Titrations in non-aqueous media. Part I. Determination of factors influencing the basicity of schiff bases in nitrobenzene solvent

Abstract

Potentiometric titrations of Schiff bases with perchloric acid in nitrobenzene solvent were carried out in order to obtain information about the factors that influence the basicities of the Schiff bases. The Schiff bases were synthesised from aromatic aldehydes and amines bearing an aromatic ring. Some contained a methylene group between the aromatic ring and the imino group and others contained a hydroxy group ortho to the imino group. For each Schiff base, an S-shaped potentiometric titration curve was obtained. From these curves half-neutralisation potentials were determined and from the latter the pK_a′ values. In these determinations the half-neutralisation potential of 0.001 M hexa(p-toluidino)cyclotriphosphazatriene [N₃P₃(NH-p-tol)₆] in nitrobenzene with perchloric acid was taken as the standard.