Synthesis of 5,7-diamino-4,6-dinitrobenzofuroxan

Abstract

5,7-Diamino-4,6-dinitrobenzofuroxan is synthesized in high yield by amination of 7-amino-4,6-dinitrobenzofuroxan with hydroxylamine in the presence of strong base such as potassium hydroxide. Acidification of the potassium salt produces a fine powder. Recrystallization of the powder by an extraction process under vacuum in solvents such as dimethylformamide results in large, cube-like crystals which can be pressed to high density explosive formulations. These explosive formulations show high performance as explosives.

What I claim is: 
     
       1. A method of synthesizing 5,7-diamino-4,6-dinitrobenzofuroxan comprising the steps of: aminating 7-amino-4,6-dinitrobenzofuroxan with a salt of hydroxylamine in the presence of a Group 1 metal hydroxide in a concentration from 0.5 N to 5 N to form a salt:   acidifying the salt with a strong acid to precipitate 5,7-diamino-4,6-dinitrobenzofuroxan as a fine powder; and,   extracting the fine powder with solvent and recrystallizing the powder to form crystals having a size above 1 m.   
     
     
       2. A method according to claim 1 in which the solvent is an organic solvent selected from acetone, dimethylformamide, acetonitrile, nitromethane and N-methylpyrrolidinone and the temperature is adjusted to 130° C. or lower by system pressure selection. 
     
     
       3. A method according to claim 1 in which the solvent extraction results in cube-like crystals having a size above 25μm. 
     
     
       4. A method according to claim 3 in which the solvent is selected from dimethylformamide, acetone or N-methylpyrrolidinone. 
     
     
       5. A method according to claim 4 in which the solvent is dimethylformamide. 
     
     
       6. A method of forming large crystals from a fine powder of 5,7-Diamino-4,6-dinitrobenzofuroxan comprising the steps of: dissolving the fine powder in solvent to form a solution; and   reprecipitating the 5,7-Diamino-4,6-dinitrobenzofuroxan from the solution by increasing concentration to form crystals having a size above 1μm.   
     
     
       7. A method according to claim 6 in which the temperature is below 130° C. 
     
     
       8. A method according to claim 7 in which the solvent is disposed in a first chamber, the fine powder is disposed in a second chamber, a porous filter separates the two chambers and the first chamber is heated to vaporize the solvent, the vapors rise into the second chamber and condense to form liquid solvent which dissolves the fine powder as it returns to the first chamber. 
     
     
       9. A method according to claim 8 in which the temperature is below 105° C. and the solvent is an organic solvent selected from acetone, dimethylformamide, acetonitrile, nitromethane and N-methylpyrrolidinone, the boiling point being adjusted by system pressure. 
     
     
       10. A method according to claim 9 in which the solvent is selected from dimethylformamide, acetone or N-methylpyrrolidinone. 
     
     
       11. A method according to claim 10 in which the solvent is dimethylformamide.