Substituted diphenylmethyl cations. Part I. Acid–base equilibria

Abstract

The ionisation of several alkyldiphenylmethanols in sulphuric acid is examined. Evidence is presented which confirms the conjecture that where possible equilibrium in these systems exists between carbonium ion and olefin. α-Substitution in the alkyl group is shown to strongly destabilise the carbonium ion through steric effects on solvation and on the planarity necessary for resonance. It is also shown that internal ‘solvation’ by a hydroxysubstituent in the alkyl group causes an unusually high slope for a plot of log (ionisation ratio)versus–H_R.