On the kinetic mechanism of the hydrogen abstraction reactions of the hydroxyl radical with CH₃CF₂Cl and CH₃CFCl₂: A dual level direct dynamics study

• Published in: Journal of computational chemistry 2010-02, Vol.31 (3), p.510-519
• Main Authors: Ji, Yue-Meng, Cao, Fenglei, Gao, Hui, Li, Xiangzhi, Zhao, Cunyuan, Su, Chengyong, Liu, Jing-Yao, Li, Ze-Sheng
• Format: Article
• Language: English
• Subjects: ab initio calculations; Absorption; Chlorofluorocarbons, Methane - chemistry; computer chemistry; Computer Simulation; Electrons; gas-phase reactions; Hydrogen - chemistry; Hydroxyl Radical - chemistry; Kinetics; Models, Chemical; Spectrophotometry; Thermodynamics
• ISSN: 0192-8651; 1096-987X
• DOI: 10.1002/jcc.21343

By means of the dual-level direct dynamics method, the mechanisms of the reactions, CH₃CF₂Cl + OH [rightward arrow] products (R1) and CH₃CFCl₂ + OH [rightward arrow] products (R2), are studied over a wide temperature range 200-2000 K. The optimized geometries and frequencies of the stationary points are calculated at the MP2/6-311G(d,p) level, and then the energy profiles of the reactions are refined with the interpolated single-point energy method at the G3(MP2) level. The canonical variational transition-state theory with the small-curvature tunneling (SCT) correction method is used to calculate the rate constants. For the title reactions, three reaction channels are identified and the H-abstraction channel is the major pathway. The results indicate that F substitution has a significant (reductive) effect on hydrochlorofluorocarbon reactivity. Also, for all H-abstraction reaction channels the variational effect is small and the SCT effect is only important in the lower temperature range on the rate constants calculation.