Mechanisms of the formation of imines in aqueous solution and the effect of the pH: a theoretical analysis

Abstract

Theoretical modeling of the formation imines in aqueous medium from the reaction of amines with aldehydes is difficult due to formation of charged species, zwitterions, acid-base equilibria and a substantial solvent effect. In this work, a model reaction of methylamine with acetaldehyde was investigated involving neutral and ionic pathways, influence of the pH and different approaches for treating the solvent effect. We have found a mechanism able to explain the fast kinetics of this system, involving the zwitterion formation followed by its isomerization to the carbinolamine and an easy iminium ion formation via an ionic elimination mechanism.