Study of solute-solvent interactions of nicotinic acid and benzoic acid in methanol and its binary solvent systems

Abstract

The apparent molar volumes, ?V, and viscosity B-coefficients, B, for nicotinic acid (NA) and benzoic acid (BA) in mixed solvents containing 10, 20, 30 mass % of n-amyl alcohol (n-AmOH) or isoamyl alcohol (i-AmOH) in methanol and in pure methanol (MeOH) were determined from the solution density and viscosity measurements at 298.15 K as function of concentrations of NA and BA. These results were, in conjunction with the results obtained in pure methanol, used to deduce the partial molar volumes of transfer, 0 ??V , and viscosity B-coefficients of transfer, ?B, for NA and BA from methanol to different mixed methanol solvents, in order to rationalize various interactions in the ternary solutions. An increase in the transfer properties of NA and BA with increasing mass % of n-AmOH and i-AmOH in methanol was observed and explained by the effect of structural changes and preferential solvation. Also, the free energies of viscous flow, ? 0? 1 ? and ? 0? ?2 , per mole of solvent and solute, respectively, were calculated and analyzed on the basis of the transition state theory of relative viscosity.