Further unusual deuterium isotope effects—βversusα—on the polarimetric rate of solvolysis of threo-1-methyl-2-phenylpropyl toluene-p-sulphonate and the question of non-classical carbonium ion intermediates

Abstract

Acetolysis, formolysis, and trifluoroacetolysis of (+)-threo-1-methyl-2-phenylpropyl toluene-p-sulphonate (I) and the deuteriated derivatives (II) and (III) gave isotope effects, k_I/k_IIversus k_I/k_III, of 1·104 versus 1·094, 1·142 versus 1·040, and 1·133 versus 1·009, respectively, which are not satisfactorily interpreted in terms of either a non-classical symmetrical phenonium ion or two rapidly equilibrating classical carbonium ions, but are claimed to be understandable in terms of a third model previously suggested by one of us.