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化学学报
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化学学报 ›› 2010, Vol. 68 ›› Issue (13): 1253-1260.    下一篇

研究论文

CH3SO＋HO2气相反应机理与主通道速率常数

卢彦霞，王文亮*，王渭娜，刘英英，张越   

  1. (陕西师范大学化学与材料科学学院 陕西省大分子科学重点实验室 西安 710062)
  • 投稿日期:2009-10-21 修回日期:2009-12-15 发布日期:2010-02-23
  • 通讯作者: 王文亮 E-mail:wlwang@snnu.edu.cn
  • 基金资助:

    国家自然科学基金(No. 20873079)资助项目

Mechanistic Study of CH3SO＋HO2 Reaction and Rate Constants of Major Channel in the Gas Phase

LU Yan-Xia, WANG Wen-Liang, WANG Wei-Na, LIU Ying-Ying, ZHANG Yue   

  1. (Key Laboratory for Macromolecular Science of Shaanxi Province, School of Chemistry and Materials Science, Shaanxi Normal University, Xi an 710062)
  • Received:2009-10-21 Revised:2009-12-15 Published:2010-02-23

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在 MPW1PW91/6-311G(d,p)水平上优化了标题反应各驻点物种的几何构型, 并在相同水平上通过频率计算和内禀反应坐标(IRC)分析对过渡态结构及连接性进行了验证. 采用QCISD(T)/6-311G(d,p)方法对所有驻点及反应路径的部分选择点进行单点能校正, 分别构建了CH3SO＋HO2反应体系的单、三重态反应势能剖面. 研究结果表明, CH3SO＋HO2反应体系存在6条反应通道7条路径, 优势通道(1) R→3IM→P1 (CH3SOH＋3O2)发生在三重态势能面上, 此通道包含两条路径, 其表观活化能分别为12.01和－30.04 kJ•mol－1, 主路径(2) R→3IM→3TS2→P1 (CH3SOH＋3O2)是一个无势垒氢迁移过程. 利用经典过渡态理论(TST)与变分过渡态理论(CVT)并结合小曲率隧道效应模型(SCT), 分别计算了主路径(2)在200～2500 K温度范围内的速率常数kTST, kCVT和kCVT/SCT, 在此温度区间内的表观反应速率常数三参数表达式为, 具有负温度系数效应. 速率常数计算结果显示, 变分效应在计算温度段内影响较小, 而量子力学隧道效应在低温段有显著影响.

关键词: CH3SO, HO2, 单重态势能剖面, 三重态势能剖面, 反应机理, 速率常数

The geometries, vibrational frequencies of all stationary points involved in the title reaction were calculated at the MPW1PW91/6-311G(d,p) level. Relationships of reactants, intermediates, transition states and products are confirmed by the intrinsic reaction coordinate (IRC) calculations. The single-point energy and the selected points along the minimum energy potential were calculated at the QCISD(T)/6-311G(d,p), as well as the singlet and triplet potential energy surfaces were investigated. The results show that there are 6 dominating reaction channels (7 pathways) for the CH3SO＋HO2 reaction system. The major channel (1) R→3IM→P1 (CH3SOH＋3O2) happened on the triplet potential energy surface included two pathways, in which apparent activation energies are 12.01 and －30.04 kJ•mol－1 respectively, and the dominant path (2) R→3IM→3TS2→P1 (CH3SOH＋3O2) is a barrierless process. The rate constants of the path (2) are evaluated by means of the classical transition state theory (TST) and the canonical variational transition state theory (CVT) in which the small-curvature tunneling correction was included. The fitted three-parameter expression for the path (2) is in the temperature range of 200～2500 K, and the rate constant display a negative temperature dependence. In addition, the variational effect was almost negligible in the entire process, while the tunneling effect is considerable at the lower temperature.

Key words: CH3SO, HO2, singlet PES, triplet PES, reaction mechanism, rate constant