Strain effects in acyl transfer reactions. Part 4. Kinetic analysis of the reaction of imidazole buffer solutions with β-propiolactone using a novel graphical method for branched, series reactions

Abstract

The imidazole-catalysed hydrolysis of β-propiolactone (oxetan-2-one) proceeds by formation and subsequent hydrolysis of 1-(3-hydroxypropionyl)imidazole. There is concurrent production of 1-(2-carboxyethyl)imidazole as the major product. Continuous monitoring of the acylimidazole intermediate enables a complete kinetic analysis to be carried out for all three processes by application of a novel graphical method for the solution of the integrated rate equation for branched, series reactions.

The formation of the acylimidazole intermediate involves nucleophilic attack of imidazole at C-1 and is catalysed by imidazole. Its hydrolysis proceeds via water, specific acid, specific base, and imidazole acid and base catalytic processes for which the rate constants are almost identical in value with those for the corresponding terms for hydrolysis of 1 -acetylimidazole. N-Alkylation of imidazole by β-propiolactone is subject to specific but not general base catalysis.