The dissociation energies of alpha-C-H bonds in nitriles and nitro compounds were determined in terms of the model of crossing parabolas from kinetic data on radical abstraction reactions. The enthalpies of formation of nitrile and nitro radicals were calculated, and the strengths of alpha-C-C bonds in the title compounds were estimated. The reactivity of nitrile and nitro radicals in H atom abstraction reactions with a number of hydrocarbons was evaluated on the basis of the data obtained.