A computational perspective on mechanism and kinetics of the reactions of CF3C(O)OCH2CF3 with OH radicals and Cl atoms at 298 K

Theoretical investigations are carried out on the gas-phase reactions of CF3C(O)OCH2CF3, 2,2,2-trifluoroethyl trifluoroacetate (TFETFA) with OH radicals and Cl atoms by means of modern DFT methods. Two conformers relatively close in energy have been identified for TFETFA, both of them are likely to be important in the temperature range of our study. Reaction profiles are modeled including the formation of two pre-reactive and post-reactive complexes. The optimized geometries, frequencies and minimum energy path are obtained at hybrid density functional model, M06-2X level using 6-31+G(d,p) basis set. The single point energy calculation was further refined by using 6-311++G(d,p) and Aug-cc-pVTZ basis sets. The existence of transition states on the corresponding potential energy surface is ascertained by performing intrinsic reaction coordinate (IRC) calculation. Theoretically calculated rate constants at 298 K and using the canonical transition state theory (CTST) are found to be in good agreement with the experimentally measured ones. Using group-balanced isodesmic reactions, the standard enthalpies of formation for CF3C(O)OCH2CF3 and radical generated by hydrogen abstraction, CF3C(O)OCHCF3, are also reported for the first time. The estimated atmospheric lifetime of TFETFA is expected to be 0.15 years.