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

The apparent molar volumes, φV, 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 me- thanol and in pure methanol (MeOH) were determined from the solution den- sity 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 φ ∆ , and vis- cosity B-coefficients of transfer, ∆B, for NA and BA from methanol to diffe- rent mixed methanol solvents, in order to rationalize various interactions in the ternary solutions. An increase in the transfer properties of NA and BA with in- creasing mass % of n-AmOH and i-AmOH in methanol was observed and ex- plained by the effect of structural changes and preferential solvation. Also, the free energies of viscous flow, ≠ ∆ 0 1 µ and ≠ ∆ 0 µ , per mole of solvent and solute, respectively, were calculated and analyzed on the basis of the transition state theory of relative viscosity.