The acid–base behaviour of cationic indicators in H2O–D2O mixtures

Abstract

The behaviour of p-nitroaniline and its N-methylated homologues and of 4,4′,4″-trimethoxytriphenylmethanol as acid–base indicators has been studied in mixtures of ordinary and heavy water. The results conform to the theory of protolytic equilibria in such media based on exchange effects. The following deuterium fractionation factors are evaluated for the exhangeable hydrogen nuclei; p-NO₂·C₆H₄[graphic omitted]HMe₂, 1·23; (p-MeO·C₆H₄)₃COH, 1·04; and (more conjecturally)p-NO₂·C₆H₄NHMe and p-NO₂·C₆H₄NH₂, 1·3.