Reliable Prediction of Shock Sensitivity of Energetic Compounds based on Small‐scale Gap Test through Their Electric Spark Sensitivity

The sensitivity of an energetic compound gives its vulnerability to accidental detonation, which is caused by an unintended stimulus. Shock and electric spark sensitivities of energetic compounds are two important sensitivity parameters for assessment of their safety in working places. Several correlations are introduced for reliable prediction of shock sensitivities of energetic compounds at 90, 95, and 98 % of theoretical maximum density (TMD) according to NSWC using Navy small‐scale gap test through their electric spark sensitivities. For 11 explosives, where experimental data of both shock and electric spark sensitivities were available, the predicted results at 90 % of TMD are compared with the quantum mechanical approach. The root‐mean‐square (rms) deviations of the new and complex quantum mechanical methods at 90 % TMD are 2.38 and 3.95 kbar, respectively, which confirmed the high reliability of the new method. For high explosives with 90, 95, and 98 % TMD, it will be shown that the predicted results of the new method are also much more reliable than one of the best available empirical approaches. A correlation between shock sensitivities on the basis of aluminum gaps with different thicknesses and the pressure required to initiate material pressed to 90 % TMD is also derived.     

Fully C/N‐Polynitro‐Functionalized 2,2′‐Biimidazole Derivatives as Nitrogen‐ and Oxygen‐Rich Energetic Salts

Through the use of a fully C/N‐functionalized imidazole‐based anion, it was possible to prepare nitrogen‐ and oxygen‐rich energetic salts. When N,N‐dinitramino imidazole was paired with nitrogen‐rich bases, versatile ionic derivatives were prepared and fully characterized by IR, and ¹H, and ¹³C NMR spectroscopy and elemental analysis. Both experimental and theoretical evaluations show promising properties for these energetic compounds, such as high density, positive heats of formation, good oxygen balance, and acceptable stabilities. The energetic salts exhibit promising energetic performance comparable to the benchmark explosive RDX (1,3,5‐trinitrotriazacyclohexane).     

1,2,4‐Triazole Links and N‐Azo Bridges Yield Energetic Compounds

Triazole links and polynitropyrazole rings give rise to compounds with energetic properties. These materials were fully characterized by NMR and infrared spectroscopy, elemental analysis, and differential scanning calorimetry (DSC). In addition, the structures of compounds 5 and 8 were confirmed by single‐crystal X‐ray diffraction analysis. Detonation properties, calculated from heats of formation and experimental densities, thermal stabilities, and impact and friction sensitivities support the potential use of these materials for explosive applications.     

Energetic 4,4′‐Oxybis[3,3′‐(1‐hydroxytetrazolyl)]furazan and Its Salts

Energetic compounds that incorporate multiple nitrogen‐rich heterocycles are of great interest for high‐density energetic materials. A facile synthetic strategy to combine an oxy bridge and furazan groups, as well as tetrazole‐ols, into a molecule ( 5 ) was found. Some energetic salts based on 5 were prepared by neutralization. All of the compounds were fully characterized. Additionally, the structure of 7 has been elucidated by single‐crystal XRD analysis. Physicochemical and energetic properties were also studied; these show that these newly designed energetic salts exhibit good thermal stabilities. Hydroxylammonium salt ( 6 ) has a detonation performance and sensitivities comparable with those of 1,3,5‐trinitroperhydro‐1,3,5‐triazine (RDX).     

Synthesis,thermal stability,heats of formation,and explosive properties of cyano-substituted di-, tri-, and tetraazidopyridines

A method of synthesis of 2,6-diazido-3,5-dicyanopyridine, 2,4,6-triazido-3,5-dicyanopyridine, and 2,3,4,5-tetraazido-6-cyanopyridine was developed. The heats of formation and explosive properties of compounds obtained were determined; kinetics and the composition of the gaseous thermolysis products were studied. The replacement of endocyclic nitrogen atoms by C-CN fragments in the aromatic ring of polyazides strongly reduces the explosive risk of these compounds with retention of the energetic properties of the molecules.     

