The stability and decomposition mechanism of the catenated nitrogen compounds

Zhao, Xiuxiu; Qi, Chao; Zhang, Rubo; Zhang, Shaowen; Li, Sheng‐Hua; Pang, Siping

doi:10.1007/s00894-015-2766-2

Cited by 9 publications

(11 citation statements)

References 21 publications

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“…Nearly all available computational results on the thermal decomposition of azobis triazoles and tetrazoles were obtained at the DFT level of theory with the B3LYP functional. − More specifically, Zhao et al studied the thermal decomposition of 1 , 2a (Chart ) and several of their isomers. The authors found that the catenation of the long nitrogen-chains facilitates the decomposition via the ring-opening and subsequent elimination of the molecular nitrogen. For 1 and 2a , the activation barriers of the rate-determining N 2 elimination steps were predicted to be 34.6 and 27.5 kcal mol –1 , respectively .…”

Section: Introductionmentioning

confidence: 99%

“…The authors found that the catenation of the long nitrogen-chains facilitates the decomposition via the ring-opening and subsequent elimination of the molecular nitrogen. For 1 and 2a , the activation barriers of the rate-determining N 2 elimination steps were predicted to be 34.6 and 27.5 kcal mol –1 , respectively . The same decomposition mechanism was proposed for 4 .…”

Section: Introductionmentioning

confidence: 99%

“…The same decomposition mechanism was proposed for 4 . The compounds without long nitrogen chains (e.g., the azobis derivatives of 1,2,4-triazole) were hypothesized to be more stable than their counterparts and to decompose via the radical rupture of the azo-bridge …”

Section: Introductionmentioning

confidence: 99%

“…However, the poor accuracy of DFT calculations (especially with the conventional B3LYP functional) for the mechanisms of thermal decomposition of energetic materials is well documented. − Thus, the accurate values of activation barriers are still unknown and, in general, the decomposition mechanisms for the bridged heterocyclic compounds 1 – 8 (Charts and ) remain unclear. Both radical (the N–N bond rupture between a bridge and a heterocycle) and molecular (the N 2 elimination from the azido intermediate) , reactions have been proposed as the decomposition channels of the species studied.…”

Section: Introductionmentioning

confidence: 99%

“…47−50 More specifically, Zhao et al 47 studied the thermal decomposition of 1, 2a (Chart 1) and several of their isomers. The authors 47 found that the catenation of the long nitrogenchains facilitates the decomposition via the ring-opening and subsequent elimination of the molecular nitrogen. For 1 and 2a, the activation barriers of the rate-determining N 2 elimination steps were predicted to be 34.6 and 27.5 kcal mol −1 , respectively.…”

Section: Introductionmentioning

confidence: 99%

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Thermal Stability of Bis-Tetrazole and Bis-Triazole Derivatives with Long Catenated Nitrogen Chains: Quantitative Insights from High-Level Quantum Chemical Calculations

