Nitraza-/Oxa-Propylene- and Hydrazonemethylene-Bridged 1,2,4-Nitraminotriazoles and Selected Salts

Two new bridged nitraminotriazoles with bridging oxapropylene and nitrazapropylene moieties were synthesized, and converted into several salts, as well as from the hydrazonemethylene bridged nitraminotriazole. All compounds were fully characterized by NMR and IR spectroscopy, elemental analysis as well as differential thermal analysis. The sensitivity towards friction and impact were determined according to BAM standard technics and the energetic properties were calculated by using the EXPLO5 computer code. The neutral compounds as well as the various salts were examined in terms of their physicochemical properties and detonation performance to each other and compared to the commonly used secondary explosive RDX.     

A Strontium‐ and Chlorine‐Free Pyrotechnic Illuminant of High Color Purity

The development of a red‐light‐emitting pyrotechnic illuminant has garnered interest from the pyrotechnics community owing to potential regulations by the United States Environmental Protection Agency (U.S. EPA) regarding the use of strontium and chlorinated organic materials. To address these environmental regulatory concerns, the development of lithium‐based red‐light‐emitting pyrotechnic compositions of high purity and color quality is described. These formulations do not contain strontium or chlorinated organic materials. Rather, the disclosed formulations are based on a non‐hygroscopic dilithium nitrogen‐rich salt that serves as both oxidizer and red colorant. These formulations are likely to draw interest from the civilian fireworks and military pyrotechnics communities for further development as they both have a vested interest in the development of environmentally conscious formulations.     

Trigger bond analysis of nitroaromatic energetic materials using wiberg bond indices

The identification of trigger bonds, bonds that break to initiate explosive decomposition, using computational methods could help direct the development of novel, “green” and efficient high energy density materials (HEDMs). Comparing bond densities in energetic materials to reference molecules using Wiberg bond indices (WBIs) provides a relative scale for bond activation (%ΔWBIs) to assign trigger bonds in a set of 63 nitroaromatic conventional energetic molecules. Intramolecular hydrogen bonding interactions enhance contributions of resonance structures that strengthen, or deactivate, the C NO₂ trigger bonds and reduce the sensitivity of nitroaniline‐based HEDMs. In contrast, unidirectional hydrogen bonding in nitrophenols strengthens the bond to the hydrogen bond acceptor, but the phenol lone pairs repel and activate an adjacent nitro group. Steric effects, electron withdrawing groups and greater nitro dihedral angles also activate the C NO₂ trigger bonds. %ΔWBIs indicate that nitro groups within an energetic molecule are not all necessarily equally activated to contribute to initiation. %ΔWBIs generally correlate well with impact sensitivity, especially for HEDMs with intramolecular hydrogen bonding, and are a better measure of trigger bond strength than bond dissociation energies (BDEs). However, the method is less effective for HEDMs with significant secondary effects in the solid state. Assignment of trigger bonds using %ΔWBIs could contribute to understanding the effect of intramolecular interactions on energetic properties. © 2018 Wiley Periodicals, Inc.     

A systematic tandem mass spectrometric study of anion attachment for improved detection and acidity evaluation of nitrogen‐rich energetic compounds

The development of rapid, efficient, and reliable detection methods for the characterization of energetic compounds is of high importance to security forces concerned with terrorist threats. With a mass spectrometric approach, characteristic ions can be produced by attaching anions to analyte molecules in the negative ion mode of electrospray ionization mass spectrometry (ESI‐MS). Under optimized conditions, formed anionic adducts can be detected with higher sensitivities as compared with the deprotonated molecules. Fundamental aspects pertaining to the formation of anionic adducts of 1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocane (HMX), 1,3,5‐trinitro‐1,3,5‐triazinane (RDX), pentaerythritol tetranitrate (PETN), nitroglycerin (NG), and 1,3,5‐trinitroso‐1,3,5‐triazinane energetic (R‐salt) compounds using various anions have been systematically studied by ESI‐MS and ESI tandem mass spectrometry (collision‐induced dissociation) experiments. Bracketing method results show that the gas‐phase acidities of PETN, RDX, and HMX fall between those of HF and acetic acid. Moreover, PETN and RDX are each less acidic than HMX in the gas phase. Nitroglycerin was found to be the most acidic among the nitrogen‐rich explosives studied. The ensemble of bracketing results allows the construction of the following ranking of gas‐phase acidities: PETN (1530‐1458 kJ/mol) > RDX (approximately 1458 kJ/mol) > HMX (approximately 1433 kJ/mol) > nitroglycerin (1427‐1327.8 kJ/mol).     

Regularity of weak solutions to rate‐independent systems in one‐dimension

We show that under some appropriate assumptions, every weak solution (e.g. energetic solution) to a given rate‐independent system is of class SBV, or has finite jumps, or is even piecewise C¹. Our assumption is essentially imposed on the energy functional, but not convexity is required.     

