Shortcomings of Basing Radical Stabilization Energies on Bond Dissociation Energies of Alkyl Groups to Hydrogen

Stabilization energies (SEH) of carbon radicals (R•) are traditionally defined as the difference between the bond dissociation energy (BDE) of CH3−H, as a reference point, and of R−H. The term “stabilization energy” implies that it is an intrinsic property of the radical and a quantitative measure of stability. Applicable only to carbon-centered radicals, SEH stabilization energies are not transferable and cannot be used to estimate carbon−carbon BDE[R−R′], symmetrical BDE[R−R], or any other BDE[R−X]. SEH values by themselves are neither an intrinsic property nor a quantitative measure of stability. There is available an alternative that is not limited only to carbon−carbon and carbon−hydrogen bonds, does not depend on any one particular molecule or BDE as a reference point, and is accurate with several hundred different types of bonds.