- Reactions of chloroethenes with atomic chlorine in air at atmospheric pressure
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Relative rate method at the temperature of 298 K and pressure of 1013 hPa and GC-MS detection were used for the study of kinetics of the reactions of Cl atoms with H2C=CCl2, cis-ClHC=CHCl, trans-ClHC=CHCl, ClHC=CCl2, and Cl2C=CCl2. The reaction products were identified by FTIR spectroscopy. A mechanism for the atmospheric degradation of chloro-ethenes has been suggested.
- Morozov,Nielsen,Morozova,Vasiliev,Loukhovitskaya
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- Kinetic and product study of the Cl-initiated oxidation of 1,2,3-trichloropropane (CH2ClCHClCH2Cl)
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The kinetics and products of the Cl atom initiated oxidation of 1,2,3-trichloropropane were studied using FTIR-smog chamber systems at (295 ± 2) K in 700-760 torr of air. The major oxidation product in terms of carbon balance was 1,3-dichloroacetone with smaller amounts of HC(O)Cl and CH2ClC(O)Cl. Chemical activation effects played a significant role in the atmospheric fate of CH2ClCHClO(·) and CH2ClCO(·)ClCH2Cl radicals. The UV-visible spectrum of CH2ClC(O)CH2Cl was measured at 270-385 nm and has a maximum at 305 nm where σ = (1.6 ± 0.2) × 10-19 sq cm/molecule (base e). Assuming a photolysis quantum yield of 1-0.04, the lifetime of CH2ClC(O)CH2Cl with respect to photolysis on a summer day of 40° latitude was 0.5-12 hr. Photolysis was likely to be the dominant atmospheric loss mechanism of CH2ClC(O)CH2Cl. The results were discussed in the context of the atmospheric chemistry of 1,2,3-trichloropropane.
- Barnes,Wallington,Inoue,Voicu,Kawasaki,Becker
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- Matrix isolation study of the photochemically induced reaction of ozone with dibromochloromethane and bromodichloromethane in solid argon at 14 K. FT-IR spectra of the complexes C(O)HCl ... BrX, C(O)HBr ... XCl, C(O)BrCl ... HX, (OC)(HCl)(Br2), (OC)(HBr)(Cl2), and (OC)(BrCl)(HX) (where X = Br or Cl)
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Quartz-filtered (λ > 240 nm) photolysis of either ozone/dibromochloromethane or ozone/bromodichloromethane in an argon matrix at 14 K has been shown by FT-IR spectroscopy to lead to the formation of the carbonyl ... Lewis acid complexes C(O)HCl ... BrX, C(O)HBr ... XCl, C(O)BrCl ... HX, and C(O)Cl2 ... HBr, where X = Br or Cl, depending on the trihalogenomethane used. Several of these complexes are new and are formed by either hydrogen halide or dihalogen abstraction reactions. Upon further irradiation the carbonyl complexes dissociate to form the new carbon monoxide complexes (OC)(HCl)(Br2), (OC)(HBr)(Cl2), and (OC)(BrCl)(HX). Thus the photo-induced reactions of ozone with trihalogenomethanes lead to the formation of new carbonyl and carbon monoxide complexes whose vibrational properties are well characterised by FT-IR spectroscopy. Suggested pathways for the photolyses are presented.
- Clark, Robin J. H.,Dann, Jonathan R.,Foley, Loraine J.
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- IR spectroscopic study of the dichloromethyl peroxyl radical and its deuterated analogs in the argon matrix
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The dichloromethyl peroxyl radical (CHCl2OO?) and its deuterated analog formed in the reaction of the corresponding dichloromethyl radicals with O2 were studied by matrix IR spectroscopy. Dichloromethyl radicals are genera
- Baskir, E. G.,Nefedov, O. M.
