p-Nitrophenolate: a probe for determining acid strength in ionic liquids

The protonation equilibrium of sodium p-nitrophenolate in [[bm.sub.2]im][N[Tf.sub.2]] and in [bmpyrr][N[Tf.sub.2]] is studied by using spectrophotometric titration in order to obtain an acidity scale in room-temperature ionic liquid solutions. The studies have shown that the carboxylic acids in ionic liquid solutions are less dissociated than in water solution and the equilibrium are affected by both the nature of the ionic liquids and the carboxylic acids.