Kinetics and mechanism of nucleophilic displacements with heterocycles as leaving groups. Part 23. Studies at the borderlines between reactions proceeding (i) via free carbocations, (ii) via rate-determining formation of ion–molecule pairs, and (iii) via rate-determining nucleophilic attack on ion–molecule pairs

Abstract

Evidence is presented to demonstrate that at the borderline between first-order reaction via nucleophilic trapping of intimate ion–molecule pairs and first-order reaction via the formation of free carbocations, both mechanisms proceed independently, without merging. Similarly at the borderline between first-order (rate-determining formation) and second-order (rate-determining nucleophilic attack) reactions of intimate ion–molecule pairs, both reactions again proceed independently.