A. M. Astakhov

Structural and kinetic regularities of thermal decomposition of gem-trinitromethylazoles in the liquid phase

Kinetics of liquid-phase thermal decomposition of a series of triazoles and tetrazoles containing a gem-trinitromethyl group were studied by manometry and photoelectrocolorimetry, and the mechanism of the thermal decomposition was established. The activation parameters of the rate-limiting stage of the process were evaluated. It was shown that the thermal stability of the gem-trinitromethyl group varies over a broad range, depending on the steric effect of the azole. The rate constant and activation energy correlate with the steric effect of the azole. The thermal decomposition of β-trinitroethylaminotetrazoles proceeds heterolytically with initial dissociation of the C-C bond to give a carbocation and the nitroform anion.

Crystal and Molecular Structure of Monoammonium Salt of 5‐nitroaminotetrazole

X‐ray structural investigation of the monoammonium salt of 5‐nitroaminotetrazole was performed. The crystals are orthorhombic: a = 10.077(1)Å, b = 17.009(1)Å, c = 6.6472(6)Å, V = 1139.33(17)Å3, space group Pbca, Z =8, ρcalc = 1.715 g/cm3. Monodeprotonation of 5‐nitroaminotetrazole during formation of the salt occurs at the N(4) nitrogen atom of the heterocycle. The anion has an almost flat structure; the bond lengths suggest delocalization of π‐electron density in the molecule. The negative charge is distributed among three nitrogen atoms and two oxygen atoms of the anion. Changes in the geometrical parameters of 5‐nitroaminotetrazole on monodeprotonation are considered.

N-Nitroimines: I. Synthesis, Structure, and Properties of 3,5-Diamino-1-nitroamidino-1,2,4-triazole

The reaction of 3,5-diamino-1,2,4-triazole with 2-methyl-1-nitroisothiourea gives 3,5-diamino-1-nitroamidino-1,2,4-triazole instead of the expected 1-[5(3)-amino-1,2,4-triazol-3(5)-yl]-2-nitroguanidine. Almost planar structure of the molecule of 3,5-diamino-1-nitroamidino-1,2,4-triazole gives rise for direct polar conjugation which is responsible for the low basicity of the amino groups.

Thermal Decomposition of 3-Nitro-1-nitromethyl-1,2,4-1H-triazole in Solution

The thermal decomposition of 3-nitro-1-nitromethyl-1,2,4-1H-triazole in 1% solution in phenyl benzoate proceeds homolytically with initial rupture of the CH2-NO2 bond. Activation parameters of the process were Ea = 172.6 kJ/mol, log A = 14.25. The initial basic pathway of fragmentation of the molecule under electron impact coincides with the first step of thermal decomposition, which is in agreement with X-ray structural and calculated quantum chemical data on bond stability in the molecule.

Kinetics and Mechanism of Liquid-Phase Thermal Decomposition of β-Cyanoethyl-N-nitramines

Termal decomposition of β-cyanoethyl-N-nitramine in melt is preceded by protonation of the amino nitrogen atom and is accompanied by evolution of nitrogen(I) oxide with formation of acrylonitrile. Thermal decomposition of bis(β-cyanoethyl)-N-nitramine under similar conditions follows a radical mechanism with initial dissociation of the NÄN bond. The same mechanism is operative in thermal decomposition of both N-nitramines in a dilute dibutyl phthalate solution.

Effect of structure on the rate and mechanism of thermolysis of some 4-substituted 3-methylfuroxans

The gas-phase thermolysis of I proceeds as a unimolecular process and is independent of the initial vapor pressure of the substance (over 190 mm Hg) and of the ratio of the reaction vessel surface to its volume (S/V = 0.55–4.62 сm). In the melt and in solution in an inert solvent dibutylphtalate (DBP) the furazans decompose according to the first-order reaction law to the conversion level of 30–45 %. The substance content in the solution (1–10 %) does not affect the reaction rate.

Crystal and Molecular Structure of 2‐nitro‐1‐ureidoguanidine

AbstractAn X‐ray structural investigation of 2‐nitro‐1‐ureidoguanidine has been carried out. The crystals are monoclinic: a = 4.4690(2)Å, b = 15.566(1)Å, c = 9.4131(7)Å, β = 94.896(5)°, V = 652.4(3)Å> 3, space group P21/n, Z = 4, ρcalc = 1.650 g/cm3. The molecule consists of two planar fragments: carbamide and nitroguanidine. The geometrical characteristics of the molecule are analyzed. The system of intra‐ and intermolecular hydrogen bonds in the crystal is considered.

Thermal Decomposition of Secondary N-nitramines Having 1,2,4-Triasole and Tetrazole Substituents

Thermal decomposition of secondary N-nitramines having azole substituents in the β position is faster by almost two orders of magnitude than the decomposition of γ-substituted analogs. The rate-determining stage is homolytic dissociation of the NÄNO2 bond. An alternative route of thermal decomposition of γ-tetrazolyl-substituted N-nitramines involves initial clavage of the tetrazole ring.

Crystal and molecular structure of 1-phenyl-2-nitroguanidine

The molecular structure of 1-phenyl-2-nitroguanidine is nonplanar, but contains two almost planar fragments: nitroguanyl and phenyl groups. Unlike previously studied nitroguanidines, in 1-phenyl-2-nitroguanidine, the nitro group is turned to the secondary amino group. However, the structural parameters of the nitroguanyl group are little different from those of nitroguanidine and its alkyl derivatives. In the benzene ring, the symmetry in the geometric parameters is not observed, which is explained by the intermolecular interaction with the neighboring molecule.

Kinetics and thermolysis mechanism of some 4-substituted 3-methylfuroxans

Thermolysis of the non-condensed furoxans containing two reaction centers for which the initiation of decomposition reaction is possible, has not been adequately studied. We explored kinetics of thermolysis of the furoxans such as: (1–15 wt %) and nature of inert solvent (trinitrobenzene, dibutylphthalate DBP) that is inherent in the homolytic process. Thermolysis of compound II in solution occurs with acceleration and unaffected by the ratio of substance mass to volume of reactionary vessel (m/V = 1.1×10–1.6×10 g cm). It has been established earlier [1] that opening of furoxan ring proceeds at the least strong transannular N(O)–O bond. As a result the low-stable structure forms, stabilizing into the former or isomeric furoxan. At elevated temperatures the furoxan ring opens at N(O)–O and С–С bonds to give the two nitrileoxide functions, which isomerize irreversibly into isocyanate under these conditions [1, 3].