Lauren A. Mitchell

Energetic Salts Based on 3,5-Bis(dinitromethyl)-1,2,4-triazole Monoanion and Dianion: Controllable Preparation, Characterization, and High Performance

Molecular modification of known explosives is considered to be an efficient route to design new energetic materials. A new family of energetic salts based on the 3,5-bis(dinitromethyl)-1,2,4-triazole monoanion and dianion were controllably synthesized by using 1-diamino-2,2-dinitroethene as a precursor. X-ray structure determination of monohydrazinium 3,5-bis(dinitromethyl)-1,2,4-triazolate (5) and monoammonium (6) and diammonium 3,5-bis(dinitromethyl)-1,2,4-triazolate hydrate (8·H2O) further confirmed the structures of these anions. In addition, as supported by X-ray data, in the monoanion system, the roving proton on the ring nitrogen rather than on the gem-dinitro carbon results in extensive hydrogen-bonding interactions and higher packing coefficients. Interestingly, 5 and 6 possess the highest calculated crystal densities, 1.965 and 1.957 g cm(-3) at 150 K, for hydrazinium and ammonium energetic salts, respectively. Energetic evaluation indicates that 5 (detonation velocity vD = 9086 m s(-1); detonation pressure P = 38.7 GPa) and 6 (vD, 9271 m s(-1); P = 41.0 GPa) exhibit great detonation properties, superior to those of current highly explosive benchmarks, such as 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX).

Taming of 3,4-Di(nitramino)furazan

Highly energetic 3,4-di(nitramino)furazan (1, DNAF) was synthesized and confirmed structurally by using single-crystal X-ray diffraction. Its highly sensitive nature can be attributed to the shortage of hydrogen-bonding interactions and an interactive nitro chain in the crystal structure. In order to stabilize this structure, a series of corresponding nitrogen-rich salts (3-10) has been prepared and fully characterized. Among these energetic materials, dihydrazinium 3,4-dinitraminofurazanate (5) exhibits a very promising detonation performance (νD = 9849 m s(-1); P = 40.9 GPa) and is one of the most powerful explosives to date. To ensure the practical applications of 5, rather than preparing the salts of 1 through acid-base reactions, an alternative route through the nitration of N-ethoxycarbonyl-protected 3,4-diaminofurazan and aqueous alkaline workup was developed.

Energetic compounds consisting of 1,2,5- and 1,3,4-oxadiazole rings

3-Nitroamino-4-(5-amino-1,3,4-oxadiazol-2-yl)furazan monohydrate (2·H2O), which is a combination of the nitroaminofurazan and 1,3,4-oxadiazole rings, was obtained by the nitration of 3-amino-4-(5-amino-1,3,4-oxadiazol-2-yl)furazan (1) with 100% nitric acid. Several energetic derivatives of 2 were prepared and fully characterized by multinuclear NMR, and IR spectroscopy, as well as elemental analysis. X-ray analyses for 1, 2·H2O and 5·H2O give insight into structural characteristics showing the presence of extensive hydrogen-bonding interactions. Most of these new materials exhibit good thermal stabilities and acceptable sensitivity values. Detonation performance numbers were obtained based on the calculated heats of formation and measured densities indicating that some of these bonded nitroaminofurazan/oxadiazole materials are comparable to RDX.

N-Oxides light up energetic performances: synthesis and characterization of dinitraminobisfuroxans and their salts

4,4′-Diamino-[3,3′-bi(1,2,5-oxadiazole)]-5,5′-dioxide and 4,4′-diamino-[3,3′-bi(1,2,5-oxadiazole)]-2,2′-dioxide were nitrated in 100% HNO3 at −10 °C to give 4,4′-dinitramino-[3,3′-bi(1,2,5-oxadiazole)]-5,5′-dioxide (3) and 4,4′-diamino-[3,3′-bi(1,2,5-oxadiazole)]-2,2′-dioxide (4). Nine nitrogen-rich salts were prepared and were characterized by infrared and multinuclear NMR spectroscopy, elemental analysis, differential scanning calorimetry (DSC) and X-ray single crystal diffraction in some cases. Their detonation properties were evaluated by EXPLO 5 code using the measured density and calculated heat of formation. The sensitivities were determined by standard BAM methods. Several of the new molecules exhibit detonation and other properties which compete with or exceed those of HMX.

Enhancing Energetic Properties and Sensitivity by Incorporating Amino and Nitramino Groups into a 1,2,4‐Oxadiazole Building Block

A single nitrogen-rich heterocyclic ring with many energetic groups is expected to exhibit excellent detonation performance. We report an effective approach for the synthesis of 3-amino-5-nitramino-1,2,4-oxadiazole, which has nitramino and amino groups in the same building block. The single-crystal X-ray structure shows layered hydrogen-bonding pairs as well as the presence of a water molecule which ensure insensitivity. Through incorporation of a cation, the hydrazinium or hydroxylammonium salts exhibit good energetic performance and acceptable sensitivities.