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p. 2236 - 2240
(2022/01/22)
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- Reactions of Three Lactones with Cl, OD, and O3: Atmospheric Impact and Trends in Furan Reactivity
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Lactones, cyclic esters of hydroxycarboxylic acids, are interesting biofuel candidates as they can be made from cellulosic biomass and have favorable physical and chemical properties for distribution and use. The reactions of γ-valerolactone (GVL), γ-crotonolactone (2(5H)-F), and α-methyl-γ-crotonolactone (3M-2(5H)-F) with Cl, OD, and O3 were investigated in a static chamber at 700 Torr and 298 ± 2 K. The relative rate method was used to determine kGVL+Cl = (4.56 ± 0.51) × 10-11, kGVL+OD = (2.94 ± 0.41) × 10-11, k2(5H)-F+Cl = (2.94 ± 0.41) × 10-11, k2(5H)-F+OD = (4.06 ± 0.073) × 10-12, k3M-2(5H)-F+Cl = (16.1 ± 1.8) × 10-11, and k3M-2(5H)-F+OD = (12.6 ± 0.52) × 10-12, all rate coefficients in units of cm3 molecule-1 s-1. An absolute rate method was used to determine k2(5H)-F+O3 = (6.73 ± 0.18) × 10-20 and k3M-2(5H)-F+O3 = (5.42 ± 1.23) × 10-19 in units of cm3 molecule-1 s-1. Products were identified for reactions of the lactones with Cl. In the presence of O2 the products are formic acid (HCOOH), formyl chloride (CHClO), and phosgene (CCl2O), and also maleic anhydride (C2H2(CO)2O) for 2(5H)-F. In addition both reactions produced a number of unidentified products that likely belong to molecules with the ring-structure intact. A review of literature data for reactions of other furans show that the reactivity of the lactones are generally lower compared to that of corresponding compounds without the carbonyl group.
- Ausmeel,Andersen,Nielsen,?sterstr?m,Johnson,Nilsson
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p. 4123 - 4131
(2017/06/23)
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- Tropospheric chemical degradation of vinyl and allyl acetate initiated by Cl atoms under high and low NOx conditions
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The products of the reactions of Cl atoms with vinyl acetate (VA) and allyl acetate (AA) have been investigated in a 1080 L chamber using in situ FTIR. The experiments were performed at 296 K and atmospheric pressure of synthetic air in the presence and in the absence of NOx. For the reaction of Cl with VA in the presence of NOx formic acetic anhydride, acetic acid and formyl chloride are the major reaction products. In the absence of NOx, the yields of these products are significantly reduced and formation of the carbon-chain-retaining compound CH3C(O)OC(O)CH2Cl is observed. For the reaction of Cl with AA in the presence of NOx acetoxyacetaldehyde and formaldehyde were observed as the main products. In contrast, without NOx, the observations support that the major reaction pathway is the formation of the carbon-chain-retaining compound CH3C(O)OCH2C(O)CH2Cl. The reaction mechanisms leading to the products are discussed. The formation of the high yields of formyl chloride and formaldehyde in the reactions of Cl with VA and AA, respectively, are at odds with currently accepted mechanistic pathways.
- Blanco, María B.,Bejan, Iustinian,Barnes, Ian,Wiesen, Peter,Teruel, Mariano A.
