SIMILARITY APPROACH TO CHEMICAL-REACTIVITY - A SIMPLE CRITERION FOR DISCRIMINATING BETWEEN ONE-STEP AND STEPWISE REACTION-MECHANISMS IN PERICYCLIC REACTIVITY

The similarity index recently proposed as a quantitative measure of th e extent of electron reorganization in chemical reactions was generali zed to be applicable not only for the discrimination of allowed and fo rbidden reaction mechanisms of concerted processes but also for a simp le evaluation of the relative ease of concerted one-step and nonconcer ted stepwise reaction paths. The applicability of the approach is demo nstrated by several examples of selected pericyclic reactions, both fo rbidden and allowed. The resulting theoretical predictions are in rema rkable agreement with available experimental and theoretical results.