Mechanism of OH-initiated atmospheric oxidation of E/Z-CF3CF = CFCF3: a quantum mechanical study

A detailed theoretical investigation was performed on the mechanisms for the reactions of E/Z-CF3CF=CFCF3 with OH radicals by means of density functional theory (DFT). The geometries and frequencies of all the stationary points and the minimum energy path (MEP) are calculated at the M06-2X/aug-cc-pVDZ level. To obtain more reliable energy information, the high-level single-point energies are further refined at the MCG3/3 level. Possible reaction pathways including the addition-elimination and the OH-initiated oxidation pathways are considered. A complete description of the possible degradation mechanisms of E/Z-CF3CF=CFCF3 in the absence and presence of O-2/NO has been presented. The calculated results demonstrate that the most accessible products are CF3, CF(OH)=CFCF3, CF(O)CHFCF3, CF3C(O)F, and CHFCF3 via the dissociation reactions starting from the addition intermediates IM1E/IM1Z in the absence of O-2/NO. While in the atmosphere, IM1E/IM1Z can further react with O-2/NO to form the likely products CF3C(O)F and HO2. The calculated results are consistent with the experimental results.