Catalysis in ester aminolysis in aprotic solvents. The amine-catalysed reaction of imidazole with 4-nitrophenyl trifluoroacetate in aqueous acetonitrile

Abstract

The imidazolysis of 4-nitrophenyl trifluoroacetate has been investigated in aqueous acetonitrile containing 0.56 mol dm^–3 of water. The reaction is found to be general base-catalysed by pyridines and 1-methylimidazole. The catalytic abilities of sterically unhindered pyridines correlate with their aqueous pK_a values with a Brønsted β value of 0.79. The high value of β is thought to reflect the electrophilicity of the substrate and the polarity of the medium.