Construction of Nitrogen-Rich Energetic Isomers Containing Multiple Hydrogen Bond Networks

Nitrogen-rich energetic materials have been the focus of a few studies on their isomers. Novel nitrogen-rich energetic compounds TZ, DTZ, and NTZ were synthesized through simple steps. The hydrogen bond networks significantly enhanced their properties (TZ, Td = 290 °C and Dv = 8370 m s-1; DTZ, Td = 282 °C and Dv = 8392 m s-1; and NTZ, Td = 272 °C and Dv = 8762 m s-1), which are superior to their isomers. This realized a balance between the energy and stability of polycyclic tetrazoles, providing insights for high-performance energetic materials.

Investigation into a Conformationally Locked (Z)-Azidoxime

High nitrogen compounds find wide use in the development of new propellants and explosives as well as pharmaceutical chemistry as bioisosteres, bacterial stains, and antifungal agents. A class of underexplored high-nitrogen materials includes azidoximes and their 1-hydroxytetrazole isomers. Azidoximes possess an energetic azide group and are quite sensitive to impact, spark, and friction. Therefore, these materials are generated in situ and cyclized under mild acidic conditions to their 1-hydroxytetrazole isomers. Recently, we synthesized a novel 1,2,4-triazine-derived azidoxime; however, upon subjecting this material to established cyclization conditions, no reaction was observed, even after prolonged reaction times with heating. Additional 1,2,4-triazine-derived azidoximes also displayed a similar lack of reactivities. This observation led us to probe the reactivity of these materials with both a DFT investigation and crystallographically based electrostatic potential mapping. In all, the lack of reactivity toward cyclization was found to be due to an inability of 1,2,4-triazine-based azidoximes to isomerize into the reactive (E)-conformation, requiring an activation energy of 26.4 kcal mol-1.

Facile synthesis of thermally stable tetrazolo[1,5-b][1,2,4]triazine substituted energetic materials: synthesis and characterization

Various thermally stable energetic materials with high nitrogen content, low sensitivity and better detonation performance were synthesized. The versatile functionalization of 1,2,4-triazine involving the introduction of oxadiazole and tetrazole is discussed. All the compounds were fully characterized using IR, multinuclear NMR spectroscopy, elemental analysis, and high-resolution mass spectrometry. Compounds 2, 3, 9 and 12 were further verified using single-crystal X-ray analysis. Compound 9 can be considered a melt-cast explosive due to its lower onset melting temperature (112 °C). The detonation velocity, pressure, density, and heat of formation of all the synthesized compounds range between 7056 and 8212 m s^-1, 17.57 and 23.78 GPa, 1.70 and 1.81 g cm^-1, and 43 and 644 kJ mol^-1, respectively. Due to the high nitrogen percentage (53 to >72%), these molecules can be used in car airbag applications. Due to the high thermal stability (>220 °C) and lower sensitivity, these compounds can be potentially used as high-performing thermally stable secondary energetic materials.

Applications of alkyl orthoesters as valuable substrates in organic transformations, focusing on reaction media

In this review we focus on applications of alkyl orthoesters as valuable and efficient substrates to perform various classes of two-component and multi-component organic reactions. The article has classified them according to two aspects, which are: (i) a focus on the reaction medium (solvent-free conditions, aqueous media, and organic solvents); and (ii) an examination of product structures. Reaction accomplishment under solvent-free conditions is an eco-friendly process with the absence of volatile toxic solvents, which puts it in line with green chemistry goals. Water is an interesting choice in organic transformations due to its inexpensiveness and safety. The authors hope their assessment will help chemists to attain new approaches for utilizing alkyl orthoesters in various organic synthetic methods. The review covers the corresponding literature up to the beginning of 2020.

Properties and Promise of Catenated Nitrogen Systems As High-Energy-Density Materials

The properties of catenated nitrogen molecules, molecules containing internal chains of bonded nitrogen atoms, is of fundamental scientific interest in chemical structure and bonding, as nitrogen is uniquely situated in the periodic table to form kinetically stable compounds often with chemically stable N-N bonds but which are thermodynamically unstable in that the formation of stable multiply bonded N₂ is usually thermodynamically preferable. This unique placement in the periodic table makes catenated nitrogen compounds of interest for development of high-energy-density materials, including explosives for defense and construction purposes, as well as propellants for missile propulsion and for space exploration. This review, designed for a chemical audience, describes foundational subjects, methods, and metrics relevant to the energetic materials community and provides an overview of important classes of catenated nitrogen compounds ranging from theoretical investigation of hypothetical molecules to the practical application of real-world energetic materials. The review is intended to provide detailed chemical insight into the synthesis and decomposition of such materials as well as foundational knowledge of energetic science new to most chemists.

