Structure of the alkaline salts of 2-phenyl- and 2-p-methoxyphenylimino-4-thiazolidinones

Abstract

The structure of the undissociated molecule of the alkali salt of 2-arylimino-4-thiazolidinone conforms with the more stable tautomer of the NH acid: the iminotautomer. In the free anion formed by the dissociation of the salt the negative charge is concentrated mainly at the ring nitrogen atom; however, a negligible resonance delocalization of the charge to the exocyclic oxygen and nitrogen atoms takes place. Such a charge distribution of the anion is also retained in the crystalline state, thanks to the fact that the lattice structure allows the coordination of the cation with the heteroatoms of the mesomeric fragment of the anion.