Kinetics and mechanisms of nucleophilic displacements with heterocycles as leaving groups. Part 8. Conductimetric and spectrophotometric rate constants for the reactions of pyridinium and related cations with piperidine in chlorobenzene

Abstract

A conductimetric method is developed to obtain rates for the title reactions for which the spectrophotometric method fails. It gives equivalent results. NN′-Dimethylthiourea displaces heterocyclic leaving groups at rates similar to those for piperidine. Compared with α-hydrogen, α-methyl groups render pyridine a less effective leaving group, whereas α-ethoxycarbonyl groups show a large rate enhancement.