Theoretical study for the reaction of C₂H₅Cl/C₂D₅Cl with Cl atom

The hydrogen/deuterium abstraction from C₂H₅Cl/C₂D₅Cl with chlorine atom has been studied by a dual-level direct dynamics method. Three H-abstraction channels have been identified. The optimized geometries and frequencies of the stationary points and the minimum-energy paths (MEPs) are calculated at the MP2/6-311G(d,p) level of theory. In order to improve the reaction enthalpy and potential barrier, single-point calculations are made at G3 level of theory. Furthermore, the rate constants for the three H-abstraction channels are evaluated using canonical variational transition state theory (CVT) with the small-curvature tunneling correction (SCT) over a wide range of temperature 220-2200 K at the G3//MP2/6-311G(d,p) level. The calculated rate constants are in reasonable agreement with the experimental values. The kinetic isotope effects for the title reaction are 'normal'. The values of k_1a/k_2a, k_1b/k_2b, and k₁/k₂ are 4.8, 2.3, and 4.5 at room temperature, respectively, and they decrease as the temperature increases. The present theoretical results are expected to be useful and reasonable to estimate the dynamical properties of these reactions over a wide temperature range where no experimental value is available.