Thermochemistry and Reaction Kinetics of Secondary Ethyl Radical of Methyl Ethyl Sulfide, CH3SCH•CH3, with 3O2 to CH2SCH(OO•)CH3

The quantum Rice-Ramsperger-Kassel (QRRK) theory is used to analyze the reaction between the activated CH3SCH•CH3 and molecular oxygen to account for further reaction and collisional and deactivation. Hydroxyl radicals initiate the oxidation of Methyl ethyl sulfide (CH3SCH2CH3) and MES (methylthioethane) under combustion conditions. The CBS-QB3 and G3MP2B3 composite and M062X/6-311+G(2d, p) DFT methods were used to study the thermochemical properties of reactants, products, and transition states. These thermochemical properties are used for the calculations of kinetic and thermochemical parameters. Under high pressure and low temperature, isomerization and stabilization of the CH3SCH(OO•)CH3 adduct are of importance. Under atmospheric pressure and at temperatures between 600 and 800 K, reactions of the chemically activated peroxy adduct become important relative to stabilization. The reaction between CH3SCH•CH3 and O2 forms an energized peroxy adduct CH3SCH(OO•)CH3 with a calculated well depth of 30.2 kcal/mol at the CBS-QB3 level of theory. Kinetic parameters are calculated using the thermochemical properties of products, reactants, and transition states obtained using the CBS-QB3 method of calculation.