Eutectic mixtures of urea and a range of quaternary ammonium salts are liquid at ambient temperatures and have interesting solvent properties.

A range of novel, moisture-stable, Lewis-acidic ionic liquids has been prepared by mixing appropriate molar ratios of MCl₂ (M = Zn and/or Sn) and quaternary ammonium salts of formula [Me₃NC₂H₄Y]Cl (Y = OH, Cl, OC(O)Me, OC(O)Ph); the influence of substituent Y and metal M on the physical properties of the melts has been investigated.

In this work the use of glycerol as a hydrogen bond donor in Deep Eutectic Solvents is studied. The physical properties of choline chloride mixtures with glycerol are quantified and it is shown that eutectic mixtures can circumvent some of the difficulties of using glycerol as a solvent viz. high viscosity and high melting point. The solvent properties are characterised using polarity parameters and the values are similar to other ionic liquids although it is shown that this procedure is a poor method of characterising Lewis basicity. The application of these liquids to the esterification of glycerol is used as a demonstration of the ability to tune a reaction with the quaternary ammonium halide acting as a quasi-protecting group. The liquids represent a sustainable way of preparing non-toxic, tuneable solvent systems.