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采用密度泛函理论的B3LYP方法,在6-311++G(d,p)基组水平上研究了CH3S自由基与HO2自由基的微观反应机理,全参数优化了反应势能面上各驻点的几何构型,振动分析和内禀反应坐标(IRC)分析结果证实了中间体和过渡态的真实性,计算所得的键鞍点电荷密度的变化情况也确认了反应过程.找到了五条可能的反应通道,对结果的分析表明:单线态反应通道(5)CH3S+HO2→CH3SOOH(1P),是所有通道中的主要反应通道.该通道不需要克服过渡态能垒,属于放热反应,在动力学和热力学上都是最为有利的.对于三线态反应通道来说,通道(1)CH3S+HO2→COM11→TS1→COM12→CH3SH+O2(3P)为主要反应通道,控制步骤的活化能为53.5 kJ/mol,能垒最低,属于放热反应,在动力学和热力学上都是有利的.
The B3LYP method of density functional theory (DFT) was used to study the microscopic reaction mechanism of CH3S radical and HO2 radical at 6-311 ++ G (d, p) basis set. The results of vibration analysis and intrinsic reaction coordinate (IRC) confirm the authenticity of intermediates and transition states, and the calculated charge-saddle point charge density also confirms the reaction process. Five possible reactions were found The results show that the singlet state reaction channel (5) CH3S + HO2 → CH3SOOH (1P) is the main reaction channel in all the channels, which does not need to overcome the energy barrier of the transition state and belongs to the exothermic reaction. For the triplet reaction channel, channel (1) CH3S + HO2 → COM11 → TS1 → COM12 → CH3SH + O2 (3P) are the main reaction channels, and the activation energy of the control step is 53.5 kJ / mol, the lowest barrier, belonging to the exothermic reaction, both in kinetics and thermodynamics are beneficial.