Direct DFT dynamics study of the addition reaction CF ₂= CHF+H→product

The addition reactions CF ₂=CHF+H→product have been studied using direct density functional theory dynamics method. All of the information along the minimum energy path (MEP) was calculated at the BHandHLYP/aug-cc-pVDZ level of theory. Energetic data along the MEP were further refined at the BHandHLYP/aug-cc-pVQZ level with the BHandHLYP/aug-cc-pVDZ optimized geometries. The barrier heights for forward reactions of C1 and C2 addition were obtained as 4.66 and 3.21 kcal mol ^-1, respectively. Reaction rate constants and activation energies were calculated for the temperature range 250-2500 K by the canonical variation transition state theory incorporating zero-curvature tunneling and small-curvature tunneling corrections. The calculated results show that the rate constants at the room temperature are in satisfactory agreement with the experimental values, and the C2 addition reaction is about 1 order of magnitude faster than that of the C1. The tunneling corrections are important for the rate constants of the hydrogen atom addition to CF ₂=CHF.