Interactions of 1-butyl-3-methylimidazolium carboxylate ionic liquids with glucose in water: a study of volumetric properties, viscosity, conductivity and NMR

Extensive applications of ionic liquids (ILs) may result in their accumulation in the ecological environment and organisms. Although ILs are popularly called “green solvents”, their toxicity, in fact, has been exhibited. Therefore the interaction of ILs with biomolecules is a cutting-edge research subject. Herein, the interactions of 1-butyl-3-methylimidazolium carboxylate ionic liquids ([C4mim][HCOO], [C4mim][CH3COO] and [C4mim][CH3CH2COO]) with glucose in water were studied for their volumetric properties, viscosity, conductivity and NMR spectra. Limiting apparent molar volumes (V0Φ,IL), viscosity B-coefficients, limiting molar conductivities (Λ0) and Walden products (Λ0η0) were evaluated for the ILs in glucose + water solutions. Volumetric interaction parameters were also obtained from the transfer volumes of the ionic liquids. The contributions of the solvent properties (B1) and the ionic liquid–solvent interactions (B2) to the B-coefficient were extracted, together with molar activation energies (Δμ0≠IL) of the ionic liquids for viscous flow of the aqueous glucose + IL solution. In addition, the 13C and 1H NMR spectra of methyl β-D-glucopyranoside and ILs in β-D-glucopyranoside + IL + D2O were studied. The NMR results show that no special and strong interactions were observed between glucopyranoside and the ILs. However, it was confirmed that the H2 on the imidazolium ring has more activity (acidity) than atoms H4 and H5. The macro-properties and their changes were also discussed in terms of the size, structure and solvation of the ILs and glucose.