A novel energetic cocrystal predicted to exhibit greater power and similar sensitivity to that of the current military standard explosive 1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX) is presented. The cocrystal consists of a 2:1 molar ratio of 2,4,6,8,10,4,6,8,10,, a powerful explosive too sensitive for military use, and HMX. A predicted detonation velocity 100 m/s higher than that of β-HMX, the most powerful pure form of HMX, was calculated for the cocrystal using Cheetah 6.0. In small-scale impact drop tests the cocrystal exhibits sensitivity indistinguishable from that of β-HMX. This surprisingly low sensitivity is hypothesized to be due to an increased degree of hydrogen bonding observed in the cocrystal structure relative to the crystals of pure HMX and CL-20. Such bonding is prevalent in this and other energetic cocrystals and may be an important consideration in the design of future materials. By being more powerful and safe to handle, the cocrystal presented is an attractive candidate to supplant the current military state-of-the-art explosive, HMX.

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▪ Abstract  Energetic materials are chemical compounds or mixtures that store significant quantities of energy. In this review, we explore recent approaches to property prediction and new material synthesis. We show how the successful design of new energetic materials with tailored properties is becoming a practical reality.

The most comprehensive approach to analyze and characterize energetic materials is suggested and applied to enable rational, rigorous design of novel materials and targeted improvements of existing materials to achieve desired properties. We report synthesis, characterization of the structure and sensitivity, and modeling of thermal and electronic stability of the energetic, heterocyclic compound, 3,4-bis(4-nitro-1,2,5-oxadiazol-3-yl)-1,2,5-oxadiazole-2-oxide (BNFF). The proposed novel, relatively simple synthesis of BNFF in excellent yields allows for an efficient scale up. Performing careful characterization indicates that these materials offer an unusual combination of properties and exhibit a relatively high energy density, high and controllable stability against decomposition, low melting temperature, and low sensitivity to initiation of detonation. First-principles calculations of activation barriers and reaction rate constants reveal the decomposition scenarios that govern the thermal stability and chemical behavior of BNFF, which appreciably differ from conventional nitro compounds. Details of the electronic structure and calculated electronic properties suggest that BNFF is an excellent candidate energetic material on its own and an attractive ingredient of modern energetic formulations to improve their stability and enable highly controllable chemical decomposition.

1IntroductionIn general, highe xplosivesa re categorized as primary,s econdary,a nd tertiary explosives, basedo nt heir sensitivity to mechanical insults. Primarye xplosivesa re very sensitive to mechanical and electricali nitiation and are used as initiating explosives in an explosivet rain. Secondary explosives are less sensitivet om echanical stimuli, although in many cases can still be somewhat sensitive materials. Te rtiary explosives are generallyv ery insensitivee xplosivesv ery often consistingo fa no xidizer and af uel, and are generallyu sed in mining. Subsets of secondary explosives are insensitive energetic compoundso rm aterials. Insensitive energetic compounds are defined as compoundst hat have relatively benign responses to externali nsults such as impact, shock, spark, friction, and heat. Understandingt he various factors that affectt he sensitivity of energetic compoundst ov arious mechanical insults plays an important role in the design of new,i nsensitive, and thermally stable higher-performance energetic materials. While there have been several excellent reviewsa nd books on new energetic compounds in the past 15 years [1-7],t his review will concentrate on insensitivee nergetic compounds. Also this paper will concentrate on insensitive energeticc ompounds and not discuss insensitivee nergetic formulationso rm ixtures or engineering methods to decrease sensitivity.Althoughs park and friction sensitivity are important, impact, shock, and thermal stabilitya re the most commonly used measurements to determine the relatives ensitivity of ag iven compoundc ompared to knowns tandards. In this paper the term insensitivity will refer mainly to impact and thermal sensitivity.I mpact sensitivity is generally measured by using a" drop hammer" impact machine, in which an anvil of ag iven weight (generally 5kg) is allowed to impact as mall sample (ca. 35 mg) of an explosive and the responsei sr ecorded. Historically,d rop hammer results (Dh 50 or H 50 )w ere reported as the height, at which there is a5 0% probabilityo fi gnition. In recenty ears, some authors are convertingt he recorded drop hammer heights to Joules and are reporting the energy required at which there is a5 0% probability of ignition. Thermal stabilitym ay be measured using several methods including differential scanning calorimetry (DSC), differential thermala nalysis (DTA), chemical reactivity test (CRT), vacuum stability test (VTS), slow cook-off test, and fast cook-off test.The industry standardf or an insensitive energetic compound is 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), ar easonably powerful explosive, whose response to shock, thermal, impact and friction insultsi ss ignificantly more benign than that of any other knownm aterial of comparable energy [8,9].T his "enhanced" insensitivity of TATB has led to as ignificant amount of studies on how various physical properties including molecular structure,c rystal structure, and crystal packing of TATB contributes to its "enhanced" insensitivity,a nd how these physical properties c...

A novel synthesis of the title compound was achieved by direct amination using Vicarious Nucleophilic Substitution (VNS) methodology. Reaction of 1,1,1-trimethylhydrazinium iodide with 3,5-dinitropyrazole in DMSO produces 4-amino-3,5-dinitro-1H-pyrazole as a 1:1 crystal solvate with DMSO. Recrystallization from water yields the monohydrated crystal. Recrystallization of the monohydrate from butyl acetate yields the compound in pure form.

Searle Scholars Foundation and the National Institutes of Health (CA33668/42056). We thank Professor S. J. Gould for copies of spectra of natural lavendamycin and Professor Kende for comparative copies of LH NMR (300and 400-MHz) spectra of authentic 14 and lavendamycin methyl ester (16). We thank Professor Danishefsky for suggestions leading to the selective hydrolysis required in the conversion of 3 to 5/6. Supplementary Material Available: Details of work described in ref 10-14 (6 pages) are provided. Ordering information may be found on any current masthead page.

Determining the unreacted equation of state of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) is challenging because it exhibits low crystal symmetry and low X-ray scattering strength. Here, we present the first high-pressure single-crystal X-ray diffraction (SXD) study of this material. Our SXD results reveal a previously unknown transition to a monoclinic phase above 4 GPa. No abrupt change of the volume occurs but the compressibility changes. Concomitant first principles evolutionary crystal structure prediction USPEX calculations confirm this transition and show that it involves a pressure-induced in-plane shift of the layers of TATB molecules with respect to the ambient-pressure phase.