Theoretical studies of the reactions of O(~3p) with halogenated methyl (Ⅰ)——Reaction mechanism of the O(~3p) + CH_2Cl reaction

摘要

The reaction of O（3P） with CH2Cl radical has been studied using ab initio molecular orbital theory. G2 （MP2） method is used to calculate the geometrical parameters, vibrational frequencies and energies of various stationary points on the potential energy surface. The reaction mechanism is revealed. The addition of O（3P） with CH2Cl leads to the formation of an energy rich intermediate OCH2Cl which can subsequently undergo decomposition or isomerization to the final products. The calculated heat of reaction for each channel is in agreement with the experimental value. The production of H+CHClO and Cl+CH2O are predicted to be the major channels. The overall rate constants are calculated using transition state theory on the basis of ab initio data. The rate constant is pressure independent and exhibits negative temperature dependence at lower temperatures, in accordance with the experimental results.