DNPA

     DNPA is the acronym for 4,4-dinitropimelic acid, another name is 4,4-dinitro-1,7-heptanedioic acid. This explosive is fairly stable to heat and shock as well as being storable at room temperature. While it is an explosive itself, it is usually used to manufacture polynitroaliphatic explosives and propellents. It may be more useful to polymerize this compound into the polyester polymer 4,4-dinitropimelyl chloride and 2,2-dinitro-1,3-propanediol.

CHEMICALS	APPARATUS
charcoal	beaker
ethyl ether	graduated cylinder
hydrochloric acid	pipet/buret
methyl alcohol	stirrer/stirring rod
methyl acrylate
potassium dinitroethanol
water

     Preparation is by two steps, the first forms the dimethyl ester of DNPA, and the second hydrolyzes it. In the first step, 1200 mL of methyl acrylate is added dropwise, with a pipet or buret, while stirring with a magnetic stirrer or stirring rod, to an aqueous solution of 2.5 moles of potassium dinitroethanol at room temperature inside a large beaker. The addition is completed in 3 hours with 8 more hours of stirring required to complete the reaction. After completion of the stirring , the ester that should have formed is extracted several times with ethyl ether, decolorized with charcoal, and the ethyl ether is removed under vacuum. The impure ester is then recrystallized from methyl alcohol. The second step hydrolyzes 39 g of the ester by refluxing it with 350 mL of 18% hydrochloric acid for several hours. After cooling, the 4,4-dinitropimelic acid is crystallized by adding water. The total yield based on potassium dinitroethanol is 55-56%. You will need a graduated cylinder for measuring liquids.

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