Element effects on the homolytic bond dissociation enthalpies of the acidic H-A bonds in HA(super .+) radical cations and their neutral precursors

Homolytic bond dissociation enthalpies of HA(super .+) radical cations are slightly lower than those of the parent HA nitrogen or oxygen acids when the atom A is oxygen or nitrogen. When the atom A is carbon the values are 30 to 50 kcal lower than those of their parents. The variation is due to the lower stabilities of the cation products in the N-H or O-H acids. Hypovalency in nitrogen cations and oxygen cations is increased by the greater nuclear charges.