Branching ratio of gas-phase reaction of CH3C(O)CHCl2 + OH: A theoretical dynamic study

A theoretical study on the atmospheric reaction of hydroxyl radical with CH3C(O)CHCl2 is investigated. Geometries and frequencies calculation have been performed at the MP2/cc-pVDZ level of theory for all stationary points, and energy values have been improved by single-point calculations using the BMC-CCSD level. Two different reaction channels have been found, abstraction and addition–elimination channels. The rate constants for this reaction have been calculated within the temperature range of 200–360 K at atmospheric pressure by means of canonical variational transition state theory incorporating with the small-curvature tunneling correction. The overall rate constant of the CH3C(O)CHCl2 + OH reaction turns out finally to be the sum of the H-abstraction and OH-addition rate constant. It was found that the contributions of the addition–elimination channel to the overall reaction can be ignore, suggesting that in the upper troposphere and lower stratosphere, this channel will be less important. The reaction proceeds through the H abstraction exclusively from chloromethyl group within the whole range of 200–360 K, which may be relevant to atmospheric chemistry. Our results show that the variational effect is small and the small-curvature tunneling effect is only important in the lower temperature range. Agreement between the calculated and experimental data available at 298 K is good.