中文摘要：

在CBS-QB3水平上研究了CH3CN和·OH反应的势能面,其中包括两个中间体和9个反应过渡态.分别给出了各主要物质的稳定构型、相对能量及各反应路径的能垒.根据计算的CBS-QB3势能面,探讨了CH3CN＋·OH反应机理.计算结果表明,生成产物P1（·CH2CN＋H2O）的反应路径在整个反应体系中占主要地位.运用过渡态理论对产物通道P1（·CH2CN＋H2O）的速率常数k1（cm3·molecule-1·s^-1）进行了计算.预测了k1（cm3·molecule-1·s^-1）在250-3000K温度范围内的速率常数表达式为k1（250-3000K）=2.06×10-20T3.045exp（-780.00/T）.通过与已有的实验值进行对比得出,在实验所测定的250-320K范围内,计算得到的k1的数值与已有的实验值比较吻合.由初始反应物生成产物P1（·CH2CN＋H2O）只需要克服一个14.2kJ·mol^-1的能垒.而产物·CH2CN＋H2O生成后要重新回到初始反应物CH3CN＋·OH,则需要克服一个高达111.2kJ·mol^-1的能垒,这就表明一旦产物P1生成后就很难再回到初始反应物.

英文摘要：

The complex potential energy surface for the reaction of ＂OH radical with CH3CN, including 2 intermediate complexes, 9 transition states, was theoretically probed at the CBS-QB3 level. The geometries and relative energies for various stationary points were determined. Based on the calculated CBS-QB3 potential energy surface, the possible reaction mechanism of ·OH＋CH3CN was proposed. The calculated results demonstrated that the formation of P1 （·CH2CN＋H2O） was the dominant reaction channel. The rate constant （k1, cm^3·molecule^-1- s^-1） of P1 was calculated by TS theory. Over the temperature range 250-3000 K, we predicted that the expression of k1 was k1 （250-3000 K）=2.06×10^20T^3.045exp（-780.00/T）. By comparing with the obtained experimental values it was shown that the values of k1 were in good agreement with the experimental results over the temperature range 250-320 K. The calculated results indicated the formation of P1 （CH3CN＋·OH） only needed a barrier of 14.2 kJ·mol^-1. While the products·CH2CN＋H2O retrograded to the reactants CH3CN＋·OH, an energy barrier of 111.2 kJ·mol^-1 was required. These results suggested that the backward direction for the pathway of formation product P1 would be difficult in the ground electronic state.