Conductance studies in amide + water mixtures. Part 5.—Tetra-alkylammonium bromides in N,N-dimethylacetamide + water mixtures at 35°C

Abstract

Precise conductance data for tetramethyl, tetraethyl and tetrabutylammonium bromides in N,N-dimethylacetamide + water mixtures (74.8 D 44.0) are reported in the concentration range 0.001–0.04 mol dm^–3 along with the solvent properties (density, viscosity and dielectric constants) at 35°C. The data have been analysed by the latest (1978) Fuoss equation. A maximum in the solvent viscosity has been observed at 1:3 mol ratio of DMA and water and is attributed to the formation of a solvated complex DMA. 3H₂O. All three salts show a maximum in Walden product at nearly 10 mol % DMA and this is attributed to the hydrophobic dehydration of tetra-alkylammonium ions by the cosolvent (DMA). Limiting equivalent conductance for a given salt shows a minimum with the change of solvent composition and in any given solvent mixture Λ₀ for the three salts studied decreases in the order Me₄NBr > Et₄NBr > Bu₄NBr. The association constant is almost negligible (K_A < 10) in most cases.