Synthesis of Bridged Tetrazoles with Promising Properties and Potential Applications by a One-Step Finkelstein Reaction.

Numerous nitramine bridged compounds which show promising combinations of properties have already been identified in the area of energetic materials. In this work, four new nitrazapropane bridged tetrazoles, as well as four new trinitrazaheptane tetrazoles and three oxapropane bridged tetrazoles were synthesized and fully characterized. These new compounds can all be synthesized by a simple, one-step synthesis using Finkelstein conditions. All of these new energetic materials were characterized using NMR spectroscopy, single crystal X-ray diffraction, vibrational analysis and elemental analysis. The thermal behaviour of these compounds was studied by differential thermal analysis (DTA) and partly by thermogravimetric analysis (TGA). The BAM standard method was used to determine the sensitivities towards impact (IS) and friction (FS). The enthalpies of formation were calculated at the CBS-4M level, and the energetic performances were calculated using the EXPLO5 (V6.06.01) computer code. The properties of the new compounds were compared to each other as well as to the known energetic material RDX. Moreover, the iron(II) and copper(II) perchlorate complexes with 1,3-bis-1,1-tetrazolylnitrazapropane as ligand were prepared and investigated.

Sensitive 1,4-Disubstituted Nitro-Containing Cubanes: Structures and Properties.

The cubane cage system is characteristic and well known for its high strain energy, qualifying it as a promising precursor for energetic materials. 1,4-Disubstituted cubanes are the easiest accessible derivatives. A further developed laboratory-scale procedure for cubane-1,4-dicarboxylic acid dimethyl ester is presented. From this central precursor, the bis-trinitroethyl and bis-nitromethyl esters as well as the bis-methylcarbamate and bis-methylnitrocarbamate were synthesized and characterized by multinuclear NMR spectroscopy and X-ray crystallography. In addition, their physical and energetic properties were determined and studied.

The Nitrate and Nitrocarbamate of 1,3,5-Trinitrocyclohexane-trimethanol and Selected Salts.

With 1,3,5-trinitrocyclohexane-1,3,5-triyl trimethanol as a precursor, available from 1,3,5-trinitrobenzene, two further nitro-containing molecules were synthesized. Via modification of the hydroxyl groups, new oxygen-rich compounds were obtained, the corresponding trinitrate and trinitrocarbamate. From the latter, various salts were obtained by treatment with bases. All compounds were fully characterized by NMR and IR spectroscopy, X-ray diffraction, and elemental and differential thermal analyses. Moreover, the sensitivity toward friction and impact was determined according to BAM standard techniques and the energetic properties were calculated by using the EXPLO5 computer code.

Investigation of deuterated FOX-7 - changes in structural behavior and energetic characteristics after deuteration under ambient conditions.

For an investigation of the deuterium effect of N-deuterated compounds on the structural and thermal behavior, 1,1-diamino-2,2-dinitroethylene (FOX-7) was deuterated by deprotonation in heavy water and subsequent acidification with D2SO4. The status of deuteration progress was monitored by infrared spectra analysis and the deuteration level was determined via1H q-NMR. The properties of FOX-7-D4 were studied by single crystal X-ray diffraction and differential thermal analysis. In addition, the activation energy of thermal decomposition was determined, and the heat of formation and zero-point energy were calculated.

Nitrocarbamoyl Azide O2NN(H)C(O)N3: A Stable but Highly Energetic Member of the Carbonyl Azide Family.

The diazotization of nitrosemicarbazide (1) resulted in the formation and isolation of nitrocarbamoyl azide (2), which was thoroughly characterized by spectroscopic and structural methods. This compound shows surprising stability but also high reactivity and sensitivity, with a melting point of 72 °C and a detonative decomposition point at 83 °C. In addition, five selected salts were synthesized by careful deprotonation. The decomposition mechanism of 2 in solution was investigated and could be clarified by performing experiments using methanol and hydrazine as trapping reagents. The energetic and physicochemical properties of all these compounds were investigated and classified.

A promising energetic biopolymer based on azide-functionalized microcrystalline cellulose: Synthesis and characterization.

