Nature of the interactions in binary mixtures of 1-butyl-3-ethylimidazolium bromide ionic liquid with methanol and ethanol

Physicochemical properties and nature of the interactions in methanol and ethanol solutions of 1-butyl-3-ethylimidazolium bromide ionic liquid, [C4C2im]Br, have been investigated experimentally measuring density over the whole composition range at selected temperatures and atmospheric pressure. From the experimental densities, the excess properties and partial molar volumes of the components at infinite dilution were calculated, as well as the excess molar expansibility at infinite dilution and isobaric thermal expansion coefficients. Obtained negative values of excess molar volumes with pronounced minimum at xIL ≈ 0.3 indicate strong ion-alcohol interactions and better packing due to differences in the size and shape of the molecules. Results are compared with those obtained for aqueous solutions of investigated ionic liquid and discussed in terms of hydrogen bond formation. Also, apparent molar volumes for {[C4C2im]Br + alcohol} systems show more pronounced deviations comparing to aqueous solutions of [C4C2im]Br confirming stronger self-association of the water molecules.