Basic Hydrolysis And Decarboxylation Of Allophanic Esters In A Combined Acetonitrile Water Mixture - Bifunctional Catalysis By An Entity Formed Between Base And Solvent

Base catalysed hydrolysis of allophanic esters-models of carboxybiotine- in acétonitrile/water mixture, shows a sharp increase in rate constant in the range of 0.1–0.3 M in water, with a maximum which is interpreted as a balance between two desolvation terms, concerning the nucleophile, the other the anionic transition state. Moreover, in acetonitrile/water mixtures at low water content (2.10 −2 M), a fast hydrolysis (k exp ⋍0.5 s −1 at 20 °C) of allophanic esters (carboxy-biotin models) is observed due to catalysis by the enolate of acetamide. This species also catalyses the decarboxylation step, likely behaving as a bifunctional catalyst.