Volumetric properties, viscosity coefficients and aggregation behaviour of DBU-acetate protic ionic liquid in molecular solvents

Abstract

The density, viscosity and conductivity of binary mixtures of 1,8-diazabicyclo [5.4.0] undec-7-en-8-ium acetate [DBUH][OAc] protic ionic liquid (PIL) with water, ethanol and acetonitrile in the concentration range of (~0.02 to ~1.0) mol·kg−1 were measured at 298.15 K. Apparent molar volumes (φV) has been obtained for aqueous and non-aqueous solutions of [DBUH][OAc] using experimental density data. The concentration dependent φV data were analyzed using Redlich-Mayer equation to estimate limiting apparent molar volume (φV0) and deviation parameters (BV and DV). The relative viscosity data of [DBUH][OAc] solutions were correlated with Jones–Dole equation for obtaining viscosity A and B coefficients. Specific conductivity data of studied PIL+ solvent mixtures were fitted using Carpena's method to evaluate critical aggregation concentration (CAC). The CAC is further used to estimate standard Gibbs energy of aggregation. From studied parameters it has been observed that PIL-water and PIL-ethanol interactions are stronger than that of PIL-acetonitrile interactions. The results are discussed in terms of effect of dielectric constant, hydrogen bonding abilities of solvents on ion-solvent, ion-ion interactions, and on aggregation behaviour of DBU-acetate.