Bicyclic High-Energy and Low-Sensitivity Regioisomeric Energetic Compounds Based on Polynitrobenzene and Pyrazoles

Abstract

With the development of synthetic methodology and crystallography of energetic materials, regiochemistry is becoming popular and vital in the design of versatile energetic compounds as well as in the thorough research on the relationship between structure and property. In this study, two regioisomeric bicyclic energetic compounds based on pyrazole and polynitrobenzene were synthesized simultaneously by a simple synthetic route, and the regioisomers could be purified by a facile approach. It is interesting to note that the ratio of the two compounds changed with temperature. From 80 to 110 °C, the proportion of compound 2 gradually enhanced with the increase in temperature. In addition, the nitramine product of compound 1 was also synthesized. The structural data of compounds 1, 2, and 3 were confirmed by X-ray single-crystal diffraction. The detonation velocities of the new compounds are in the range of 8436–8788 m s–1 and impact sensitivities are between 15 and 27.5 J, of which compounds 2 and 3 not only present superior sensitivities to those of the classical high-energy explosive RDX (7.5 J) but also exhibit comparable detonation velocities to the measured RDX powder (V D = 8796 m s–1), calculated by EXPLO5 as 8788 and 8526 m s–1, respectively. Moreover, compounds 1 and 2 show good thermal stability with decomposition temperatures up to 263 and 287 °C, which is higher than that of RDX (T dec: 204 °C). All of the above information indicates that these compounds are high-energy, low-sensitivity energetic materials featuring prospective applications.

Can Catenated Nitrogen Compounds with Amine-like Structures Become Candidates for High-Energy-Density Compounds?

“…In fact, the amine-like structure proposed in this paper can be regarded as a special case of designing energetic materials with the amino group as the bridging group. Some studies − have shown that the use of the amino bridging strategy is an effective way to construct heat-resistant energetic compounds, which further suggests that the amine-like catenated nitrogen compounds designed in this paper are potential energetic materials.…”

Polynitro-functionalized 4-phenyl-1H-pyrazoles as heat-resistant explosives

“…The signals corresponding to chemically non-equivalent nitrogens were identified by comparing them with the analogous compounds previously reported in the literature. 11–15 The methyl-substituted nitrogen atoms (N1) of the pyrazole ring in these compounds were found to be shielded (−183.80 to −186.23 ppm) compared to the other ring nitrogen (N2) of the pyrazole ring (−76.72 to −78.41 ppm). In compound 5 , the signal corresponding to the nitro groups (N5/N6) present in the benzene moiety was found to be downfield shifted at −16.33 ppm compared to the signals (−28.62 and −33.71 ppm) of the nitro groups (N3/N4) present on the pyrazole moiety.…”

“…[7][8][9][10] However, it is observed that due to high carbon content, most of these polynitrobenzene-based energetic compounds exhibit poor energetic performance. 11,12 Recently, there has been a surge in the number of new energetic compounds based on nitrogen and oxygen-rich heterocyclic ring systems like azoles, oxadiazoles, pyrazine, tetrazene, etc. [13][14][15][16][17][18][19][20][21][22] Energetic materials with such nitrogen-based heterocyclic rings as their backbone are highly endothermic and considered environmentally friendly as they release non-toxic dinitrogen (N 2 ) gas after their decomposition.…”

Concise synthesis of a fused energetic pyrazolotriazine with good performance

“…[4][5][6] Various potential safety problems could occur during preparation, transportation, storage, or application. 7 There is a push to research and develop a new generation of insensitive high-energy materials (IHEMs). 8 Generally, nitrogen-rich ring-fused energetic compounds feature a large number of NQN and N-N bonds, a planar conjugated molecular structure, strong hydrogen bonding 9 and p-p interactions, as well as layer crystal packing.…”

“…4–6 Various potential safety problems could occur during preparation, transportation, storage, or application. 7 There is a push to research and develop a new generation of insensitive high-energy materials (IHEMs). 8…”