The problem of the tautomerism of 2-iminothiazolidin-4-one and some of its derivatives

IR spectroscopy is used to investigate imino-amine tautomerism of 2-iminothiazoliin-4-one and 2-phenyl (p-tolyl, benzyl)imino derivatives of thiazolidin-4-one. It is shown that in the crystalline state 2-iminothiazolidin-4-one exists in the 2-imino form, while in solution (chloroform) it exists in the amino form. 2-Phenyl- and 2-p-tolylimino derivatives of thiazolidin-4-one exist in the imino form, while 2-benzyl-iminothiazolidin-4-one exist in the amino form.