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

© 2015 Elsevier Ltd. All rights reserved. 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 = 0.1 MPa). 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.