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p. 48154 - 48163
(2015/06/16)
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- Atmospheric chemistry of t-CF3CHCHCl: Products and mechanisms of the gas-phase reactions with chlorine atoms and hydroxyl radicals
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FTIR-smog chamber techniques were used to study the products and mechanisms of the Cl atom and OH radical initiated oxidation of trans-3,3,3-trifluoro-1- chloro-propene, t-CF3CHCHCl, in 700 Torr of air or N 2/O2 diluent at 296 ± 2 K. The reactions of Cl atoms and OH radicals with t-CF3CHCHCl occur via addition to the CC double bond; chlorine atoms add 15 ± 5% at the terminal carbon and 85 ± 5% at the central carbon, OH radicals add approximately 40% at the terminal carbon and 60% at the central carbon. The major products in the Cl atom initiated oxidation of t-CF3CHCHCl were CF3CHClCHO and CF3C(O)CHCl2, minor products were CF3CHO, HCOCl and CF3COCl. The yields of CF3C(O)CHCl2, CF3CHClCOCl and CF3COCl increased at the expense of CF3CHO, HCOCl and CF3CHClCHO as the O2 partial pressure was increased over the range 10-700 Torr. Chemical activation plays a significant role in the fate of CF3CH(O)CHCl2 and CF 3CClHCHClO radicals. In addition to reaction with O2 to yield CF3COCl and HO2 the major competing fate of CF 3CHClO is Cl elimination to give CF3CHO (not C-C bond scission as previously thought). As part of this study k(Cl + CF 3C(O)CHCl2) = (2.3 ± 0.3) × 10-14 and k(Cl + CF3CHClCHO) = (7.5 ± 2.0) × 10-12 cm3 molecule-1 s-1 were determined using relative rate techniques. Reaction with OH radicals is the major atmospheric sink for t-CF3CHCHCl. Chlorine atom elimination giving the enol CF3CHCHOH appears to be the sole atmospheric fate of the CF 3CHCHClOH radicals. The yield of CF3COOH in the atmospheric oxidation of t-CF3CHCHCl will be negligible (3CHCHCl. the Owner Societies 2012.
- Andersen, M. P. Sulbaek,Nielsen,Hurley,Wallington
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experimental part
p. 1735 - 1748
(2012/04/23)
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- Atmospheric chemistry of CF3CF{double bond, long}CH2: Products and mechanisms of Cl atom and OH radical initiated oxidation
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The products of Cl atom and OH radical initiated oxidation of CF3CF{double bond, long}CH2 were studied in 700 Torr of N2/O2 diluent at 296 ± 1 K. The reactions of Cl atoms and OH radicals with CF3CF{double bond, long}CH2 proceed via electrophilic addition to the double bond. The reaction with chlorine atoms proceeds 56 ± 5% via addition to the central carbon. The chlorine atom initiated oxidation of CF3CF{double bond, long}CH2 gives CF3C(O)F in a molar yield which is indistinguishable from 100% and independent of [O2], and HC(O)Cl in a molar yield which increased from 30% to 59% as [O2] was increased from 3 to 700 Torr. The OH radical initiated oxidation of CF3CF{double bond, long}CH2 gives CF3C(O)F as major product in a yield of 91 ± 6%. The results are discussed with respect to the atmospheric chemistry and environmental impact of CF3CF{double bond, long}CH2.
- Hurley,Wallington,Javadi,Nielsen
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experimental part
p. 263 - 267
(2008/10/09)
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- Rate coefficients and mechanisms of the reaction of Cl-atoms with a series of unsaturated hydrocarbons under atmospheric conditions
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The rate coefficients and mechanisms of the reaction of Cl-atoms with a series of unsaturated hydrocarbons under atmospheric conditions were studied. It was observed the product yielded from both trans-2-butene and 1-butene were found to be oxygen dependent. The results showed that the variation of the product yielded with O2 in the case of 1-butene resulted from competitive reaction pathways for the two β-chlorobutoxy radicals involved in the oxidation.
- Orlando, John J.,Tyndall, Geoffrey S.,Apel, Eric C.,Riemer, Daniel D.,Paulson, Suzanne E.
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p. 334 - 353
(2007/10/03)
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- NOVEL COMPOUNDS USEFUL AS NEURO-PROTECTIVE AGENTS
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This invention relates to novel phenyl oxazoles, thiazoles, oxazolines, oxadiazoles and benzoxazoles useful as neuro-protective agents.
