Modulation in physico-chemical characteristics of some polyhydroxy solutes in presence of l-glycine: Volumetric and NMR spectroscopic approach

Abstract

Volumetric and 1H and 13C NMR spectroscopic studies have been exploited to study molecular interactions of some polyhyroxy solutes with l-glycine in aqueous solutions. Apparent molar volumes, V2,ϕ for monosaccharides; (+)-d-mannose, (+)-d-glucose, and (−)-l-sorbose, disaccharides; (+)-maltose monohydrate, and (+)-cellobiose, deoxy-derivatives of hexoses; 6-deoxy-d-mannose, 2-deoxy-d-glucose, methyl glycopyranosides; (+)-methyl α-d-mannopyranoside, and (+)-methyl α-d-glucopyranoside, and polyols; d-mannitol, d-sorbitol, and myo-inositol in 0.05, 0.15, 0.25, 0.35 and 0.50molkg−1 aqueous solutions of l-glycine have been determined from density, ρ data measured at 288.15, 298.15, 308.15 and 318.15K under atmospheric pressure, p=0.1MPa. The data were processed to obtain the standard partial molar volumes, V2° at infinite-dilution and the corresponding volumes of transfer, ΔtrV2° of solutes from water to aqueous solution of l-glycine. Other parameters such as partial molar expansion coefficients (∂V2°/∂T)P and their second-order derivatives (∂2V2°/∂T2)P, and pair and higher-order volumetric interaction coefficients (VAB and VABB) have also been obtained. These parameters have been utilized to discuss various types of interactions on the basis of co-sphere overlap model. 1H and 13C NMR spectroscopic studies for polyhydroxy solutes were carried out in 0.10molkg−1l-glycine prepared in 9:1 (w/w) H2O–D2O solvent. NMR results show more downfield shift in ternary system than in pure l-glycine solution, hence suggesting that hydrophilic–ionic interactions predominate over hydrophilic/hydrophobic–hydrophobic interactions occurring between solute and l-glycine molecules.