Ion-Solvent Interaction in Aqueous Solutions of Alkali Metal Salts of 2,6-Dihydroxy-,2,4-Dihydroxy-and 2-Hydroxy-4-Aminobenzoic acids

Abstract

Measurements of the relative viscosities of aqueous solutions of a series of alkali metal salts of 2,6-dihydroxybenzoic acid and sodium salts of 2,4-dihydroxy- and 2-hydroxy-4-aminobenzoic acids in the temperature range 298–308 K show that while 2,6-dihydroxybenzoate acts as a water structure breaker, 2,4-dihydroxy and 2-hydroxy-4-aminobenzoate systems enforce the structure of water. The structure disrupting property of 2,6-dihydroxybenzoate is due to formation of strong intramolecular hydrogen bonds between the carboxylate group and the two adjacent hydroxyl groups. A number of physico- chemical parameters such as hydration number, ionic radii and thermodynamic parameters for viscous flow (using Feakin's model) have been calculated.