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- Temperature-dependent rate coefficient measurements for the reaction of bromine atoms with trichloroethene, ethene, acetylene, and tetrachloroethene in air
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In this article, rate coefficients for the reaction of Br atoms with a series of unsaturated species (trichloroethene, k1; ethene, k2; acetylene, k3; and tetrachloroethene, k4) are reported in 700 Torr air over the temperature range 228-298 K. The data were obtained in a temperature-regulated environmental chamber/FTIR spectrometer system, using standard relative rate techniques, with the reaction of Br with CH2O and CH3CHO as the reference reactions. Room-temperature values for k1 through k4 were found to be 1.56×10-13, 1.23×10-13, 2.86×10-14, and -16 cm3 molecule-1 s-1, respectively, in reasonable accord with previously available data. At 240 K, values of k1 = 1.77×10-12, k2 = 5.76×10-13, k3 = 3.97×10-14, and k4 = 3.22×10-15 cm3 molecule-1 s-1 are reported. These k2 and k3 values are 2-3 times lower than those currently in use, which are obtained by extrapolation of previous measurements made over the range 298-350 K. An investigation of the mechanism of the Br-atom-initiated oxidation of acetylene, trichloroethene, and tetrachloroethene was also conducted as a function of temperature. Although no temperature dependence to the product yields was observed for any of the systems studied, the product distributions were found to be altered by the presence of NOx in the case of trichloroethene and tetrachloroethene. An anomalously low rate coefficient for the reaction of Br with glyoxal (HC(O)CHO, a product of acetylene oxidation), k17 = 1.1×10-14 cm3 molecule-1 s-1, is also reported.
- Ramacher, Bjoern,Orlando, John J.,Tyndall, Geoffrey S.
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p. 198 - 211
(2007/10/03)
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- Compounds useful as neuro-protective agents
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This invention relates to novel phenyl oxazoles, thiazoles, oxazolines, oxadiazoles and benzoxazoles useful as neuro-protective agents.
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- Method for treating neuropathic pain
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The present invention provides a method for treating neuropathic pain comprising administering an analgesic dosage of a compound of formula I to an animal in need of such treatment certain phenyl oxazoles or phenyl thiazoles.
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- Method for treating pain
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The present invention provides a method for treating pain using a composition comprising certain phenyl oxazoles or phenyl thiazoles in combination with a Drug Useful in the Treatment of Pain.
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- Use of phenyl oxazole or phenyl thiazole derivatives for treating neuropathic pain
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The present invention provides a method for treating neuropathic pain comprising administering an analgesic dosage of a compound of formula I to an animal in need of such treatment certain phenyl oxazoles or phenyl thiazoles.
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- Method for treating pain
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The present invention provides a method for treating pain using a composition comprising certain phenyl oxazoles or phenyl thiazoles in combination with a Drug Useful in the Treatment of Pain.
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- Use of phenyl oxazole or phenyl thiazole derivatives for treating pain
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The present invention provides a method for treating pain comprising administering to an animal in need of such treatment, an analgesic dosage of certain phenyl oxazoles or phenyl thiazoles.
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- FT-IR product studies of the Cl-initiated oxidation of CH3Cl in the presence of NO
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The Cl-atom initiated oxidation of CH3Cl has been studied at 296 K using two different FTIR/environmental chamber systems. In the presence of NO, the carbon-bearing products observed are HCOCl, HCHO, and CO, with yields in 700 Torr of air of (56 ± 10), (32 ± 6), and (12 ± 5)%, respectively. This product distribution is different from previous studies conducted in the absence of NO, in which a nearly 100% yield of HCOCl was obtained. The different product distribution observed in the presence of NO is attributed to the formation and subsequent decomposition of chemically activated CH2ClO2 radicals, formed in the exothermic reaction of CH2ClO2 with NO.
