An Infrared Study of Tautomerism in Acetohexamide Polymorphs

Abstract

Infrared data determined for known polymorphic forms and some new derivatives of acetohexamide and related compounds support the view that acetohexamide polymorphs exhibit keto-enol tautomerism. They indicate that type A polymorphs exist in the enol form, probably stabilized by intramolecular bonding between an O—H and S=O group to form a six-membered ring. Type B polymorphs exist in the keto form with the urea carbonyl group intermolecularly bonded to a sulphonamide N—H. The new evidence disputes previous interpretations of the data.