C-H and C-halogen bond dissociation energies for fluorinated and chlorinated methane evaluated with hybrid B3LYP density functional theory methods and their comparison with experimental data and the CBS-Q ab initio computational approach

The C-H and C-halogen bond dissociation-energies (BDEs) were computed with the hybrid B3LYP/6-311 + G(2d,2p) theory model for chlorinated and fluorinated methane. All computed values were substantially lower (5-10 kcal mol(-1)) than the experimental values. To obtain better agreement, a correlation factor was introduced. When this factor was applied, excellent agreement between the B3LYP/6-311 + G(2d,2p) computed energies and the experimental BDEs was observed. On the other hand, the CBS-Q ab initio computational approach generated BDEs which are in good agreement with experimental values without a correction factor. (C) 1998 Elsevier Science B.V.