A nonequilibrium kinetic model of high-resolution vibrational energy transfer in RDX from selective IR excitation.

In this paper, we develop a model based on a second quantization-with anharmonic phonon scattering and the phonon Boltzmann transport equation-to study precise high-resolution nonequilibrium vibrational energy transfer (VET) under selective phonon excitation in cyclotrimethylene trinitramine. We simulate mid-infrared pump-probe spectroscopy and observe a prompt appearance (<1 ps) of broad-spectrum intensity, which agrees well with experimental data in the literature. The selective excitation of phonons at different frequencies reveals distinct VET pathways and the kinetic evolution of mode occupations as the system reaches a new equilibrium temperature.

Sequential, Electrochemical-Photochemical Synthesis of 1,2,4-Triazolo-[4,3-a]pyrazines.

1,2,4-triazolo-[4,3-a]pyrazine was prepared via a two-step electrochemical, photochemical process. First, a 5-substituted tetrazole is electrochemically coupled to 2,6-dimethoxypyrazine to yield 1,5- and 2,5- disubstituted tetrazoles. Subsequent photochemical excitation of the 2,5-disubstituted tetrazole species using an ultraviolet lamp releases nitrogen gas and produces a short-lived nitrilimine intermediate.

Investigation into a Conformationally Locked -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.

Energetic Salts of a Tri-Annulated Ring System.

Energetic salts of a triazolyl-tetrazinyl-aminotriazine ring system are characterized as energetic materials. Previously known sodium, ammonium, hydrazinium, barium, and triaminoguanidinium salts as well as the parent free acid were synthesized according to literature procedures and fully characterized for the first time as energetic materials. The silver salt was also synthesized and characterized for the first time as an energetic material.

Exploring Cuneanes as Potential Benzene Isosteres and Energetic Materials: Scope and Mechanistic Investigations into Regioselective Rearrangements from Cubanes.

Cuneane is a strained hydrocarbon that can be accessed via metal-catalyzed isomerization of cubane. The carbon atoms of cuneane define a polyhedron of the point group with six faces─two triangular, two quadrilateral, and two pentagonal. The rigidity, strain, and unique exit vectors of the cuneane skeleton make it a potential scaffold of interest for the synthesis of functional small molecules and materials.

Approach to High-Nitrogen Materials with Dual-Use Properties via Tetraaza-Nazarov Cyclization.

In this report, we describe the application of an electrocyclization toward the synthesis of a high-nitrogen heterocycle. It entails the synthesis of a novel, high-nitrogen, 2-3-disubstituted tetrazolium salt via the tetraaza-Nazarov cyclization (4π electrocyclization) of 3-bromo-1,5-bis(3-nitro-1,2,4-triazole-1-5-yl)-formazan (BDNF). The cyclization takes place under mild conditions using the oxidant phenyliodine(III) diacetate (PIDA).

Single-Crystal Diffraction, Raman Spectroscopy, and Density Functional Theory of DTO [-(1,7-Dinitro-1,2,6,7-tetrahydro-[1,3,5]triazino[1,2-][1,3,5]oxadiazin-8(4H)-ylidene)nitramide].

A combined experimental and modeling study of energetic compound -(1,7-dinitro-1,2,6,7-tetrahydro-[1,3,5]triazino[1,2-][1,3,5]oxadiazin-8(4H)-ylidene)nitramide [CHNO, (DTO)] has been performed. We report its crystal structure, solid-phase heat of formation, and its vibrational and electronic structure obtained by single-crystal X-ray diffractometry, Raman spectroscopy, and density functional theory (DFT). DTO exhibits two adjoining six-membered rings, a triazine ring (CN) and an oxadiazine ring (CNO) ring containing two nitro functional groups and one nitroamino group.

3-Methyl-1,2,3-triazolium-1-dinitromethylylide and the strategy of zwitterionic dinitromethyl groups in energetic materials design.

3-Methyl-1,2,3-triazolium-1-dinitromethylylide, an exemplary zwitterionic energetic molecule, is the first fully-studied energetic material making use of the zwitterionic dinitromethyl functional group. This compound has impact and friction sensitivities of 8 J and 144-160 N respectively with a detonation velocity of 8162 m s.