- Bilde, Merete,Orlando, John J.,Tyndall, Geoffrey S.,Wallington, Timothy J.,Hurley, Michael D.,Kaiser
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p. 3963 - 3968
(2007/10/03)
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- Temperature dependence of the rate coefficients for the reaction of chlorine atoms with chloromethanes
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Rate coefficients for the reaction of Cl atoms with CH3Cl (k1), CH2Cl2 (k2), and CHCl3 (k3) have been determined over the temperature range 222-298 K using standard relative rate techniques. These data, when combined with evaluated data from previous studies, lead to the following Arrhenius expressions (all in units of cm3 molecule-1 s-1): k1 = (2.8±0.3)×10-11 exp(-1200±150/T); k2 = (1.5±0.2)×10-11 exp(-1100±150/T); k3 = (0.48±0.05)×10-11 exp(-1050±150/T). Values for k1 are in substantial agreement with previous measurements. However, while the room temperature values for k2 and k3 agree with most previous data, the activation energies for these rate coefficients are substantially lower than previously recommended values. In addition, the mechanism of the oxidation of CH2Cl2 has been studied. The dominant fate of the CHCl2O radical is decomposition via Cl-atom elimination, even at the lowest temperatures studied in this work (218 K). However, a small fraction of the CHCl2O radicals are shown to react with O2 at low temperatures. Using an estimated value for the rate coefficient of the reaction of CHCl2O with O2 (1×10-14 cm3 molecule-1 s-1), the decomposition rate coefficient for CHCl2O is found to be about 4×106 s-1 at 218 K, with the barrier to its decomposition estimated at 6 kcal/mole. As part of this work, the rate coefficient for Cl atoms with HCOCl was also been determined, k7 = 1.4×10-11 exp(-885/T) cm3 molecule-1 s-1, in agreement with previous determinations.
- Orlando, John J.
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p. 515 - 524
(2007/10/03)
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- An infrared study of the reaction of acetylene halides: HCCCl with O2
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The reaction of HCCCl with O2 has been investigated by using the FTIR/matrix isolation technique. The twin-jet codeposition and merged single jet deposition at short sample distances, in either the gas phase or an Ar matrix, gave no apparent new band. Many new peaks were observed as the merged length increased to 19 cm. From the position of the new absorptions, CO, CO2, and formyl chloride (HCOCl) are observed as major products. Glyxoal chloride (HCOCOCl) is tentatively assigned as an intermediate and is isolated for the first time in this study. The possible reaction mechanism is also discussed.
- Hwang, Mei-Lee,Hsu, Wei-Liang
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- FTIR study of the Cl- and Br-atom initiated oxidation of trichloroethylene
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The Cl- and Br- initiated oxidations of CHCl=CCl2 in 700 torr of air at 296 K have been studied using a Fourier transform infrared spectrometer. Rate constants k(Cl + CHCl=CCl2) = (7.2 ± 0.8) × 10-1 and k(Br + CHCl=CCl2) = (1.1 ± 0.4) × 1013 cm3 molecule-1 s-1 were determined using a relative rate technique with ethane and ethylene as references, respectively. The major products observed were CHXClC(O)Cl, (X = Cl or Bl), CHClO, and CCl2O. Combining results obtained for the Cl-initiated oxidation of CHCl2 - CHCl2, we deduced that Cl-addition on trichloroethylene occurs via channel 1a, Cl + CHCl=CCl2 → CHCl2-CCl2, (100 ± 12)%. Self-reaction of the subsequently generated peroxy radicals CHCl2-CCl2O2 leads to CHCl2CCl2O radicals which were found to decompose via channel 8a, CHCl2C(O)Cl + Cl, (91 ± 11)% of the time, and channel 8b, CHCl2 + CCl2O. (9 ± 2)%. The reaction Br + CHCl=CCl2 → CHBrCl-CCl2 (17a) accounted for ≥(96 ± 11)% of the total reaction. Decomposition of the CHBrCl-CCl2O radicals proceeds (≥93 ± 11)% via CHBrClC(O)Cl + Cl. As part of this work, k(Cl + CHCl2C(O)Cl) = (3.6 ± 0.6) × 10-14and k(Cl + CHCl2-CHCl2) = (1.9 ± 0.2) × 10-13 cm3 molecule-1 s-1 were measured. Errors reported above include statistical uncertainties (2σ) and estimated systematic uncertainties.
