HOMOLYTIC AND HETEROLYTIC X-C BOND-ENERGIES .1. HOMOLYTIC BOND-ENERGIES IN COMMON UNSATURATED ORGANIC-COMPOUNDS

It is shown that the homolytic bond dissociation energy (BDE), DH-degr ees(X-R), of the X-C bond in allylic, propargylic, benzylic, cyanated, and unsaturated compounds can be estimated by the simple equation DH- degrees(X-R) = DH-degrees(X-C(CH3)mH3-m) + E(s) + DELTAV(nb): where X is a wide variety of univalent atoms or substituents; R is an allylic, propargylic, benzylic, cyanated, or unsaturated group; DH-degrees(X-C (CH3)mH3-m) are the X-C BDEs in the model saturated compounds; m is th e degree of methyl substitution of the group R; E(s) is the p-pi reson ance stabilization energy (RSE) of the given conjugated radical R; DEL TAV(nb) is the steric compression relief and/or the net change of inte ractions between nonbonding atoms in the compounds RX and in the radic al R and in X resulting from the C-X bond cleavage.