Theoretical investigation on the atmospheric fate of the CF3C(O)OCH(O)CF3 radical: alpha-ester rearrangement vs. oxidation

Abstract

A detailed quantum chemical study is performed on the unimolecular decomposition reaction of the alkoxy radical, CF₃C(O)OCH(O)CF₃ produced from CF₃C(O)OCH₂CF₃, trifluoroethyl trofluoroacetate (TFETFA) at the MPWB1K and M06-2X level of theories using the 6-31+G(d,p) basis set. Five plausible decomposition pathways including reaction with O₂, α-ester rearrangement and thermal decomposition (C–C, C–H and C–O bonds scission) have been considered in detail. Out of the five prominent decomposition channels, our results reveal that reaction with O₂ is the dominant path for the decomposition of the CF₃C(O)OCH(O)CF₃ radical in the atmosphere involving the lowest energy barrier which is in accordance with recent experimental findings. Our theoretical results also suggest that α-ester rearrangement leading to the formation of trifluoroacetic acid (TFA) has a negligible contribution for decomposition of the title alkoxy radical. The thermal rate constants for the above decomposition pathways are evaluated using Canonical Transition State Theory (CTST) at 298 K.