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.     

Periodate salts as pyrotechnic oxidizers: development of barium- and perchlorate-free incendiary formulations

In a flash: pyrotechnic incendiary formulations with good stabilities toward various ignition stimuli have been developed without the need for barium or perchlorate oxidizers. KIO(4) and NaIO(4) were introduced as pyrotechnic oxidizers and exhibited excellent pyrotechnic performance. The periodate salts may garner widespread use in military and civilian fireworks because of their low hygroscopicities and high chemical reactivities.     

The Lithium Salts of Bis(azolyl)borates as Strontium- and Chlorine-free Red Pyrotechnic Colorants

After concerns regarding the use of chlorinated material for pyrotechnic items had reinforced, the action of the U.S. Environmental Protection Agency on health concerns about strontium ushered in a new era in the production of red light. Lithium was shown to impart red color to a pyrotechnic flame, however only a very narrow selection of such formulations can be found in the literature. Dihydrobis(azolyl)borates are a well investigated, easily accessible class of materials which have been proven to be suitable as pyrotechnic coloring agents. With their high nitrogen contents such moieties should also meet the requirements of a low combustion temperature and a reducing flame atmosphere for a lithium-based red-burning composition. This work evaluates the capability of the lithium salts of dihydrobis(pyrazol-1-yl)borate, dihydrobis(1,2,4-triazol-1-yl)borate, and dihydrobis(tetrazol-1-yl)borate to serve as red color imparters. The latter compounds were characterized by multinuclear NMR experiments, IR spectroscopy, elemental analysis, and single-crystal X-ray diffraction and were investigated with respect to their thermal stabilities as well as sensitivities toward various ignition stimuli.     

Metal Salts of Dinitro‐, Trinitropyrazole,and Trinitroimidazole

The syntheses of alkali and earth alkaline dinitropyrazolate (DNP), trinitropyrazolate (TNP), and trinitroimidazolate (TNI) salts are reported. Additionally, copper trinitroimidazolate was synthesized. Their characterization by NMR spectroscopy, mass spectrometry, elemental analysis, and vibrational spectroscopy is reported as well. Crystal structures of compound Ba(DNP)₂ ( 9 ), which crystallizes with one molecule of methanol and ethyl ether as well as of compounds Sr(TNP)₂ · 3H₂O ( 12 ), Ba(TNP)₂ · 3H₂O ( 13 ), and LiTNI · 3H₂O ( 14 ) were determined. The energetic and thermal properties were measured as well. Green‐ and red‐burning pyrotechnic formulations containing barium salts 9 and 13 as well as strontium salts 8 and 12 serving as colorants are tested. Additionally, formulations using Sr(TNP)₂ · 3H₂O ( 12 ) and Ba(TNP)₂ · 3H₂O ( 13 ) as the oxidizer and colorant at the same time were examined. The formulations were investigated with regard to their combustion behavior and performances such as burn time, dominant wavelength, spectral purity, luminous intensity, and luminous efficiency. The sensitivities towards ignition stimuli and the decomposition temperatures were determined as well.     

Green Colorants Based on Energetic Azole Borates

The investigation of green‐burning boron‐based compounds as colorants in pyrotechnic formulations as alternative for barium nitrate, which is a hazard to health and to the environment, is reported. Metal‐free and nitrogen‐rich dihydrobis(5‐aminotetrazolyl)borate salts and dihydrobis(1,3,4‐triazolyl)borate salts have been synthesized and characterized by NMR spectroscopy, elemental analysis, mass spectrometry, and vibrational spectroscopy. Their thermal and energetic properties have been determined as well. Several pyrotechnic compositions using selected azolyl borate salts as green colorants were investigated. Formulations with ammonium dinitramide and ammonium nitrate as oxidizers and boron and magnesium as fuels were tested. The burn time, dominant wavelength, spectral purity, luminous intensity, and luminous efficiency as well as the thermal and energetic properties of these compositions were measured.     

Chlorine‐Free Pyrotechnics: Copper(I) Iodide as a “Green” Blue‐Light Emitter

The generation of blue‐light‐emitting pyrotechnic formulations without the use of chlorine‐containing compounds is reported. Suitable blue‐light emission has been achieved through the generation of molecular emitting copper(I) iodide. The most optimal copper(I) iodide based blue‐light‐emitting formulation was found to have performances exceeding those of chlorine‐containing compositions, and was found to be insensitive to various ignition stimuli.     