Extreme fluxes in solar energetic particle events: Methodological and physical limitations

In this study, all available data on the largest solar proton events (SPEs), or extreme solar energetic particle (SEP) events, for the period from 1561 up to now are analyzed. Under consideration are the observational, methodological and physical problems of energy-spectrum presentation for SEP fluxes (fluences) near the Earth's orbit. Special attention is paid to the study of the distribution function for extreme fluences of SEPs by their sizes. The authors present advances in at least three aspects: 1) a form of the distribution function that was previously obtained from the data for three cycles of solar activity has been completely confirmed by the data for 41 solar cycles; 2) early estimates of extremely large fluences in the past have been critically revised, and their values were found to be overestimated; and 3) extremely large SEP fluxes are shown to obey a probabilistic distribution, so the concept of an “upper limit flux” does not carry any strict physical sense although it serves as an important empirical restriction. SEP fluxes may only be characterized by the relative probabilities of their appearance, and there is a sharp break in the spectrum in the range of large fluences (or low probabilities). It is emphasized that modern observational data and methods of investigation do not allow, for the present, the precise resolution of the problem of the spectrum break or the estimation of the maximum potentialities of solar accelerator(s). This limitation considerably restricts the extrapolation of the obtained results to the past and future for application to the epochs with different levels of solar activity.     

Proton Fluxes in the Neutral Sheet: A Case Study by the DOK2 on Interball-1

On December 3, 1996, in the time interval with low geomagnetic activity, the Interball-1 satellite crossed the neutral sheet of geomagnetic tail from north to south at the radial distance 25R _E. Characteristics of proton and electron fluxes 20 keV measured by DOK2 spectrometer are presented. High anisotropy of proton fluxes was observed. Fluxes of protons and their anisotropy are modulated by magnetic field. In a region where the total magnetic field is low and proton fluxes are high the anisotropy is lower and energy spectra of protons are harder than in another region. In the latter one (after 20:17 UT) when the total magnetic field is higher mainly due to an increase of |B _x | (B _x <0), DOK2 observes the increase of proton flux anisotropy. These fluxes have character of spikes. The detailed proton energy spectra shows that the spikes with duration of few seconds are characterised by very quick change of spectral slope. Proton spikes are accompanied by the increases of electron fluxes in the earthward direction. When B _x >0, the proton fluxes in earthward direction predominate. In the time with B _x <0 we observe the proton fluxes in the tail direction. This is in a good agreement with the measurements of bipolar fluxes on Geotail reported by Petrukovich et al. [J. Geophys. Res. 26 (1999) 2909]. We suppose that the cause of these bipolar proton fluxes is the reconnection of geomagnetic field lines during the growth phase of geomagnetic substorm.     

A new class of flexible energetic salts, part 6: the structures of the hydrazinium and hydroxylammonium salts of dinitramide

The crystal structures of two amine base salts, the hydrazinium, 1, and the hydroxylammonium, 2, of dinitramide have been determined. 1 crystallizes in the monoclinic space group P 2₁/c with cell dimensions a = 8.312(3), b = 5.654(1), c = 10.659(3) Å, = 93.73(3)°, while 2 crystallizes in the orthorhombic space group Pcab (nonstandard setting of Pbca) with cell dimensions a = 6.439(2), b = 12.470(4), c = 30.816(14) Å. The structures of 1 and 2 contain protonated amine cations and dinitramide anions linked by hydrogen bonding. In addition, in 2 there are both neutral and zwitterionic hydroxylamine moieties involved in the hydrogen bonding scheme. Thus in 2 the complete formula unit is (NH₃ ⁺OH)₂[N₃O₄ ^–]₂ · (NH₂OH) middot; (NH₃ ⁺O^–), and in this structure the hydroxylamine exists in its three possible forms: protonated, neutral, and zwitterionic. In both structures the conformations adopted by the dinitramine anions can be related to the types of hydrogen bonds it forms with the surrounding amine cations.     

1,1-二(2,4,6-三硝基苯甲酰胺基)-2,2-硝基乙烯的合成

以1,1-二氨基-2,2-二硝基乙烯(FOX-7)和2,4,6-三硝基苯甲酰氯(TNBC)为原料反应合成得到了1,1-二(2,4,6-三硝基苯甲酰胺基)-2,2-二硝基乙烯,并通过单因素试验和正交试验方法,分别探讨了反应介质、缚酸剂、反应温度和反应时间等对产物产率的影响,得到适宜的工艺条件为:FOX-7与TNBC物质的量的比1∶2.4,以四氢呋喃(THF)为反应介质,N,N-二甲基甲酰胺(DMF)为缚酸剂,反应温度0℃,反应时间48 h,产率可达94％.采用紫外可见光谱(UV-Vis)、核磁共振氢谱(1H NMR)、核磁共振碳谱(13C NMR)、红外光谱(FT-IR)、质谱(MS)及元素分析等对产物的结构进行了表征.利用差热分析仪对产物热稳定性进行了研究,结果表明,产物在空气中分解峰值温度为167℃,理论计算爆速为7.434km· s-1,爆压为23.67 GPa.