The 5-(isopropylidene)-2-thiobarbituric acid: Preparation, crystal structure, thermal stability and IR-characterization

5-(Isopropylidene)-2-thiobarbituric acid (1), C7H8N2O2S, has been crystallized by reacting 2-thiobarbituric acid with excessing acetone for 5-6 days under ambient conditions. The pale yellow crystals have been investigated using X-ray single crystal and powder techniques and characterized by differential scanning calorimetry, thermogravimetry and infrared spectroscopy. The compound crystallizes in the monoclinic system with a = 8.8268(19) angstrom, b = 12.044(3) angstrom, c = 8.0998(19) angstrom, beta = 105.388(6)degrees, Z = 4, V = 830.2(3) angstrom(3), space group P2(1/)c. The geometric parameters of the heterocycle of the molecule 1 are similar to those found previously for the molecule of thionedicarbonyl tautomer in polymorphic modifications of 2-thiobarbituric acid. Infrared spectroscopy also evidences the thionedicarbonyl structure of the 1 heterocyclic ring. Intermolecular N-H center dot center dot center dot O hydrogen bonds join the molecules in the chains along b axis. The 1 compound is thermally stable up to 230.0 degrees C and melts with decomposition at 261.4 degrees C. The results of mass spectrometric analysis are consistent with the structural parameters found by X-ray diffraction methods. (C) 2014 Elsevier B.V. All rights reserved.