Synthesis of aprotic ionic liquids

Ionic liquids (ILs) are typically a salt in the liquid state. They have been intensively investigated for many applications, including as solvents, electrolytes, catalysts, energy storage materials and lubricants, owing to their synthetic flexibility; there is a large number of different possible combinations of anions and cations, which can lead to ILs with very distinct properties. However, there is no standard methodology for the synthesis of ILs, with the quality of these being based solely on the internal experience of each research group. This Primer provides a guide to IL synthetic practices, outlining considerations when choosing the synthetic route as well as evaluating the advantages and disadvantages of each route. The Primer serves as a reference for both new and experienced researchers, to help determine whether the IL from a specific route will be suitable for their intended application, be it ultra-pure, fast or cheap.