Explosive and thermic compositions or charges – Containing nitrated organic compound – Nitrated acyclic – alicyclic or heterocyclic amine
Reexamination Certificate
2000-01-18
2001-11-06
Richter, Johann (Department: 1621)
Explosive and thermic compositions or charges
Containing nitrated organic compound
Nitrated acyclic, alicyclic or heterocyclic amine
C544S298000, C548S323500, C564S487000, C564S509000
Reexamination Certificate
active
06312538
ABSTRACT:
The invention relates to a new chemical compound, viz. 1,1-diamino-2,2-dinitroethylene, which is suitable for use as an insensitive explosive. The invention also concerns an intermediate for the compound and a method for preparing the compound and the intermediate.
J. Org. Chem. 1992, 57, pp 235-241; Baum, K. et al states 1,1-diamino-2,2-dinitroethylene as an interesting target molecule in research concerning explosives since it was assumed to have interesting properties as explosive. In spite of many experiments however, it has previously not been possible to prepare the compound.
The present invention presents a method of preparing 1,1-diamino-2,2-dinitroethylene.
The invention is defined by the claims.
According to the invention, 1,1-diamino-2,2-dinitroethylene is prepared by nitrating a starting compound consisting of a heterocyclic 5- or 6-ring containing the structural element
wherein Y is an alkoxy group, with a nitrating acid at a low temperature, preferably 0-30° C., and by selecting the acidity of the nitrating acid for obtaining a substantial yield of a product containing the structural element
and by hydrolysing said product in an aqueous medium for separating 1,1-diamino-2,2-dinitroethylene. Y in the structural element [2] can be for instance methoxy-, ethoxy-, t-butoxy-.
The invention also relates to an intermediate, suitable for preparing 1,1-diamino-2,2-dinitroethylene, consisting of a heterocyclic 5- or 6-ring of the general formula
wherein n is at least 1.
The intermediate can easily be separated by hydrolysis in an aqueous medium, whereby 1,1-diamino-2,2-dinitroethylene settles out.
The intermediate is prepared according to the nitrating process included in the preparation of 1,1-diamino-2,2-dinitroethylene. In the nitration, a precipitate forms which is separated from the reaction mixture. The precipitate consists of a compound containing the structural element [3]. This primarily formed product can (depending on the starting compound) be highly unstable owing to the presence of a gem-dinitro group, C(NO
2
)
2
, on a carbon atom in the heterocyclic ring. However, this group decomposes quickly to a keto group, C═O, which results in a more stable and practically useful intermediate. The intermediate according to the invention contains at least one keto group on the heterocyclic ring.
As starting compound for the nitration, use can be made of 2-methyl-1,3,4-triazines of the general formula
and isomers thereof, wherein X
1
and X
2
are equal or different and selected from a group consisting of —H, ═O, —Cl, —Br, ═N—OH, —SH, —NH
2
and —NH—R wherein R=alkyl group.
Other suitable starting compounds are 2-methyl-1,3,4—triazoles of the general formula
and isomers thereof, wherein Y is an alkoxy group, for instance —OMe, —OEt, —OtBu, and X is selected from a group consisting of ═O, —Cl, —Br, ═N—OH, —SH, —NH
2
and —NH—R wherein R=alkyl group.
Further suitable starting compounds are 2-methyl-1,3-diazines of the general formula
and isomers thereof, wherein Y is an alkoxy group, e.g. —OMe, OEt, OtBu, and X
1
and X
2
are equal or different and selected from a group consisting of ═O, —Cl, —Br, ═N—OH, —SH, —NH
2
and —NH—R wherein R=alkyl group
An example of such a compound is 2-methyl-4,6-pyrimidindione
Other suitable starting compounds are 2-methyl-1,3-diazoles of the general formula
and isomers thereof, wherein Y is an alkoxy group, e.g. —OME, —OEt, —OtBu, and X
1
and X
2
are equal or different and selected from a group consisting of —H, ═O, —Cl, —Br, ═N—OH, —SH, —NH
2
and —NH—R wherein R=alkyl group.
