Bond dissociation energies in nitramines

Abstract

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

Enthalpy of formation of CL-20

“…The results of such calculations with two sets of enthalpies of formation for cyclic nitramines (1)(2)(3)(4)(5)(6) are given in Table 2. The reactions with self-consistent enthalpies of formation of 1-6 give very close values, in the range of 7.5 kJ/mol; the average of 9 reactions is 500.3 kJ/mol.…”

“…Because of this, it is difficult to estimate the accuracy of such calculations for CL-20. This molecule contains 30 nonhydrogen atoms and to date, a small number of calculations have been published for such large molecules.Table 1shows that the value calculated in this work from atomization reaction using the G4(MP2) method (523.1 kJ/mol) differs by 25 kJ/mol from the value calculated by the T1 method reaction can be approximately estimated by comparison of calculated and experimental values for cyclic nitramines(1)(2)(3)(4)(5)(6).Table 3shows that the calculated values for 1-6 (these molecules contain from 9 to 20 heavy atoms) are 6-18 kJ/mol larger than the recommended experimental values. 523.1 kJ/mol.…”

“…Isodesmic reactions with cyclic nitramines (1-6) 1 (CH) 6 (NNO 2 ) 6 (7) + 4 C 6 H 12 (cyclohexane) + 6 CH 4 → 6 (CH 2 ) 5 NNO 2 (1) + 3 CH 3 CH 3 500.6 475.4 571.4 2 (CH) 6 (NNO 2 ) 6 (7) + 3 C 4 H 8 (cyclobutane) + 6 CH 4 → 3 (CH 2 ) 4 (NNO 2 ) 2 (2) + C 6 H 12 (cyclohexane) + 3 CH 3 CH 3 500.6 475.4 550.5 3 (CH) 6 (NNO 2 ) 6 (7) + 2 CH 4 + CH 3 CH 3 → (CH 2 ) 4 (NNO 2 ) 2 (2) + 2 (CH 2 ) 3 (NNO 2 ) 2 (3) 497.0 487.4 577.4 4 (CH) 6 (NNO 2 ) 6 (7) + 3 C 3 H 6 (cyclopropane) + 6 CH 4 → 3 (CH 2 ) 3 (NNO 2 ) 2 (3) + C 6 H 12 (cyclohexane) + 3 CH 3 CH 3 502.0 487.6 556.9 5 (CH) 6 (NNO 2 ) 6 (7) + 3 CH 3 CH 3 → 2 (CH 2 ) 3 (NNO 2 ) 3 (4) + C 6 H 12 (cyclohexane) 499.5 524.5 544.8 6 (CH) 6 (NNO 2 ) 6 (7) + 2 C 3 H 6 (cyclopropane) + 6 CH 4 → 2 (CH 2 ) 3 (NNO 2 ) 3 (4) + C 6 H 12 (cyclohexane) + 3 CH 3 CH 3 504.5 529.5 544.8 7 (CH) 6 (NNO 2 ) 6 (7) + 2 C 4 H 8 (cyclobutane) + 6 CH 4 → 2 (CH 2 ) 4 (NNO 2 ) 3 (5) + C 6 H 12 (cyclohexane) + 3 CH 3 CH 3 498.6 534.8 531.7 8 (CH) 6 (NNO 2 ) 6 (7) + 4 CH 4 → 2 (CH 2 ) 4 (NNO 2 ) 3 (5) + CH 3 CH 3 497.7 533.9 545.7 9 2 (CH) 6 (NNO 2 ) 6 (7) + 6 CH 3 CH 3 → 3 (CH 2 ) 4 (NNO 2 ) 4 (6) + 2 C 6 Isodesmic reactions without cyclic nitramines 10 (CH) 6 (NNO 2 ) 6 (7) + 6 CH 4 + 3 CH 3 CH 3 → 6 CH 3 N(NO 2 )CH 3 + C 6 H 12 (cyclohexane) 509.9 595.7 11 (CH) 6 (NNO 2 ) 6 (7) + 6 CH 4 + 3 CH 3 CH 3 → 6 CH 3 NHNO 2 + 2 C 6 H 12 (cyclohexane) 515.1 598.9 12 (CH) 6 (NNO 2 ) 6 (7) + 9 CH 3 CH 3 → 3 C 4 H 10 N 2 (piperazine) + 6 CH 3 CH 2 NO 2 531.8 512.5 13 (CH) 6 (NNO 2 ) 6 (7) + 6 CH 4 → 3 CH 3 N(NO 2 )(CH 2 ) 2 N(NO 2 )CH 3 522.8 586.4 14 (CH) 6 (NNO 2 ) 6 (7) + 6 CH 3 CH 2 CH 2 CH 3 → 3 CH 3 N(NO 2 )(CH 2 ) 2 N(NO 2 )CH 3 + 3 C 6 H 12 (cyclohexane) 512.7 554.3 15 (CH) 6 (NNO 2 ) 6 (7) + 9 CH 3 CH 3 → 6 C 2 H 5 N(NO 2 )C 2 H 5 525.7 567.2 16 (CH) 6 (NNO 2 ) 6 (7) + 9 CH 3 CH 2 CH 2 CH 3 → 6 C 2 H 5 N(NO 2 )C 2 H 5 + 3 C 6 H 12 (cyclohexane) 513.3 564.2 17 (CH) 6 (NNO 2 ) 6 (7) + 7 CH 3 CH 2 CH 2 CH 3 → C 10 H 16 (adamantane) + 6 C 2 H 5 N(NO 2 )C 2 H 5 524.7 554.2 18 (CH) 6 (NNO 2 ) 6 (7) + 9 CH 3 CH 3 + 2 C 6 H 12 (cyclohexane) → 6 C 5 H 11 N (piperidine) + 6 CH 3 NO 2 534.4 507.1 19 2 (CH) 6 (NNO 2 ) 6 (7) + 13 C 6 H 12 (cyclohexane) → 3 C 6 H 12 N 4 (urotropin) + 12 C 6 H 11 NO 2 (nitrocyclohexane) 537.8 457.7 average of 10 reactions 522.8 549.9 difference between maximum and minimum values 27.9 141.2…”

“…CL-20 exists in four different polymorphs (labeled as α, β, γ, and ε) under ambient conditions [2], from which the ε-CL-20 phase is the most stable [3]. The experimentally determined enthalpy of formation ( 298 f H Δ ) of ε-CL-20 [4][5][6] is of the order of ~400 kJ/mol ( Table 1). The close estimate of the enthalpy of formation of solid CL-20 was obtained by the empirical approaches [8,9] and atom equivalent method [13][14][15] developed for the prediction of enthalpies of formation of energetic compounds.…”

Bond energies and the enthalpies of formation of mono- and polyradicals in nitroakanes 3. Nitroalkanes C4–C7

“…Interestingly, the dissociation ener gies of the N-NO 2 bonds in the secondary nitramines are about 46 kcal mol -1 lower than in the radicals R • N-NO 2 . 15 As an example, Table 5 presents a number of D(С-C) values for molecules and radicals including, for compari son, some compounds containing no nitro groups. The introduction of nitro groups at carbon atoms strengthens the nearest С-C bond while long range interactions of nitro groups weaken this bond; this is consistent with the conclusions 1,3,4 about the effect of nitro groups on the energies of С-C bonds in molecules.…”