The acidities of weak acids. Part I. A new method for determining pKa values in the range 12–24

Abstract

A kinetic method of determining weak acidities, based on following the rates of detritation of a ‘standard’ carbon acid in a series of dimethyl sulphoxide–water solutions containing a fixed concentration of hydroxide ions, both in the presence and absence of a second acid, is reported. The method, which has been established by redetermining the acidities of some diphenylamine and aniline-type indicators is well suited to studying acids (pK_a values in the range 12–24) whose absorption spectra do not undergo significant change on ionisation.