Conductance study on the association behaviour of quaternary ammonium salts in hydrogen-bonding solvents

Abstract

Conductance measurements have been carried out at 25°C on the following systems: tetrabutyl- and tetrahexyl-ammonium perchlorates in methanol + dioxan mixtures, and tetrabutylammonium perchlorate in acetonitrile + dioxan and acetonitrile + carbon tetrachloride mixtures. The analysis of the association behaviour of these electrolytes in methanol + dioxan, in pure methanol and in water, shows that only in aqueous solutions does the association increase with increasing alkyl chain length.

This experimental evidence can be rationalized, qualitatively, on the basis of two different mechanisms of association: ion-pairing due to Diamond mechanism and to electrostatic interactions.