Thermodynamics of solvation of DL-á-amino butyric acid in aqueous dimethyl sulfoxide at 298.15 K

Author(s): S.Roy, K.Mahali, S.Mondal, B.K.Dolui

The thermodynamics of interactions in terms of total transfer Gibbs free energy, G0 (i) t  and entropy, S 0 (i) t  as well as by the terms of chemical transfer free energy ( 0 ( ) , G i t ch  ) and entropy ( 0 ( ) , S i t ch  ) of DL- á-amino butyric acid in aqueous mixture of dimethyl sulfoxide at 298.15 K, is discussed here in the paper. For the evaluation of these factors, solubilities of this amino acid have been measured by ‘formol titrimetry’ method at five equidistant temperatures i.e. from 288.15 to 308.15 K in different composition of the protophilic dipolar aprotic dimethylsulfoxide (DMSO). The various solvent parameters as well as thermodynamic parameters like molar volume, densities, dipole moment and solvent diameter of aqueous solution of aprotic dimethylsulfoxide have also been reported here. The chemical effects of the transfer Gibbs energies ( G0 (i) t ,ch  ) and entropies of transfer ( S0 (i) t ,ch  ) have been obtained after elimination of cavity effect and dipole-dipole interaction effects from the total transfer energies. The chemical contribution of transfer energetics of DL-á-amino butyric acid is mainly guided by the composite effects of increased dispersion interaction, basicity effect and decreased acidity, hydrogen bonding effects, hydrophilic hydration and hydrophobic hydration of aqueous DMSO mixtures as compared to that of reference solvent, water.

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