Proton transfer from heterocyclic compounds. Part I. Some benzimidazoles

Abstract

Measurements are reported at 85° on the rates of detritiation of several benzimidazoles specifically labelled at C-2. Rate–pH profiles as well as the effects of substituents on rates suggest that the mechanism is the same as that operating in other five-membered heterocyclic compounds, namely an initial protonation at the basic N-3 followed by a rate determining abstraction of tritium by hydroxide ions to give an ylide intermediate. The results for [2-³H]-1,3-dimethylbenzimidazolium bromide support this conclusion.