Ab initio direct dynamics studies of the hydrogen abstraction on the reaction of Cl with CHBrF₂

Ab initio direct dynamics methods have been used to study the hydrogen abstraction reaction of CHBrF₂+Cl→CBrF₂+HCl. The optimized geometries and frequencies of the reactants, transition states and products are calculated at the BH&H-LYP/6-311G(d,p) level. The minimum energy path (MEP) are obtained by the intrinsic reaction coordinate theory at the same level, and the energies along the MEP are further refined at the QCISD(T)/6-311+G(2df,2p)(single-point) level. The rate constants are calculated by using the improved canonical variational transition state theory incorporating with small-curvature tunneling correction (ICVT/SCT) in the temperature range 200-500 K. The theoretical rate constants are quantitatively in agreement with available experimental values. For the title reaction, both the variational effect and the tunneling effect are small.