物理化学学报 >> 2015, Vol. 31 >> Issue (5): 859-865.doi: 10.3866/PKU.WHXB201503131

理论与计算化学 上一篇    下一篇

过氧烷基自由基分子内氢迁移反应类速率常数的计算

李尚俊1, 谈宁馨2, 姚倩1, 李泽荣1, 李象远2   

  1. 1 四川大学化学学院, 成都610064;
    2 四川大学化学工程学院, 成都610065
  • 收稿日期:2014-11-27 修回日期:2015-03-11 发布日期:2015-05-08
  • 通讯作者: 李泽荣 E-mail:lizerong@scu.edu.cn
  • 基金资助:

    国家自然科学基金(91441114)资助项目

Calculation of Rate Constants for Intramolecular Hydrogen Migration Reactions of Alkylperoxy Radicals

LI Shang-Jun1, TAN Ning-Xin2, YAO Qian1, LI Ze-Rong1, LI Xiang-Yuan2   

  1. 1 College of Chemistry, Sichuan University, Chengdu 610064, P. R. China;
    2 College of Chemical Engineering, Sichuan University, Chengdu 610065, P. R. China
  • Received:2014-11-27 Revised:2015-03-11 Published:2015-05-08
  • Contact: LI Ze-Rong E-mail:lizerong@scu.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (91441114).

摘要:

过氧烷基自由基分子内氢迁移是低温燃烧反应中的一类重要基元反应. 本文用等键反应方法计算了该类反应的动力学参数. 所有反应物、过渡态、产物的几何结构均在B3LYP/6-311+G(d,p)水平下优化得到. 本文提出了用过渡态反应中心几何结构守恒作为反应类判据, 并将该分子内氢迁移反应分为四类, 包括(1,3)、(1,4)、(1,5)、(1,n) (n=6, 7, 8)氢迁移类. 分别将这4 类反应类中最小反应体系作为类反应的主反应, 并分别在B3LYP/6-311+G(d,p)低水平和CBS-QB3 高水平下得到其近似能垒和精确能垒. 其余氢迁移反应作为目标反应, 在B3LYP/6-311+G(d,p)低水下计算得到其近似能垒, 再采用等键反应方法校正得到目标反应的精确反应势垒和精确速率常数. 研究表明, 采用等键反应方法只需在低水平用从头算计算就可以得到大分子反应体系的高精度能垒和速率常数值, 且本文按等键反应本质的分类方法更能揭示反应类的本质, 并对反应类的定义给出了客观标准. 本文的研究为碳氢化合物低温燃烧模拟中重要的过氧烷基分子内氢迁移反应提供了准确的动力学参数.

关键词: 反应类等键反应方法, 反应势垒, 速率常数, 过氧烷基分子内氢迁移反应

Abstract:

Intramolecular hydrogen migration in alkylperoxy reactions is one of the most important reaction classes in hydrocarbon combustion at low temperatures. In this study, the kinetic parameters for reactions in this class were calculated using the isodesmic reaction method. The geometries for all the reactants, transition states, and products were optimized at the B3LYP/6-311+G(d,p) level. A criterion based on conservation of the reaction-center geometry of the transition state was proposed for the reaction class, and the intramolecular hydrogen migration reactions studied were divided into four classes, i.e., (1,3), (1,4), (1,5), and (1,n) (n=6, 7, 8) hydrogen migration. The simplest reaction system for each reaction class was defined as the principal reaction; the approximate single-point energies were obtained at the low level of B3LYP/6-311+G(d,p) and accurate single-point energies were obtained at the high level of CBS-QB3. The other reactions in this class were chosen as the target reactions and the approximate single-point energies were obtained at the B3LYP/6- 311+G(d,p) level. The energy barriers and rate constants of these target reactions were corrected using the isodesmic reaction method. The results showed that accurate energy barriers and rate constants for the reactions of large molecules can be obtained by a relatively low level method using the isodesmic reaction method. In this study, classification of the basic isodesmic reaction showed the essential features of the reaction classes. The present work provides accurate kinetic parameters for modeling intramolecular hydrogen migration reactions of hydrocarbons at low temperatures.

Key words: Isodesmic reaction method for the reaction class, Reaction barrier, Rate constant, Intramolecular hydrogen migration reactions of alkylperoxy radicals

MSC2000: 

  • O643