- Catoire,Ariya,Niki,Harris
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p. 695 - 704
(2007/10/03)
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- FTIR Kinetic and Mechanistic Study of the Atmospheric Chemistry of Methyl Thiolformate
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Some aspects of the atmospheric chemistry of methyl thiolformate (CH3SCHO), a recently detected intermediate in the oxidation of dimethyl sulfide, have been investigated at 298 K and 1000 mbar total pressure in large reaction chambers using long path in situ FTIR absorption spectroscopy for the analysis.Rate coefficients of (1.11 +/- 0.22)E-11 and (5.80 +/- 0.80)E-11 cm3 molecule-1 s-1 have been determined for its reaction with OH radicals and Cl atoms, respectively.The UV spectrum of CH3SCHO has been measured in the range 220-355 nm and a lower limit of 5.4 days determined for its atmospheric photolytic lifetime.Detailed product analyses have made for the OH and Cl initiated photooxidation of CH3SCHO.Strong SO absorption bands observed in both systems are tentatively assigned to CH3SOCHO in the OH system and to CH3SOCl in the Cl system.The first gas-phase spectra of CH3SCl and CH3SOCl are also presented.The results are discussed with respect to the atmospheric chemistry of CH3SCHO and possible consequences for the photooxidation mechanism of dimethyl sulfide.
- Patroescu, Iulia V.,Barnes, Ian,Becker, Karl H.
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p. 17207 - 17217
(2007/10/03)
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- Kinetics of the cross reactions of CH3O2 and C2H5O2 radicals with selected peroxy radicals
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The kinetics of the reactions of selected peroxy radicals (RO2) with CH3O2 and with C2H5O2 have been investigated using two techniques: excimer-laser photolysis and conventional flash photolysis, both coupled with UV absorption spectrometry. Radicals were generated either by photolysis of molecular chlorine in the presence of suitable hydrocarbons or by photolysis of the appropriate alkyl chloride. All such cross-reaction kinetics were investigated at 760 Torr total pressure and room temperature except for the reaction of the allylperoxy radical with CH3O2, for which the rate constant was determined between 291 and 423 K, resulting in the following rate expression: k15 = (2.8 ± 0.7) × 10-13 exp[(515 ± 75)/T] cm3 molecule-1 s-1. Values of (2.0 ± 0.5) × 10-13, (1.5 ± 0.5) × 10-12, (9.0 ± 0.15) × 10-14, -12, (2.5 ± 0.5) × 10-12, and (8.2 ± 0.6) × 10-12 (units of cm3 molecule-1 s-1) have been obtained for the reactions of CH3O2 radicals with C2H5O2, neo-C5H11O2, c-C6H11O2, C6H5CH2O2, CH2ClO2, and CH3C(O)O2, respectively, and (1.0 ± 0.3) × 10-12, (5.6 ± 0.8) × 10-13, (4.0 ± 0.2) × 10-14, and (1.0 ± 0.3) × 10-11 (units of cm3 molecule-1 s-1) for the reactions of C2H5O2 with CH2=CHCH2O2, neo-C5H11O2, c-C6H11O2, and CH3C(O)O2 radicals, respectively. These rate constants were obtained by numerical simulations of the complete reaction mechanisms, which were deduced from the known mechanisms of the corresponding peroxy radical self-reactions. A systematic analysis of propagation of errors was carried out for each reaction to quantify the sensitivity of the cross-reaction rate constant to the parameters used in kinetic simulations. The rate constant for a given cross reaction is generally found to be between the rate constants for the self-reactions of RO2 and CH3O2 (or C2H5O2). However, when the RO2 self-reaction is fast, the cross reaction with CH3O2 (or C2H5O2) is also fast, with similar rate constants for both reactions, suggesting that these particular peroxy radical cross reactions can play a significant role in the chemistry of hydrocarbon oxidation processes in the troposphere and in low-temperature combustion. Relationships between cross-reaction and self-reaction rate constants are suggested.
