Theoretical investigations on the reaction kinetics of CH3OCl/CD3OCl with chloride ion

The kinetics of the multiple-channel reactions between CH3OCl/CD3OCl and chloride ion are studied. The optimized geometries and frequencies of the stationary points are calculated at the MP2/aug-cc-pvdz (aug-cc-pv(D+d)z for Cl) level of theory. The minimum-energy paths (MEPs), the potential barriers, and the single-point calculations are made at the CCSD(T)/aug-cc-pvtz (aug-cc-pv(T+d)z for Cl) level. Furthermore, the rate constants of the three channels are calculated using CVT with the SCT correction over a wide temperature range of 200–3000 K. The results show that the anti-E2 channel is the dominant channel over the entire studied temperature range, and the corresponding rate constants indicate negative temperature dependence in the low temperature range and positive temperature dependence in the medium and high temperature range. The kinetic isotope effects (KIEs) for each channel are separable. The values of kH1/kD1, kH2/kD2, and kH3/kD3 are 1.37, 0.91, and 2.85 at room temperature, respectively. Four factors affecting the kinetic isotope effects of all the channels have been analyzed, and the vibrational contribution is the dominant factor in determining whether the overall KIE is normal or reverse for each of the three studied channels. The three-parameter Arrhenius expressions for the overall reactions are also given. The present theoretical results are expected to be useful and accurate in estimating the dynamical properties of these reactions over a wide temperature range where no experimental values are available.