THE PREDICTION OF BOND-DISSOCIATION ENERGIES FOR COMMON ORGANIC-COMPOUNDS

An empirical equation has been developed which reproduces bond dissociation energy (BDE) values for 65 common organic compounds with an average deviation of less than 0.6 kcal mol-1. The equation is DH-degrees(R-X)est = DH-degrees(CH3-X)obs - m(6.33 + 0.36 m -V(x)/0.67 + 0.21 m) + DELTAV(nb) where DH-degrees(R-X)est is the bond strength to be estimated (for R = ethyl, sec-propyl or t-butyl); X is one of a wide variety of substituents; DH-degrees(CH3-X)obs is the key experimentally measured (CH3-X) bond strength; m is the number of methyl groups substituted in CH3; V(x) is the covalent potential; DELTAV(nb) is the relief of steric strain between non-bonded atoms when the free radical pair is separated. The equation thus takes into account both inductive effects, related to a new scale of electronegativity, and structural effects.