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1.
Andre Silva Pimentel Geoffrey S. Tyndall John J. Orlando Michale D. Hurley Timothy J. Wallington Mads P. Sulbaek Andersen Paul Marshall Theodore S. Dibble 《国际化学动力学杂志》2010,42(8):479-498
Formates are produced in the atmosphere as a result of the oxidation of a number of species, notably dialkyl ethers and vinyl ethers. This work describes experiments to define the oxidation mechanisms of isopropyl formate, HC(O)OCH(CH3)2, and tert‐butyl formate, HC(O)OC(CH3)3. Product distributions are reported from both Cl‐ and OH‐initiated oxidation, and reaction mechanisms are proposed to account for the observed products. The proposed mechanisms include examples of the α‐ester rearrangement reaction, novel isomerization pathways, and chemically activated intermediates. The atmospheric oxidation of isopropyl formate by OH radicals gives the following products (molar yields): acetic formic anhydride (43%), acetone (43%), and HCOOH (15–20%). The OH radical initiated oxidation of tert‐butyl formate gives acetone, formaldehyde, and CO2 as major products. IR absorption cross sections were derived for two acylperoxy nitrates derived from the title compounds. Rate coefficients are derived for the kinetics of the reactions of isopropyl formate with OH (2.4 ± 0.6) × 10?12, and with Cl (1.75 ± 0.35) × 10?11, and for tert‐butyl formate with Cl (1.45 ± 0.30) × 10?11 cm3 molecule?1 s?1. Simple group additivity rules fail to explain the observed distribution of sites of H‐atom abstraction for simple formates. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 479–498, 2010 相似文献
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The kinetics of elementary gas phase reactions involved in the oxidation of reduced sulfur species, H2S, CS2, OCS, CH3SH, CH3SCH3, and CH3SSCH3, to SO2 (or other products) are reviewed. The reactions with OH and NO3 which are the processes that initiate the degradation of the above compounds have been evaluated. Reactions of key intermediates, HS, HSO, CH3S, and CH3SO, are discussed. Whenever possible, recommendations for the rate coefficients are made and the need for further work indicated. The review has been carried out with the atmospheric chemistry in mind by looking at the laboratory based kinetics data. This review also provides information that will help model the Earth's sulfur cycle. 相似文献
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D A Tyndall 《Magnetic resonance imaging》1990,8(4):423-433
This investigation was undertaken in order to ascertain the combined effects of magnetic resonance imaging (MRI) fields and x-irradiation on the developing eye of the mouse strain C57B1/6J. Dams in groups of 15 were subjected to absorbed doses of 5, 15, and 30 cGy. Other dams (N = 15) were exposed to T2 spin-echo MRI fields under clinically realistic conditions following exposure to 30 cGy of x-irradiation. The developing eye was the biological end point studied. It was found that the 30-cGy dose resulted in teratogenic significance (p less than or equal to .05) for the C57B1/6J mouse. Groups exposed to both types of radiation fields demonstrated malformation levels similar to the 30-cGy irradiated animals with no additive or synergistic effects detected. The malformation rates and degree of statistical significance varied somewhat with unit of measurement, and analytical method. The results confirmed low level X-ray teratogenicity and suggested that the MRI techniques employed for this investigation did not enhance the teratogenicity of x-irradiation on eye malformations produced in the C57B1/6J mouse. 相似文献