Brighter‐ and Longer‐Burning Barium‐Free Illuminants for Military and Civilian Pyrotechnics

The development of barium‐free pyrotechnic illuminants is described. Heavy metal barium nitrate oxidizer and strontium nitrate oxidizer were replaced with sodium nitrate to adequately address environmental concerns while providing the brightest possible illuminant. The new formulations further address environmental concerns and mitigate single‐point‐of‐failure through the replacement of polyester‐based Laminac 4116/Lupersol binder system with the epoxy‐based Epon 813/Versamid 140 binder system. The new formulations were found to burn longer and brighter than the control with a low sensitivity to various ignition stimuli.     

Chlorine‐Free Red‐Burning Pyrotechnics

The development of a red, chlorine‐free pyrotechnic illuminant of high luminosity and spectral purity was investigated. Red‐light emission based solely on transient SrOH_(g) has been achieved by using either 5‐amino‐1H‐tetrazole or hexamine to deoxidize the combustion flame of a Mg/Sr(NO₃)₂/Epon‐binder composition and reduce the amount of both condensed and gaseous SrO, which emits undesirable orange‐red light. The new formulations were found to possess high thermal onset temperatures. Avoiding chlorine in these formulations eliminates the risk of the formation of PCBs, PCDDs, and PCDFs. This finding, hence, will have a great impact on both military pyrotechnics and commercial firework sectors.     

High‐Nitrogen‐Based Pyrotechnics: Perchlorate‐Free Red‐ and Green‐Light Illuminants Based on 5‐Aminotetrazole

Prototype testing of perchlorate‐free hand‐held signal illuminants for the US Army’s M126 A1 red‐star and M195 green‐star parachute illuminants are described. Although previous perchlorate‐free variants for these items have been developed based on high‐nitrogen compounds that are not readily available, the new formulations consist of anhydrous 5‐aminotetrazole as the suitable perchlorate replacement. Compared to the perchlorate‐containing control, the disclosed illuminants exhibited excellent stabilities toward various ignition stimuli and had excellent pyrotechnic performance. The illuminants are important from both military and civil fireworks perspectives, as the perchlorate‐free nature of the illuminants adequately address environmental concerns associated with perchlorate‐containing red‐ and green‐light‐emitting illuminants.     

Synthesis and Investigation of Energetic Boron Compounds for Pyrotechnics

The energetic boron esters tris(1‐ethyl‐5‐aminotetrazolyl) borate, tris(2‐ethyl‐5‐aminotetrazolyl) borate, tris(1‐ethyltetrazolyl) borate, tris(2‐ethyltetrazolyl) borate, and tris(2‐(3‐nitro‐1, 2,4‐triazolyl)ethyl) borate were synthesized and analyzed by NMR and IR spectroscopy, elemental analysis, and mass spectrometry. Two tetracoordinate borates potassium tetrakis(3‐nitro‐1, 2,4‐triazolyl)borate and potassium bis(4, 4′,5, 5′‐tetranitro‐2, 2′‐bisimidazolyl)borate were synthesized and fully characterized as well. Moreover, the energetic and thermal properties of the energetic boron esters and tetracoordinate borates were determined. The ¹¹B NMR chemical shifts of potassium tetrakis(3‐nitro‐1, 2,4‐triazolyl)borate and potassium bis(4, 4′,5, 5′‐tetranitro‐2, 2′‐bisimidazolyl)borate were calculated and compared to the experimental values. Tris(1‐ethyl‐5‐aminotetrazolyl) borate was tested as colorant in pyrotechnic formulations with respect to the combustion behavior and color properties as well as the energetic and thermal properties.     

Perchlorate‐Free Pyrotechnic Formulations Utilizing Energetic Chlorine Donors: 1‐CDN, 11‐CDN, 13‐CDN

Several novel materials were investigated as energetic chlorine donors, specifically for the preparation of perchlorate‐free pyrotechnic formulations with low‐smoke output. The novel compounds, 2‐chloromethyl‐2‐methyl‐5,5‐dinitro‐1,3‐dioxane (1‐CDN), 2,2‐bis(chloromethyl)‐5,5‐dinitro‐1,3‐dioxane (13‐CDN), and 2‐(dichloromethyl)‐2‐methyl‐5,5‐dinitro‐1,3‐dioxane (11‐CDN), were formulated with a variety of fuels and oxidizers and their resulting colored flames analyzed for color quality. The preparation and preliminary characterization of these energetic chlorine donors are described.     

