Sugar-derived ionic liquids

Ionic liquids (ILs) are special molten salts with melting points below 100 degrees C that are typically constituted of organic cations (imidazolium, pyridinium, sulfonium, phosphonium, etc.) and inorganic anions. Due to their ionic nature, they are endowed with high chemical and thermal stability, good solvent properties, and non-measurable vapor pressure. Although the recycling of ILs partly compensate their rather high cost, it is important to develop new synthetic approaches to less expensive and environmentally sustainable ILs based on renewable raw materials. In fact, most of these alternative solvents are still prepared starting from fossil feedstocks. Until now, only a limited number of ionic liquids have been prepared from renewable sources (e.g., hydroxy acids, amino acids, terpenes), and even less from naturally occurring carbohydrates. This short review describes the synthesis and applications of chiral and achiral ILs obtained from inexpensive sugars.