An analysis of the cross-combination ratio of the rate constants ϕ in terms of the statistical adiabatic channel model allows to factorize ϕ into two contributions: one due to the motion along the reaction coordinates and another due to the reaction transitional modes. ϕ for the CH3/CCl3, CH3/C2H3, CH3/C3H5, CH3/C2H5 and C2H5/C3H5 radical pairs were calculated.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas