Enthalpies of transfer of amino acids from water to aqueous solutions of sodium nitrate and sodium perchlorate at T = 298.15 K

Abstract

Enthalpies of solution of glycine, l -alanine and l -serine in water and aqueous solutions of NaNO 3 and NaClO 4 have been determined at T = 298.15 K with a calorimeter. Enthalpies of transfer (Δ tr H) from water to aqueous solutions of salts were derived and interpreted in terms of electrostatic interaction and structural interaction. Δ tr H decreases with increasing salt concentration in the composition range studied. The transfer enthalpies of amino acids from water to NaNO 3 solution and low concentration NaClO 4 solution vary in the sequence l -serine < glycine < l -alanine while glycine < l -serine < l -alanine in NaClO 4 solution above 2 mol kg −1. The difference may be due to ion association at high concentration, weakening the interaction with l -serine more than with glycine.