Comparative study of thermal stability and combustion of dinitropyrazole isomers

Sinditskii, Valery P.; Hoang, Trung H.; Smirnova, A. D.; Egorshev, V.Y.; Yudin, N. V.; Вацадзе, И. А.; Далингер, И. Л.

doi:10.1016/j.tca.2018.07.006

Cited by 11 publications

(11 citation statements)

References 20 publications

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“…Pyrazole and imidazole are structural isomers involving two N atoms. Many studies have been carried out to study their thermal decomposition, through experimental and theoretical methods. − The unimolecular decomposition mechanism of triazoles and tetrazoles was also reported, and the stability and preferred initial channels were systematically compared. Until now, few investigations have been conducted on the thermal decomposition mechanism of oxadiazole compounds.…”

Section: Introductionmentioning

confidence: 99%

Initial Steps and Thermochemistry of Unimolecular Decomposition of Oxadiazole Energetic Materials: Quantum Chemistry Modeling

et al. 2021

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In order to resolve the existing discrepancies in the mechanism and key intermediates of oxadiazole thermolysis, the initial decomposition pathways of oxadiazoles have been studied comprehensively using the M062X method for optimization and CBS-QB3 and DLPNO-CCSD(T) methods for energies. The transformation from the furoxan ring to nitro group was suggested as a potential decay channel of furoxan compounds. Results of thermochemistry calculations showed that the preferred decomposition reaction of oxadiazoles is the ring-opening through the cleavage of the O−C or O−N bond. The introduction of the nitro group has little effect on the preferential path of oxadiazole thermal decomposition, but a great impact on the energy barrier. The lowest energy barrier and bond dissociation energy of NO 2 loss of azoles were comprehensively studied based on the quantum chemistry calculations. The initial decay steps of 3,4-dinitrofurazanfuroxan and benzotrifuroxan were also studied to give insights into the mechanism of primary stages of thermal decomposition of oxadiazoles.

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Section: Introductionmentioning

confidence: 99%

Initial Steps and Thermochemistry of Unimolecular Decomposition of Oxadiazole Energetic Materials: Quantum Chemistry Modeling

et al. 2021

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“…Previous studies mainly focused on the physicochemical properties of pyrazoles and imidazoles. − N 2 extrusion is suggested to be the favorable channel of pyrazoles through the flash vacuum pyrolysis experiment , and the first principles study . The possible pathways in the thermal decomposition of pyrazole and its nitro derivatives were presumed based on the thermogravimetric–differential thermal analysis (TG–DTA) results .…”

Section: Introductionmentioning

confidence: 99%

Comparative Quantum Chemistry Study on the Unimolecular Decomposition Channels of Pyrazole and Imidazole Energetic Materials

et al. 2021

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The difference in the initial decomposition step of pyrazoles and imidazoles was explored using the M062X method for optimization and G4-MP2 and approximated CCSD(T) methods for energies. Laplacian bond order analysis was used to study the effect of the nitro group on the bond strength and predict the bond dissociation energy (BDE) of the ring. Thermochemistry results show that the most possible decay channel of 1H-pyrazole and 3-nitropyrazole is the N 2 elimination, while the preferred initial step of 1H-imidazole is the CHN elimination. However, the nitro−nitrite isomerization dominates the decomposition of other nitro derivatives of 1H-pyrazole and 1H-imidazole. As for the formation of HO and HONO, the high energy barrier makes it difficult to take place. Based on the analysis of the lowest energy barrier and the BDE of NO 2 loss, it can be concluded that imidazoles are more stable than pyrazoles. This work contributes to revealing the difference in the initial step of energetic isomers and the understanding of the decomposition mechanism of energetic azoles.

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“…The development of salts and cocrystals has become more and more popular in the field of energetic materials, since salt formation and cocrystallization can help to modulate the acidity and stability of the original energetic compound. As a potential candidate for melt-cast explosives, 3,4-dinitropyrazole (DNP) has attracted a great deal of attention. − It is nonhygroscopic with a melting point of 85–87 °C and possesses better detonation properties and sensitivity in comparison to the prevalent melt-cast explosive 2,4,6-trinitrotoluene (TNT) . However, the acidity of DNP (p K a = 5.48) makes it corrosive and prone to react with metals, which can restrict the process ability, shelf life, and extensive applications: i.e., DNP requires more attention due to the chemical instability originating with the highly acidic proton.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, their densities are different (ρ = 1.682 g/cm 3 for our salt; ρ = 1.704 g/cm 3 for the reported salt 2 ), which can be partially attributed to the different measurement temperatures (296(2) K in our test; 173 K in ref 2). Salt II crystallizes in the monoclinic space group P2 1 /c containing four molecules per unit cell with a density of 1.718 g/cm 3 . The stoichiometric ratio of the DNP anion and ED cation in one salt II molecule is 1:2, and two C−H•••O intramolecular HBs exist (Figure 3a).…”

Section: ■ Introductionmentioning

confidence: 99%

Origins of Salt Formation and Cocrystallization: A Combined Experimental and Theoretical Study

Yang

Yin

Gong

et al. 2020

Crystal Growth & Design

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Three DNP (3,4-dinitropyrazole) salts and one DNP cocrystal were synthesized and characterized by IR, elemental analysis, and single-crystal X-ray diffraction. DSC analysis shows that hydrazine hydrate (HH), ethanediamine (ED), aminoguanidine (AG), and urea (U) all make DNP prone to decomposition, demonstrating that salt formation and cocrystallization are two strategies to modulate the thermal stability and the coformers play a vital role in the performance of the target products. Hirshfeld surfaces suggest that O•••H close contacts make the greatest contribution to the stabilization of I− IV. Electrostatic potential and pK a values give a reasonable explanation that DNP forms salts I−III with HH, ED, and AG, while it forms cocrystal IV with U. The hydrogen-bonding interactions were evaluated by the quantum theory of atoms-in-molecules (AIM) and the independent gradient model (IGM), further revealing that DNP and U prefer to form a cocrystal, rather than a salt or as the individual compounds. The systematic experimental and theoretical work gives a clear comparison of the salt and cocrystal formation processes and explains their origins on the atomic scale, which can prompt the development of the design and synthesis of new salts and cocrystals.

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Comparative study of thermal stability and combustion of dinitropyrazole isomers

Cited by 11 publications

References 20 publications

Initial Steps and Thermochemistry of Unimolecular Decomposition of Oxadiazole Energetic Materials: Quantum Chemistry Modeling

Initial Steps and Thermochemistry of Unimolecular Decomposition of Oxadiazole Energetic Materials: Quantum Chemistry Modeling

Comparative Quantum Chemistry Study on the Unimolecular Decomposition Channels of Pyrazole and Imidazole Energetic Materials

Origins of Salt Formation and Cocrystallization: A Combined Experimental and Theoretical Study

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