- Villenave, Eric,Lesclaux, Robert
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p. 14372 - 14382
(2007/10/03)
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- Atmospheric chemistry of 1,2-dichloroethane: UV spectra of CH2ClCHCl and CH2ClCHClO2 radicals, kinetics of the reactions of CH2ClCHCl radicals with O2 and CH2ClCHClO2 radicals with NO and NO2, and fate of the alkoxy radical CH2ClCHClO
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A pulse radiolysis technique was used to measure the UV absorption spectra of CH2ClCHCl and CH2ClCHClO2 radicals over the range 230-300 nm. At 250 nm, σ(CH2ClCHCl) = (1.7 ± 0.2) × 10-18 and σ(CH2ClCHClO2) = (3.5 ± 0.5) × 10-18 cm2 molecule-1. The observed self-reaction rate constant for CH2ClCHCl radicals, defined as -d[CH2ClCHCl]/dt = 2k4[CH2ClCHCl]2 was k4 = (2.0 ± 0.3) × 10-11 cm3 molecule-1 s-1. The rate constant for reaction of CH2ClCHCl radicals with O2 in one bar of SF6 diluent was (2.4 ± 0.3) × 10-12 cm3 molecule-1 s-1. The rate constants for the reactions of CH2ClCHClO2 radicals with NO and NO2 were k5 ≥ 9 × 10-12 and k6 = (9.8 ± 0.6) × 10-12 cm3 molecule-1 s-1, respectively. The rate constant for the reaction of F atoms with CH2ClCH2Cl was k3 = (2.6 ± 0.2) × 10-11 cm3 molecule-1 s-1. The reaction of CH2ClCHClO2 radicals with NO produced NO2 and, by implication, CH2ClCHClO radicals. A FTIR spectroscopic technique showed that CH2ClCHClO radicals undergo both reaction with O2 and decomposition via intramolecular 3-center HCl elimination. In 700 Torr of air at 296 K the rate constant ratio KO2/kdecomp = (2.3 ± 0.2) × 10-20 cm3 molecule-1. A lower limit of 4 × 105 s-1 was deduced for the rate of intramolecular 3-center HCl elimination from CH2ClCHClO radicals at 296 K in 1 bar of SF6 diluent. As part of this work a relative rate technique was used to measure rate constants of (1.3 ± 0.2) × 10-12 and (6.4 ± 1.4) × 10-14 cm3 molecule-1 s-1 for the reactions of Cl atoms with CH2ClCH2Cl and CH2ClC(O)Cl, respectively. All experiments were performed at 296 K. Results are discussed in the context of the atmospheric chemistry of 1,2-dichloroethane.
- Wallington, Timothy J.,Bilde, Merete,Mogelberg, Trine E.,Sehested, Jens,Nielsen, Ole J.
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p. 5751 - 5760
(2007/10/03)
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- FTIR Spectroscopic Study of the Cl-Atom-Initiated Reactions of Ethylene Oxide in O2/N2 Diluent
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A long-path FTIR spectroscopic study of the Cl-atom-initiated reactions of ethylene oxide was carried out at 297+/-2 K in the photolysis (300 mn) of mixtures containing and Cl2 in both the torr millitorr ranges in 700 Torr of N2 or O2/N2 diluent.In 700 Torr of N2, the only primary product detected was , formed via (1) Cl+ -> + HCl followed by (2) + Cl2 -> + Cl.Thus, the cyclic oxiranyl radical formed in reaction 1 was sufficiently long-lived to react with Cl2.An upper limit value of k34 s-1 has been esmimated for the rate constant of the possible oxiranyl-to-vinoxy isomerization: (3) -> CH2CHO.The yield decreased with increase in added O2 due to the occurrence of reaction 4: (4) + O2 (+M) -> (+M).A value of k2/k4=2.0+/-0.4 was derived from the O2 dependence of the yield.In 700 Torr of air, the observed products included C-O-C bonded compounds HC(O)OCHO and CH2(OH)OCHO, and one-carbon species CO, CO2, HCHO, and HC(O)OH, but not C-C bonded products.The preferential formation of C-O-C rather than C-C bonded products suggests the predominant cleavage of the C-C bond rather than the C-O bond in a three membered ring precursor radical.The most likely candidate is the cyclic radical formed via self-reaction, i.e. -> + O2.A detailed mechanism is proposed for the oxidation of the radical leading to the formation of the observed products.
- Chen, J.,Young V.,Hooshiyar, P. A.,Niki, H.,Hurley, M. D.
