CONDUCTIVITIES AND ION ASSOCIATION OF QUATERNARY AMMONIUM CARBOXYLATES IN GAMMA-BUTYROLACTONE

The conductivities for eighteen quaternary ammonium carboxylates in gamma-butyrolactone have been measured at 25-degrees-C, which have been recently used as high performance liquid electrolytes in aluminum electrolytic capacitors. The limiting molar conductivities and the ion association constants of these electrolytes were calculated by the Shedlovsky extrapolation method. The single ion limiting molar conductivities of carboxylate ions were 24.8, 20.2 and 18.9 S cm2 mol-1 for bimaleate, biphthalate and benzoate ion, respectively. The single ion limiting molar conductivities of quaternary ammonium ions decreased in the order: Me4N+ 23.1 > Me3EtN+ 22.7 > Me2(CH2)4N+ 22.3 > Me2Et2N+ 22.0 > MeEt3N+ 21.3 > Et4N+ 20.6 S cm2 mol-1. The ion association constants increased as the ionic radius of a quaternary ammnonium ion and the acidity of a carboxylic acid decreased.