Kinetics and mechanisms of nucleophilic displacements with heterocycles as leaving groups. Part 11. ρ* plots for the solvolysis of 1-s-alkyl-5,6-dihydro-2,4-diphenylbenzo[h]quinolinium cations

Abstract

The ρ* values for (1c–h) for (i) solvolysis in trifluoroacetic acid (–5.7), (ii) for solvolysis in pentanol (–1.2), and (iii) for unimolecular reaction with piperidine in chlorobenzene (–3.1) are discussed with respect to (a) the hypothesis that ρ* is a measure of the cation character of the transition state and (b) the S_N2 (intermediate) mechanism. The results are explained for (i) in terms of determining ion-molecule pair dissociation, for (ii) as rate determining S_N2 type solvent attack, and for (iii) as rate-determining ion-molecule pair formation.