Collision and Activated Complex Theories for Bimolecular Reactions

By using the principles of classical mechanics, the specific rates k′ of bimolecular reactions which proceed without activation energies were obtained by taking the average of πbc2g, where bc is the critical impact parameter and g is the relative molecular velocity. The result is k′=(β/μ)(kT)(s−4)/28C2/8.Here, C and s are the constants appearing in the attractive potential, C/rs(s>2), between two reacting molecules separated by a distance r, β is a dimensionless quantity involving s, μ is the reduced mass, and other symbols have their usual meaning. After substituting proper potential parameters into the above equation, we obtained the rates of the reactions for the systems, ion-molecule and radical-radical, in exact agreement with the rates in the literature obtained using the activated complex theory. The reason for the agreement was considered, and it was shown that under two conditions pointed out in the text the equations of k′ obtained from the activated complex theory transform to those derived from the classical collision theory.