Reaction mechanism and product branching ratios of OH+C₂H₃F reaction: A theoretical study

Ab initio CCSD(T)/CBS//B3LYP/6-311G(d,p) calculations of the potential energy surface for possible dissociation channels of HOC2H3F, as well as Rice-Ramsperger-Kassel-Marcus (RRKM) calculations of rate constants, were carried out, in order to predict statistical product branching ratios in dissociation of HOC2H3F at various internal energies. The most favorable reaction pathway leading to the major CH2CHO+HF products is as the following: OH+C2H3F→i2→TS14→i6→TS9→i3→TS3→CH2CHO+HF, where the ratedetermining step is HF elimination from the CO bridging position via TS11, lying above the reactants by 3.8 kcal/mol. The CH2O+CH2F products can be formed by F atom migration from Cβ to Cα position via TS14, then H migration from O to Cα position via TS16, and C-C breaking to form the products via TS5, which is 1.8 kcal/mol lower in energy than the reactants, and 4.0 kcal/mol lower than TS11.