Thermochemistry and Initial Decomposition Pathways of Triazole Energetic Materials

Abstract

A thorough investigation of the initial decomposition pathways of triazoles and their nitro-substituted derivatives has been conducted using the MP2 method for optimization and DLPNO-CCSD(T) method for energy. Different initial thermolysis mechanisms are proposed for 1,2,4-triazole and 1,2,3-triazole, the two kinds of triazoles. The higher energy barrier of the primary decomposition path of 1,2,4-triazole (H-transfer path, ∼52 kcal/mol) compared with that of 1,2,3-triazole (ringopen path, ∼45 kcal/mol) shows that 1,2,4-triazole is more stable, consistent with experimental observations. For nitro-substituted triazoles, more dissociation channels associated with the nitro group have been obtained and found to be competitive with the primary decomposition paths of the triazole skeleton in some cases. Besides, the effect of the nitro group on the decomposition pattern of the triazole skeleton has been explored, and it has been found that the electron-withdrawing nitro group has an opposite effect on the primary dissociation channels of 1,2,4-triazole derivatives and 1,2,3-triazole derivatives.

Theoretical Perspective on the Sensing Mechanism of a Novel Fluorescent Probe for Nitramine Explosives: The Role of Radical Reactions

“…It should be noted that the free energy of TS1, which is supposed to be higher than the energies of its reactant and product (herein, IM1 and IM2), however, is slightly lower. This is a common problem for transition states with low energy barriers, − which is caused by the calculation method error. The energy criteria for transition state optimization and IRC calculation are based on electronic energy, whereas the energy profiles we have presented in the figure are based on Gibbs free energy, which takes the entropy effect into consideration, and thus better describe the real reaction process.…”

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

“…From previous studies, the possible initial decomposition reaction of pyrazole is the formation of N 2 and vinylcarbene, − and the energy barrier is 68.6 kcal/mol, which is about half that of OA1. This channel is also important for triazoles , and tetrazoles, and the energy barriers are lower than that of pyrazole. Therefore, the N 2 formation channel dominates the unimolecular thermal decomposition of pyrazole, triazole, and tetrazole, whereas decay of OA1 is more difficult through this pathway owing to the high barrier.…”

“…The energy diagrams of the LEB of pyrazole, imidazole and their nitro derivatives are shown in Figures S1–S8. The detailed data are shown in Figure S3, and the data of triazoles and tetrazoles are taken from refs , , respectively.…”

“…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.…”

1,2,3‐Triazoles by Click Chemistry Using Azido Esters as a Precursor

“…The decomposition of these compounds is predominantly through the generation of dinitrogen which makes them very promising candidates for highly energetic materials for industrial or military applications [14][15][16][17]. Triazoles are new binder cure systems in the initial stage of develop-ment for high-energy explosive and propellant formulations [18][19][20][21].…”