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Kinetic mechanism of the hydrogen abstraction reactions of the chlorine atoms with CH 3 CF 2 Cl and CH 3 CFCl 2 : A dual level direct dynamics study
Author(s) -
Ji Yuemeng,
Zhao Xiaolei,
Li Zesheng,
Liu Jingyao
Publication year - 2007
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.20665
Subject(s) - chemistry , hydrogen atom abstraction , reaction rate constant , reactivity (psychology) , isodesmic reaction , reaction mechanism , chlorine , elementary reaction , atmospheric temperature range , computational chemistry , hydrogen , standard enthalpy of formation , thermodynamics , kinetics , physics , organic chemistry , catalysis , medicine , alternative medicine , pathology , quantum mechanics
The mechanisms of the reactions: CH 3 CFCl 2 + Cl (R1) and CH 3 CF 2 Cl + Cl (R2) are studied over a wide temperature range (200–3000 K) using the dual‐level direct dynamics method. The minimum energy path calculation is carried out at the MP2/6‐311G(d,p) and B3LYP/6‐311G(d,p) levels, and energetic information is further refined by the G3(MP2) theory. The H‐abstraction from the out‐of‐plane for (R1) is the major reaction channel, while the in‐plane H‐abstraction is the predominant route of (R2). The canonical variational transition‐state theory (CVT) with the small‐curvature tunneling (SCT) correction method is used to calculate the rate constants. Using group‐balanced isodesmic reactions and hydrogenation reactions as working chemical reactions, the standard enthalpies of formation for CH 3 CFCl 2 , CH 3 CF 2 Cl, CH 2 CFCl 2 , and CH 2 CF 2 Cl are evaluated at the CCSD(T)/6‐311 + G(3df,2p)//MP2/6‐311G(d,p) level of theory. The results indicate that the substitution of fluorine atom for the chlorine atom leads to a decrease in the CH bond reactivity with a small increase in reaction enthalpies. Also, for all reaction pathways the variational effect is small and the SCT effect is only important in the lower temperature range on the rate constants. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007