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John J. Orlando Geoffrey S. Tyndall Eric C. Apel Daniel D. Riemer Suzanne E. Paulson 《国际化学动力学杂志》2003,35(8):334-353
Rate coefficients and/or mechanistic information are provided for the reaction of Cl‐atoms with a number of unsaturated species, including isoprene, methacrolein ( MACR ), methyl vinyl ketone ( MVK ), 1,3‐butadiene, trans‐2‐butene, and 1‐butene. The following Cl‐atom rate coefficients were obtained at 298 K near 1 atm total pressure: k(isoprene) = (4.3 ± 0.6) × 10?10cm3 molecule?1 s?1 (independent of pressure from 6.2 to 760 Torr); k( MVK ) = (2.2 ± 0.3) × 10?10 cm3 molecule?1 s?1; k( MACR ) = (2.4 ± 0.3) × 10?10 cm3 molecule?1 s?1; k(trans‐2‐butene) = (4.0 ± 0.5) × 10?10 cm3 molecule?1 s?1; k(1‐butene) = (3.0 ± 0.4) × 10?10 cm3 molecule?1 s?1. Products observed in the Cl‐atom‐initiated oxidation of the unsaturated species at 298 K in 1 atm air are as follows (with % molar yields in parentheses): CH2O (9.5 ± 1.0%), HCOCl (5.1 ± 0.7%), and 1‐chloro‐3‐methyl‐3‐buten‐2‐one (CMBO, not quantified) from isoprene; chloroacetaldehyde (75 ± 8%), CO2 (58 ± 5%), CH2O (47 ± 7%), CH3OH (8%), HCOCl (7 ± 1%), and peracetic acid (6%) from MVK ; CO (52 ± 4%), chloroacetone (42 ± 5%), CO2 (23 ± 2%), CH2O (18 ± 2%), and HCOCl (5%) from MACR ; CH2O (7 ± 1%), HCOCl (3%), acrolein (≈3%), and 4‐chlorocrotonaldehyde (CCA, not quantified) from 1,3‐butadiene; CH3CHO (22 ± 3%), CO2 (13 ± 2%), 3‐chloro‐2‐butanone (13 ± 4%), CH2O (7.6 ± 1.1%), and CH3OH (1.8 ± 0.6%) from trans‐2‐butene; and chloroacetaldehyde (20 ± 3%), CH2O (7 ± 1%), CO2 (4 ± 1%), and HCOCl (4 ± 1%) from 1‐butene. Product yields from both trans‐2‐butene and 1‐butene were found to be O2‐dependent. In the case of trans‐2‐butene, the observed O2‐dependence is the result of a competition between unimolecular decomposition of the CH3CH(Cl)? CH(O?)? CH3 radical and its reaction with O2, with kdecomp/kO2 = (1.6 ± 0.4) × 1019 molecule cm?3. The activation energy for decomposition is estimated at 11.5 ± 1.5 kcal mol?1. The variation of the product yields with O2 in the case of 1‐butene results from similar competitive reaction pathways for the two β‐chlorobutoxy radicals involved in the oxidation, ClCH2CH(O?)CH2CH3 and ?OCH2CHClCH2CH3. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 334–353, 2003 相似文献
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Upper limits of 4×10−20 and 7×10−20 cm3 molecule−1 s−1 were established for the gas-phase reactions of H2O2 with O3 and NO, respectively. These reactions are too slow to explain features observed in the atmospheric vertical profile of H2O2. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 707–709, 1998 相似文献
7.
The reaction Cl + CH3CHO → HCl + CH3CO (1) was studied using flash photo‐lysis / tunable diode laser absorption spectroscopy to monitor the production of HCl. The rate coefficient, k1, was measured to be (7.5 ± 0.8) × 10−11 cm3 molecule−1 s−1 at 298 K. HCl (v = 0) and HCl† (v = 1) were measured directly in this study and the yields of HCl (v = 0, 1, >1) for the reaction of Cl with CH3CHO were determined to be 0.44 ± 0.15, 0.56 ± 0.15, and <0.04, respectively. The rate coefficient for the quenching of HCl† (v = 1) by CH3CHO was k17e = (4.8 ± 1.2) × 10−11 cm3 molecule−1 s−1. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 766–775, 1999 相似文献
8.
