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. (C) 2013 Elsevier B.V. All rights reserved.