Direct dynamics study on the hydrogen abstraction reaction of CH3CH2F with O(3P)

A direct dynamics method is employed to study three channels of the hydrogen abstraction reaction of CH3CH2F with O(P-3) based on the potential surface calculated at the QCISD(T)/6-311G(d,p)//MP2(full)/6-311G(d,p) dual-level. The calculated potential barriers are 11.08 kcal/mol for the alpha-H abstraction channel, 14.39 and 14.08 kcal/mol for the two channels associated with the beta-H abstraction. The rate constants of the reactions are evaluated by means of the canonical variational transition-state theory (CVT) with small-curvature tunneling (SCT) correction in the temperature range of 200-3000 K. The dynamics calculations indicate that the variational effect is small for all the channels, and the tunneling effect is considerable in the lower temperature range for the calculation of the rate constants. At 298 K, the rate constants of alpha-H and beta-H abstraction reactions are 5.22 X 10(-17), 1.30 X 10(-19) cm(3) molecule(-1) s(-1), and when up to about 1250 K, the values are 5.10 X 10(-13), 5.22 X 10(-13) cm(3) molecule(-1) s(-1), respectively. It is shown that at the lower temperature the main reaction process is the alpha-H abstraction, while beta-H abstraction will compete kinetically with the alpha-H abstraction as the temperature increases. (c) 2006 Elsevier B.V. All rights reserved.