FOX-7

• FOX -7
• DADE
• DADNE
• 1,1- diamino-2 ,2- dinitroethen

Fixed

• α - form 1.88 g · cm -3
• β - form 1.80 g · cm -3

From 180 ° C decomposition

Insoluble in water, slightly soluble in acetonitrile and cyclohexanone are soluble in DMSO, dimethylformamide and N-methylpyrrolidone

Template: Infobox chemical / molecular formula search available

For Diaminodinitroethylen three isomeric structures can be formulated. Of the possible isomers of 1,1- diamino-2 ,2- dinitroethylen (1), trans-1 ,2 -diamino -1 ,2- dinitroethylen (2) and cis-1 ,2 -diamino -1 ,2- dinitroethylen ( 3) is so far only former synthetically accessible.

1,1- diamino-2 ,2- dinitroethylen (FOX -7 or DADE ) is an energy-rich chemical compound which is suitable as the basis for highly sensitive and yet insensitive explosives. For the two 1,2- diamino-1 ,2- dinitroethylen isomers there is so far only theoretical, quantum-chemical calculations. A real production and characterization of the two compounds is still pending.

History

The synthesis of 1,1- diamino-2 ,2- dinitroethylen derivatives has been described as early as 1992. Starting from 1,1- diiodo -2 ,2- dinitroethylen can be obtained through the sales alkylamines with the corresponding 1,1 - dialkyl -2 ,2- dinitroethylen connections. The reaction with ammonia yielded the reaction product of the ammonium salt and thus not Cyanodinitromethan the base compound, 1,1- diamino-2 ,2- dinitroethylen. 1,1 -Diamino -2 ,2- dinitroethylen (FOX -7) was first synthesized in 1998 at FOI (Swedish Defence Research Agency ). With a yield < 10% of this synthetic route is not meaningful, despite the inexpensive starting material 2-methyl -imidazole commercially.

Production and representation

The production of Diaminodinitroethylen is performed only in small batch sizes, resulting in a relatively high price for the compound results. An optimized synthesis with a yield > 90% of proceeds from 2,6- dihydroxy-4- methylpyrimidin, which is converted by a nitration in mixed acid to a tetra nitro intermediate. The intermediate product is then hydrolysed to the target compound, dinitromethane, and carbon dioxide. The starting compound 2,6- dihydroxy-4- methylpyrimidine is accessible by the cyclization of acetamidine hydrochloride with diethyl malonate in the presence of sodium and ethanol.

A check of conversion is possible here on separation by liquid chromatography using special graphite columns.

Properties

Physical Properties

1,1- diamino-2 ,2- dinitroethylen form yellow crystals. The compound shows a polymorphic behavior. At room temperature, the α - form is available, which converts to the β - form upon heating at 114 ° C. This phase transition is reversible. A further conversion to the γ - form is observed at 173 ° C. The γ - form is metastable and converts only slowly and incompletely during cooling in the low-temperature form α to. For the connection, no melting point can be found, as DSC measurements from 180 ° C show already a strongly exothermic decomposition reaction. Single crystal of crystallized from NMP / water α - form revealed a monoclinic crystal structure. The presence of electron-donating and electron-withdrawing groups in the molecule leads to a change bond lengths. The bond lengths of the carbon -carbon bond is 145.6 pm with the typical bond lengths between a single bond or double bond with 154 pm to 134 pm. The connection thus does not have a pure double bond structure. It may be formulated two resonance structures, wherein the imine is present more polar. This is also confirmed by the observed chemical properties such as in electrophilic additions.

In the molecule, there are two strong intramolecular hydrogen bonds between the NH and NO functions. This results in a planar Grundstrukturdes molecule. In the crystal lattice forms on basic intermolekulerer hydrogen bonds a wavy layer structure. The crystal structure of the β - form is orthorhombic. The γ - form exhibits a monoclinic crystal lattice with the space group P21 / n

The compound is virtually insoluble in water. In other solvents such as acetone, ethyl acetate or acetonitrile, the solubility is low with < 0.5 g/100 ml. Better solubility are observed in N, N -dimethylformamide at 21 g/100 ml in N-methyl -2-pyrrolidone of 32 g/100 ml and 45 g/100 ml in dimethyl sulfoxide.

