Phase equilibria in the thiourea-benzene system

Phase equilibria in the thiourea (host)-benzene (guest) binary system with clathrate formation were studied over the temperature range 260–460 K by physicochemical analysis methods. The stoichiometry and conditions of the existence of the 2.40(±0.02)(NH₂)₂CS · C₆H₆ compound, which incongruently decomposed at 358.7 K into rhombic thiourea and the guest component, were determined. The parameters of the Bravaisrhombohedral cell of the clathrate (space group R \(\bar 3\) c) were found to be a = 15.921(6), c = 12.417(8) Å, and V = 2725(5) ų; d _calc = 1.192 g/cm³ and d _expt = 1.195(7) g/cm³. The packing of guest molecules in the rhombohedral host framework was modeled taking into account stoichiometry and unit cell parameters to show that benzene molecule planes were tilted with respect to the c channel axis with the formation of a monomolecular closely packed chain in the guest subsystem.