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...

Based on the experimental results and the published data, the enthalpies of formation of ethane and propane nitro derivatives were obtained for both the standard state and gas phase. The bond dissociation energies of the ethane and propane nitro derivatives were calculated using the enthalpies of atomization and the energies of nonvalent interactions of nitro groups. The calculated values were compared with the kinetic data on thermal decomposition. The bond dissociation energies in radicals of the ethane and propane nitro derivatives were also calculated using the enthalpies of atomization and the energies of nonvalent interactions of nitro groups. Regularities of changes in the bond dissociation energies of the ethane and propane nitro derivatives and their radicals were established.Key words: thermochemical properties, bond dissociation energy, nonvalent interactions, enthalpy of radical formation, enthalpy of atomization, energy of substitution, ethane nitro derivatives, propane nitro derivatives.Nitroalkyl radicals are intermediates of many reac tions of synthesis and decomposition of high energy com pounds. Knowledge of the enthalpies of radical formation is necessary for calculations of enthalpies of chemical reactions and for prediction of the most probable reaction mechanisms. The bond dissociation energies and the en thalpies of formation of radicals and molecules are related by the following equationwhere D(R 1 -R 2 ) is the dissociation energy of the com pound R 1 R 2 to the radicals R 1 and R 2 ; ΔH f°( R 1 ), ΔH f°( R 2 ), and ΔH f°( R 1 R 2 ) are the enthalpies of formation of the radicals R 1 and R 2 , and compound R 1 R 2 in the gas phase under standard conditions, respectively. In the present work, it is assumed that the dissociation energy of the R-NO 2 bond is equal to the activation energy of mono molecular thermal decomposition of nitrogen containing compounds proceeding by a radical mechanism (E a ).

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