Prototropic tautomerism and absorption spectra of substituted 4-hydroxyhexahydropyrimidinethiones-2

The IR and UV absorption spectra of the products of reaction of certain -isothiocyanoketones with ammonia, primary, and secondary amines are studied. It is shown that ammonia and primary amines usually give substituted 4-hydroxyhexahydropyrimidinethiones-2, which in the solid state are involved in intermolecular association due to hydrogen bonding. Solutions of these compounds exhibit ring-chain tautomerism equilibrium between a cyclic hydroxy form and an acyclic oxo form related to the class of oxoalkylthioureas. The reaction products both from -isothiocyanoketones and secondary amines, are substituted thioureas, both in the crystalline state and in solution. All the substances studied have a thione structure.