Thermodynamic and kinetic analysis on the reaction of dimethyl sulfide radical with oxygen

Document Type

Article

Publication Date

4-15-2012

Abstract

Thermochemical properties of methylthiol-methylhydroperoxide, CH 3SCH 2OOH and its two terminal radicals resulting from the loss of hydrogen atoms, viz. CH 3SCH 2OOA· and CA·H 2SCH 2OOH, are important to understand the stability, reaction paths, and kinetics of the reactions of dimethyl sulfide and related sulfur-containing hydrocarbons in the atmosphere and the combustion processes. Thermochemical properties ΔH o f, S(T) and C p(T) and internal rotation potentials for reactants, intermediates, and transition states in the methylthiomethyl (CH 3SCA·H 2) radical + O 2 reaction system are analyzed to evaluate reaction paths and kinetics versus temperature and pressure. Isodesmic reaction analysis is used to determine the enthalpies of formation (ΔH o f298) using density functional B3LYP/6-311G(d,p) and complete basis set extrapolation CBS-QB3 computational methods. Entropy and heat capacities C p(T) are determined using geometric parameters and vibration frequencies obtained at B3LYP/6-311G(d,p) level of calculation. ΔH f o 298 values estimated at the CBS-QB3 level (units: kcal mol -1) are CH 3SCA·H 2 (32.7), CH 3SCH 2OOH (-29.1), CH 3SCH 2OOA· (5.2), CA·H 2SCH 2OOH (11.5). Quantum Rice-Ramsperger-Kassel analysis is used to calculate energy-dependent rate constants, k(E), and master equation is used to account for collisional stabilization of peroxy adduct and the hydroperoxide isomer. The methylthiomethyl radical associates with O 2 to form a methylthiomethyl peroxy radical with a well depth of 27.49 kcal mol -1. The peroxy radical can dissociate back to reactants, isomerize via hydrogen shift to form a hydroperoxide methyl radical CA·H 2SCH 2OOH, decompose via hydrogen transfer, and undergo subsequent low-energy beta scission to form CH 3SC(=O)H and OH radical. The peroxy radical can also attack the sulfur atom via TS3 to form CH 3S(=O) + CH 2O product set. The CA·H 2SCH 2OOH isomer can decompose via an elimination transition state to CH2=S + CH2=O + OH, or through a four-member ring transition state to 1,3-Oxathietane + OH products. © 2011 Wiley Periodicals, Inc.

Identifier

84858078773 (Scopus)

Publication Title

International Journal of Quantum Chemistry

External Full Text Location

https://doi.org/10.1002/qua.23171

e-ISSN

1097461X

ISSN

00207608

First Page

1945

Last Page

1958

Issue

8

Volume

112

This document is currently not available here.

Share

COinS