We have studied the rate of 15 reactions of acyl transfer from O-acyl salts of 4-dimethylaminostyryl-4′-pyridine N-oxide to 4-morpholinopyridine and 4-dimethylaminopyridine N-oxides in acetonitrile solutions. Analysis of the results based on the Shaik – Pross approach and the Marcus equation shows that if the structure of the acyl group is varied, then the reactivity is determined by such parameters as the resonance interaction in the transition state (B) or the internal barrier (ΔG ≠ 0) of the reaction.