et al. 2020

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Azobis tetrazole and triazole derivatives containing long catenated nitrogen atom chains are of great interest as promising green energetic materials. However, these compounds often exhibit poor thermal stability and high impact sensitivity. Kinetics and mechanism of the primary decomposition reactions are directly related to these issues. In the present work, with the aid of highly accurate CCSD(T)-F12 quantum chemical calculations, we obtained reliable bond dissociation energies and activation barriers of thermolysis reactions for a number of N-rich heterocycles. We studied all existing 1,1′-azobistetrazoles containing an N 10 chain, their counterparts with the 5,5′-bridging pattern, and the species with hydrazo-and azoxy-bridges, which are often present energetic moieties. The N 8 -containing azobistriazole was considered as well. For all compounds studied, the radical decomposition channel was found to be kinetically unfavorable. All species decompose via the ring-opening reaction yielding a transient azide (or diazo) intermediate followed by the N 2 elimination. In the case of azobistetrazole derivatives, the calculated effective activation barriers of decomposition are ∼26−33 kcal mol −1 , which is notably lower than that of tetrazole (∼40 kcal mol −1 ). This fact agrees well with the low thermal stability and high impact sensitivities of the former species. The activation barriers of the N 2 elimination were found to be almost the same for the azobis compounds and the parent tetrazole, and the effective decomposition barrier is determined by the thermodynamics of the tetrazole−azide rearrangement. In comparison with 1,1′-azobistetrazole, the hydrazo-bridged compound is more stable kinetically due to the lack of pi-conjugation in the azide intermediate. In turn, the azoxy-bridged compounds are entirely unstable due to tremendous azide stabilization by the hydrogen bond formation. In general, the 5,5′-bridged species are more thermally stable than their 1,1′-counterparts due to a much higher barrier of the N 2 elimination. Apart from this, the highly accurate gas-phase formation enthalpies were calculated at the W1−F12 level of theory for all species studied.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Thermal Stability of Bis-Tetrazole and Bis-Triazole Derivatives with Long Catenated Nitrogen Chains: Quantitative Insights from High-Level Quantum Chemical Calculations

et al. 2020

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Nitrogen Catenation: Polyazoles and Polyazines

Politzer¹,

Murray²

2017

Patai's Chemistry of Functional Groups

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Polyazoles and polyazines are, respectively, five‐ and six‐membered nitrogen heterocycles. An interesting difference between their geometries is that it is possible in polyazoles (but not in polyazines) to distinguish between formal single and formal double bonds. Our particular focus in this chapter is on those polyazoles and polyazines that feature three or more linked nitrogens in their rings (nitrogen catenation). The presence of ring nitrogens is destabilizing, especially when they are linked. Several possible factors that may be responsible for this effect of catenation are discussed in detail, and it is emphasized that these factors are not mutually exclusive or independent of each other. The electrostatic potentials of the molecules of interest are analyzed and related to their relative stabilities. N‐oxide formation is one means of mitigating the destabilization caused by nitrogen catenation. The acidity/basicity of these polyazoles and polyazines is examined in terms of their electrostatic potentials and local ionization energies. Polyazoles and polyazines have been found to provide good molecular frameworks for energetic materials; this application is briefly mentioned.

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N‐Oxides of Polyazoles and Polyazines

Politzer

Murray

2019

Patai's Chemistry of Functional Groups

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The N‐oxide bond, which will be written as N→O, is formally coordinate covalent, with both electrons being provided by a covalently bonded nitrogen. A more realistic description is that the nitrogen lone pair is polarized toward the oxygen by the electric field of the latter. Our present focus is upon the N‐oxides of polyazoles and polyazines, particularly those having three or more linked (catenated) nitrogens. The N→O linkage is inductively electron withdrawing. In resonance delocalization, it is intrinsically a donor of electronic charge although this can be partially countered by electron‐donating substituents. A significant feature of the N→O linkage is that it can somewhat mitigate the destabilization associated with nitrogen catenation. This is discussed in terms of the molecular electrostatic potentials. N‐oxides of polyazoles and polyazines can be prepared by oxidizing the heterocyclic precursors; the sites can to some extent be predicted in terms of local ionization energies (or local polarizabilities), but other factors can also be involved. The current interest in N‐oxides as high explosives is briefly discussed.

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The stability and decomposition mechanism of the catenated nitrogen compounds

Cited by 9 publications

References 21 publications

Thermal Stability of Bis-Tetrazole and Bis-Triazole Derivatives with Long Catenated Nitrogen Chains: Quantitative Insights from High-Level Quantum Chemical Calculations

Thermal Stability of Bis-Tetrazole and Bis-Triazole Derivatives with Long Catenated Nitrogen Chains: Quantitative Insights from High-Level Quantum Chemical Calculations

Nitrogen Catenation: Polyazoles and Polyazines

N‐Oxides of Polyazoles and Polyazines

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