Dissociation constants of substituted phenols and homoconjugation constants of the corresponding phenol–phenolate systems in acetonitrile

Abstract

Dissociation constants of 25 phenols and homoconjugation constants of 14 phenol–phenolate systems in acetonitrile have been determined from emf measurements. From these results a linear relationship log K^AN_a= 1.9 pK_a^H2O+ 8.3 has been derived. Stronger homoconjugation of weaker proton donors has been found to be a result of various (steric, inductive, mesomeric, charge delocalization) effects; however, the increase of homoconjugation constants with electron density at the phenolic oxygen seems to be unquestionable. Ten hydrogen bis-phenolates were prepared to complete this study, some of which crystallized well from water.