Theoretical study of the reaction of CF3O radicals with CO

The potential energy surface for the reaction of the CF3O radicals with CO was investigated. The geometries and vibrational frequencies of the reactants, transition states, intermediates, and products were calculated at the UB3LYP/6-311+G(2d,p), UB3LYP/6-311+G(3df,2p) and UMP2/6-311+G(2d,p) levels of theory. The energies were improved by using the G2M(CC2) and G3B3 methods. The calculation suggests the reaction proceeds via either the fluorine abstraction of CF3O by CO to produce FCO + CF2O with a high energy barrier or the barrierless association of the reactants to form the trans-CF3OCO intermediate. The trans-CF3OCO is predicted to undergo subsequent isomerization to cis-CF3OCO or dissociate directly to the products FCO + CF2O and CF3 + CO2. The collisional stabilization of trans-CF3OCO is dominant at room temperature, while trans-CF3OCO isomerizing to cis-CF3OCO followed by dissociating to CF3 + CO2 is accessible when temperature rises. The reason for only trans-CF3OCO without cis-CF3OCO observable in Ashen's experiment [S.V. Ahsen, J. Hufen, H. Willner, J.S. Francisco, Chem. Eur. J. 8 (2002) 1189] is cis-CF3OCO can be produced only via the isomerization of trans-CF3OCO, and its yield is inappreciable at a low experimental temperature. The enthalpies of formation for the two conformations of CF3OCO have been deduced: ΔfH0∘ (trans-CF3OCO) = −196.25 kcal mol−1, ΔfH298.15∘ (trans-CF3OCO) = −197.46 kcal mol−1, ΔfH0∘ (cis-CF3OCO) = −193.64 kcal mol−1, and ΔfH298.15∘ (cis-CF3OCO) = −194.90 kcal mol−1.