Conductance studies of tetra-alkylammonium bromides in 2-methoxyethanol at 25 °C

Abstract

Conductance measurements are reported for six symmetrical tetra alkylammonium halides, R₄NBr (R = ethyl to heptyl) and two ‘reference electrolyte’, viz. tetrabutylammonium tetrabutylborate (Bu₄NBBu₄) and tetrabutylammonium tetraphenylborate (Bu₄NBPh₄) in 2-methoxyethanol (ME) at 25 °C. The data have been analysed by the 1978 Fuoss conductance equation in terms of the limiting molar conductivity, Λ⁰, the association constant, K_A, and the association distance, R. The limiting ion conductances have been determined from the appropriate division of the Λ⁰-values of Bu₄NBBu₄ and Bu₄NBPh₄. The results indicate that all these salts are highly associated in this solvent medium. The K_A values are generally found to decrease with increasing cationic size from Et₄N⁺ to heptyl₄N⁺ but decreases sharply for Pr₄NBr. The individual limiting ion conductance (λ⁰_±) obtained separately from the two reference electrolytes are in good agreement with each other, suggesting that any one of them can be used as a reference electrolyte in ME. The Walden products and the Stokes radii of the ions have been evaluated. The values indicate that R₄N⁺ ions are poorly solvated in this solvent medium.