R. S. Stepanov

Structure-kinetics relationships of thermodestruction of some framework nitramines

Thermal decomposition of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (HNIW, CL-20) and its oxa-analogs containing four and three nitramine fragments, in the gas phase and in solution predominantly follows the first order kinetics, whereas in the solid phase it proceeds with acceleration. Replacement of the two nitramine groups in the five-membered cycles of the molecule CL-20 by oxa groups practically does not affect the rate of decomposition of oxanitroderivatives in the solid phase. Substitution of the nitro group in one of oxa-nitroderivatives by R = H, NO, COCH3, CH2N(NO2)CH3 differently affects the rate of decomposition. For R = H the rate of decomposition increases; when R = COCH3, CH2N(NO2)CH3, it decreases; for R = NO, the rate of decomposition remains constant. For the studied compounds the activation parameters of thermal decomposition are determined in the solution, the gas phase, and the solid phase. In general, the reactivity of nitramines depends on the length of the weakest bond N-NO2, which is affected by the conformation of the nitro group.

1,2-dinitroguanidine.

The title compound, CH(3)N(5)O(4), is almost planar, and the conformation is fixed by two intramolecular N-H...O hydrogen bonds. Owing to the delocalization of pi-electron density over the whole molecule, there is through-conjugation, with the C-N, N-N and N-O bond lengths having values intermediate between those typical for the corresponding single and double bonds.

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.

KINETICS AND MECHANISM OF THERMAL DECOMPOSITION OF HMX WITH METAL CUPFERRONATE ADDITIVES

The kinetic features of the thermal decomposition of HMX with metal cupferronate additives, in which the nucleophilic detachment of a proton in HMX by a phenylnitric-oxide anion-radical plays an important role, are established. The logarithms of the rate constants for the decomposition of HMX correlate with the ratio of the charge of the metal cation in the cupferronate to its radius, which indicates a different reactivity of the anion-radical owing to the polarizing effect of the cation.

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 5-Nitraminotetrazole of 3-Azolylamino-2-polyfluorobenzoylacrylates

Thermal decomposition of 5-nitraminotetrazole in solid phase and diluted solutions in aprotic solvents was investigated. The kinetic and thermodynamic parameters of the process were established. A mechanism of unimolecular decomposition was assumed including isomerization into the nitroguanyl azide followed by decomposition of he azide function.

Kinetics of Thermal Decomposition of Polyfunctional Substituted Azido-1,2,4-triazoles

The structural and kinetics regularities and the mechanism of the limiting step of thermal decomposition of the polyfunctional substituted 1,2,4-triazoles in the melt and in solutions of inert solvents were established. The activation parameters of the limiting step were determined. Polyfunctional substituents are found to show little effect on the rate of thermal decomposition of azide group in the azole ring.

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.

2-nitrimino-1-nitroimidazolidine.

The molecule of the title compound, C(3)H(5)N(5)O(4), has a planar geometry. Due to the presence of a second nitro group, the lengths of the two conjugated C--N bonds are different. Nevertheless, the conjugation of the nitrimine group spreads to the nitramine group. Intermolecular N--H...O bonds connect molecules into dimers in the crystal structure.