Thermodynamic properties of d-glucose in aqueous 1-hexyl-3-methylimidazolium bromide solutions at 298.15 K

Various thermodynamic and thermophysical properties, such as density, molar conductivity, and refractive index for {d-glucose + ionic liquid, 1-hexyl-3-methylimidazolium bromide ([HMIm]Br), + H2O} solutions have been measured at 298.15 K. The calculated volumetric properties containing standard partial molar volumes (Vϕ0) and corresponding transfer volumes (ΔtrVϕ0) were used to interpret solute–solvent interactions. An increase was observed in the Vϕ0 and ΔtrVϕ0 values with increasing the ionic liquid concentration. This observation indicates that there are interactions between [HMIm]Br and the hydrophilic OH and O groups of d-glucose, providing that the ionic liquid has a dehydration effect on the d-glucose solutions. To confirm this result, limiting molar conductivities (Λ0) and ion association constants (Ka) for [HMIm]Br in aqueous d-glucose solutions have been estimated by low concentration Chemical Model (lcCM). These quantities decrease with increasing the concentration of d-glucose, suggesting strong interactions between the ionic liquid and d-glucose. The values of molar refractions (RD) obtained from refractive index measurements show an increase upon increasing both d-glucose and the ionic liquid concentrations. It was also attempted to make a comparison between the results obtained here and those of our previous works to investigate the effect of the cation size of ionic liquid on the solute–solvent interactions.

► Thermodynamic properties of d-glucose + [HMIm]Br + H2O solutions were studied. ► Densities, conductivities, and refractive indices of the solutions were measured. ► Interactions of the ionic liquid with the polar groups of d-glucose were observed. ► These interactions increase with the rise of the concentration of the ionic liquid.