decomposes at 243 °C
2,2',4,4',6,6'-hexanitrodiphenylamine, also known as dipicrylamine, hexamine, hexamin, heksyl, hexil, hexamite, hexite, or usually hexyl, was first prepared back in 1874 and was used as early as 1910 in both world wars, mostly by the Germans. Other scientific names include 2,4,6-trinitro-N-(2,4,6-trinitrophenyl)- benzenamine; 2,4,6-Trinitro-N-(2,4,6-trinitrophenyl)benzenamine; and Bis(2,4,6-trinitrophenyl)amine. Foreign names include esanitrodifenilammina o exiI in Italian; hexanitrodifenilamina o hexamina in Spanish; and gheksonitrodifenilamin in Russian.
Hexyl forms yellow needles in its crystalline state and decomposes slightly at its melting point of 243-245 °C. Hexyl is slightly hygroscopic at room temperature so keep it stored tightly away from air. Hexyl is very toxic, attacking the skin and causing severe burns. It causes respiratory irritation of the nose and throat if inhaled. Hexyl is not really a sensitive compound, it can be heated up to 250 °C before detonating if heated at a rate of 5 °C a minute. It can be detonated by severe shock, but you would have to treat it pretty badly. Drop tests caused detonations when a 2 kg weight fell from 60 cm. The explosive power is around 6900 m/s and increases with greater density to around 7150 m/s at 1.67 g/cc which is comparable to TNT.
The Germans and the Japanese used this explosive in admixture with TNT in torpedoes, sea mines, depth charges, and bombs. Commercially this explosive was used in compositions called Neurodits. The Swedish used it in compositions called Novit. The Germans mixed it with aluminum powder in compositions called Schieewolle 18, and it was also used in German skip bombs. The Japanese used it in compositions called Seigata (aka Type 97), and Otsu-B.
This preparation will be carried out in two stages forming dinitrophenylamine, tetranitrophenylamine, and finally hexanitrodiphenylamine. 70 mL of aniline and 32 g of pure calcium carbonate are stirred up together with 300 mL of water in a 500-mL beaker to form a homogeneous suspension, and the mixture is heated to about 60 °C. 150 g of previously melted dinitrochlorobenzene is slowly added by pouring in a fine stream from a beaker while the stirring is continued and the mixture is gradually heated to about 90 °C, the rate of heating being regulated by the progress of the reaction which can be determined by the formation of dinitrophenylamine. The product is poured over a filter to collect the crystals, washed with hydrochloric acid to free it from aniline and calcium carbonate, then with water until free from chlorides, and dried in an oven at 100 °C.
In the first stage, 50 g of finely powdered dinitrodiphenylamine (formed from the above process) is added in small portions to 315 mL of 50-55% nitric acid in a 500-mL beaker, which is stirred vigorously while the temperature is maintained at 50-60 °C. The progress of the nitration is followed by observing the color change from the red of the dinitro compound to the yellow of the tetranitrodiphenylamine. After the dinitrodiphenylamine has been added, the temperature is raised to 80-90 °C and kept there for two hours longer while the stirring is continued. After the mixture has cooled, the product is filtered off directly, washed with water until free from acid, and dried in the air or in an oven at 100 °C.
In the second stage, 50 g of tetranitrodiphenylamine (formed in the first stage) is added slowly from a pipet or buret, with stirring, over one hour, to a mixture of 170 mL of 100% nitric acid and 140 mL of 100% sulfuric acid in a 500-mL beaker. After all of the tetranitrodiphenylamine has been added, the mixture is allowed to stand for 3 hours at room temperature, and is then drowned in ice water. The hexanitrodiphenylamine that should have formed is filtered off, washed thoroughly with water, dried in the air, and recrystallized from acetone with the addition of petroleum ether. You will need a graduated cylinder for measuring liquids, a stirring rod or magnetic stirrer for mixing, and a thermometer to monitor the temperature.
Into a 1000-mL Florence flask containing 500 mL of concentrated sulfuric acid (100%) slowly add, while swirling the flask, 50 g of roughly ground diphenylamine. Into a 5-L round-bottomed flask immersed in an ice bath place 333 mL (500 g) of fuming nitric acid (100% with 5-10% dissolved nitrogen dioxide). Set the flask up for addition and slowly add the sulfuric acid solution drop by drop to the nitric acid while maintaining a temperature of 30 C. After adding all of the solution heat the flask on a steam bath until no more nitrogen dioxide gas escapes (CAUTION: this gas is toxic, use adequate ventilation!). The blue colored solution should fade and yellow crystals will precipitate. Allow the mixture to cool to room temperature and then slowly pour it into a large container of 5 L of ice water. Pour this solution over a filter to collect the product and wash it thoroughly first with cold and then with hot water until no trace of acid remains. Dry the product in an oven at 100 C. Yield is about 88 g. The product may be purified by recrystallization from 75% nitric acid.
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