Influence of –SO3H functionalization (N-SO3H or N-R-SO3H, where R = alkyl/benzyl) on the activity of Brönsted acidic ionic liquids in the hydration reaction

Sulfonic acid group functionalized imidazole based Brönsted acidic ionic liquids (BAILs) were synthesized and their activities were investigated in the hydration reaction of alkynes. The Hammett acidity order determined from UV–visible spectroscopy of BAILs is consistent with their activity order observed in hydration reactions. Theoretical studies further help to establish the structure–activity relationship. Recycling experiments suggest that these novel BAILs can be reused without significant loss in activity. Applicability of BAILs in hydration reaction opens a non-toxic, economical, and eco-friendly route to synthesize alkyl ketones from alkynes.