Ab initio direct dynamics studies on the reaction of H atom with CH₃CH₂Cl

The multiple channel reaction H + CH₃CH₂Cl → products has been studied by the ab initio direct dynamics method. The potential energy surface information is calculated at the MP2/6-311 G(d,p) level of theory. The energies along the minimum energy path are further improved by single-point energy calculations at the PMP4(SDTQ)/6-311 + G(3df,2p) level of theory. For the reaction, four reaction channels (one chlorine abstraction, one α-hydrogen abstraction, and two β-hydrogen abstractions) have been identified. The rate constants for each reaction channel are calculated by using canonical variational transition state theory incorporating the small-curvature tunneling correction in the temperature range 298-5000 K. The total rate constants, which are calculated from the sum of the individual rate constants, are in good agreement with the experimental data. The calculated temperature dependence of the branching fractions indicates that for the title reaction, H-abstraction reaction is the major reaction channel in the whole temperature range 298-5000 K.