Kinetics and mechanism of hydrolysis of benzimidazolylcarbamates

Journal of the Brazilian Chemical Society

F. P. Norberto²  S. P. Santos²  J. Iley¹  D. B. Silva²  M. Corte Real¹ 

[1] ,Universidade de Lisboa Faculdade de Ciências Centro de Química e Bioquímica Lisboa ,Portugal

关键词: reaction mechanisms;    kinetics;    heterocycles;    carbamates;    benzimidazole;   

DOI  :  10.1590/S0103-50532007000100019

来源: SciELO

【 摘 要 】

Synthesis of new 2-aminobenzimidazole-1-carbamates was accomplished by carbamoylation of 2-aminobenzimidazole using different substituted phenyl chloroformates. The aqueous hydrolysis of the new compounds was examined in the pH range 1-13 at 25 ºC. The evaluated kinetic parameters led to the conclusion that up to pH 4 reaction proceeds by a bimolecular attack of water to the N-protonated substrate. This is the first time this behavior is described for carbamates, and can be ascribed to the higher basicity of the benzimidazolyl moiety when compared with the carbonyl oxygen. For higher values of pH, the results are consistent with a B Ac2 mechanism with nucleophilic catalysis, but while between pH 4 and pH 7 water acts as the nucleophile, for pH> 7 the hydroxide ion is the acting species.

【 授权许可】

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