Theoretical study of the kinetics of hydrogen abstraction in reactions of simple hydrogen compounds with triplet difluorocarbene

The stationary points of H-atom abstraction reactions of triplet CF2(3B1) with XHn (n = 1–4: X = H, F, Cl, Br, O, S, N, P, C and Si) were computed using UCCSD(T) methods with 6-311++G(3df,2p) and aug-cc-pVTZ basis sets. Covalent surface crossing heights, calculated using the X–H and C–H bond dissociation energies of XHn and of the CHF2 product, correlate well with the computed classical barrier heights. Within each group of co-reactants, the barrier heights increase with increasing X–H bond dissociation energy, whereas the C–H bond lengths of the transition structures decrease. H-abstractions remain energy-demanding processes for second-row X atoms, but become more facile for their third-row X counterparts.