The dissociation energies of CH4 and C2H2 revisited

The bond dissociation energies of CH4, C2H2, and their fragments are investigated using basis set extrapolations and high levels of correlation. The computed bond dissociation energies (De) are accurate to within 0.2 kcal/mol. The agreement with the experimental (D0) values is excellent if we assume that the zero-point energy of C2H is 9.18 kcal/mol. The effect of core (carbon 1s) correlation on the bond dissociation energies of C–H bonds is shown to vary from 0.2 to 0.7 kcal/mol and that for C–C bonds it varies from 0.4 to 2.2 kcal/mol.