ChemInform Abstract: STERIC EFFECTS ON REACTION RATES. IV. EVALUATION OF THE KETONE MODEL FOR THE SOLVOLYSIS TRANSITION STATE OF SECONDARY P‐TOLUENESULFONATES

Abstract

SummaryThe rates of solvolysis of secondary p-toluenesulfonates in acetic acid or 97% trifluoroethanol are interpreted in terms of strain changes between substrate and the corresponding ketone. Such strain changes are obtained from force-field calculations (AE,,) and from equilibration of alcohols and ketones (AG,,). This simple model reproduces the behaviour of substrates reacting by k,-pathways to afford unstrained carbenium ions. Anchimeric assistance and leaving group hindrance in the transition state are recognized in clear-cut cases by deviations from the expected reactivity. However, the model breaks down when highly strained carbenium ions of the cyclobutyl or 7-norbornyl type are involved.