Does the variation of the alkyl chain length on N1 and N3 of imidazole ring affect physicochemical features of ionic liquids in the same way?

Abstract

In this manuscript bromide based ionic liquid, namely 1-butyl-3-ethylimidazolium bromide, [C4C2Im]Br, was synthesized and fully characterized by NMR, IR, thermogravimetric and TOC measurements. Also, density, viscosity and electrical conductivity of the pure [C4C2Im]Br were measured. Ten times lower viscosity and two times higher electrical conductivity were observed in the case of [C4C2Im]Br comparing to 1-butyl-3-methylimidazolium based ionic liquid. Physicochemical properties and nature of the interactions in aqueous [C4C2Im]Br solutions have been investigated measuring density over the whole composition range at different temperatures at atmospheric pressure (p=0.1MPa). Volumetric properties of binary liquid mixture in whole concentration range were studied in the temperature range from (293.15 to 323.15)K and in diluted solutions in the range from (293.15 to 308.15)K. From calculated volumetric properties for ([C4C2Im]Br+H2O) binary mixtures it was observed that ethyl group on N3 imidazolium atom leads to considerably weaker hydration of the [C4C2Im]+ compared to 1-butyl-3-methylimidazolium cation, [C4C1Im]+. In addition, coefficients of the Masson’s equation indicate weak ion–ion interactions in the studied aqueous solution, while positive value obtained using Hepler’s equation indicates structure making properties of [C4C2Im]+ cation.