Theoretical Studies on the Reactions CH3SCH3 with OH, CF3, and CH3 Radicals

The multiple-channel reactions OH + CH3SCH3 -> products, CF3 + CH3SCH3 -> products, and CH3 + CH3SCH3 -> products are investigated by direct dynamics method. The optimized geometries, frequencies, and minimum energy path are all obtained at the MP2/6-31+G(d,p) level, and energetic information is further refined by the MC-QCISD (single-point) method. The rate constants for eight reaction channels are calculated by the improved canonical variational transition state theory with small-curvature tunneling contribution over the temperature range 200-3000 K. The total rate constants are in good agreement with the available experimental data and the three-parameter expressions k(1) = 4.73 x 10(-16) T-1.89 exp(-662.45/T), k(2) = 1.02 x 10(-32) T-6.04 exp(933.36/T), k(3) = 3.98 x 10(-35) T-6.60 exp(660.58/T) (in unit of cm(3) molecule(-1) s(-1)) over the temperature range of 200-3000 K are given. Our calculations indicate that hydrogen abstraction channels are the major channels and the others are minor channels over the whole temperature range. (C) 2010 Wiley Periodicals, Inc. J Comput Chem 31: 2794-2803, 2010