Hasson AS Tyndall GS Orlando JJ Singh S Hernandez SQ Campbell S Ibarra Y 《The journal of physical chemistry. A》2012,116(24):6264-6281
An important chemical sink for organic peroxy radicals (RO(2)) in the troposphere is reaction with hydroperoxy radicals (HO(2)). Although this reaction is typically assumed to form hydroperoxides as the major products (R1a), acetyl peroxy radicals and acetonyl peroxy radicals have been shown to undergo other reactions (R1b) and (R1c) with substantial branching ratios: RO(2) + HO(2) → ROOH + O(2) (R1a), RO(2) + HO(2) → ROH + O(3) (R1b), RO(2) + HO(2) → RO + OH + O(2) (R1c). Theoretical work suggests that reactions (R1b) and (R1c) may be a general feature of acyl peroxy and α-carbonyl peroxy radicals. In this work, branching ratios for R1a-R1c were derived for six carbonyl-containing peroxy radicals: C(2)H(5)C(O)O(2), C(3)H(7)C(O)O(2), CH(3)C(O)CH(2)O(2), CH(3)C(O)CH(O(2))CH(3), CH(2)ClCH(O(2))C(O)CH(3), and CH(2)ClC(CH(3))(O(2))CHO. Branching ratios for reactions of Cl-atoms with butanal, butanone, methacrolein, and methyl vinyl ketone were also measured as a part of this work. Product yields were determined using a combination of long path Fourier transform infrared spectroscopy, high performance liquid chromatography with fluorescence detection, gas chromatography with flame ionization detection, and gas chromatography-mass spectrometry. The following branching ratios were determined: C(2)H(5)C(O)O(2), Y(R1a) = 0.35 ± 0.1, Y(R1b) = 0.25 ± 0.1, and Y(R1c) = 0.4 ± 0.1; C(3)H(7)C(O)O(2), Y(R1a) = 0.24 ± 0.15, Y(R1b) = 0.29 ± 0.1, and Y(R1c) = 0.47 ± 0.15; CH(3)C(O)CH(2)O(2), Y(R1a) = 0.75 ± 0.13, Y(R1b) = 0, and Y(R1c) = 0.25 ± 0.13; CH(3)C(O)CH(O(2))CH(3), Y(R1a) = 0.42 ± 0.1, Y(R1b) = 0, and Y(R1c) = 0.58 ± 0.1; CH(2)ClC(CH(3))(O(2))CHO, Y(R1a) = 0.2 ± 0.2, Y(R1b) = 0, and Y(R1c) = 0.8 ± 0.2; and CH(2)ClCH(O(2))C(O)CH(3), Y(R1a) = 0.2 ± 0.1, Y(R1b) = 0, and Y(R1c) = 0.8 ± 0.2. The results give insights into possible mechanisms for cycling of OH radicals in the atmosphere. 相似文献
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Christelle Lemaitre-Guillier Agns Chartier Christelle Dufresne Antonin Douillet Stphanie Cluzet Josep Valls Nicolas Aveline Xavier Daire Marielle Adrian 《Molecules (Basel, Switzerland)》2022,27(18)
The present study is aimed at determining whether leaf volatile organic compounds (VOCs) are good markers of the grapevine response to defence elicitors in the field. It was carried out in two distinct French vineyards (Burgundy and Bordeaux) over 3 years. The commercial elicitor Bastid® (Syngenta, Saint-Sauveur, France) (COS-OGA) was first used to optimise the VOCs’ capture in the field; by bagging stems together with a stir bar sorptive extraction (SBSE) sensor. Three elicitors (Bastid®, copper sulphate and methyl jasmonate) were assessed at three phenological stages of the grapevines by monitoring stilbene phytoalexins and VOCs. Stilbene production was low and variable between treatments and phenological stages. VOCs—particularly terpenes—were induced by all elicitors. However, the response profiles depended on the type of elicitor, the phenological stage and the vineyard, and no sole common VOC was found. The levels of VOC emissions discriminated between weak (Bastid® and copper sulphate) and strong (methyl jasmonate) inducers. Ocimene isomers were constitutively present in the overall blends of the vineyards and increased by the elicitors’ treatments, whilst other VOCs were newly released throughout the growing seasons. Nonetheless, the plant development and climate factors undoubtedly influenced the release and profiles of the leaf VOCs. 相似文献
10.
D.W.T. Griffith G.S. Tyndall J.P. Burrows G.k. Moortgat 《Chemical physics letters》1984,107(3):341-346
High-resolution FTIR-isolation spectra of chlorine nitrate in nitrogen and argon matrices have been studied and a full analysis based on planar ClONO2 and known impurities carried out. No evidence for isomers of ClONO2 has been found; if present, their concentrations must be less than 1% of parent ClONO2. 相似文献