ADN

     ADN, or ammonium dinitramide, is the newest wonder propellant everyone wants to use in rockets. Unfortunately, ammonium dinitramide is very expensive to manufacture costing anywhere between $3000 and $5000 a pound! As a rocket propellant it is superior to the usual lineup of ammonium perchlorate and others. It is environmentally benign as its reaction products are only air, it is lighter than most other propellants, and it is more powerful. Using ammonium dinitramide to power the space shuttle, for example, would reduce the fuel weight by 40% and increase thrust by 10%. Ammonium dinitramide was first theorized in the 1989 by Dr. Jeffrey Bottaro and soon thereafter was prepared in the lab at the Office of Naval Research. The Soviets are thought to be the first to use ammonium dinitramide in rockets, likely in violation of the patent rights. Ammonium dinitramide has a wide verity of uses including the aforementioned rocket propellant, other uses include gun propellants, air bag gas generating charges, a phase transfer catalyst for removing heavy metals from waste water, and as a blood pressure medication. The race is still on to see who can develop an economical synthesis for ammonium dinitramide.

CHEMICALS	APPARATUS
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     Synthesis 1:
Into a 250 mL Erlenmeyer flask combine 3 g of potassium dinitramide and 3 g of finely powdered ammonium sulfate. Add 100 mL of isopropyl alcohol and heat the flask, while stirring, until all of the solids dissolve. Place the flask in a cold water bath to precipitate the byproduct of potassium sulfate. Filter to remove the crystals of sulfate and gently heat the filtrate to concentrate it to a fraction of its volume. Pour the concentrate into a beaker containing an excess of petroleum ether to precipitate ammonium dinitramide. Filter to collect the crystals and dry them in an oven at 50 C.

      Synthesis 2:
Prepare a mixture of 7.5 g of ammonium N-nitrourethane suspended in 200 mL of methylene chloride. Cool this mixture to -50 C in an acetone-dry ice bath. Prepare a second mixture of 45 mL of dinitrogen tetroxide in 200 mL of dry methylene chloride. Cool this mixture to -78 C in an acetone-dry ice bath. Bubble ozone into the second mixture, while stirring, until it is a dark blue color. While bubbling the ozone allow the mixture to warm up to -30 C. The mixture will now consist of dinitrogen pentoxide in methylene chloride. Combine the two mixtures an let them sit for 1 hour. During this time the temperature of the reaction mixture is allowed to warm to -30 C. Bubble ammonia gas into the mixture to raise the pH to 10. Filter to collect any insoluble material and add it to a beaker containing 150 mL of acetonitrile. Stir the acetonitrile mixture for 20 minutes before filtering to remove any remaining undissolved impurities. The filtrate is poured into a 4”x1” column containing 230-400 mesh silica gel. The ammonium dinitramide is eluted by adding acetonitrile. The resulting eluted filtrate is concentrated to 30 mL and treated with 30 mL of chloroform to precipitate pure ammonium dinitramide. The crystals are filtered to collect them and allowed to dry. Final yield is about 4 g or 60%.

      Synthesis 3:
Prepare a mixture of 8.8 g of hydrofluoric acid and 40 g of ethylnitrate in 300 mL of dry nitromethane. Place this mixture in a salt-ice bath and cool to 10 C. Slowly add 100 g of boron trifluoride to the mixture while keeping the temperature between 10 and 15 C. A few minutes after the addition filter to collect the crystals of nitronium tetrafluorate that form. Wash the crystals with two 400 mL portions of a 1:1 mixture of methylene chloride and nitromethane, and then with one 400 mL portion of methylene chloride. Place the nitronium tetrafluorate crystals into a beaker containing 400 mL of methylene chloride. Cool the contents to -78 C in an acetone-dry ice bath. Bubble 35 g of anhydrous ammonia into the beaker over a period of 2 hours while stirring. Continue stirring the mixture for 12 hours while allowing it to warm to room temperature. Filter to collect the solid material and wash it with 400 mL of methylene chloride. Add the crystals to 150 mL of acetone and stir for 1 hour. Add 150 mL of ethyl acetate to the mixture and filter to remove any undissolved material. Gently heat the filtrate solution to dryness to obtain crude ammonium dinitramide. The ammonium dinitramide can be purified by recrystallizing from n-butanol. Final yield is about 5.5 g or 21%.

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