Direct dynamics study of hydrogen abstraction using density functional theory: CF₃CHFCF₃ + O(³P) → CF₃CFCF₃ + OH reaction

A dual-level direct dynamics method is employed for the dynamics of the hydrogen abstraction reaction CF₃CHFCF₃ + O(³P) using density functional theory with the 6-311G(d,p) and 6-311++G(3df,2p) (single-point) basis sets. Two DFT methods, B3LYP and B3PW91, produce similar results for the geometries, frequencies, and energetics of the stationary points, in good agreement with the corresponding experimental values. The classical energy profile is corrected with the interpolated single-point energy (ISPE) approach. The variational transition-state calculations are carried out with small curvature tunneling (SCT) at 300-2000 K. Agreement between the theoretical and experimental values is good for the rate constants and activation energy calculated at the B3LYP/6-311++G(3df,2p)//B3LYP/6-311G(d,p) level in the measured temperature range 586-726 K. It is shown that the variational effect is significant for this reaction, and the tunneling effect is small.