A Comparison of the Structure, Synthesis, and Properties of Insensitive Energetic Compounds

Abstract

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...

Trimerization of 4‐Amino‐3,5‐dinitropyrazole: Formation, Preparation, and Characterization of 4‐Diazo‐3,5‐bis(4‐amino‐3,5‐dinitropyrazol‐1‐yl) pyrazole (LLM‐226)

“…LLM‐226 is composed of two amino‐dinitropyrazole moieties and one diazopyrazole, in which the nitro and diazo groups are attached to different pyrazole rings. The arrangement of the amino and nitro groups on the pyrazole rings are expected to provide additional stabilization through a strong intermolecular and intramolecular hydrogen bonding, similar to those found in known thermally stable and insensitive compounds such as 1,3,5‐triamino‐2,4,6‐trinitrobenzene and 2,6‐diamino‐3,5‐dinitropyrazine‐1‐oxide (LLM‐105) . Indeed, X‐ray analysis indicates that the molecule of LLM‐226 has four pairs of intramolecular hydrogen bonds and one strong intermolecular bonding between amino and nitro groups (Table ).…”

“…Of course, many factors could affect the sensitivity of an energetic material. In solid state, the manner of a molecular packing may make a great contribution to sensitivity of the material . As expected, there is no hydrogen bonding between the diazo and the amino group, but there are existing strong short contacts between the diazo and the nitro groups.…”

Ecotoxicity of the insensitive munitions compound 3-nitro-1,2,4-triazol-5-one (NTO) and its reduced metabolite 3-amino-1,2,4-triazol-5-one (ATO)

“…The nitro heterocyclic compound 3-nitro-1,2,4-triazol-5-one (NTO) is one of the insensitive munitions constituents of important explosive formulations, such as IMX-101, IMX-104, and PAX48, which were recently approved by the U.S. Army as a safer and effective alternative to replace cyclotrimethylene trinitramine (RDX) in large caliber munitions [1]. The constituents of these new formulations are more stable and safer for troops due to their lower likelihood for unintended explosions.…”

Synthetic Studies of 2,6‐Diamino‐3,5‐Dinitropyrazine‐ 1‐Oxide (LLM‐105) from Discovery to Multi‐Kilogram Scale

“…The unique properties of TATB, i. e., the extraordinary thermal stability (m.p. > 370 8C), high crystal density (1.94 g/cm 3 ) and low sensitivity to external stimuli has been attributed to the graphitic-like crystal structure that results from the combination of the high-symmetry of the molecule along with a high degree of intermolecular and intramolecular hydrogen bonding [1,2]. (Figure 1)These unique properties of TATB that may be partially attributed to the alternating array of amino-and nitro-groups, has led us to investigate the synthesis of various heterocycles containing alternating array of amino-and nitro-groups [3][4][5].…”

“…After addition, the white slurry was refluxed 3 h, cooled to room temperature, poured into ice water (8 L) and the resulting precipitate was collected by suction filtration. After drying under suction on the filter paper 1 h (2,6-dimethoxypyrazine is volatile at room temperature and significant amounts may be lost if left to dry under suction for a prolonged period), the solid was dissolved in CH 2 2-Chloro-6-methoxypyrazine (CMP) [42]: With stirring, 2,6-dichloropyrazine (80 g, 0.54 mol) was added slowly portion-wise to a solution of NaOMe (30 g, 0.56 mol) in MeOH (400 ml). The reaction mixture was refluxed 6 h, cooled to room temperature, poured into ice water (1 L) and the resulting precipitate was collected by suction filtration.…”