During recent years, the role of the ionic liquids (ILs) transferred to non-solvent applications such as catalysts. From them, Brønsted acidic ionic liquids (BAILs) have attracted special attention as efficient catalysts for the synthesis of valuable chemicals. The current review deals with the applications of BAILs as clean and versatile replacements for the traditional homogeneous acid catalysts such as H2SO4, HCl and H3PO4. The article covers the applications of BAILs in several essential organic reactions with excellent industrial and synthetic impacts such as: hydration and dehydration; oxidation; biodiesel production via transesterification and esterification; alkylation and biomass transformations. The versatilities and adaptabilities of BAILs in various reactions are predicted as the start of a new era in acid-catalyzed transformations.
