Ab initio study of the potential energy surface and product branching ratios for the reaction of O(~1D) with CH_3CH_2Br

摘要

The potential energy surface of O(~1D) + CH_3CH _2Br reaction has been studied using QCISD(T)/6-311++G(d,p)//MP2/6- 311G(d,p) method. The calculations reveal an insertion-elimination reaction mechanism of the title reaction. The insertion process has two possibilities: one is the O(~1D) inserting into C-Br bond of CH3CH 2Br producing one energy-rich intermediate CH_3CH _2OBr and another is the O(~1D) inserting into one of the C-H bonds of CH_3CH_2Br producing two energy-rich intermediates, IM1 and IM2. The three intermediates subsequently decompose to various products. The calculations of the branching ratios of various products formed though the three intermediates have been carried out using RRKM theory at the collision energies of 0, 5, 10, 15, 20, 25, and 30 kcal/mol. CH _3CH_2O + Br are the main decomposition products of CH _3CH_2OBr. CH_3COH + HBr and CH_2CHOH + HBr are the main decomposition products for IM1; CH_2CHOH + HBr are the main decomposition products for IM2. As IM1 is more stable and more likely to form than CH_3CH_2OBr and IM2, CH_3COH + HBr and CH_2CHOH + HBr are probably the main products of the O(~1D) + CH_3CH_2Br reaction. Our computational results can give insight into reaction mechanism and provide probable explanations for future experiments.