4,4'-Dinitrimino-5,5'-diamino-3,3'-azo-bis-1,2,4-triazole: A High-Performing Zwitterionic Energetic Material.

Mixed acid nitration of electrochemically generated 4,4',5,5'-tetraamino-3,3'-azo-bis-1,2,4-triazole (TAABT) generated the novel energetic material 4,4'-dinitrimino-5,5'-diamino-3,3'-azo-bis-1,2,4-triazole (DNDAABT). Various energetic salts of DNDAABT were also prepared and characterized to confirm their structures and determine their explosive sensitivities and performances. The free acid of DNDAABT exists as a zwitterionic molecule that leads to a high-density material with predicted detonation parameters comparable to those of TKX-50 (bis(hydroxylammonium) 5,5'-bis(tetrazolate-1 -oxide).

1,3,4,5-Tetraamino-1,2,4-triazolium Cation: An Energetic Moiety.

The amination of 3,4,5-triamino-1,2,4-triazole with -tosylhydroxylamine yielded the nitrogen-rich 1,3,4,5-tetraamino-1,2,4-triazolium cation as its tosylate salt. Subsequent metathesis reactions produced energetic salts with various energetic anions, including perchlorate, nitrate, nitrotetrazolate, and bistetrazolate diolate. All energetic salts possess relatively high heats of formation, thermal sensitivities, and detonation velocities and pressures.

Synthesis and Characterization of the Potential Melt-Castable Explosive 3-(1,2,4-Oxadiazolyl)-5-Nitratomethyl Isoxazole.

The synthesis of 3-(1,2,4-oxadiazolyl)-5-nitratomethyl isoxazole (C H N O ), its physical properties, and its theoretical performances are described. This energetic material was found to have a melting point range of 76.6-79.

Heterocyclic Nitrilimines and Their Use in the Synthesis of Complex High-Nitrogen Materials.

We show the ability of a nitrilimine prepared from 3-amino-5-nitro-1,2,4-triazole to undergo various cyclization and rearrangement reactions, giving a beautiful diversity of nitrogen-rich heterocyclic products. This chemistry includes the first cyclization of a nitrilimine with a diazonium species, giving a tetrazole, a previously unknown transformation, as well as leading to the creation of several new energetic materials with backbones not available by traditional techniques. New materials prepared were characterized both chemically (multinuclear NMR, IR, mass spectrometry, and elemental analysis) and energetically, with sensitivities and performances reported.

Tailoring Energetic Sensitivity and Classification through Regioisomerism.

The azo-coupling of 1- and 2-amino-4-nitro-1,2,3-triazole yielded two new energetic compounds whose detonation properties compete with that of HMX. Though the calculated performances are impressive, the regioisomers have differing sensitivities and detonation behavior. One has sensitivities similar to a very sensitive primary explosive, while the other has sensitivities more comparable to a sensitive secondary explosive.

Heuristics for chemical species identification in dense systems.

A new approach to identify chemical species from molecular dynamics (MD) simulations of reacting materials under extreme temperatures and pressures is presented. The approach is based on bond-distance and vibrational criteria, derived from the examination of atomic behavior during a density functional theory MD simulation of an overdriven shock of the explosive pentaerythritol tetranitrate. For comparison, the trajectory was analyzed using popular bonding criteria commonly used in analysis of reactive MD simulations, including distance, distance-time, and bond-order criteria.

Sensitive Energetics from the -Amination of 4-Nitro-1,2,3-Triazole.

Energetic N-amino-C-nitro compounds 1-amino-4-nitro-1,2,3-triazole and 2-amino-4-nitro-1,2,3-triazole are characterized for the first time as energetic materials. These compounds were characterized chemically by nuclear magnetic resonance (NMR), Infrared spectroscopy and X-ray crystallography. Compounds were also characterized energetically by differential scanning calorimetry (DSC), impact, and friction and found to possess sensitivities and performances classifying them as primary explosives with PETN-like performance.

Tetrazole Azasydnone (C N O H) And Its Salts: High-Performing Zwitterionic Energetic Materials Containing A Unique Explosophore.

This work reports the first compound containing both a tetrazole and an azasydnone ring, a unique energetic material. Several energetic salts of the tetrazole azasydnone were synthesized and characterized, leading to the creation of new secondary and primary explosives. Molecular structures are confirmed by H and C NMR, IR spectroscopy, and X-ray crystallographic analysis.

