Nitrodiazene oxides: a unique nitrogen- and oxygen-containing functional group

Nitrogen-/oxygen-containing functional groups (N/O groups) may be found in a wide variety of areas such as agriculture, drug design and energetic materials. Exploring the chemistry and synthesis of N/O groups is desirable as compounds containing their functionality may prove to be invaluable in a variety of fields. A unique N/O functional group which may offer additional insight into the design of high-heteroatom content systems is the 2-nitrodiazene-1-N-oxide group (NDO group). While unique on their own, NDOs combine the well-known azoxy (N(O)=N) and nitro (-NO2) groups into a single unique N/O functional group. Although NDOs may offer superior densities and enthalpies of formations relative to their nitro counterparts, NDOs have been significantly less investigated than their nitro-bearing counterparts. This work will discuss NDOs in chemical literature from their initial discovery to modern synthesis techniques, energetic properties and chemical stability.

Design and Synthesis of Energetic Melt-Castable Materials by Substituent-Specific Modification

With the increase in the demand for high-performance composite explosives, the search for advanced energetic melt-castable compounds has attracted increasing attention in the field of energetic materials. Herein, two new energetic materials with nitromethyl and azidomethyl substituents (1-(nitromethyl)-3,4-dinitro-1H-pyrazole (NMDNP) and 1-(azidomethyl)-3,4-dinitro-1H-pyrazole (AMDNP) were prepared by the substituent modification of a potential melt-castable molecule ((3,4-dinitro-1H-pyrazol-1-yl) methyl nitrate, MC-4), respectively. NMDNP exhibited a suitable melting point (90 °C), good thermal stability (Td : 185 °C) and excellent detonation performance (8484 m s-1 ) and impact sensitivity (25 J), thereby demonstrating promise as an energetic melt-castable material. Simultaneously, compared with the nitrato-methyl and azidomethyl substituents, the nitromethyl substituent exhibited greater advantages in regulating performance.

Chemical Descriptors for a Large-Scale Study on Drop-Weight Impact Sensitivity of High Explosives

The drop-weight impact test is an experiment that has been used for nearly 80 years to evaluate handling sensitivity of high explosives. Although the results of this test are known to have large statistical uncertainties, it is one of the most common tests due to its accessibility and modest material requirements. In this paper, we compile a large data set of drop-weight impact sensitivity test results (mainly performed at Los Alamos National Laboratory), along with a compendium of molecular and chemical descriptors for the explosives under test. These data consist of over 500 unique explosives, over 1000 repeat tests, and over 100 descriptors, for a total of about 1500 observations. We use random forest methods to estimate a model of explosive handling sensitivity as a function of chemical and molecular properties of the explosives under test. Our model predicts well across a wide range of explosive types, spanning a broad range of explosive performance and sensitivity. We find that properties related to explosive performance, such as heat of explosion, oxygen balance, and functional group, are highly predictive of explosive handling sensitivity. Yet, models that omit many of these properties still perform well. Our results suggest that there is not one or even several factors that explain explosive handling sensitivity, but that there are many complex, interrelated effects at play.

Probing the Reaction Mechanisms of 3,5-Difluoro-2,4,6-Trinitroanisole (DFTNAN) through a Comparative Study with Trinitroanisole (TNAN)

To probe the thermal decomposition mechanisms of a novel fluorinated low-melting-point explosive 3,5-difluoro-2,4,6-trinitroanisole (DFTNAN), a comparative study with trinitroanisole (TNAN) was performed under different heating conditions. The thermal decomposition processes and initial reactions were monitored by DSC-TG-FTIR-MS and T-jump-PyGC-MS coupling analyses, respectively. The results show that fluorine decreased the thermal stability of the molecular structure, and the trigger bond was transferred from the ortho-nitro group of the ether to the para-nitro group. The possible reaction pathway of DFTNAN after the initial bond breakage is the rupture of the dissociative nitro group with massive heat release, which induces the ring opening of benzene. Major side reactions include the generation of polycyclic compounds and fluorine atom migration. Fluorine affects the thermal stability and changes the reaction pathway, and fluorinated products appear in the form of fluorocarbons due to the high stability of the C-F bond.

Two novel TNB energetic cocrystals with low melting point: a potential strategy to construct melt cast explosive carriers

Two novel low melting-point cocrystals with high performances were obtained by cocrystallizing TNB with 1,4-DNI and DNMT, namely TNB/1,4-DNI (1) and TNB/DNMT (2).

Molecular dynamics simulation of 1-methyl-4,5-dinitroimidazole (MDNI)/1-methyl-3,4,5-trinitropyrazole (MTNP) eutectic mixtures

1-Methyl-4,5-dinitroimidazole (MDNI)/1-methyl-3,4,5-trinitropyrazole (MTNP) mixtures with different mass ratios were investigated by a combination of theory and experiment. The melting points were predicted using the relationships of specific volume versus temperature, non-bond energy versus temperature, and diffusion coefficient versus temperature, and compared with the experimental values. It was found that the melting point values obtained from the three relationships were in good agreement with the experimentally measured melting points with little error. The interactions between MDNI/MTNP were analyzed by binding energy and RDF, and the results showed that, as the temperature increased, the intermolecular interactions weakened, the binding energy decreased, and the stability of the system decreased. The comprehensive results show that mixture 4 (MDNI/MTNP = 60/40) has a low melting point value and good compatibility, and the detonation velocity and density are improved compared with TNT and MDNI, which is expected to be further applied in melt-cast explosives.

Exploration of low-melting energetic compounds: influence of substituents on melting points

The substituent effect of low melting point compounds reduces sensitivity and improves explosive performance.

Efficient synthesis of N-methyltetranitropyrrole: A stable, insensitive and high energy melt-castable material

1-Methyl-2,3,4,5-tetranitropyrrole is the first pyrrole based stable and insensitive high energy density material at par or slightly better than RDX.

5,6-Di(2-fluoro-2,2-dinitroethoxy)furazano[3,4-b]pyrazine: a high performance melt-cast energetic material and its polycrystalline properties

A new high-energetic and insensitive melt-cast material was synthesized, and its polycrystalline properties were characterized and theoretically investigated.

Energetic π-conjugated vinyl bridged triazoles: a thermally stable and insensitive heterocyclic cation

A new family of vinyl bridged energetic nitrogen-rich salts with diversiform crystal-packing, good thermal stabilities, detonation performance and insensitive properties were synthesized and fully characterized.

A melt castable energetic cocrystal

Cocrystallization leads to melt-state stabilization of the thermally unstable energetic 4-amino-3,5-dinitropyrazole, allowing for production of a melt castable cocrystalline explosive.