Theoretical study of the reactions CF₃CH₂OCHF ₂+OH/C1 and its product radicals and parent ether (CH ₃CH₂OCH₃) with OH

A dual-level direct dynamic method is employed to study the reaction mechanisms of CF₃CH₂OCHF₂ (HFE-245fa2; HFE-245mf) with the OH radicals and Cl atoms. Two hydrogen abstraction channels and two displacement processes are found for each reaction. For further study, the reaction mechanisms of its products (CF₃CH₂OCF ₂ and CF₃CHOCHF₂) and parent ether CH ₃CH₂OCH₃ with OH radical are investigated theoretically. The geometries and frequencies of all the stationary points and the minimum energy paths (MEPs) are calculated at the B3LYP/6-311G(d,p) level. The energetic information along the MEPs is further refined at the G3(MP2) level of theory. For reactions CF₃CH₂OCHF₂ + 0H/Cl, he calculation indicates that the hydrogen abstraction from -CH₂- group is the dominant reaction channel, and the displacement processes may be negligible because of the high barriers. The standard enthalpies of formation for the reactant CF₃CH₂OCHF₂, and two products CF₃CH₂OCF₂ and CF₃CHOCHF₂ are evaluated via group-balanced isodesmic reactions. The rate constants of reactions CF₃CH₂OCHF₂ + 0H/C1 and CH ₃CH₂OCH₃ + OH are estimated by using the variational transition state theory over a wide range of temperature (200-2000 K). The agreement between the theoretical and experimental rate constants is good in the measured temperature range. From the comparison between the rate constants of the reactions CF₃CH₂OCHF₂ and CH₃CH₂OCH₃ with OH, it is shown that the fluorine substitution decreases the reactivity of the C-H bond.