Feuerwerk

Pyrotechnic is an old empiric science on the borderline between chemistry, technics, chemical and process engineering and art and it maintains its position as an integral part of events in culture and tradition. This contribution presents the steps a firework has to pass to develop from mere chemistry to the final show. Some chemical background, information about pyrotechnic mixtures like black powder, firework star mixtures, oscillating mixtures like blinking stars and whistles are explained as well as the manufacture of selected pyrotechnic items. Aspects of production and handling safety of exhibition fireworks and the recent developments in legislation like the pyrotechnics directive, the CE‐ standardisation and REACH are touched. Although the commercial environment is getting tougher the fascination for the pyrotechnic phenomena are still alive and may initiate the motivation for the reader to get involved in the exciting topic of pyrotechnics and the associated fields of science.     

解读《有机化合物命名原则-2017》 ——新老命名原则的比较及常见取代基的命名

The differences between "Nomenclature of Organic Compounds-2017" and "Nonmenclature of Organic Chemistry (1980)" issued by Chinese Chemical Society are described. The general principles and numbering methods for naming substituent groups commonly used in organic chemistry for undergraduates are analyzed and explained; the proper systematic names are recommended to benefit classroom teaching and academic communication. Moreover, the principles such as systemization, standardization, simplification, uniformization, and "looking afterward" are proposed. Some recommendations are further presented:1) numbering the carbon skeleton of the substituent without compulsory numbering rule always begins at the point of attachment; 2) only preserving a minority of trivial names (common names); 3) naming methanoyl (formyl)-analogue groups following the name of methanoyl.     

Biologically active molecules with a "light switch"

Biologically active compounds which are light-responsive offer experimental possibilities which are otherwise very difficult to achieve. Since light can be manipulated very precisely, for example, with lasers and microscopes rapid jumps in concentration of the active form of molecules are possible with exact control of the area, time, and dosage. The development of such strategies started in the 1970s. This review summarizes new developments of the last five years and deals with "small molecules", proteins, and nucleic acids which can either be irreversibly activated with light (these compounds are referred to as "caged compounds") or reversibly switched between an active and an inactive state.     

Utility of the ion-pair formation for spectrophotometric determination of terfenadine in pure form and in some pharmaceutical formulations

A spectrophotometric procedure for the determination of terfenadine and a number of its pharmaceutical preparations has been developed that offers advantages of simplicity, rapidity, sensitivity and stability indication over the official USP (1995) method. The proposed method is based on the formation of ion-pairs by the reaction of terfenadine with some chromotropic acid mono- and bis-azo dyes. Different variables affecting the ion-pair formation were studied and optimized. At the maximum absorption of 557, 521, 592 and 543 nm, Beer's law is obeyed in the range 0.2–18.6, 0.2–16.4, 0.2–25.0 and 0.2–22.2 g ml^–1 on using reagents I, II, III and IV, respectively. The stoichiometric ratio and stability of each ion-pair were estimated and the mechanism of the reaction is discussed. The molar absorptivity and Sandell sensitivity of the produced ion-pairs were calculated in addition to Ringbom optimum concentration ranges. Statistical treatment of the experimental results indicates that the procedures are precise and accurate. Excipients used as additives in pharmaceutical formulations did not interfere in the proposed procedures. The reliability of the methods was established by parallel determination against the official USP method. The procedures described were successfully applied to the determination of the bulk drug and its pharmaceutical formulations by applying the standard addition technique.     

A mixed-valence, hexadecamolybdenum cluster with an MoVI cubane "jewel" in a "setting" of five molybdateVI-linked dinuclear MoV nits

The hexadecanuclear, mixed-valence cluster [Mo(16)O(42)(OH)(2)(3-iPrC(3)H(3)N(2))(12)].H(2)O (1), has been synthesized and characterized by X-ray crystallography, IR spectroscopy and mass spectrometry. The C(2)-symmetric complex consists of a cubane Mo(VI) (4)O(4) "jewel" held in a 10-point "setting" comprised of five dinuclear Mo(V) units tethered together by two tetrahedral Mo(VI) centers. The dinuclear units are ligated by twelve 3-isopropylpyrazole units that interact with the Mo--O framework through a network of hydrogen bonds. Structural parameters, charge requirements, and bond valence sum analyses support the assignment of +5 and +6 oxidation states to the dinuclear and cubane/tetrahedral Mo centers, respectively. Space filling models reveal that the pyrazole groups coat much of the surface of the molecule, apart from a number of oxo-rich seams that trace a chiral pattern across the surface. Complex 1 exhibits a unique structure that combines moieties generally atypical of polyoxometalates, viz., a Mo cubane containing only two terminal oxo ligands, and three distinct Mo(V) (2) units (including a 5-coordinate Mo center) tethered into a 10-point "setting" by tetrahedral Mo(VI) centers.     

