KINETICS AND MECHANISM OF THE IMIDAZOLE-CATALYSED HYDROLYSIS OF SUBSTITUTED N-BENZOYLIMIDAZOLES

Article abstract of DOI:10.1002/poc.610070807

Imidazole (Imz)-catalysed hydrolysis of benzoate esters proceeds via the intermediate formation of N-benzoylimidazoles.This paper considers the second step of this reaction, viz., Imz-catalysed hydrolysis of N-(4-X-benzoyl)imidazoles, X = CH3, H, Cl, CN and NO2, and N-(disubstituted benzoyl)imidazoles, 2-chloro-4-nitro, 2,4-dinitro and 3,5-dinitro, in water-acetonitrile mixtures (10percent or 14percent, v/v, in organic solvent).On the basis of catalytic rate constants and the kinetic solvent isotope effect, it is shown that catalysis by Imz is of the general-base type.Unexpectedly, the hydrolysis of N-(2,4-dinitrobenzoyl)imidazole was found to be slower than that of N-(4-nitrobenzoyl)imidazole.It is shown that this reactivity order is due to a combination of a steric effect and stabilization of the reactant state due to a donor-acceptor interaction between the Imz moiety and the 2,4-dinitrophenyl ring.