The azasydnone unit is a promising explosophoric block for future generations of highly thermostable and dense energetic materials.

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The enthalpies of formation in the standard state and in the gas phase were recommended for a series of secondary nitramines and n butyldinitramine on the basis of the experimental enthalpies of combustion and vaporization and literature data. An analysis of the main thermo chemical values (the enthalpies of formation in the gas phase and the enthalpies of atomization) showed that the energy properties of the nitramine group are independent of the structure of the molecules studied and of the number of functional groups in them. The enthalpies of formation of the alkylnitramine radicals were determined. The values obtained make it possible to calcu late the bond dissociation energies in the nitramines and their radicals of different structures.Key words: thermochemical properties, bond dissociation energy, enthalpy of combustion, enthalpy of vaporization, activation energy of thermal decomposition, enthalpy of formation, enthalpy of atomization.Secondary N nitroamines (nitramines) are presently used widely as components of energetic compositions. These compounds correspond to high requirements im posed on the energy, thermal stability, density, rheology, and compatibility with other components. Therefore, sec ondary nitramines are traditional objects of investigation. Both new and earlier studied compounds are studied with the further development of the methods for synthesis and purification of these substances and improvement of the analytical and experimental procedures, including ther mochemical methods.The purpose of this work is to determine the enthalpy characteristics of secondary nitramines and N,N butyl dinitroamine (butyldinitramine) in the standard state and in the gas phase to complete the thermochemical data base for energetic compounds with the general formula C a H b O c N d . The bond dissociation energies and the en thalpies of radical formation were calculated from the ther mochemical and kinetic data.Success in the synthesis of the dinitramide salts 1 and the preparation of related alkyldinitramines 2 made it pos sible to study the thermochemical characteristics and the kinetics of the gas phase radical thermal decomposition of methyldinitramine 3 and the thermal decomposition of a series of alkyldinitramines. 4 It was shown 4 that all alkyl dinitramines studied decompose via the radical mecha nism with the elimination of the NO 2 group at the first stage. Therefore, if the data on the enthalpies of formation

The enthalpies of formation of nitromethane derivatives were obtained on the basis of experimental and literature data. The procedure for the calculation of the bond dissociation energies in nitromethanes from the atomization enthalpies and energies of nonvalent interac tions of nitro groups was proposed. The calculated values were compared with the data on the thermal decomposition kinetics. The atomization enthalpies and energies of nonvalent interac tions of nitro groups were also used for the calculation of the bond dissociation energies in radicals.The bond dissociation energies and formation enthal pies of radicals are most important energy characteristics of molecules and intermediate reaction products (inter mediates). These values determine stability of compounds and affect the mechanism and kinetics of conversion of substances, including the intensity of chain processes. 1 The bond dissociation energies and enthalpies of forma tion of radicals and substances in the gas phase are related by the equationwhere D(R 1 -R 2 ) is the dissociation energy of compound R 1 R 2 to radicals R 1 and R 2 ; ΔH°f(R 1 ), ΔH°f(R 2 ), and ΔH°f(R 1 R 2 ) g are the formation enthalpies of radicals R 1 , R 2 , and compound R 1 R 2 in the gas phase under standard conditions. It follows from Eq. (1) that the dissociation energy of bond is equal to the energy that should be tran ferred to the molecule (radical) for its dissociation to rad icals R 1 and R 2 . The dissociation energies of bonds are usually determined by using the kinetic data on the activa tion energies (Е а ) of monomolecular radical reactions of thermal decomposition. It is assumed 1 that the enthalpy of backward process (formation of a molecule from radi cals) is zero. For such compounds as polynitroalkanes, nitrates, and secondary nitroamines, thermal decomposi tion proceeds as the monomolecular radical reaction with the dissociation of the C-NO 2 , O-NO 2 , or N-NO 2 radicals. 2,3 If the enthalpy of the backward reaction of radical association is considered equal to zero, then the dissociation energy of the R-NO 2 bond is equal to the activation energy of thermal decompositionIt was concluded 4 on the basis of the theory of absolute reaction rates that the difference between D and E a in cludes RT and depends on the differences between the heat capacities of the products and reactants in the disso ciation reaction and on the differences of the heat capaci ties of the transition state and initial radicals in recombi nation. The integrals taken of the heat capacity differenc es have different signs, and various molecules at certain temperatures exactly obey Eq. (2).The differences between D and E a can be estimated from the statistical mechanics equations if the parameters of geometric structures, inter nal rotation barriers, and vibration frequencies of poly atomic particles are known. These calculations are rather difficult for the classes of compounds studied in this work and, hence, we will use Eq. (2).Equations (1) and (2) are used for the determination of...

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Enthalpies of formation and solution of hydrazinium, guanidinium, aminoguanidinium, and triaminoguanidinium salts of nitric and dinitramidic (HN(NO 2 ) 2 , DN) acids were deter mined by combustion and solution calorimetry methods. Enthalpies of formation of respective cations in infinitely dilute aqueous solution were calculated using the enthalpy of formation of the nitrate ion. The enthalpy of formation of the DN acid anion was determined based on the enthalpy of formation and solution of the acid salts. The weight average enthalpy of formation of the DN acid anion equal to 8.40±0.13 kcal mol -1 was obtained. The enthalpy of solution of ammonium dinitramide (ADN) was measured (8.71±0.01 kcal mol -1 ). From these data, the enthalpy of formation of ADN was calculated (-32.14±0.14 kcal mol -1 ). The energy of com bustion of ADN was measured by the calorimetry method, and the enthalpy of formation of ADN was calculated for a sample with purity above 99.9% (-32.20±0.19 kcal mol -1 ). The weight average enthalpy of formation of ADN equal to -32.16±0.11 kcal mol -1 is recom mended for use. Enthalpies of formation of sodium, potassium, and cesium salts of DN acid were determined.Synthesis of salts of dinitramidic (DN) acid HN(NO 2 ) 2 can be considered as a significant achievement in the chemistry of nitro compounds. Ammonium dinitramide (ADN), which for the first time was synthesized at the N. D. Zelinsky Institute of Organic Chemistry, AS USSR, 1,2 and later in the USA, 3 is of practical interest.Calorimetric methods -calorimetry of combustion and reaction calorimetry -are widely used for the deter mination of thermochemical properties of DN salts in the present work. Joint application of the calorimetric meth ods allows not only determining the principal thermo chemical characteristics of the salt compounds, but also correlating of the calculated enthalpies of formation of the salts, which allows increasing reliability of these data.The enthalpy of formation of the salt is related to the enthalpies of formation of the constituent ions by follow ing equation:where Cat is a cation, An is an anion. The enthalpies of formation (ΔH°f[Cat•An] cr ) and so lution (ΔH°s ol [Cat•An] cr ) of the salt are in the left part of the Eq. (1), and the enthalpies of formation of the cat ion (ΔH°f[Cat + ] aq ) and the anion (ΔH°f[An -] aq ) in the infinitely dilute solution are in the right part of the equation. The enthalpy of formation of salts with composition C a H b O c N d can be found by combustion calorimetry ac cording to the following equation: ΔH°f[Cat•An] cr + ΔH°c[Cat•An] cr = = a•ΔH°f[CO 2 ] g + (b/2)ΔH°f[H 2 O] l .(2)Thus, the enthalpy of formation of an unknown ion can be calculated by Eq. (1), if the enthalpy of formation of the salt is determined beforehand from data on the combustion and the enthalpy of solution of the salt is measured.If there are several salts with the same ion, then the values of the enthalpy of formation of this ion, obtained according to Eqs (1) and (2), must be equal within the limits of measur...

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