Abstract: The density functional calculations were used to explore the dissociation energies of [N(CH3)4]+ and [P(CH3)4]+ and their derivatives from substitution of H for CH3. The results show that the dissociation energies of C—N and C—P bonds gradually increase as the number of hydrogen atoms bonded to N or P increases in the derivatives, showing a remarkable effect of the intramolecular structural environment on the dissociation of the bonds. This dependence of bond dissociation energies on the local structural environment can be ascribed to the hyperconjugation interactions between the C—H bond and lone single electron of N or P. On the basis of NBO analyses, the bonding properties of dissociated fragments and their effects on dissociation energies were discussed.

Key words: Density functional theory, Dissociation energy, Natural bond orbital(NBO) analyses