Understanding the influence of external perturbation on aziridinium ion formation.

A density functional theory study is performed to understand the effect of discrete water molecules during Az+ion formation in nitrogen mustards. A comparative study in gas phase, and implicit and explicit solvation models of three drug molecules (mustine, chlorambucil and melphalan) is reported. Noteworthy changes in the structure and C–N stretching frequencies of the transition states have been observed in the presence of explicit water molecules. Presence of explicit water molecules reduces the positive charge around the tricyclic Az+ring, and hence stabilising it. Both activation energy and rate constants are seen to be significantly affected in the presence of discrete water molecules. [ABSTRACT FROM PUBLISHER]