【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.更多还原

【Abstract】 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, cm3·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)=2.06×10-20T3.045exp(-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.更多还原