Free radical addition: Factors determining the activation energy

Empirical relations describing the reactivity of reagents in radical addition reactions and the results of quantum-chemical calculations of the activation energy of these processes are considered. The experimental data obtained for the addition of atoms and radicals to molecules with multiple bonds are analysed in terms of the parabolic model. The following characteristics and factors are shown to affect the activation energy of radical addition: the reaction enthalpy, the strength of the arising bond, the radius of the atom having a free valence, the presence of a π bond adjacent to the reaction centre, the interaction of two polar groups, the multidipole interaction, the steric factor, the non-linearity of the reaction centre, and the force constants of the reacting bonds. The bibliography includes 85 references.