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p. 4071 - 4077
(2007/10/02)
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- Photooxidation of exhaust pollutants: III. Photooxidation of the chloroethenes: Degradation efficiencies, quantum yields and products
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The photochemical decomposition and oxidation of the chloroethenes C2H4-XClX (x=1-4) was investigated in the gas phase by irradiation with a low pressure mercury lamp in an oxygen atmosphere. Degradation efficiencies directly depend on the number of chlorine atoms both at 185 and 254 nm. The quantum yields for degradation increase from 2-3 for vinyl chloride to > 100 for tri- and tetrachloroethene at 185 nm in the 10-3 bar concentration range. At 254 nm we measured nearly time independent quantum yields of around 10 for tri- and 40 for tetrachloroethene. The photooxidation products and their mechanism of formation are discussed in detail.
- Guertler,Moeller,Sommer,Mueller,Kleinermanns
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p. 1671 - 1682
(2007/10/03)
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- Photooxidation of exhaust pollutants - II. Photooxidation of chloromethanes: Degradation efficiencies, quantum yields and products
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The photochemical decomposition and oxidation, of CHxCly (x = O-3, y = 4-x) was investigated in the gas phase by irradiation with a low pressure mercury lamp in an oxygen atmosphere. The degradation efficiency depends on the concentration of the pollutant, the power output of the UV-lamp and the irradiation time. The quantum yields for degradation at 185 nm were measured to be around 1 at low CHxCly concentration in the 10-3 range. For CH2Cl2 and CHCl3 however, we observed a drastic increase of the quantum yields to values up to one hundred at high CHxCly concentration in the 10-2 range. For CH3Cl and CCl4 no significant increase of quantum yield with concentration was found. In addition to the main products HCl, phosgene and formyl chloride we found CO, CO2 and formic acid. The mechanisms of their formation are discussed in detail.
- Guertler,Kleinermanns
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p. 1289 - 1298
(2007/10/03)
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- FTIR Study of the Mechanism of the Cl and Br Atom Initiated Oxidation of Acetylene
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FTIR analysis of the products of the Cl and Br atom initiated oxidation of C2H2 at 700 Torr total pressure of N2/O2 diluent and 296 +/- 2 K has shown that the (halovinyl)peroxy radical (XCH=CHOO; X = Cl or Br) formed primarily undergoes isomerization followed by unimolecular dissociation to (a) HC(O)X + HCO, (b) HC(O)CHO + X, and (c) HX + CO + HCO.The branching ratios determined were a:b:c = 0.26:0.21:0.53, for X = Cl, and 0.17:0.09:0.74, for X = Br, independent of O2 pressure in the range 10-700 Torr.The formation of O3 in ca. 10percent yield, depending on O2 pressure, was observed in both the Cl and Br atom initiated oxidations, and it is proposed that a small fraction of the (halovinyl)peroxy radicals reacts with O2 to form O3 and a (halovinyl)oxy radical (XCH=CHO).It is noted that addition of a halogen atom to acetylene can produce both cis and trans isomers of both the halovinyl and the (halovinyl)peroxy radicals.On steric grounds, the isomerization rate may be slower for the cis form of the (halovinyl)oxy radical than for the trans form, thereby leading to the formation of O3 preferentially via (cis-halovinyl)oxy radical.Evidence for the formation of HO radical was also obtained in both the Cl and Br atom initiated oxidations, and this has been attributed to the O2 reaction of the (halovinyl)oxy radical: XCHCHO + O2 -> >XCH(OO)CHO> -> HC(O)X + CO + HO.
- Yarwood, G.,Peng, N.,Niki, H.
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p. 7330 - 7337
(2007/10/02)
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- Kinetics of Oxidation of Methanol, Ethanol and n-Propanol by t-Butyl Hypochlorite
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The kinetics of oxidation of ethanol (methanol or n-propanol) with t-BuOCl have been investigated at 40 deg C.The order of reaction is one each with respect to ethanol and t-BuOCl.The effect of ionic strength, and various metallic chlorides on the reaction rate has been studied.The various activation parameters have been evaluated.A mechanism involving ester formation is proposed.
- Kudesia, V. P.,Sharma, B. K.
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