Preferential solvation of ions in mixed solvents. Part 4.—Preferential solvation of Cu+ in acetone + acetonitrile and N,N-dimethylacetamide + acetonitrile mixtures using conductance measurements

Abstract

The molar conductances of Bu₄NBPh₄, Bu₄NClO₄ and CuClO₄·4AN have been measured in the concentration range (0.3–90)× 10^–4 mol dm^–3 in acetone (Ac), acetonitrile (AN) and N,N-dimethylacetamide (DMA) and in Ac + AN and DMA + AN mixtures containing 12.0, 33.2, 58.2, 73.4 and 93.2 mol % AN at 25 °C. The conductance data in all cases have been analysed by the 1957 Fuoss–Onsager conductance equation to obtain Λ₀ and K_A values for the electrolytes. The Λ₀ values have been split into the limiting ion conductances (λ^o_i) using a model recently proposed by Gill and Cheema. Good applicability of this model to some organic solvents has also been demonstrated. The present model gives a better splitting than that obtained by use of Gill's equation: λ^o_i=ZF²/6πNη₀[r_i–(0.0103ε₀+r_y)]. The non-linear variation of the true solvated radii (r_i) of Cu⁺ with solvent composition in the binary mixtures shows the strong preferential solvation of Cu⁺ by AN in Ac + AN mixtures over the whole solvent composition range, by AN in DMA-rich region and by DMA in the AN-rich region of the DMA + AN mixtures.