叠氮多硝基化合物的合成

在成功制备出含能增塑剂－1,11－二叠氮基－2,2,10,10－四硝基－5,7－二氧杂－十一烷的基础上,我们合成出它的一些衍生物,如1,1,1,9,9,9－六硝基－4,6－二氧杂－壬烷,1,4－二叠氮基－2－,2－二硝基丁烷,5,5－二硝基1,3－二氧杂－环庚烷和1－叠氮基－3,3,3－三硝基丙烷,并讨论了它们的性质。     

Energetic Trinitro‐ and Fluorodinitroethyl Ethers of 1,2,4,5‐Tetrazines

Several new energetic ethyl ethers of 1,2,4,5‐tetrazine have been synthesized. These molecules display good thermal stability, good oxygen balance, and high densities. Included in these studies are a 2,2,2‐trinitroethoxy 1,2,4,5‐tetrazine and two fluorodinitroethoxy 1,2,4,5‐tetrazines. One of these compounds was converted into the di‐N‐oxide derivative. The sensitivity of these materials towards destructive stimuli was determined, and overall the materials show promising energetic performance properties.     

Towards a Fundamental Understanding of Urea and Thiourea inclusion Compounds

This article reviews some of the fundamental scientific issues associated with solid inclusion compounds, and describes the approaches and strategies that may be used to investigate the structural, dynamic and chemical properties of these systems. Two particular families of solid organic inclusion compounds - the urea and thiourea inclusion compounds - are highlighted. In order to understand the fundamental nature of these solids, it has been necessary to apply a wide range of experimental, computational and theoretical approaches. Each technique provides information on a different aspect of the solid, and the combined information obtained from these complementary approaches allows a comprehensive understanding to be established. Several issues of contemporary interest for urea and thiourea inclusion compounds are described, and the approaches that have been taken towards a fundamental understanding of these systems are explained.     

Dimethoxycarbonyl Groups Surrounding a Symmetric Diaminobistetrazole Ring: Exploring New Green Energetic Materials

A novel oxygen‐containing dimethoxycarbonyl diaminobistetrazole ( 1 ) was synthesized via a facile strategy. The sodium salt ( 2 ) based on this ligand was prepared and these two compounds were fully characterized by using elemental analysis, IR and mass spectrometry and single‐crystal X‐ray diffraction. Their density, heats of formation, thermal stability and sensitivity, as well as the energetic properties from EXPLO5 code were investigated. These newly synthesized compounds possess high positive heats of formation and detonation heats. Compound 1 exhibits good detonation performance and acceptable stability, and might be a potential eco‐friendly alternative of lead azide. The present study contributes to the development of tetrazole derivatives as new energetic materials.     

3,6‐Dinitropyrazolo[4,3‐c]pyrazole‐Based Multipurpose Energetic Materials through Versatile N‐Functionalization Strategies

A family of 3,6‐dinitropyrazolo[4,3‐c]pyrazole‐based energetic compounds was synthesized by using versatile N‐functionalization strategies. Subsequently, nine ionic derivatives of the N,N′‐(3,6‐dinitropyrazolo[4,3‐c]pyrazole‐1,4‐diyl)dinitramidate anion were prepared by acid‐base reactions and fully characterized by infrared, multinuclear NMR spectra, and elemental analysis. The structures of four of these compounds were further confirmed by single‐crystal X‐ray diffraction. Based on their different physical and detonation properties, these compounds exhibit promising potential as modern energetic materials and can be variously classified as green primary explosives, high‐performance secondary explosives, fuel‐rich propellants, and propellant oxidizers.     

A New Method for Assessment of Performing Mechanical Works of Energetic Compounds by the Cylinder Test

A new method is introduced for assessment of performing mechanical works of energetic compounds by cylinder wall velocities of CHNOFCl energetic compounds on the basis of the cylinder test. Four suitable decomposition paths are used to evaluate the number of moles of gaseous detonation products per gram of explosive, the average molecular weight of these gases, and the heat of detonation in calories per gram by considering different decomposition products HF, HCl, CO, N₂, H₂O, H₂, and CO₂. For CHNO and fluoro energetic compounds, the predicted cylinder wall velocities of these compounds give more reliable results than one of the best available empirical methods. The predicted root mean square (rms) deviations of cylinder wall velocities of the new model for some chloro explosives at actual radial expansions 0.6 and 1.9 mm are 0.010 and 0.062 km · s^–1, which show high reliability of the new method.     

