Theoretical study on the Br + CH₃SCH₃ reaction

The multiple-channel reactions Br + 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 G3(MP2) (single-point) theory. The rate constants for every reaction channels, Br + CH₃SCH₃ → CH₃SCH₂ + HBr (R1), Br + CH₃SCH₃ → CH₃SBr + CH₃ (R2), and Br + CH₃SCH₃ → CH₃S + CH ₃Br (R3), are calculated by canonical variational transition state theory with small-curvature tunneling correction over the temperature range 200-3000 K. The total rate constants are in good agreement with the available experimental data, and the two-parameter expression k(T) = 2.68 × 10 ^-12 exp(-1235.24/7) cm³/(molecule s) over the temperature range 200-3000 K is given. Our calculations indicate that hydrogen abstraction channel is the major channel due to the smallest barrier height among three channels considered, and the other two channels to yield CH₃SBr + CH₃ and CH₃S + CH₂Br are minor channels over the whole temperature range.