X-ray crystallographic and theoretical study of 4-cyclohexyl-5-(2-furyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione

In order to investigate the molecular geometry, structural analysis of the title compound (4a) was carried out by single crystal X-ray diffraction. Tautomeric properties and conformations were investigated by semi-empirical (AM1) and ab initio quantum mechanical (RHF/6-31G) calculations. The compound prefers thione tautomer in the solid state. On the other hand, semiempirical calculations show that in the gas phase the thiol tautomer is energetically favored in most cases.