Dual-level direct dynamics study on the hydrogen abstraction reaction of fluorine atom with 1,1-difluoro-1-chloroethane

Abstract

The kinetic properties of the reaction of F atoms with CH2H′CF2Cl are investigated by a dual-level direct dynamics method. Optimized geometries and frequencies of all the stationary points and extra points along the minimum-energy path (MEP) are obtained at the MPW1K/6–311+G(d,p) level of theory. Two complexes with energy less than that of the reactants are located in the two reactant paths, respectively. The energy profiles of two reactions are refined with the interpolated single-point energies (ISPE) method at the G3(MP2)/MPW1K level. The rate constants are evaluated using the canonical variational transition state theory (CVT) with a small-curvature tunneling correction (SCT) over a wide range of temperature 200–2000 K. Agreement between the calculated CVT/SCT rate constant and the experimental value is good at 295 K. Our calculations show that the reaction path CH2H′CF2Cl + F → CH2CF2Cl + H′F (Ra) is the major reaction path below 400 K. Moreover, the contribution of CH2H′CF2Cl + F → CHH′CF2Cl + HF (Rb) to the whole reaction increases with the temperature increasing and exceeds path Ra to be the major reaction path.