Preparation and Hydrophilicity/Lipophilicity of Solubility-Switchable Ionic Liquids.

Various solubility-switchable ionic liquids were prepared. Their syntheses were readily achieved in a few steps from glyceraldehyde dimethylacetal or its derivatives. Pyridinium, imidazolium, and phosphonium derivatives also exhibited solubility-switchable properties; acetal-type ionic liquids were soluble in organic solvents, while diol-type ones exhibited a preference for being dissolved in the aqueous phase. The solubility of the ionic liquids prepared in this study also depended on the number of carbon atoms in the cationic parts of the ionic liquids. Interconversion between the diol-type and the acetal-type ionic liquids was readily achieved under the standard conditions for diol acetalization and acetal hydrolysis. One of the prepared ionic liquids was also examined as a solvent for an organic reaction.