Theoretical study on the reaction Br + CH₂BrCl

By means of direct dynamics methods, the theoretical investigations are carried out on the multiple-channel reaction Br + CH₂BrCl. The optimized geometries, frequencies, and minimum energy path (MEP) are all obtained at the MP2/6-311+G(d,p) level, and energetic information is further refined at the QCISD(T)/6-311+G(3df,2p) (single-point) level. The rate constants for three reaction channels, H-abstraction, Br-abstraction, and Cl-abstraction, are calculated by the improved canonical variational transition state theory (ICVT) with small-curvature tunneling (SCT) contributions over the wide temperature region 200-4000 K. The theoretical three-parameter formula of overall rate constants is given as k = 9.93 × 10^-19T^2.48 exp (-3890.89/T) (in cm³ molecule^-1 s^-1). Furthermore, the rate constants of reverse reaction CHBrCl + HBr → Br + CH₂BrCl (R-1) are in good agreement with the available experimental data. For the title reaction, H-abstraction reaction channel is the predominant channel in the lower temperatures while as the temperature increases, the contributions of Br- and Cl-abstraction channels should be taken into account.