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DFT and Ab initio direct dynamics studies on the hydrogen abstraction reactions of chlorine atoms with CH 4− n F n ( n = 1–3)
Author(s) -
Xiao JingFa,
Li ZeSheng,
Liu JingYao,
Sheng Li,
Sun ChiaChung
Publication year - 2002
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.10165
Subject(s) - chemistry , hydrogen atom abstraction , ab initio , adiabatic process , quantum tunnelling , potential energy surface , computational chemistry , reaction rate constant , hydrogen , atmospheric temperature range , atomic physics , thermodynamics , physics , quantum mechanics , kinetics , organic chemistry
A direct dynamics study is carried out for the hydrogen abstraction reactions Cl + CH 4− n F n ( n = 1–3) in the temperature range of 200–1000 K. The minimum energy paths (MEPs) of these reactions are calculated at the BH&H‐LYP/6‐311G(d,p) level, and the energies along the MEPs are further refined at the QCISD(T)/6‐311+G(2df,2p) and QCISD(T)/6‐311+G(d,p) (single‐point) level. The rate constants obtained by using the improved canonical variational transition state theory incorporating small‐curvature tunneling correction (ICVT/SCT) are in good agreement with the available experimental results. It is shown that the vibrational adiabatic potential energy curves for these reactions have two barriers, a situation similar to the analogous reactions CH 3 X+Cl (X=Cl, Br). The theoretical results show that for the title reactions the variational effect should not be neglected over the whole considered temperature range, while the small‐curvature tunneling effect is only important in the lower temperature range. The effects of fluorine substitution on the rate of this kind of reactions are also examined. © 2002 Wiley Periodicals, Inc. J Comput Chem 23: 1456–1465, 2002