Energetic N,N′‐Ethylene‐Bridged Bis(nitropyrazoles): Diversified Functionalities and Properties

Abstract

A new class of N,N'-ethylene-bridged bis(nitropyrazoles) was synthesized and fully characterized. The highly efficient formation of the N,N'-ethylene bridge was accomplished using dibromoethane and ammonium or potassium pyrazolate. Further functional-group transformations of diaminobis(pyrazole) and dichlorobis(pyrazole) gave rise to diversified derivatives, including dinitramino-, diazido- and hexanitrobis(pyrazole). Single-crystal X-ray diffractions were obtained for hexanitro and diazido derivatives to illustrate the structural characteristics. Heats of formation and detonation performance were calculated by using Gaussian 03 and EXPLO5 v6.01 programs, respectively. Because of the different functionalized groups, the impact and friction sensitivities of these new compounds range from insensitive to sensitive. Among them, the hexanitro derivative displays the most promising overall energetic properties (density (ρ)=1.84 g cm(-3) ; decomposition temperature (Td )=250 °C; detonation pressure (P)=34.1 GPa; detonation velocity (vD )=8759 m s(-1) ; impact sensitivity (IS)=25 J; friction sensitivity (FS)=160 N), which is competitive with those of 1,3,5-trinitrotriazacyclohexane (ρ=1.80 g cm(-3) ; Td =205 °C; P=35.0 GPa; vD =8762 m s(-1) ; IS=7 J; FS=120 N).

Dancing with Energetic Nitrogen Atoms: Versatile N-Functionalization Strategies for N-Heterocyclic Frameworks in High Energy Density Materials

“…In the presence of tetraethylammonium bromide as phase transfer catalyst, N,N′-ethylene bridged 4-amino-3,5-dinitropyrazole (1-21) was obtained using dibromoethane and ammonium 4-amino-3,5-dintropyrazolate (Scheme 3b). 12 Subsequent transformations of 1-21 involving nitration, oxidation, azidation, and diazotization gave rise to diversified HEDMs (1-22−1-25) with excellent energetic performance. When compared with our previous study of N,N′-ethylene tetrazoles, these 1,2,4-triazole-and pyrazole-based energetic analogues …”

N‐Acetonitrile Functionalized Nitropyrazoles: Precursors to Insensitive Asymmetric N‐Methylene‐C Linked Azoles

“…However,m ethylene-bridged compounds are less explored, in part because of the greater difficulty in synthesis, and the lack of asuitable approachtobond different types of energetic rings. [10] Among the known all-carbon-nitrated azoles only 3,4,5-trinitropyrazole (TNP) exhibitsb othh igh thermal stability (T dec = 260 8C) and good energetic properties (Dv = 9253 ms À1 and P = 38.6 GPa), but its highly acidic NH bond (pK a = 2.35) precludesp ractical applications.[11] Various approaches have been used to address this problem such as (i)salt formation, [7b] (ii) Nmethylation, [12] (iii) N,N'-ethylene bridging, [13] and (iv) N-hydroxylation; [7a] however,all of these result in materials with reduced densities, energetic performance, and nitrogen content (Figure 1). In this work, an ew approacht of ine-tune energetic properties of nitropyrazoles by first reacting their derivatives with chloroacetonitrile to reach N-acetonitrile derivatives and then by means of click reactions to convert the cyano to tetrazole to form asymmetric N-methylene-C bridged azole-based energetic compounds is demonstrated.…”

“…All the compounds were thoroughly characterized by IR and NMR [ 1 H, 13 C{ 1 H}, 15 N]s pectroscopy,e lemental analysis, and differential scanning calorimetry (DSC), and for two compounds,f urther supported by single-crystal X-ray diffraction studies.H eats of formation and detonation performances were calculated using Gaussian 03 and EXPLO5 v6.01 programs, respectively.I nitial studies show that this new approach is promisingf or synthesizing less sensitivee nergetic compoundsw ith finetuned properties.…”

“…Various approaches to remove the acidic NH proton in TNP. [7,12,13] Scheme1.The synthetic route to 2 and 3 and the energetic salts of 2.…”

“…The option of salt formation allows the synthesis of energetic azido derivatives (11)(12)(13)w ith acceptable sensitivities. These methylene-bridgeda symmetric compounds are found to be more dense, energetic, nitrogen-rich, and thermally stable than the analogous N,N'-ethylene-bridged asymmetric compounds.…”