Mechanistic significance of the magnitude of cross‐interaction constants

The relationship between the magnitude of the cross‐interaction constant, |ρ ij |, and the force constant of activation, Δ F ‡ ij , has been derived and their equivalence has been shown, where Δ F ‡ ‡ = (force constant in the transition state, Δ F ‡ ij ‐ force constant in the ground state, F 0 ij ). When bond formation is involved in the activation process, Δ F ‡ ij becomes equal to F ‡ ij and |ρ ij | is inversely related to the distance, r ‡ ij , between reaction centres R i and R j . However, for bond‐breaking processes, interpretation of |ρ ij | becomes complicated, since Δ F ‡ ij = F ‡ ij − F 0 ij may be negative or positive depending on the relative size of F ‡ ij and F 0 ij . Some examples of re‐examination are given for various cases of |ρ ij | in the bond‐breaking processes.