The reaction mechanisms and kinetics of CF_3CHFOCH_3 and CHF_2CHFOCF_3 with atomic chlorine: a computational study

摘要

Due to their lack of effect on the ozone depletion, hydrofluoroethers are considered as potential candidates for third generation refrigerants. In the present work, the mechanisms and kinetics of reaction of the Cl atom with CF_3CHFOCH_3 and CHF_2CHFOCF_3 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 –CH_3 group in CF_3CHFOCH_3 and H-abstraction from the –CHF_2 group in CHF_2CHFOCF_3 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 CHF_2CHFOCF_3 with the Cl atom are 4.27× 10~(?15) cm~3 molecule~(?1) s~(?1), which is consistent with the experimental value of (1.2 ± 2.0) × 10~(? 1 5) cm~3 molecule~(?1) s~(?1).