In the current investigation, azidodeoxy-microcrystalline cellulose nitrate (AMCCN) as a novel promising nitrogen-rich energetic biopolymer was synthesized, and its features were compared to those of azidodeoxy-pristine cellulose nitrate (APCN), conventional cellulose nitrate (PCN) and microcrystalline cellulose nitrate (MCCN). The produced nitrated samples and their precursors were fully characterized using various analytical techniques. In addition, the heats of combustion and mechanical sensitivities of all nitrated biopolymers were evaluated, and their energetic performances were predicted by EXPLO5 V6.04 software. The obtained results provide evidence for the effectiveness of the applied chemical functionalization approach to synthesize the relatively insensitive AMCCN and APCN with nitrogen content of 22.75 % and 22.50 %, density of 1.718 g/cm3 and 1.706 g/cm3, and detonation velocity of 7707 m/s and 7533 m/s, respectively, which are higher than those of PCN. This work opens avenues to design promising energetic biopolymers based on renewable microcrystalline cellulose for potential application in advanced high performance solid propellants and explosives.

Solid-State and Gas-Phase Structures and Energetic Properties of the Dangerous Methyl and Fluoromethyl Nitrates.

An improved synthesis of the simplest nitric acid ester, methyl nitrate, and a new synthesis of fluoromethyl nitrate use the metathesis of the corresponding iodomethanes with silver nitrate. Both compounds were identified by spectroscopy and the structures determined for in situ grown crystals by X-ray diffraction as well as in the gas phase by electron diffraction. Fluorination leads to structures with shorter C-O and N-O bonds, has an energetically destabilizing effect and increases friction sensitivity, but decreases detonation performance.

Energetic Metal and Nitrogen-Rich Salts of the Pentaerythritol Tetranitrate Analogue Pentaerythritol Tetranitrocarbamate.

The tetravalent pentaerythritol tetranitrocarbamate (PETNC) is deprotonated by nitrogen-rich, alkaline, alkaline earth metal, and silver bases to form the corresponding salts. Thorough analysis and characterization by multinuclear NMR, vibrational spectroscopy, elemental analysis, thermoanalytical techniques, and single crystal X-ray diffraction was performed. Furthermore, the energies of formation for the nitrogen-rich salts were calculated utilizing the Gaussian program package. The detonation performances were calculated with the Explo5 (V6.03) computer code, and the sensitivities toward impact and friction were determined and compared to the neutral PETNC and pentaerythritol tetranitrate (PETN). Ecotoxicological studies of the ammonium and guanidinium salt using Vibrio fischeri bacteria complete this study.

Synthetic Routes to a Triazole and Tetrazole with Trinitroalkyl Substitution at Nitrogen.

Two N-substituted trinitroalkyl azoles, one triazole, and one tetrazole were synthesized and isolated via efficient cyclization reactions. Both materials were thoroughly characterized, and their structures were confirmed by X-ray diffraction. The formation of the N-trinitroethyl substituted triazole proceeds unexpectedly via nitrosation of an N-substituted diaminomaleonitrile initially with HNO3 and subsequently confirmed with HNO2. The N-trinitropropyl substituted tetrazole was prepared via a standard cyclization route from trinitropropylammonium chloride with orthoformate and azide.

Molecular Structure of Isocyanic Acid, HNCO, the Imide of Carbon Dioxide.

Isocyanic acid, HNCO, the imide of carbon dioxide, was prepared by reaction of stearic acid and potassium cyanate (KOCN) at 60 °C in a sealed, thoroughly dried reactor. Interestingly, its crystal structure, solved by X-ray single crystal diffraction at 123(2) K, shows a group-subgroup relation for the NCO- anion to carbon dioxide: (for CO2, cP12, Pa3̅, a = 5.624(2) Å, 150 K, C-O 1.151(2) Å; for HNCO, oP16, Pca21, a = 5.6176(9), b = 5.6236(8), c = 5.6231(7) Å, 123(2) K). Precise positions of H, N, C, and O were determined by DFT calculations with WIEN2k leading to interatomic distances C-O 1.17, C-N 1.22, N-H 1.03, and -N-H···N 2.14 Å, and the interatomic angle N-C-O 171°.

Synthesis and Properties of Tetranitro-Substituted Adamantane Derivatives.

