The role played by the enthalpy of reactions in the disproportionation of free radicals

A semiempirical model of radical disproportionation was suggested. The reaction was modeled by an intersection of two potential curves describing stretching vibrations of interacting bonds. One of these curves was a parabola (stretching vibration of the attacked bond), and the other, a Morse curve (stretching vibration of the arising bond). Equations describing an increase in the interatomic distance in the reaction center of the transition state of such reactions as a function of the enthalpy of the reaction were obtained. A comparison of the calculation results and experimental data was performed to derive equations that described the rate constant for disproportionation as a function of bond elongation in the transition state and reaction enthalpy. A simple method for calculating interatomic distances in the reaction center of the reactions was suggested. Rate constants for several unstudied radical disproportionation reactions were calculated. The problem of the competition of disproportionation at various reaction centers was considered.