The use of ionic liquids as alternatives to traditional molecular solvents is a rapidly expanding field. Their many advantages, including negligible vapor pressures, tunable miscibilities and the ease of product isolation, mean that they have been considered (and shown to be effective) as solvents for a range of reactions. However, the outcomes of many of these organic processes differ on changing solvent to an ionic liquid. For these ionic liquid media to be truly considered as alternative solvents, these differences must be understood. This article seeks to extend this understanding by reviewing the variations in the outcome of organic processes along with the fundamental physical properties of ionic liquids that differ from molecular liquids. A case study on nucleophilic substitutions is used to demonstrate the usefulness of our approach.