Thermodynamic solvation of a series of homologous α-amino acids in non-aqueous mixture of ethylene-glycol and N,N-dimethyl formamide

Kalachand Mahali, Sanjay Roy, Bijoy Krishna Dolui

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Dept. of Chemistry, Shibpur Dinabundhoo Institution(College), Howrah, India.

DOI: 10.4236/jbpc.2011.23022                

Abstract

Standard free energies (ΔG⁰_t(i) ) and entropies (ΔS⁰_t(i)) 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 measure-ments at five equidistant temperatures i.e from 15 to 35⁰C. The observed ΔG⁰_t(i) and TΔS⁰_t(i) Vs composition profiles are complicated because of the various interaction effects. The chemical effects of the transfer Gibbs energies (ΔG⁰_t.ch(i)) and entropies of transfer (ΔS⁰_t.ch(i)) have been obtained after elimination of cavity effect, estimated by the scaled particle theory and dipole-dipole interaction effects, estimated by the use of Keesom-orientation expression. The chemical contributions of transfer energetics of homologous α-amino acids are guided by the composite effects of increased dispersion interaction, basicity and decreased acidity, hydrogen bonding effects and solvophobic solvation of ethylene glycol and N, N-dimethyl formamide mixed solvent as compared to that of reference solvent (ethylene glycol).

Keywords

Non-Aqueous Solvent System; Transfer Energetic; Zwitterions; α-Amino Acids; Solvophobic Solvation

Conflicts of Interest

The authors declare no conflicts of interest.

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