Polynitro-Functionalized Dipyrazolo-1,3,5-triazinanes: Energetic Polycyclization toward High Density and Excellent Molecular Stability

A new fused N-heterocyclic framework, dipyrazolo-1,3,5-triazinane, was synthesized and the physiochemical properties of its derivatives were investigated to evaluate the integrated energetic performance. In contrast to 1,3,5-trinitro-1,3,5-triazinane (RDX) featuring a distorted chair confirmation, polynitro-functionalized dipyrazolo-1,3,5-triazinanes have nearly planar backbones, thereby enhancing the density and thermal stability. Among these new energetic tricyclic compounds, 5 a and 12 show favorable crystal densities of 1.937 g cm⁻³ and 1.990 g cm⁻³ at 150 K, respectively, which rank highest in triazinane-based energetic compounds. Additionally, this synthetic approach was carried out to form seven-membered and eight-membered rings, giving rise to tetranitro dipyrazolo-1,3,5-triazepane ( 5 b ) and tetranitro dipyrazolo-1,3,5-triazocane ( 5 c ), respectively.     

Synthesis of a One‐dimensional Coordination Polymer Based on Copper(II) Nitrate and 1,2‐Bis(5‐monomethylhydrazinyl‐1H‐tetrazolyl)ethane

A one‐dimensional coordination polymer based on copper(II) nitrate and 1,2‐bis(5‐monomethylhydrazinyl‐1H‐tetrazolyl)ethane as ligand was prepared. The thermal and physical stability was determined by differential scanning calorimetry and BAM methods. The polymer was investigated by vibrational spectroscopy and single X‐ray diffraction. Moreover, the ligand itself and the 1,2‐bis(1H‐tetrazolyl)ethane were characterized as energetic material by bomb calorimetric measurements along with calculations using the EXPLO5 software. Both compounds have moderate energetic properties along with a high thermal and physical stability. These findings render these compounds into promising environment friendly gas generating agents.     

N‐Diazo‐Bridged Nitroazoles: Catenated Nitrogen‐Atom Chains Compatible with Nitro Functionalities

N‐diazo‐bridged azoles were synthesized based on oxidative coupling of N‐aminoazoles. Incorporation of extended catenated nitrogen‐atom chains with nitro groups led to compounds with favorable functional compatibilities. This combination gives rise to a series of high‐density energetic materials (HEDMs) with high heats of formation, enhanced densities, positive oxygen balances, and good detonation properties while retaining excellent thermal stabilities and relatively low impact sensitivities. Calculated and experimental studies showed the delicate balance between the length of the nitrogen atom chain, energetic performance, and inherent stability, thus, providing a promising strategy for designing advanced energetic materials.     

Searching for a new family of modified CL-20 cage derivatives with high energy and low sensitivity

A new family of energetic caged compounds was designed by introducing -NH- into the CL-20 skeleton and their energetic properties and impact sensitivity were investigated by using density functional theory. The results indicate that favorable substitution positions of the amine groups in the skeleton is helpful for increasing the heats of formation. Most of the seven compounds have high crystal densities above 1.9 g/cm³. Five compounds have the predominant detonation properties over CL-20. The derivatives with one NH₂ group have lower impact sensitivity than those with two NH₂ groups. Taking the detonation performance and impact sensitivity into consideration, four compounds may be selected as the potential candidates of high energy density compounds.     

