Approaches to 1,4-Disubstituted Cubane Derivatives as Energetic Materials: Design, Theoretical Studies and Synthesis

Novel 1,4-disubstituted cubane derivatives have been designed and selected ones have been successfully synthesized and characterized by various analytical and spectroscopic techniques, including single-crystal X-ray analysis. A detailed computational study at B3LYP/6-311++G(d,p) level of theory revealed that all newly designed 1,4-disubstituted cubane derivatives possess higher densities, higher density-specific impulse and superior ballistic properties when compared to conventional fuels, for example, RP-1. These compounds also exhibit acceptable kinetic and thermodynamic stabilities which were evaluated in terms of their HOMO-LUMO energy gap and bond dissociation energies, respectively, and are superior to TEX and many other compounds containing explosophoric groups. These results provide novel insights into the possible application of cubane-based energetic materials.

Guanidinium 5,5'-Azotetrazolate: A Colorful Chameleon for Halogen-Free Smoke Signals

A progressive halogen‐free multicolored smoke system to obtain white, red, violet, yellow, green, and blue smoke color is presented. The nitrogen‐rich salt guanidinium 5,5′‐azotetrazolate (GZT), which is usually applied as a gas generator or propellant ingredient, was combined with different smoke dyes (Solvent Red 1, Solvent Violet 47, Solvent Green 3, Solvent Yellow 33). These two‐component smoke mixtures offer a convenient and safe multicolor approach without the need for potassium chlorate or any other hazardous material. The common smoke characteristics with respect to burn time/burn rate, yield factor, transfer rate, as well as energetic properties were determined and compared with classic chlorate‐based formulations currently used. To the best of our knowledge, nothing comparable is known in the literature and a completely new research area in modern pyrotechnics is opened.

A Synthetic Route Toward Tetrazoles: The Thermolysis of Geminal Diazides

A new synthetic route toward the tetrazole core is described, which is based on a general fragmentation pattern that was found in a range of compounds featuring geminal diazido units. Through a simple two-step procedure, the synthesis of structurally diverse target compounds containing a tetrazole, such as tetrazoloquinoxalinones, benzoylaryltetrazoles, tetrazolotriazinones, and tetrazoloazepinones, was easily accomplished, starting from broadly accessible substrates (i.e., oxindoles, diarylethanones, pyrazolones, and phenanthrols). The initial oxidative diazidation reaction with iodine and sodium azide under mild conditions is followed by the thermal fragmentation under microwave irradiation, leading to the tetrazole products. Noteworthy, an experimental solution is presented in which the potentially hazardous diazide intermediates are not isolated and the concentration of crude reaction mixtures containing diazides is not required to achieve the tetrazoles in good yields.

Pyrazole-Tetrazole Hybrid with Trinitromethyl, Fluorodinitromethyl, or (Difluoroamino)dinitromethyl Groups: High-Performance Energetic Materials

High-nitrogen-content compounds have attracted great scientific interest and technological importance because of their unique energy content, and they find diverse applications in many fields of science and technology. Understanding of structure-property relationship trends and how to modify them is of paramount importance for their further improvement. Herein, the installation of oxygen-rich modules, C(NO₂ )₃ , C(NO₂ )₂ F, or C(NO₂ )₂ NF₂ , into an endothermic framework, that is, the combination of a nitropyrazole unit and tetrazole ring, is used as a way to design novel energetic compounds. Density, oxygen balance, and enthalpy of formation are enhanced by the presence of these oxygen-containing units. The structures of all compounds were confirmed by XRD. For crystal packing analysis, it is proposed to use new criterion, Δ_OED , that can serve as a measure of the tightness of molecular packing upon crystal formation. Overall, the materials show promising detonation and propulsion parameters.

Prospective Symbiosis of Green Chemistry and Energetic Materials

A global increase in environmental pollution demands the development of new "cleaner" chemical processes. Among urgent improvements, the replacement of traditional hydrocarbon-derived toxic organic solvents with neoteric solvents less harmful for the environment is one of the most vital issues. As a result of the favorable combination of their unique properties, ionic liquids (ILs), dense gases, and supercritical fluids (SCFs) have gained considerable attention as suitable green chemistry media for the preparation and modification of important chemical compounds and materials. In particular, they have a significant potential in a specific and very important area of research associated with the manufacture and processing of high-energy materials (HEMs). These large-scale manufacturing processes, in which hazardous chemicals and extreme conditions are used, produce a huge amount of hard-to-dispose-of waste. Furthermore, they are risky to staff, and any improvements that would reduce the fire and explosion risks of the corresponding processes are highly desirable. In this Review, useful applications of almost nonflammable ILs, dense gases, and SCFs (first of all, CO₂ ) for nitration and other reactions used for manufacturing HEMs are considered. Recent advances in the field of energetic (oxygen-balanced and hypergolic) ILs are summarized. Significant attention is paid to the SCF-based micronization techniques, which improve the energetic performance of HEMs through an efficient control of the morphology and particle size distribution of the HEM fine particles, and to useful applications of SCFs in HEM processing that makes them less hazardous.

Insensitive energetic 5-nitroaminotetrazolate ionic liquids

Combustible 5-nitroaminotetrazolate-based energetic ionic liquids with high stability as well as environmentally friendly decomposition gases were prepared and fully characterized.

Synthesis and characterization of a new family of energetic salts based on a guanidinium cation containing a picryl moiety

A series of energetic salts based on a guanidinium cation containing a picryl moiety was successfully synthesized and characterized.

Energetic N-trinitroethyl-substituted mono-, di-, and triaminotetrazoles

A series of dense energetic N-trinitroethyl-substituted mono-, bis-, and tri-5-aminotetrazoles were obtained by reacting primary amines with in situ generated cyanogen azide, followed by the trinitroethyl functionalization that involves a condensation of a hydroxymethyl intermediate (prepared by a reaction with formaldehyde) with trinitromethane. These compounds were fully characterized by using multinuclear NMR spectroscopy, IR, elemental analysis, differential scanning calorimetry (DSC), and, in one case with 9, with single-crystal XRD analysis. The heats of formation for all compounds were calculated with Gaussian 03 and then combined with experimental densities to determine the detonation pressures (P) and velocities (D(v)) of the energetic materials. Interestingly, most of them exhibited high density, good thermal stability, acceptable oxygen balance, positive heat of formation, low impact sensitivity, and excellent detonation properties, which highlighted their practical application potentials as a fascinating class of highly energetic materials.

Nitramines with varying sensitivities: functionalized dipyrazolyl-N-nitromethanamines as energetic materials

1,3-Dichloro-2-nitro-2-azapropane is an excellent precursor to dense energetic functionalized dipyrazolyl-N-nitromethanamines. This new family of energetic compounds was fully characterized by using (1)H, (13)C, and (15)N NMR and IR spectroscopy, differential scanning calorimetry, elemental analysis, and impact sensitivity tests. Additionally, single-crystal X-ray structuring was done for 3 and 5·CH3CN, which gave insight into structural characteristics. The experimentally determined densities of 2-9 fall between 1.69 and 1.90 g cm(-3). Heats of formation and detonation properties were calculated by using Gaussian 03 and EXPLO5 programs, respectively. The influence of different energetic moieties on the structural and energetic properties was established theoretically.