanced superhalogens properties.

Rapid and reliable determination of the halogenating peroxidase activity in blood samples.

PubMed

Flemmig, Jörg; Schwarz, Pauline; Bäcker, Ingo; Leichsenring, Anna; Lange, Franziska; Arnhold, Jürgen

2014-12-15

By combining easy and fast leukocyte enrichment with aminophenyl-fluorescein (APF) staining we developed a method to quickly and specifically address the halogenating activity of the immunological relevant blood heme peroxidases myeloperoxidase and eosinophil peroxidase, respectively. For leukocyte enrichment a two-fold hypotonic lysis procedure of the blood with Millipore water was chosen which represents a cheap, fast and reliable method to diminish the amount of erythrocytes in the samples. This procedure is shown to be suitable both to human and murine blood micro-samples, making it also applicable to small animal experiments with recurring blood sampling. As all types of leukocytes are kept in the sample during the preparation, they can be analysed separately after discrimination during the flow cytometry analysis. This also holds for all heme peroxidase-containing cells, namely neutrophils, eosinophils and monocytes. Moreover additional parameters (e.g. antibody staining) can be combined with the heme peroxidase activity determination to gain additional information about the different immune cell types. Based on previous results we applied APF for specifically addressing the halogenating activity of leukocyte peroxidases in blood samples. This dye is selectively oxidized by the MPO and EPO halogenation products hypochlorous and hypobromous acid. This approach may provide a suitable tool to gain more insights into the immune-physiological role of the halogenating activity of heme peroxidases. Copyright © 2014 Elsevier B.V. All rights reserved.

Cyclic Triimidazole Derivatives: Intriguing Examples of Multiple Emissions and Ultralong Phosphorescence at Room Temperature.

PubMed

Lucenti, Elena; Forni, Alessandra; Botta, Chiara; Carlucci, Lucia; Giannini, Clelia; Marinotto, Daniele; Pavanello, Alessandro; Previtali, Andrea; Righetto, Stefania; Cariati, Elena

2017-12-18

The performance of solid luminogens depends on both their inherent electronic properties and their packing status. Intermolecular interactions have been exploited to achieve persistent room-temperature phosphorescence (RTP) from organic molecules. However, the design of organic materials with bright RTP and the rationalization of the role of interchromophoric electronic coupling remain challenging tasks. Cyclic triimidazole has been shown to be a promising scaffold for such purposes owing to its crystallization-induced room-temperature ultralong phosphorescence (RTUP), which has been associated with H-aggregation. Herein, we report three triimidazole derivatives as significant examples of multifaceted emission. In particular, dual fluorescence, RTUP, and phosphorescence from the molecular and supramolecular units were observed. H-aggregation is responsible for the red RTUP, and Br substituents favor yellow molecular phosphorescence while halogen-bonded Br⋅⋅⋅Br tetrameric units are involved in the blue-green phosphorescence. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hydrogen bonding in phytohormone-auxin (IAA) and its derivatives

NASA Astrophysics Data System (ADS)

Kojić-Prodić, Biserka; Kroon, Jan; Puntarec, Vitomir

1994-06-01

The significant importance of hydrogen bonds in biological structures and enzymatic reactions has been demonstrated in many examples. As a part of the molecular recognition study of auxins (plant growth hormones) the influence of hydrogen bonding on molecular conformation, particularly of the carboxyl group, which is one of the biologically active ligand sites, has been studied by X-ray diffraction and computational chemistry methods. The survey includes about 40 crystal structures of free auxins such as indol-3-ylacetic acid and its n-alkylated and halogenated derivatives but also bound auxins such as N-(indol-3-ylacetyl)- L-amino acids, and carbohydrate conjugates. The study includes hydrogen bonds of the NH⋯O and OH⋯O types. The classification of hydrogen bond patterns based on the discrimination between the centrosymmetric and non-centrosymmetric space groups and several examples of hydrogen bond systematics on graph set analysis are also shown.