Structure and Thermal Properties of 2,2'-Azobis(1H-Imidazole-4,5-Dicarbonitrile)-A Promising Starting Material for a Novel Group of Energetic Compounds

A high-nitrogen compound, 2,2'-azobis(1H-imidazole-4,5-dicarbonitrile) (TCAD), was synthesized from commercially available 2-amino-1H-imidazole-4,5-dicarbonitrile. It was characterized with infrared and nuclear magnetic resonance spectroscopy. Its structure was determined by single crystal X-ray diffraction. The crystal of TCAD tetrahydrate is monoclinic, with space group P2₁/c with crystal parameters of a = 10.2935(2) Å, b = 7.36760(10) Å, c = 20.1447(4) Å, V = 1500.27(5) ų, Z = 4, and F(000) = 688. Computational methods were used in order to fully optimize the molecular structure, calculate the electrostatic potential of an isolated molecule, and to compute thermodynamic parameters. TCAD has very high thermal stability with temperature of decomposition at 369 °C. Kinetics of thermal decomposition of this compound were studied and apparent energy of activation as well as the maximum safe temperature of technological process were determined.

One-Pot Acid-Promoted Synthesis of 6-Aminopyrazolopyrimidines from 1H-Pyrazol-5-yl-N,N-dimethylformamidines or 5-Amino-1H-pyrazole-4-carbaldehydes with Cyanamide

A convenient and efficient one-pot acid-promoted synthesis of 6-aminopyrazolo[3,4-d]pyrimidine has been developed by treatment of 1H-pyrazol-5-yl-N,N-dimethylformamidines or 5-amino-1H-pyrazole-4-carbaldehydes with cyanamide (NH₂C≡N) in an acid-mediated solution. This synthetic route involves four steps of deprotection, imination, the key acid-promoted heterocyclization, and aromatization. On the basis of optimized studies, methanesulfonylchloride is considered to be the best solvent. Furthermore, the microwave-assisted synthetic technique was also carried out to improve the major product 6-aminopyrazolo[3,4-d]pyrimidines in this method. Moreover, our proposed mechanism was confirmed in this study, which demonstrates that N-[(5-amino-1,3-diaryl-1H-pyrazol-4-yl)methylene]cyanamide is the intermediate.

Synthesis of 3,5-ditetrazolyl-1,2,4-triazole-based complexes: a strategy for developing C–N-linked triheterocyclic energetic compounds

Two complexes based on the novel C–N-linked triheterocyclic compound 3,5-ditetrazolyl-1,2,4-triazole (DTT) were reported for the first time. The present study has contributed to the field of C–N-linked polyheterocyclic systems and has provided a new insight into the design and synthesis of new energetic materials.

Synthesis of high-performance insensitive energetic materials based on nitropyrazole and 1,2,4-triazole

A new family of symmetric nitropyrazole and 1,2,4-triazole derivatives and its energetic salts were obtained. The positive effect of ternary hydrogen bonds improve the performances of target compounds.

Materials with good energetic properties resulting from the smart combination of nitramino and dinitromethyl group with furazan

The combination of nitramino and dinitromethyl group with furazan gave novel energetic materials with good energetic properties.

Evaluation of thermal stability and acoustic fingerprint spectra of energetic 1,2,4-triazoles based on bond lengths of chemical substituents using pulsed photoacoustic technique

We investigated the effect of the bond lengths of the chemical substituents on the thermal stability of newly synthesized nitro rich 1,2,4-triazoles such as P-Me-DNPT, P-OMe-DNPT, and P-NH₂-DNPT using pulsed photoacoustic pyrolysis technique.

Crystal structure of 2-azido-1H-imidazole-4,5-di-carbonitrile

In the title compound, C5HN7, the nitrile and azido substituents are close to being coplanar with the central ring. Mol-ecules in the crystal are linked via an N-H⋯N hydrogen bond to a nitrile acceptor, forming a chain extending along the c-axis direction.

The nitration pattern of energetic 3,6-diamino-1,2,4,5-tetrazine derivatives containing azole functional groups

A study of nitration patterns was conducted on 3,6-diamino-1,2,4,5-tetrazines derivatives, revealing the specificity of their nitration, as well as the stability of the formed nitramines towards hydrolysis.

Structure and properties of 1-amino-2-nitroguanidinium nitrate

A nitrogen-rich energetic material 1-amino-2-nitroguanidinium nitrate was fully investigated.

Energetic salts prepared from phenolate derivatives

Energetic salts with 1 : 1, 2 : 1, and 3 : 1 charge ratios (cation : anion) based on various nitrogen-rich cations and phenolate anions have been synthesized by a straightforward and simple method.