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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.
The potential energy surfaces of CH3CN and · OH reactions are studied at CBS-QB3 level, including two intermediates and nine transition states. The stable configurations, relative energies and energy of each reaction path Based on the calculated CBS-QB3 potential energy surface, the reaction mechanism of CH 3 CN + · OH was discussed.The calculated results show that the reaction pathway of product P1 (· CH 2 CN + H 2 O) is dominant in the whole reaction system.Using the transition state theory, The rate constant k1 (cm3 · molecule-1 · s-1) of the channel P1 (· CH2CN + H2O) was calculated and the rate of k1 (cm3 · molecule-1 · s-1) in the temperature range of 250-3000 K was predicted The constant expression is k1 (250-3000K) = 2.06 × 10-20T3.045exp (-780.00 / T). By comparing with the existing experimental data, it can be obtained from the range of 250-320K The value of k1 is in good agreement with the existing experimental data. The product P1 (· CH2CN + H2O) from the initial reaction only needs to overcome an energy barrier of 14.2 kJ · mol-1, and the product · CH2CN + Back to the initial reactant CH3CN + · OH, then need to overcome a high energy barrier of 111.2kJ · mol-1, which shows that once the product P1 is difficult to generate Back to the initial reactant.