V. V. Zakharov

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

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 E1 and E2 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) Å, b = 10.8490(18) Å, c = 10.9878(19) Å, V = 1242.9(4) Å3; 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 E2 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.

Kinetics of reversible polymorphic transitions in high-energy compounds. Phase transformations in octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine

The kinetics of reversible phase transitions (PTs) in various polymorphs (α, β, γ, δ, and ɛ) of polycrystalline octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) is investigated by means of differential isothermal and scanning calorimetry. The rate of the β → δ PT is limited by the nucleation process occurring during the induction period. In a general case, the distribution density for the induction times is a superposition of continuous and discrete functions. The reverse δ → β PT obeys the first-order kinetic law. The effects of mechanical exposure on the kinetics and the PT products of the different polymorphs of HMX is investigated by FTIR spectroscopy.

Synthesis of 4-bromocubane-1-carbaldehyde

Oxidation of 4-bromo-1-hydroxymethylcubane and 1,4-bis(hydroxymethyl)cubane with the 2,2,6,6-tetramethylpiperidine-N-oxyl-trichloroisocyanuric acid-sodium bicarbonate system afforded the corresponding aldehydes. 4-Bromocubanecarbaldehyde was also obtained in high yield by reduction of 4-bromocubanecarboxylic acid and its methyl ester with bis(N-methylpiperazinyl)aluminum hydride.

CUBANE DERIVATIVES. 3. SYNTHESIS AND MOLECULAR STRUCTURE OF 1,4-BIS(HYDROXYMETHYL)CUBANE

An efficient procedure for the preparation of 1,4-bis(hydroxymethyl)cubane by reduction of cubane-1,4-dicarboxylic acid or its dimethyl ester with aluminum hydride was developed. The molecular structure of 1,4-bis(hydroxymethyl)cubane was established by X-ray diffraction analysis.

Kinetics of reversible polymorphic transition in energetic materials. Phase transitions α → β and β → α in 1,1-diamino-2,2-dinitroethylene

Differential scanning calorimetry and isothermal calorimetry are used to study the kinetics of the α → β polymorphic transformation (PT) in 1,1-diamino-2,2-dinitroethylene (DADNE). The kinetics of the β → α PT in DADNE is investigated by infrared spectrophotometry. The α → β phase transition is described by the first-order autocatalysis equation. The activation energy and the rate constant are determined. The rate of the β → α PT is described by the kinetic law for two parallel first-order processes. The rate constants for these processes are obtained.

2,4,6-Triazido-1,3,5-Triazine, 2,4,6-Triazidopyrimidine, and 2,4,6-Triazidopyridine as Precursors of Carbon Nitride Materials

The thermolysis of 2,4,6-triazido-1,3,5-triazine (I), 2,4,6-triazidopyrimidine (II), and 2,4,6-triazidopyridine (III) and its products were studied by DSC, mass spectrometry, IR spectroscopy, and electron microscopy. The thermal transformations of I gave planar nets formed by polyconjugated C–N bonds arranged into bundle aggregates. The thermolysis product of III consists of low-molecular compounds and has globular morphology. The thermolysis of II resulted in a mixture of products of both types, among which the planar nets were dominant. The relationship between the structure of the products of the thermal transformations of I, II, and III and the kinetic characteristics of these processes was discussed.

Kinetics of direct and reverse polymorphic transformations in molecular crystals of energetic compounds

The β → γ polymorphic transformation (PT) in polycrystalline 1,1-diamino-2,2-dinitroethylene (DADNE) was studied by isothermal calorimetry. The kinetics of the β → γ PT, like that of the α → β process studied earlier, follows the first-order autocatalytic equation. The rate constants and activation energy of the process were determined. The kinetics of the reverse β → α and γ → α PTs in DADNE was studied by IR spectroscopy. The rates of the β → α and γ → α PTs follow first-order kinetics with the rate constants that depend on morphological features of the crystals. The general features of the kinetics of direct and reverse polymorphic transformations in molecular crystals of energetic compounds are discussed.

Crystallization and phase homogeneity of [1,2,5]oxadiazolo[3,4-e][1,2,3,4]tetrazine-4,6-dioxide–2,4-dinitro2,4-diazapentane molecular complex

The thermally reversible processes of melting and crystallization of the [1,2,5]oxadiazolo[3,4-e][1,2,3,4]tetrazine-4,6-dioxide–2,4-dinitro-2,4-diazapentane equimolar molecular complex produced in various technological modes of its isolation from the melt are studied and optimized by using turbidimetry, optical microscopy, and differential scanning calorimetry. The kinetic factors of the stepwise crystallization of the complex related to both the formation of nucleation sites and growth of the crystals are identified. A colorimetric method for controlling the phase purity and evaluating the content of impurities in the molecular complex after their preliminary identification by infrared spectroscopy is developed.

Thermal decomposition of 2,4-diazido-6-trinitromethyl-1,3,5-triazine, 2,4-dimethoxy-6-trinitromethyl-1,3,5-triazine, and 2,4-diazido-6-methoxy-1,3,5-triazine

The thermal decomposition of 2,4-diazido-6-trinitromethyl-1,3,5-triazine, 2,4-dimethoxy-6-trinitromethyl-1,3,5-triazine, and 2,4-diazido-6-methoxy-1,3,5-triazine in a melt was studied by differential scanning calorimetry, thermogravimetry, manometry, mass spectrometry, and IR spectroscopy. The kinetics of these reactions was investigated, and the activation parameters were determined. The gaseous products of the decomposition of 6-trinitromethyl-2,4-diazido-1,3,5-triazine were N2, NO, N2O, CO, and CO2 in a molar ratio of 1: 2: 1: 0.6: 1 and pronounced amounts of NO2. A comparison of kinetic data for the compounds under study indicated that the azide groups in 2,4-diazido-6-trinitromethyl-1,3,5-triazine were thermally more stable than the trinitromethyl group.

Thermal transformations of a molecular complex of [1,2,5]oxadiazolo[3,4-e][1,2,3,4]tetrazine-4,6-di-N-oxide with 2,4-dinitro-2,4-diazopentane

Differential scanning calorimetry and infrared spectroscopy are used to study the transformations of a stoichiometric (1: 1) crystalline molecular complex (MC) of [1,2,5]oxadiazolo[3,4-e][1,2,3,4] tetrazine-4,6-di-N-oxide with 2,4-dinitro-2,4-diazapentane in various temperature regimes. The temperature dependence of the effective rate constant for the thermal decomposition of MC is described by the Arrhenius equation with effective values of the activation energy and preexponential factor of (130.7 ± 3.5) kJ/mol and 108.80 ± 0.41 s−1, respectively. The formation of a liquid molecular complex during the spontaneous cooling of MC is proven.