Dinitrobenzene comes in three isomers, they are ortho, meta, and para-dinitrobenzene. The most important explosive isomer is meta-dinitrobenzene, or just m-dinitrobenzene, other names include dinitrobenzol; 1,3-dinitrobenzene; 2,4-dinitrobenzene; binitrobenzene; and 1,3-dinitrobenzol. This material was used as a replacement for TNT back in World War I since it was somewhat more economical. The Russians used dinitrobenzene from 1914 to 1918 as a filling for naval mines, in Germany it was called Di-Füllpulver, DiFp for short, for use in shells. An earlier explosive called Hellhoffites mixed nitric acid and dinitrobenzene, this was used in 1897-1880. This compound was first prepared by St. C. Deville in 1841 by treating benzene with concentrated nitric acid and boiling. I should warn you that this particular substance is very toxic, poisoning may be caused by inhaling the vapors or by absorption through the skin. The volatility is rather low but a concentration as low as 1 mg per cubic meter of air can cause acute poisoning. Poisoning is more likely in warm weather when the vapor pressure is higher due to the increased temperature. So keep it cool, donít touch it and wear some sort of respirator. Frequent exposure and past poisoning will increase the probability of future poisoning. Women, especially, should stay away as it affects them more than men. The sensitivity of m-dinitrobenzene is quite low, it requires an initiator charge to detonate it. This procedure requires nitrobenzene as the main ingredient, the preparation of which is in the synthesis section. This procedure makes about 92% meta, and an 8% mix of ortho and para isomers.
|ethyl alcohol||Erlenmeyer flask|
|nitric acid||graduated cylinder|
|sodium hydrogen sulphite||stirring rod|
To prepare dinitrobenzene, heat a mixture of 14 mL of concentrated sulfuric acid and 10 mL of concentrated nitric acid in an open Erlenmeyer flask in a boiling water bath in an area with good ventilation. 10 g of nitrobenzene is added gradually over a period of 30 minutes. The mixture is allowed to cool somewhat, then drowned in cold water. The dinitrobenzene should separate as a solid. Crush it under water with a stirring rod, wash with water, and recrystallize from ethyl alcohol or nitric acid. Dinitrobenzene crystallizes from nitric acid in beautiful needles which are practically colorless. Further purification by removing the ortho and para isomers can be achieved by reacting the product with sodium sulphite, it is not necessary to do this, but it will give a highly refined product. The dinitrobenzene is added to a 33% sodium hydroxide solution and heated to 50 °C while vigerously stirring. The temperature must be monitored with a thermometer to insure it does not rise above 80-85 °C. The total washing time is 30 minutes. During the washing, the pH must be alkaline, test often with pH paper. If at any point the pH is not alkaline, add more sodium hydroxide solution. Next, sulphitation of dinitrobenzene is done by adding cold water to the above alkaline solution until the temperature falls to 66 °C. Then, a solution of sodium sulfite, prepared by mixing a 40% solution of sodium hydrogen sulphite with half its volume of 33% sodium hydroxide solution, is added. Maintain the temperature at 66-73 °C while stirring for 2 hours. Afterwards, cool the mix to 50 °C and the purified dinitrobenzene will precipitate into large crystals. The majority of the liquor can be decanted off and the crystals poured over a filter to collect them. Wash the crystals throughly by repeated rinsings with water. The final product can be dried at 135 °C under reduced pressure. You will need a graduated cylinder for measuring liquids.
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