KINETICS AND MECHANISM OF PHASE-TRANSITIONS IN THE CRYSTALS OF 2,4,6-TRINITROTOLUENE AND BENZOTRIFUROXANE

Three polymorphs (I, II, III) of 2,4,6-trinitrotoluene (C7H5N3O6) have been grown under different conditions. A comprehensive X-ray study has been carried out for I and II. The phase transition I-II has been investigated in the temperature range 55-75-degrees-C. The three polymorphs are characterized as follows: (I) a = 20.041(20), b = 15.013(8), c = 6.0836(5) angstrom, V = 1830.45 angstrom3, d(c) = 1.647, z = 8, space group P2(1)ca; (II) a = 21.407(20), b = 15.019(8), c = 6.0932(5) angstrom, gamma = 111.00(02)-degrees, d(c) = 1.648, z = 8, space group P2(1)/b; (III) a = 40.0, b = 14.89, c = 6.09 angstrom, orthorhombic crystal system. In addition, two polymorphic modifications (monoclinic and orthorhombic) benzotrifuroxan (C6N6O6) have been obtained under different conditions of synthesis and a comprehensive X-ray study of them has been carried out. The phase transition in benzotrifuroxan is observed in the temperature range 100-135-degrees-C. Kinetic parameters of the phase transitions have been determined and peculiarities of the mechanisms of the processes discussed. The two polymorphs are characterized as follows: (A) a = 14.661(4), b = 10.219 (2), c = 12.032(3) angstrom, gamma = 103.72(2)-degrees, V = 1751.2 angstrom3, d(c) = 1.911, z = 8, space group P2(1)/a; (B) a = 6.923(1) b = 19.516(3), c = 6.518(1) angstrom, V = 8800.7 angstrom3, d(c) = 1.901, z = 4, space group P na2(1). (C) 1994 Academic Press, Inc.