Connecting energetic nitropyrazole and aminotetrazole moieties with N,N′-ethylene bridges: A promising approach for fine tuning energetic properties

A new approach for fine tuning the properties of energetic compounds through bonding of energetic pyrazoles with tetrazole moieties by means of N,N′-ethylene bridges is described. Reactions of various pyrazole derivatives with 2-haloethylamines, followed by reaction with cyanogen azide resulted in the formation of compounds having ethylene-bridged 5-aminotetrazole and nitropyrazole. Further reactions on this basic framework resulted in various energetic compounds having mono, di or tri nitro-substituted pyrazole moieties, and an amino or nitroimino-substituted tetrazole ring. All the compounds were thoroughly characterized by IR, and NMR [1H, 13C{1H}, 15N] spectra, elemental analysis, and differential scanning calorimetry (DSC). Some of them were also structurally characterized with single-crystal X-ray diffraction studies. Heats of formation and detonation performance for all the energetic compounds were calculated using Gaussian 03 and EXPLO5 v6.01 programs, respectively. Initial studies showed that the properties of energetic compounds can indeed be fine-tuned by careful selection of the number and nature of energetic groups on the pyrazole and tetrazole rings.

Asymmetric N,N′-ethylene-bridged azole-based compounds: Two way control of the energetic properties of compounds

Reactions of various energetic pyrazole, triazole and tetrazole salts with 1-(2-bromoethyl)-5-aminotetrazole, in the presence of a phase transfer catalyst, resulted in new asymmetric N,N′-ethylene-bridged azole-based energetic compounds having diversified functionalities and properties. The availability of the aminotetrazole moiety for conversion to nitroimino(tetrazole) provides a route for further modifying energetic properties. All the compounds were thoroughly characterized by IR, NMR [1H, 13C{1H}, 15N], elemental analyses, and differential scanning calorimetry (DSC). Some were also further characterized using single-crystal X-ray diffraction studies. Impact and friction sensitivities were measured and heats of formation and detonation performances were calculated. Results show that combination of different energetic heterocycles broadens options for the design of desirable energetic compounds.

C–N bonded energetic biheterocyclic compounds with good detonation performance and high thermal stability

New C–N bonded energetic biheterocyclic compounds were synthesized using cine substitution of 1,3-dinitro-1,2,4-triazole with different energetic moieties. All the compounds were fully characterized by multinuclear NMR and infrared spectra, and elemental analyses. The structures of 4, 7, 9, and 11 were confirmed by single-crystal X-ray structure analyses. Their physicochemical properties, such as density, thermal stability and sensitivity towards impact and friction, were studied. All of the compounds have high thermal stability. The detonation properties were calculated with EXPLO5 V6.01 based on experimental densities and calculated heats of formation.

N-functionalized nitroxy/azido fused-ring azoles as high-performance energetic materials

A series of fused ring-based nitrate esters/azides and a coupled-ring-based nitrate ester were prepared using a simple and efficient nitrogen-functionalization approach. All new energetic compounds were fully characterized. Structures of four (1–4) were further confirmed by single crystal X-ray diffraction. These nitrate esters have good thermal stabilities and high densities. Energetic performance was evaluated by using EXPLO5 v6.01 based on measured densities and calculated heats of formation (Gaussian 03 (Revision D. 01)). The results show that some of the representative fused ring-based nitrate esters exhibit good detonation properties, for example, 1 (vD, 8674 m s−1; P, 33.1 Gpa) and 2 (vD, 8669 m s−1; P, 33.4 Gpa), that approach those of current high explosive benchmarks, such as 1,3,5-trinitroperhydro-1,3,5-triazine (RDX). Sensitivity data based on impact and friction tests show these compounds have better stabilities than the traditional nitrate ester explosive, pentaerythritol tetranitrate (PETN).

Small Cation‐Based High‐Performance Energetic Nitraminofurazanates

Large nitramino-substituted furazan anions were combined with small cations (hydroxylammonium, hydrazinium, and ammonium) to form a series of energetic salts that was fully characterized. The structures of several of the compounds (1 a, 2 a, 3 a, and 4 a) were further confirmed by single-crystal X-ray diffraction. Based on their physiochemical properties, such as density, thermal stability, and sensitivity, together with the calculated detonation properties, it was found that they exhibit good detonation performance and have potential application as high-energy-density materials.