The molar enthalpy is ΔfH0 = -130 kJ / mol. The NMR spectra of the compound set quite easily Represents the 1H - NMR spectrum shows only at 8.77 ppm a broad peak resulting from the NH protons. In the 13C NMR spectrum shows two peaks at 128.5 ppm for the nitro- substituted carbon atom and at 158.8 ppm for the carrying the amino carbon atom.

Thermal stability and explosive properties

1,1- diamino-2 ,2- dinitroethylen shows no melting point during heating. In thermoanalytical measurements, a two-step decomposition with a heat of decomposition of -1427 J / g is observed from 180 ° C. The decomposition mechanism has been considered theoretically in terms occurring between joints and leads to the final products of carbon monoxide, nitrogen and water.

Important figures such as the explosion heat of explosion, the detonation velocity or the detonation pressure were estimated using different methods of calculation or determined by various measurement methods experimentally. Calculated values ​​for the heat of explosion between 4442 J · g -1 and 4884 J · g -1, for the detonation velocity between 8453 m · s -1 and 8869 m · s -1 and for the detonation pressure between 29.3 GPa and 34, 0 GPa. The experimentally determined values ​​are for the detonation energy 4860 J · g -1, the detonation velocity between 8325 m · s -1 and 8405 m · s- 1 and the detonation pressure 28.4 GPa. The connection is with an impact energy 11-40 Nm sensitive to impact. The impact sensitivity depends on the grain size distribution of the material tested. Up to a friction force of 353 N no friction sensitivity was observed.

Chemical Properties

The compound has acidic properties. In the presence of bases can be a deprotonation. The pKa value is about 10.6. In a reaction with potassium hydroxide solution at low temperatures can be the potassium salt as a white, isolate a crystalline solid. Heating to 70 ° C and the potassium hydroxide solution leads to a basic hydrolysis, wherein the potassium salt of Dinitromethans and urea are formed.

Due to the high polarity differences in the molecule itself interesting aspects for chemical reactions arise. The compound can be in the presence of acetic anhydride or weiternitriert trifluoroacetic anhydride using nitric acid. The resulting tetra- nitro compound is thermally unstable. A decomposition is relevant starting at room temperature. At -20 ° C, the compound can be stored for about a week. A decomposition in ammoniacal acetonitrile solution gives the ammonium salt of the Trinitromethans and nitroguanidine.

The halogenation with N-bromosuccinimide or N- chlorosuccinimide in the nitration is carried out analogously to the bearing, the geminal carbon atom and a nitro group to an amino group. Oxidation with 30% hydrogen peroxide in sulfuric acid, or with trifluoroacetic acid results in the release of nitrous acid and dinitrogen trioxide to Diaminoessigsäure.

1,1- diamino-2 ,2- dinitroethylen can be used as a starting material for the production of tetrazoles. Thus is achieved by the reaction with trimethylsilyl azide in DMSO with the formation of 5 - Amidinotetrazols the Tetrazolringbildung. By basic hydrolysis of the potassium salt of tetrazole -5- carboxylic acid amide can be obtained. Its reaction with methyl iodide results in the two isomers 1- methyltetrazole -5 -carboxamide and 2- methyltetrazole -5 -carboxamide.

Use

Due to its acidic properties may FOX- 7 are reacted with basic and nucleophilic substances to produce more high-energy substances. So is the reaction with guanidinium chloride in the presence of potassium hydroxide, the Guadidiniumsalz G (FOX -7). The higher nitrogen content in the molecule results in thermal decomposition of a higher evolution of gas, which enables use in propellant charges.