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Thermal decomposition of hexanitrohexaazaisowur~zitane (HNIW) in the solid state and in solution was studied by thermogravimetry, manometry, optical microscopy, and IR spectroscopy. The kinetics of the reaction in the solid state is described by the first-order equation of autocatalysis. The rate constants and activation parameters of HNIW thermal decomposition in the solid state and solution were determined. The content of N 2 amounts to approximately half of the gaseous products of HNIW therrnolysis. The thermolysis of HN IW and its burning are accompanied by the formation of a condensed residue. During these processes, five of six nitro groups of the HNIW molecule are removed, and one NO 2 group remains in the residue, which contains amino groups and no C--H bonds.

Stuctural transformations of 1,1‐diamino‐2,2‐dinitroethene (FOX‐7) were investigated in the temperature range 298–513 K by means of DSC, TG, isothermal calorimetry, PXRD, IR spectroscopy, and electron microscopy. The data obtained confirm the existence of the high‐temperature δ‐FOX‐7 polymorph stable above 480 K. The heat effect of the γ→δ transformation is − 4.6 J g−1 (−680 J mol−1). Metastable γ‐phase formed in the reverse process δ→γ has a perfect crystal structure and is stable towards thermal decomposition. Possible mechanisms of sharp deceleration of thermal decomposition of FOX‐7 at the 40 % conversion are discussed.

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The primary stage of the decomposkion of compounds RN(NOz)CH2C(NO,)2X is the homokytic cleavage of the C--NO 2 bond, at X = NO 2 and N--NO~ bond at X = F. The inductive effect of substituents decreases the dissociation energies of the C--N and N--N bonds by 1--2 kcal tool -1. Kinetic effects caused by the spatial interaction of groups and by stepwise decomposition of polyfunctional compounds are descnbed.Key words: nitro compounds, nitramines, thermolysis, interaction of groups, reaction mechanism; kinetics.Although thermal decomposition of secondary nitramines has been studied in numerous works, 1 these reactions have not been adequately investigated. Many problems concerning the influence of substituents and the medium on the rate and mechanism of decomposition remain unsolved. Decomposition of simple nitramines normally starts with homolytic cleavage of the N--N bond, whose strength depends relatively sLi~tty on the substituents. However, when some substituents, for example an F atom and a carbonyl group t or a furazan ring, z are present in the ct-or [3-position with respect to the nitramino group or when the decomposition is carried out in a hydrocarbon medium, 3 its mechanism and rate sharply change. The process is accompanied by intramolecular rearrangements and intermo-[ecular interactions, whose mechanisms are unknown. The kinetics of decomposition of nitro-derivatives of nitramines, which constitute a large group of highenergy compounds, have not been studied either. The molecules of these compounds incorporate two or several reaction centers, which interact and compete with one another in the primary decomposition reactions.Therefore, in this work, we studied the kinetics and mechanisms of the initial (non-catalytic) steps of thermolysis of trmitromethyl and fluorodinitromethyl derivatives of secondary nitramines in the liquid phase. As typical representatives, we chose the following cornpounds:Decomposition of compounds 2, 3, and 5 has been studied previously 4 but only under conditions of fast heating. It was found that NO 2 is formed as a primary thermotysis product; however, this fact hardly makes it possible to elucidate the nature of the primary step of decomposition. The kinetic approach appears more promising for this purpose. We carried out a formal kinetic analysis of the decomposition of heterofunctional compounds under isothermal conditions, distinguished the initial step, determined its kinetic parameters, and compared these parameters with known characteristics of the decomposition of monofunctionat compounds, viz., nitramines or polynitroalkanes.For this approach, accuracy of kinetic measurements is an important point. Therefore, the reactions were studied mostly in dilute solutions, i.e., under conditions where the perturbing influences of admixed catalytic or autocatalytic processes is almost entirely eliminated. To analyze the products of decomposition and to elucidate the possible role of intermolecu[ar interactions in the initial stages of the process, some experiments were carried ...

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