Direct dynamics study on the reaction of 1, 1-difluoroethane with hydrogen trioxide radical

We present a theoretical study of the hydrogen abstraction reaction from CH3CHF2 by the HOOO radical. Two different reactive sites of 1, 1-difluoroethane molecule, CH3 and CHF2 groups have been investigated, and results confirm that the CHF2 group is a highly reactive site. In this study, the geometries and harmonic vibrational frequencies of all stationary points are calculated at the MPW1K/6-31+G(d, p) and BHandHLYP/6-31+G(d, p) levels of theory. The minimum energy paths (MEPs) are obtained at the MPW1K/6-31+G(d, p) level of theory. To refine the energies along the MEPs of each channel, single-point energy calculations are performed by CCSD/cc-pVTZ method. The rate constants are evaluated with the conventional transition-state theory (TST), the canonical variational transition-state theory (CVT), the microcanonical variational transition-state theory (μVT), the CVT coupled with the small-curvature tunneling (SCT) correction (CVT/SCT), and the μVT coupled with the Eckart tunneling correction (μVT/Eckart) based on the ab initio calculations in the temperature range of 200–3000 K. The fitted three-parameter Arrhenius expressions of the calculated CVT/SCT and μVT/Eckart rate constants of the H abstraction from CHF2 group are kCVT/SCT(T) = 2.89 × 10−19T0.75e(−10964.0/T) and kμVT/Eckart(T) = 2.68 × 10−13 T−0.70 e(−12302.2/T), respectively. The fitted three-parameter Arrhenius expressions of the calculated CVT/SCT and μVT/Eckart rate constants of the H abstraction from CH3 group are kCVT/SCT(T) = 1.40 × 10−19 T1.03 e(−12271.6/T) and kμVT/Eckart(T) = 1.18 × 10−17 T0.61 e(−13159.7/T), respectively.