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

An empirical equation has been developed which reproduces bond dissoci ation energy (BDE) values for 65 common organic compounds with an aver age 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 estim ated (for R = ethyl, sec-propyl or t-butyl); X is one of a wide variet y of substituents; DH-degrees(CH3-X)obs is the key experimentally meas ured (CH3-X) bond strength; m is the number of methyl groups substitut ed 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.