In this article the standard free energies (ΔG t 0 (i)) and entropies (ΔS t 0 (i)) of transfer of four homologous α-amino acids including glycine (Gly), DL-alanine (DL-Ala), DLα-amino butyric acid (DL-Aba.) and DL-nor-valine (DL-n-Val) from ethylene glycol (EG) to nonaqueous mixtures of ethylene glycol and dimethyl sulfoxide (DMSO) at 298.15 K are reported. The Gibbs energies of solutions have been determined from solubility measurements of each amino acid at different temperatures, that is, from 288.15 to 308.15 K by "formol titrimetry". The chemical parts of free energies (ΔG t,ch 0 (i)) and entropies (TΔS t,ch 0 (i)) of transfer of the homologous α-amino acids have been computed by subtracting the cavity effects and dipole−dipole interaction effects from the total transfer energies. The characteristics of the solvation thermodynamics of α-amino acids in EG-DMF and EG-ACN mixed solvent systems studied earlier are also discussed here for comparison.
Standard free energies (t) and entropies (t) of transfer of some homologous α-amino acids viz. glycine (gly), Dl-alanine (ala), Dl-α-amino butyric acid (aba) and Dl-nor-valine (nor-val) from protic ethylene glycol (EG) to dipolar aprotic N,N-dimethyl formamide (DMF) have been evaluated from solubility measurements at five equidistant temperatures i.e. from 15˚C to 35˚C. The observed t and t vs composition profiles are complicated because of the various interaction effects. The chemical effects of the transfer Gibbs energies (t ch ,
Solvation thermodynamic data of dl-serine and dl-phenylalanine in aqueous mixtures of dimethylsulfoxide at 298.15 K were determined from solubility measurement.
The solubilities of D,L-alanine and D,L-serine in aqueous sodium chloride (NaCl) and potassium chloride (KCl) solutions are determined at five equidistant temperatures by using "formol titrimetry". The thermodynamic parameters such as standard transfer Gibbs energies, entropies, and enthalpies have been evaluated at 298.15 K. Other important related parameters like molar mass, density, molar volume, dipole moment, and solvent diameter, etc., of the experimental solutions are also determined in the present study. ΔG t,ch 0 (i), i.e., chemical effects of the transfer Gibbs energies, and TΔS t,ch 0 (i), i.e., chemical effects of the transfer entropy of these amino acids, are also evaluated and discussed, the factors which are dependent on mainly nature of the solute, solvent, interactions between solute and solvent, etc. The nature and the extent of the involved factors, which are influencing the solvation of the amino acids in aqueous NaCl and KCl solutions, are also explained by the different physical and analytical approaches.
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