物理化学学报 >> 2008, Vol. 24 >> Issue (04): 587-594.doi: 10.3866/PKU.WHXB20080408

研究论文 上一篇    下一篇

·OH自由基与CH3CN反应机理及动力学

田燕; 何天敬; 陈东明; 刘凡镇   

  1. 中国科学技术大学化学物理系, 合肥 230026; 安徽农业大学理学院, 合肥 230036
  • 收稿日期:2007-11-22 修回日期:2008-01-30 发布日期:2008-04-07
  • 通讯作者: 何天敬 E-mail:tj16@ustc.edu.cn

Reaction Mechanism and Kinetics for the Reaction of ·OH+CH3CN

TIAN Yan; HE Tian-Jing; CHEN Dong-Ming; LIU Fan-Chen   

  1. Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, P. R. China; School of Science, Anhui Agricultural University, Hefei 230036, P. R. China
  • Received:2007-11-22 Revised:2008-01-30 Published:2008-04-07
  • Contact: HE Tian-Jing E-mail:tj16@ustc.edu.cn

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250-3000 K温度范围内的速率常数表达式为k1(250-3000 K)=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250-320 K 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14.2 kJ·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111.2 kJ·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.

关键词: ·OH自由基, CH3CN, 反应机理, CBS-QB3

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.

Key words: ·OH radical, CH3CN, Reaction mechanism, CBS-QB3

MSC2000: 

  • O641