Theoretical Studies of the Gas-Phase Reactions of S-Methyl Methanesulfinothioate (Dimethyl Thiosulfinate) with OH and Cl Radicals: Reaction Mechanisms, Energetics, and Kinetics.
J Phys Chem A
; 123(39): 8448-8459, 2019 Oct 03.
Article
em En
| MEDLINE
| ID: mdl-31265290
ABSTRACT
The mechanisms, energetics, and kinetics of the gas-phase reactions of terrestrial plant-derived dimethyl thiosulfinate (DMTS) with the atmospheric oxidants OH and Cl radicals were investigated using high-level ab initio calculations. The results show that the addition of OH and Cl radicals to the sulfinyl [-S(âO)] of DMTS, followed by S(âO)-S single bond cleavage to form methanesulfinic acid + CH3S⢠and methanesulfinyl chloride + CH3Sâ¢, respectively, are the more dominant reactions. The barrier heights for the reactions with OH and Cl radicals were found to be -5.6 and -12.7 kcal/mol relative to the energies of the starting reactants, respectively, when computed at the CCSD(T)/aug-cc-pVTZ//M06-2X/6-311++G(3df,3pd) level of theory. The rate constants for all possible pathways of DMTS + â¢OH/â¢Cl reactions were investigated using the MESMER kinetics code over the temperature range between 200 and 300 K. The calculated global rate constants for the DMTS + â¢OH and DMTS + â¢Cl reactions at 300 K were found to be 1.42 × 10-11 and 3.72 × 10-11 cm3 molecule-1 s-1, respectively. In addition, the thermochemistry of all possible paths and branching ratios was determined. The atmospheric chemistry implications of the DMTS + â¢OH/â¢Cl reactions are discussed.
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2019
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Article