Rate Constants for CF3 + H2 → CF3H + H and CF3H + H → CF3 + H2 Reactions in the Temperature Range 1100−1600 K

The shock tube technique coupled with H-atom atomic resonance absorption spectrometry has been used to study the reactions (1) CF 3 + H 2 → CF 3 H + H and (2) CF 3 H + H → CF 3 + H 2 over the temperature ranges 1168−1673 K and 1111−1550 K, respectively. The results can be represented by the Arrhenius expressions k 1 = 2.56 × 10 -11 exp(−8549 K / T ) and k 2 = 6.13 × 10 -11 exp(−7364 K / T ), both in cm 3 molecule -1 s -1 . Equilibrium constants were calculated from the two Arrhenius expressions in the overlapping temperature range, and good agreement was obtained with the literature values. The rate constants for reaction 2 were converted into rate constants for reaction 1 using literature equilibrium constants. These data are indistinguishable from direct k 1 measurements, and an Arrhenius fit for the joint set is k 1 = 1.88 × 10 -11 exp(−8185 K / T ) cm 3 molecule -1 s -1 . The CF 3 + H 2 → CF 3 H + H reaction was further modeled using conventional transition-state theory, which included ab initio electronic structure determinations of reactants, transition state, and products.