Thermal and Sensitiveness Determination of Cubanes: Towards Cubane-Based Fuels for Infrared Countermeasures

As infrared seeking technology evolves, threats are better able to distinguish defensive infrared (IR) flares from true targets. Spectrally matched flares, which generally employ carbon-based fuels, are better able to decoy some advanced missiles by more closely mimicking the IR emission of the target. Cubane is a high-energy carbon-based scaffold which may be suitable for use as a fuel in spectrally matched flares. The enthalpy of formation and strain energy of a series of cubanes was predicted in silico, and their thermal and impact stability examined. All were found to undergo highly exothermic decomposition in sealed cell differential scanning calorimetry, and two cubanes subsequently underwent quantitative sensitiveness testing. Despite their F of I values being in the secondary explosive range, cubane-1,4-dicarboxylic acid (F of I=70) and 4-carbamoylcubane-1-carboxylic acid (F of I=90) were identified as potentially useful fuels for pyrotechnic infrared countermeasure flare formulations.     

Studies on the ageing of a magnesium-strontium nitrate pyrotechnic composition using isothermal microcalorimetry and thermal analysis techniques

The ageing behaviour of a pyrotechnic composition containing equal parts by mass of magnesium and strontium nitrate has been followed by isothermal microcalorimetry. The measurements were carried out on the samples at 50 °C and 65% relative humidity in air using closed ampoules. The results have been compared to those obtained for magnesium powder under the same conditions. Following an initial induction period, the pyrotechnic compositions reacted at a much faster rate than magnesium powder alone. The main reaction products were found to be magnesium hydroxide and strontium nitrite; the amounts formed have been correlated with the cumulative heats of ageing. In addition, the influence of the ageing process on the pyrotechnic reaction has been studied by high temperature differential scanning calorimetry (DSC) and by modulated temperature DSC.     

Polishing a diamond in the rough: "Cu--H" catalysis with silanes

The value of a novel chemical transformation is often underappreciated at the time of its discovery. The reasons are doubtlessly manifold, but the "chemical zeitgeist" subtly determines how the new reaction will be received by the chemical community. The enantioselective reduction of carbonyls by copper-catalyzed hydrosilylation was certainly outshone by other asymmetric hydrogenation techniques. A seminal report at an early stage indicated the considerable potential of this catalytic process, yet it was disregarded for more than a decade. A refined mechanistic picture in connection with a plethora of new chiral ligands then led to copper-catalyzed 1,2- as well as 1,4-reductions of carbonyl compounds with excellent levels of enantioselection at high substrate-to-catalyst ratios and even more remarkable substrate-to-ligand ratios. The tide is turning for inexpensive copper catalysts in asymmetric hydride transfer reactions!     

The influences of combinative effect of temperature and humidity on the thermal stability of pyrotechnic mixtures containing strontium nitrate as oxidizer

The influences of combinative effect of temperature and humidity on the thermal stabilities of three pyrotechnic compositions are investigated in the study. The thermal behavior for each pyrotechnic is analyzed by SETARAM thermal analyzer. Activation energy is determined by Kissinger method and critical temperature of thermal explosion (T _b) of pyrotechnic compositions is also calculated. The results of thermal analysis revealed that relative humidity could decrease the thermal stability of pyrotechnic mixtures. The critical temperature of thermal explosion (T _b) of each pyrotechnics decreased as the relative humidity increasing. Based on the value of T _b, the thermal stabilities of the pyrotechnic mixtures are in the order of S_r(NO₃)₂/Mg₄Al₃/PVC/PF > S_r(NO₃)₂/S_rCO₃/KClO₄/Mg₄Al₃/PVC/PF > S_r(NO₃)₂/KClO₄/Mg₄Al₃/PVC/PF. The thermal stability of S_r(NO₃)₂/Mg₄Al₃/PVC/PF show the best thermal stability than other two mixtures whether it is in the condition of humidity or not.