The mechanism of exchange of intramolecularly hydrogen-bonded protons in a diamide

Abstract

Two alternative mechanisms for the exchange of intramolecularly hydrogen-bonded protons in a diamide have been theoretically studied by means of the AM1 method. Direct abstraction, and rotation about the C–N bond followed by abstraction, have been considered for both the base-catalysed and the acid-catalysed exchange. From the results obtained in this paper it can be concluded that the base-catalysed exchange takes place by direct abstraction, the internal hydrogen bond clearly retarding the proton exchange. Conversely, the internal hydrogen bond does not appreciably retard acid-catalysed proton exchange.