Examples of such compounds are
In the nitration use is made of a conventional nitrating system consisting of nitric acid or nitric acid in combination with another acid, i.e. a nitrating acid. In the first place nitric acid/sulphuric acid (HNO
3
/H
2
SO
4
) are preferred, but other conceivable nitrating acids are nitric acid/perchloric acid (HNO
3
/HClO
4
), nitric acid/phosphoric acid (HNO
3
/H
3
PO
4
), nitric acid/diphosphoric pentoxide (HNO
3
/P
2
O
5
), nitric acid/acetic acid, nitric acid/acetic acid anhydride, nitric acid/trifluoroacetic acid and nitric acid/trifluoroacetic acid anhydride.
The nitration is carried out at a low temperature, e.g. 0-30° C., and with a moderate acidity of the nitrating system, e.g. 100% nitric acid and 80-100% sulphuric acid. Under these conditions, a precipitate of a product containing the structural element [3] forms in the reaction mixture. Depending on the starting compound and the used nitrating acid, temperature and acidity may need be adjusted to give an optimal yield of the product. Particularly good results have been achieved with nitric acid (100%) and sulphuric acid (90-95%), a temperature of 10-25° C., especially 15-20° C., and a molar ratio of nitric acid to substrate of 2.0-6.0:1, preferably 3.5-4.0:1.
This precipitated product can be removed from the reaction mixture, dissolved in an aqueous medium and hydrolysed, whereby the product separates 1,1-diamino-2,2-dinitroethylene, which settles out as bright yellow crystals in the aqueous medium.
The precipitated product can also, as mentioned above, be isolated as an intermediate for subsequent use for preparing 1,1-diamino-2,2-dinitroethylene. The stability of this product, however, can be limited.
1,1-diamino-2,2-dinitroethylene can also be recovered more directly without the product from the nitration first being separated by the step of adding the reaction mixture from the nitration to an aqueous medium, whereby the desired compound settles out and can be separated. In some cases, especially when the starting compound is a heterocyclic 5-ring, it may be necessary to neutralise the aqueous medium for the product containing the structural element [3] to be hydrolysed and separate 1,1-diamino-2,2-dinitroethylene.
The neutralisation can be made until the solution becomes basic, preferably at pH 8-9. The neutralisation is suitably made with an aqueous solution of ammonia, e.g. 25% ammonia solution.
The reaction will now be described in more detail, nitration of 2-methylimidazole [13] being used as a typical example.
Nitration of imidazole and 2-methylimidazole has usually been carried out with nitric acid or potassium nitrate in an aqueous sulphuric acid (70-90%) at an increased temperature (80-120° C.) and resulted in 4(5)mono-nitro derivative as the main product. According to the invention, the nitration as carried out at a low temperature, preferably 0-30° C., and especially 10-25° C. For the majority of the starting compounds, a nitrating temperature of 15-20° C. has been found to be most favorable. In addition to the temperature, the acidity of the nitrating system is important to what products are being formed.
Nitration of 2-methylimidazole at 15-25° C. with 100% HNO
3
in 101-105% H
2
SO
4
mainly resulted in 2-methyl-4(5)-nitroimidazole and a certain amount of parabanic acid. Nitration with 100% HNO
3
in 80-100% H
2
SO
4
gave a very small amount of 2-methyl-4(5)-nitroimidazoie, more parabanic acid and a precipitate of a gem-dinitro derivative 2-(dinitromethylene)-5,5,-dinitro-4-imidazolone of the formula
In nitration with 100% HNO
3
in 90% H
2
SO
4
at 15-18° C., the gem-nitro derivative was recovered in 15% yield. The compound [17] is unstable at room temperature and decomposes within 3-5 hours while emitting NO
x
and forms 2-(dinitromethylene)-4,5-imidazoledione of the formula
When dissolved this decomposition proceeds considerably more quickly. The acid compound [18] is thermally stable but sensitive to nucleophiles such as water and ethanol. No spectral data of the compound [17] could be obtained since the compound was very sensitive and explosive.
13
C NMR spectrum for the compound [18] resulted in the three signals 157.7, 149.4, 130.1. The compound [18] decomposed slowly in DMSO while forming parabanic acid. The compound [17] as well as [18] dissolve
Langlet Abraham
Latypov Nikolai
Wellmar Ulf
Davis Brian J.
Jacobson & Holman PLLC
Richter Johann
Totalforsvarets Forskningsinstitut
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