Thermodynamic Function for Transfer of Some Carboxylic Acids from Water to Alcohol-Water Mixtures

摘要

The solubilities of benzoic acid, 3-; 4-methylbenzoic acid, 2-; 3-; 4-aminobenzoic acid, 2-; 3-; 4-nitrobenzoic acid, 1-; 2-naphthoic acid, pyridine-2-carboxylic acid and pyridine-4-carboxylic acid have been determined in water and water + methanol mixtures. From the solubilities data, free energy of solutions of these acids were found using the relationship delta G = - RT lnS. The thermodynamic transfer functions were derived from delta G values as these substances get transfer from aqueous to aquo-alcoholic mixtures. It has been found that the solubilities of these substances increased with increase of temperature as well as with increase of methanolic contents in the mixtures. The thermodynamic transfer function indicate that the nature of solute is one of the determining factors for the study of ion-solvent and solvent-ion-solvent interaction. These interactions have been attributed to resonance, steric, dispersion and conjugative effects of the substituents on the benzene, pyridine and naphthalene ring.