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Thermodynamic studies of solvation of a series of homologous -amino acids in aqueous mixtures of protic ethylene glycol at 298.15K

S.Roy, K.Mahali, B.K.Dolui

Standard transfer Gibbs energies, G0 t(i) of a series of homologous á-amino acids(i) like glycine (gly), dl-alanine (ala), dl - -amino butyric acid (aba) and dl -nor- valine (n-val) from water to aqueous mixture of protic ethylene glycol (EG) with 0, 20, 40, 60, 80 and 100 wt%EGcompositions have been determined by measuring solubility of these amino acids at 250C using ‘formal titrimetryÂ’. The chemical effects of the transferGibbs energies of the á-amino acids(i), G0 t,ch(i) have been obtained by subtracting the cavity effects, G0 t,cav(i),estimated by the scaled particle theory and dipole-dipole interaction effects, G0 t,d-d(i) calculated by means of the Keesom orientation expression. G0 t,ch(i) are dictated by decreased hydrophobic hydration(HbH) and the superimposed increased acidity and increased dispersion effects of EG-water mixtures as compared to that in water.