Phase equilibria and structural phase transformations in the furazano[3,4-e]tetrazine-4,6-dioxide-2,4-dinitro-2,4-diazapentane system

Abstract

The phase diagram of the binary furazano[3,4-e]tetrazine-4,6-dioxide (1)-2,4-dinitro-2,4-diazapentane (2) system was studied by differential thermal analysis and microcalorimetry. The branches of the liquidus lines of this system were calculated. The eutectic point coordinates and monoeutectic equilibrium lines were refined. The components of the system under study were shown to interact with each other to form two low-melting-point eutectics E 1 and E 2 and a stoichiometric (in a 1: 1 molar ratio) molecular compound, viz., crystalline complex 1·2. According to the single-crystal X-ray diffraction data, complex 1·2 belongs to the orthorhombic crystal system (space group P212121, a = 10.4264(17) A, b = 10.8490(18) A, c = 10.9878(19) A, V = 1242.9(4) A3; Z = 4). In the structure of 1·2, molecules 1 and 2 are ordered. The nitro oxygen atoms form close contacts with the nitrogen atoms of the N→O groups and the system of the tetrazine ring, as well as with the carbon atoms of bicyclic compound 1. The reversible crystallization—melting processes of complex 1·2 and the eutectic E 2 were studied by turbidimetry. The sensitivity of molecular complex 1·2 to mechanical and thermal effects and its tendency to detonation were studied in relation to compound 1. The formation of the complex was found to lead to an increase in the critical diameter of detonation from 0.04 to 0.7 mm, in the minimum drop height for the determination of the impact sensitivity from 30–70 to 150–200 mm (P = 2 kg), and in the temperature of extensive decomposition from 135 to 168 °C.