Zhu Shuangfei, Yang Wei, Gan Qiang, Feng Changgen
State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081, China.
School of Materials Science & Engineering, Beijing Institute of Technology, Beijing 100081, China.
J Phys Chem A. 2021 Dec 9;125(48):10340-10350. doi: 10.1021/acs.jpca.1c08274. Epub 2021 Nov 29.
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 1-pyrazole and 3-nitropyrazole is the N elimination, while the preferred initial step of 1-imidazole is the CHN elimination. However, the nitro-nitrite isomerization dominates the decomposition of other nitro derivatives of 1-pyrazole and 1-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 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.
采用M062X方法进行优化，G4-MP2方法和近似的CCSD(T)方法计算能量，探究了吡唑和咪唑初始分解步骤的差异。利用拉普拉斯键级分析研究硝基对键强度的影响，并预测环的键解离能（BDE）。热化学结果表明，1-吡唑和3-硝基吡唑最可能的衰变通道是N消除，而1-咪唑的首选初始步骤是CHN消除。然而，硝基-亚硝酸盐异构化主导了1-吡唑和1-咪唑其他硝基衍生物的分解。至于HO和HONO的形成，高能垒使其难以发生。基于对最低能垒和NO损失的BDE的分析，可以得出结论，咪唑比吡唑更稳定。这项工作有助于揭示含能异构体初始步骤的差异，并有助于理解含能唑类的分解机理。
