Ionic liquids have been proposed as functional replacements for harmful and hazardous volatile organic solvents. However, limiting their use in this way does not fully explore the potential chemical benefits of their solvating properties, which stem from the inherent differences between ionic liquids and single molecule solvents. These differences can be used to facilitate alternative and improved reaction outcomes. This review will highlight a range of examples, involving materials preparation and organic synthesis, in which substantial progress towards the understanding and targeted application of ionic liquids is demonstrated. In addition, a number of studies will be cited where unanticipated outcomes have been observed and the relationships between these outcomes and ionic liquid structural effects will be analysed, casting new light onto these studies.