Several new nitro-substituted adamantane compounds based on adamantane-1,3,5,7-tetrol were synthesized and the previously only briefly reported tetranitrate was reinvestigated. The materials were completely characterized by spectroscopic methods including some by X-ray diffraction. The energetic properties, thermal stabilities, and sensitivities of the nitrocarbamate, nitrocarbamate salt, and nitrate were determined and compared to current composites in terms of potential high-energy dense oxidizers (HEDOs). Furthermore, the enthalpies of all compounds were calculated, and their energetic performances investigated by using the EXPLO5 code.

Higher Performance and Safer Handling: Formulation Based on 2,2,2-Trinitroethyl Formate and Nitrocellulose.

A new, green propellant formulation based on the high-energy dense oxidizer (HEDO) 2,2,2-trinitroethyl formate (TNEF) and nitrocellulose (NC) was prepared and thermally investigated using non-isothermal thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Scanning electron microscopy (SEM) was used to check the crystals of the oxidizer and the homogeneity of the new propellant formulation (NC-TNEF). The burning behavior of NC-TNEF was recorded by high-speed camera to observe the smoke produced. A high specific impulse (Is =257.4 s) was obtained from the characteristics calculation of the new propellant formulation by using EXPLO5_V6.03 software. The NC-TNEF mixture did not show any endothermic peak and its exothermic peak was at 204.6 °C, which means that a composite might be formed. The activation energy of the NC-TNEF was in the range of 184-190 kJ mol-1 . NC-TNEF has a higher performance and a lower hazard compared with the double-base propellant.

Tetranitromethane: A Nightmare of Molecular Flexibility in the Gaseous and Solid States.

After numerous attempts over the last seven decades to obtain a structure for the simple, highly symmetric molecule tetranitromethane (C(NO2 )4 , TNM) that is consistent with results from diffraction experiments and spectroscopic analysis, the structure has now been determined in the gas phase and the solid state. For the gas phase, a new approach based on a four-dimensional dynamic model for describing the correlated torsional dynamics of the four C-NO2 units was necessary to describe the experimental gas-phase electron diffraction intensities. A model describing a highly disordered high-temperature crystalline phase was also established, and the structure of an ordered low-temperature phase was determined by X-ray diffraction. TNM is a prime example of molecular flexibility, bringing structural methods to the limits of their applicability.

The Exciting Chemistry of 1,1-Diamino-2,2-dinitroethene and 1-Amino-1-hydrazino-2,2-dinitroethene.

1,1-Diamino-2,2-dinitroethene (FOX-7) is a relatively new highly energetic material, with good explosive performance and low sensitivity against mechanical stimuli and thermal stress. Therefore, on the one hand, FOX-7 is very stable and a starting material with fairly low reactivity. On the other hand, chlorosulfonyl isocyanate ClSO2NCO is a very reactive reagent and represents a highly activated form of isocyanic acid HNCO. New derivatives of FOX-7 and its hydrazine analogue 1-amino-1-hydrazino-2,2-dinitroethene, as well as unusual potassium salts, are described. Besides the usual spectroscopic characterization, the structures of all compounds were investigated and discussed by single-crystal X-ray diffraction. The compounds demonstrate good thermal stabilities, very high densities, and excellent sensitivity values. The heats of formation were calculated, and together with the room-temperature densities, the energetic parameters were estimated. The compounds are potential candidates as insensitive high-energy-density materials and starting materials for further chemistry.

Convenient synthesis of energetic polynitro materials including (NO2)3CCH2CH2NH3-salts via Michael addition of trinitromethane.

The nucleophilic Michael addition of nitroform with acrylamide creates a variety of energetic products. Several interesting compounds with a trinitromethyl group were synthesized, among them salts containing the trinitropropylammonium cation, [(NO2)3CCH2CH2NH3]X. Owing to their positive oxygen balance, the suitability of these compounds as potential high-energy dense oxidizers (HEDOs) in energetic formulations was investigated and discussed. Furthermore, numerous important and reactive compounds for the continuing synthesis of molecules with a high oxygen balance are presented. All compounds were fully characterized, including multinuclear NMR spectroscopy, vibrational analysis (IR, Raman), elemental analysis, as well as single crystal X-ray diffraction. Thermal stabilities were studied using differential scanning calorimetry and sensitivity data against friction, impact and electrostatic discharge were collected. The energies of formation were calculated using Gaussian 09 and energetic properties, such as the specific impulse and detonation velocity, were predicted with the EXPLO5 (V6.02) computer code.

