The reaction mechanisms and kinetics of CF3CHFOCH3 and CHF2CHFOCF3 with atomic chlorine: a computational study

Due to their lack of effect on the ozone depletion, hydrofluorocthers are considered as potential candidates for third generation refrigerants. In the present work, the mechanisms and kinetics of reaction of the Cl atom with CF3CHFOCH3 and CHF2CHFOCF3 were investigated theoretically using quantum chemical methods and transition state theory. Four reaction pathways for the title reaction were explored. By using conventional transition state theory with Eckart tunneling correction, the rate constants of the title reaction were obtained over the temperature range 200-300 K. Kinetic calculations demonstrate that H-abstraction from the -CH3 group in CF3CHFOCH3 and H-abstraction from the -CHF2 group in CHF2CHFOCF3 are major reaction pathways, with the barrier heights of the two paths calculated to be -1.04 and 4.33 kcal mol(-1), respectively. However, the contribution of H-abstraction from the -CHFO- group for the two reactions should also be taken into account with increased temperature. At 298 K, the calculated overall rate constants of the reaction of CHF2CHFOCF3 with the Cl atom are 4.27 x 10(-15) cm(3) molecule(-1) s(-1), which is consistent with the experimental value of (1.2 +/- 2.0)x 10(-15) CM3 molecule(-1) s(-1).