Synthesis of Erythritol Tetranitrate Derivatives: Functional Group Tuning of Explosive Sensitivity.

Understanding the factors that affect explosive sensitivity is paramount to the safe handling and development of new explosives molecules. Erythritol tetranitrate (ETN) is an explosive that recently has attracted significant attention in the explosives community because of its ease of synthesis and physical properties. Herein, we report the synthesis of ETN derivatives using azide, nitramine, and nitrate ester functional groups.

Bis(Nitroxymethylisoxazolyl) Furoxan: A Promising Standalone Melt-Castable Explosive.

The synthesis and crystal structure of the heterocyclic explosive bis(nitroxymethylisoxazolyl) furoxan, C H N O , are described. In addition, we report its physical properties and theoretical performance. This material was found to exhibit standalone melt-castable explosive properties, with a melting point of 89.

Bis(1,2,4-oxadiazolyl) Furoxan: A Promising Melt-Castable Eutectic Material of Low Sensitivity.

A scalable synthesis of bis(1,2,4-oxadiazoyl) furoxan, C H N O , its physical properties, and its theoretical performance values are described. Previous attempts to synthesize this compound required expensive reagents, and/or time-consuming synthesis processes and low overall yields. In addition to disclosing a streamlined synthesis of bis(1,2,4-oxadiazolyl) furoxan, we report its molecular configuration and crystal structure, as well as its correct melting point.

Impact of Stereo- and Regiochemistry on Energetic Materials.

The synthesis, physical properties, and calculated performances of six stereo- and regioisomeric cyclobutane nitric ester materials are described. While the calculated performances of these isomers, as expected, were similar, their physical properties were found to be extremely different. By alteration of the stereo- and regiochemistry, complete tunability in the form of low- or high-melting solids, stand-alone melt-castable explosives, melt-castable explosive eutectic compounds, and liquid propellant materials was obtained.

Ray tracing calculations in simulated propellant flames with detailed chemistry.

Optical measurements in propellant flames are necessary to understand the combustion physics, yet these conditions provide challenges in probing the flame and may introduce uncertainty into the measurement. This work reports the use of simulations of an ammonium perchlorate propellant flame with finite rate chemistry to understand the role of ammonium perchlorate particle size and pressure on the uncertainty of imaging-based measurements on propellant flames. A two-dimensional ray tracing code was developed to incorporate the effects of the species concentration and temperature gradients on ray refraction within propellant flames.

Density Functional Theory and Experimental Studies of the Molecular, Vibrational, and Crystal Structure of Bis-Oxadiazole-Bis-Methylene Dinitrate (BODN).

Density function theory (DFT) and experimental characterization of energetic materials play important roles in understanding molecular structure-property relations and validating models for their predictive capabilities. Here, we report our modeling and experimental results on the molecular, vibrational, and crystal structure of energetic bis-oxadiazole-bis-methylene dinitrate (BODN) obtained by molecular DFT (M-DFT) at the B3LYP- 6-31G** level, crystal DFT (C-DFT) using the Perdew-Burke-Ernzerhof functional optimized with norm-conserving pseudopotentials, X-ray diffractometry, infrared and Raman spectroscopy, and thermogravimetric analysis. Both models predict well the experimental bond lengths, bond angles, and torsion angles of BODN.

Simple and Efficient Synthesis of Explosive Cocrystals containing 3,5-Dimethylpyrazol-1-yl-substituted-1,2,4,5-tetrazines.

The reaction of 3,4-dinitropyrazole, 5-nitrotetrazole, or 4-nitro-1,2,3-triazole with 1,2,4,5-tetrazines substituted with 3,5-dimethylpyrazolyl (dmp) groups results in energetic cocrystals after 1 minute of reflux and cooling to room temperature in yields of 89-92 %. Hydrogen-bonding between the dmp group to the N-H of the energetic heterocycles are the predominant interaction that stabilizes the new cocrystals. Each cocrystal packs in a different lattice structure and the cocrystals with sheet-like and herring-bone crystal packing orientations are less sensitive than the cocrystal with the interlocked structure.