4,5-Dicyano-1,2,3-Triazole—A Promising Precursor for a New Family of Energetic Compounds and Its Nitrogen-Rich Derivatives: Synthesis and Crystal Structures

The nitrogen-rich compounds and intermediates with structure of monocyclic, bicyclic, and fused rings based on 1,2,3-triazole were synthesized and prepared by using a promising precursor named 4,5-dicyano-1,2,3-triazole, which was obtained by the cyclization reaction of diaminomaleonitrile. Their structure and configurational integrity were assessed by Fourier transform-infrared spectroscopy (FT-IR), mass spectrometry (MS), and elemental analysis (EA). Additionally, fourteen compounds were further confirmed by X-ray single crystal diffraction. Meanwhile, the physical properties of four selected compounds (3·H₂O, 6·H₂O, 10·H₂O, and 16) including thermal stability, detonation parameters, and sensitivity were also estimated. All these compounds could be considered to construct more abundant 1,2,3-triazole-based neutral energetic molecules, salts, and complex compounds, which need to continue study in the future in the field of energetic materials.     

Polynitro‐Functionalized Dipyrazolo‐1,3,5‐triazinanes: Energetic Polycyclization toward High Density and Excellent Molecular Stability

A new fused N‐heterocyclic framework, dipyrazolo‐1,3,5‐triazinane, was synthesized and the physiochemical properties of its derivatives were investigated to evaluate the integrated energetic performance. In contrast to 1,3,5‐trinitro‐1,3,5‐triazinane (RDX) featuring a distorted chair confirmation, polynitro‐functionalized dipyrazolo‐1,3,5‐triazinanes have nearly planar backbones, thereby enhancing the density and thermal stability. Among these new energetic tricyclic compounds, 5 a and 12 show favorable crystal densities of 1.937 g cm⁻³ and 1.990 g cm⁻³ at 150 K, respectively, which rank highest in triazinane‐based energetic compounds. Additionally, this synthetic approach was carried out to form seven‐membered and eight‐membered rings, giving rise to tetranitro dipyrazolo‐1,3,5‐triazepane ( 5 b ) and tetranitro dipyrazolo‐1,3,5‐triazocane ( 5 c ), respectively.     

Experimental and Theoretical Studies on Some Energetic Functionalized Trimethylamine Derivatives

The synthesis and structural properties (from X‐ray diffraction or B3LYP/6‐31G(d) calculations) of three energetic compounds derived from tris(chloromethyl)amine and of tris(chloromethyl)amine itself were investigated and compared to those of compounds with similar structures. The compounds have almost planar NC₃ units at their amine center, and the substituents bound to the CH₂ groups tend to be reactive towards further substitution. Multiple hyperconjugation was used to explain these observations.     

Alkyl-Bridged Nitropyrazoles – Adjustment of Performance and Sensitivity Parameters

Starting from 3,5-dinitro-4-methylaminopyrazole ( 2 ), six different energetic salts and three new derivatives of methylene bridged nitropyrazoles were synthesized. The derivatives bear a methylamino ( 4 ), methylnitramino ( 5 ), and azido group ( 7 ). All compounds were intensively characterized using single crystal X-ray diffraction, multinuclear NMR spectroscopy, IR spectroscopy, mass spectrometry, elemental analysis and DTA/TGA measurements. The sensitivities were determined according to BAM standard methods and the energetic properties calculated using the EXPLO5 code. The energetic salts were compared with each other and with ANTA in terms of their energetic properties. On the basis of the methyl- and ethyl bridged derivatives, it was shown how the introduction of methylamino ( 4 ) and methylnitramino ( 5 ) groups in an alkyl-bridged nitropyrazole system modify its properties (performance & sensitivities). In addition, azido compound 7 was contrasted with its literature-known constitutional isomer and investigated for its suitability as a potential metal-free primary explosive.     

High-pressure studies of pharmaceutical compounds and energetic materials

The effects of high pressure on pharmaceutical compounds and energetic materials can have important implications for both the properties and performance of these important classes of material. Pharmaceutical compounds are frequently subjected to pressure during processing and formulation, causing interconversion between solid forms that may affect properties such as solubility and bio-availability. Energetic materials experience extremes of both pressure and temperature under conditions of detonation and deflagration, causing changes in properties such as sensitivity to shock and chemical reactivity. This tutorial review outlines the various methods used to study these materials at high pressure, describes how pressure can be used to explore polymorphism, and provides examples of compounds that have been studied at high pressure.