Classical carbonium ions. Part VII. Nucleophilic assistance by solvent during acetolysis of secondary alkyl derivatives

Abstract

Two different methods recently described for estimating the nucleophilic assistance by solvent in the solvolysis of (a) secondary alkyl bromides and (b) secondary alkyl arenesulphonates, have been simultaneously applied to secondary alkyl picrates, using tertiary alkyl 2,4-dinitrophenyl ethers as a point of reference. To a first approximation they give similar results and confirm earlier conclusions; their difference allows the estimation of small (ca. 4 kJ mol^–1) amounts of anchimeric assistance in 2-adamantyl and 1,2,2-trimethylpropyl systems. It is concluded that these secondary solvolyses are well described as ‘S_N1 reactions,’ but not as ‘limiting.’