For reactions CH 3CHFCH 3 and CH 3CH 2CH 2F with OH radicals, the channels of H-abstraction from −CHF− and −CH 2− groups are the major reaction channels, respectively, at lower temperature. The results show that both the variation effect and the SCT contribution play an important role in the calculation of the rate constants. The canculated CVT/SCT rate constants are consistent with available experimental data. The rate constants are evaluated by canonical variational transition state theory (CVT) with the small-curvature tunneling correction method (SCT) over a wide temperature range 200−2000 K. To improve the reaction enthalpy and potential barrier of each reaction channel, the single point energy calculation is performed by the MC-QCISD/3 method. There are complexes at the reactant side or exit route, indicating these reactions may proceed via indirect mechanisms. The geometries and frequencies of all the stationary points are optimized by means of the DFT calculation. The hydrogen abstraction reactions of CH 3CHFCH 3 and CH 3CH 2CH 2F with the OH radicals have been studied theoretically by a dual-level direct dynamics method.
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