Ab initio study of the energetics and thermodynamics of hydrogen abstraction from fluoromethanes by O(3P). II: CFnH4−n+O(3P)→CFnH4−n…O→CFnH3−n+OH (n=0,1,2)

Hydrogen abstractions by O(3P) from a set of fluorinated methanes, CFnH4−n+O(3P)→CFnH4−n…O→CFnH3−n+OH (n=0,1,2), were studied using ab initio methods. Geometries of the reactants and transition states were optimized at the UMP2/6-311G** level of theory, and activation energies were calculated using a modified Gaussian 2 (Ĝ2) theory. The potential-energy curves for the transition states were computed in order to obtain the transmission coefficients, κ, for the reactions studied. We found that κaver=1.12±0.01. Activation energies, activation enthalpies and rate constants were computed. Good agreement, (the average difference is 0.9±0.4 kcal/mol for the present study), was found between the ab initio activation energies, ΔG‡theor., and the experimental activation energies, ΔG‡expt′l.