Improving the Energetic Properties of Dinitropyrazoles by Utilization of Current Concepts

Abstract

The syntheses of two different isomeric dinitropyrazole N-oxides are described and compared to each other. 3,4-Dinitropyrazole-1N-oxide (2) and 3,5-dinitropyrazole-1N-oxide (4) were used, and four different nitrogen-rich salts were synthesized in order to enhance performance and sensitivity values. Furthermore, two methylene-bridged isomeric dinitropyrazoles were synthesized by using diiodomethane. The obtained compounds were characterized by using low-temperature single-crystal X-ray diffraction, IR spectroscopy, multinuclear NMR spectroscopy, mass spectrometry, elemental analysis and DSC measurements. The bridged compounds show a high thermal stability (T dec. : 319°C and 330°C) whereas the ionic compounds [a] 4125 Scheme 1. Synthesis of bis(3,5-dinitro-pyrazol-1-yl)methane (1), bis(3,4-dinitro-pyrazol-1-yl)methane (3), 3,4-dinitropyrazol-1-oxide (2) and 3,5-dinitropyrazol-1-oxide (4) as well as the ionic derivatives of 2 and 4.

Recent Advances in Synthesis and Properties of Nitrated-Pyrazoles Based Energetic Compounds

“…The efforts to developing N-oxidation of dinitropyrazoles have been made recently. Bölter et al [94] introduced -OH on N atom of 3,4-DNP and 3,5-DNP, and obtained several salts (Figure 17, Scheme A). From Table 8, these compounds were less sensitive than RDX, and did not exhibited excellent detonation properties.…”

“…In addition, the synthetic routes are economical. Afterwards, their group used a similar route to prepare bis(3,4-dinitro-1 H -pyrazol-1-yl)methane ( 89 ) and bis(3,5-dinitro-1 H -pyrazol-1-yl)methane ( 90 ) with high decomposition temperature and low sensitivities having capability as future energetic materials ( Table 13 ) [ 94 ]. Gozin et al [ 124 ] explored the possible influence factor of the thermostable property of explosives, and under the guidelines they proposed, they synthesized the compounds 91 and 92 with excellent thermal stability and moderate sensitivities shown in Figure 31 and Table 13 .…”

“…Physical and computational properties of ionic salts of dinitropyrazoles. The data of compounds 42a-43d are from reference[94], the data of compounds…”

Combining Performance with Thermal Stability: Synthesis and Characterization of 5‐(3,5‐Dinitro‐1H‐pyrazol‐4‐yl)‐1H‐tetrazole and its Energetic Derivatives

“…[14,15] Especially azoles like pyrazoles, triazoles, tetrazoles or oxygen containing five-membered heterocycles like furazan or oxadiazoles have proven to be good building blocks of novel energetic materials. [17][18][19][20][21] Pyrazoles are particularly suitable because they have a relatively high heat of formation (HoF) and still exhibit high thermal stability, which is due to the three linked carbon atoms. In addition, energetic modifications, such as nitration or oxidation, can be carried out rather simply [22,23] ( Figure 1a).…”

“…Thermal ellipsoids represent the 50 % probability level and hydrogen atoms are shown as small spheres of arbitrary radius. Selected bond lengths /Å and angles /°: C2-C4 1.465(2), C1-N4 1.4445(19), C3-N3 1.444(2), O3-N4-C1 116.80(12), O2-N3-C3 117.61(12), O2-N3-C3-C2 -3.9(2), O3-N4-C1-N2 -2.4(2), C1-C2-C4-N8 129.02(17).…”