N-Nitrosarcosine: An Economic Precursor for the Synthesis of New Energetic Materials.

New energetic compounds have been synthesized starting from the readily available N-(cyanomethyl)-N-methylamine. From this, N-nitrosarcosine was prepared in few steps, which serves as a starting material for the synthesis of oxygen-rich compounds. The compounds were thoroughly characterized including multinuclear NMR and vibrational spectroscopy and also molecular structures by single X-ray diffraction were obtained. Their energetic properties were determined including the sensitivities towards impact and friction, their heat of formations were calculated and the detonation and combustion parameters were predicted using EXPLO5 V6.02.

Isolation of a Moderately Stable but Sensitive Zwitterionic Diazonium Tetrazolyl-1,2,3-triazolate.

An unexpected formation of a diazonium compound was observed by nitration of an amino substituted triazolyl tetrazole with mixed acid. The crystal structure determination revealed a zwitterionic diazonium tetrazolyl-1,2,3-triazolate, whose constitution was supported by NMR and vibrational spectroscopic analysis. The thermal stability and sensitivity toward impact and friction were determined. In contrast, diazotriazoles are rather unstable and are mainly handled in solution and/or low temperatures, which is not the case for this diazonium tetrazolyl-1,2,3-triazolate, being stable at ambient temperature.

Carbonyl Diisocyanate CO(NCO)2: Synthesis and Structures in Solid State and Gas Phase.

A modified synthesis for carbonyl diisocyanate, CO(NCO)2, starting from trichloroisocyanuric acid and diphosgene is described. In addition to the previously reported (13)C NMR resonances, the (15)N NMR shift is determined for the first time. The structure in the solid state was determined by X-ray diffraction (XRD) on in situ grown crystals, that in the gas phase was experimentally determined by electron diffraction (GED) and for single molecules theoretically by quantum-chemical calculations. The structures are compared and discussed with related systems. Quantum-chemical calculations as well as GED and XRD prove syn-syn to be the conformation of lowest energy. In quantum-chemical calculations and GED the presence of a syn-anti conformer was confirmed and the structure of this conformer was determined.

Energetic Sila-Nitrocarbamates: Silicon Analogues of Neo-Pentane Derivatives.

Four silanes based on the neo-pentane skeleton Me4-xSi(CH2R)x containing carbamate groups (x = 1-4, R = OC(O)NH2) have been prepared via the corresponding alcohols Me4-xSi(CH2OH)x, starting from the chlorosilanes Me4-xSiClx. Subsequent nitration leads to the corresponding primary nitrocarbamates (R = OC(O)NHNO2), examined for the purpose as potential energetic materials, including the silicon analogue of pentaerythritol tetranitrocarbamate (sila-PETNC) and a siloxane based nitrocarbamate side-product. All compounds were thoroughly characterized by spectroscopic methods including X-ray diffraction. Thermal stabilities and sensitivities toward impact and friction were examined, as well as detonation values by calculating energies of formation using the EXPLO5 V6.02 software.

Efficient Synthesis of Primary Nitrocarbamates of Sugar Alcohols: From Food to Energetic Materials.

The synthesis of various new polyvalent nitrocarbamates derived from sugar alcohols was accomplished by an economically benign two-step synthesis. The precursor carbamates were synthesized with the reagent chlorosulfonyl isocyanate (CSI) and further nitrated using mixed acid. The starting materials, sugar alcohols, are renewable biomass, mainly used in food and cosmetic industry. The structures of one carbamate and one nitrocarbamate were exemplary described by single-crystal X-ray-analysis. The heat of formation is calculated by the use of isodesmic reactions and the energetic performance data were estimated. All compounds were fully characterized by elemental analysis, vibrational spectroscopy, (1)H, (13)C, and (14/15)N NMR spectroscopy and thermal analysis (DSC). The nitrocarbamates exhibit good detonation performance and have significantly lower sensitivities compared to the commonly used nitrate ester explosive PETN.