Metal-hydroxide-promoted hydrolysis of 1-acetylimidazole and its relevance to carbonic anhydrase activity

Abstract

The hydrolysis of 1-acetylimidazole in the presence of exchange-inert metal complexes, [Co(NH₃)₅(OH)]²⁺, [Cr(OH₂)₅(OH)]²⁺, and [Cr(NH₃)₅(OH)]²⁺, has been studied in aqueous solution at 25.0 °C and I= 1.0 mol dm^–3(Na[ClO₄]). The processes appear to be predominantly nucleophilic in character as demonstrated by the reaction of [Co(NH₃)₅(OH)]²⁺ with the amide where [Co(NH₃)₅(OCOCH₃)]²⁺ is isolated in 93% of the theoretical yield. By analogy with the corresponding reactions of the 1-acetyl-3-methylimidazolium cation, a mechanism is featured favouring acetylimidazolium ion and metal hydroxide as the kinetically significant species. These aspects are discussed in relation to possible mechanisms for carbonic anhydrase activity.