The Chemistry of Powder and Explosives - Sciencemadness Dot Org

TETRYL 177
All the above-indicated intermediates have been isolated from
the reaction. The last step is interesting because it is a reversible
nitration. If tetryl is dissolved in concentrated (95 per cent)
sulfuric acid and allowed to stand, the nitro group on the nitrogen
is replaced by hydrogen, and nitric acid and trinitromethylanilino
(methylpicramide), m.p. 111.8-112.4°, are formed. 80 Tetryl accordingly
gives up this nitro group, and only this one, in the
nitrometer. In the industrial preparation of tetryl, the usual
method is to dissolve the dimethylaniline in concentrated sulfuric
acid and then to carry out all the reactions in one stage. The
process has been the subject of many careful studies, among
which those of Langenscheidt, 81 van Duin, 82 Knowles, 83 Wride, 84
Desvergnes, 85 and Bain 86 are especially to be noted. The crude
tetryl contains impurities which must be removed by boiling the
finely comminuted substance in water, and by dissolving the
crude material in benzene and filtering for the removal of insoluble
materials. For the industrial crystallization of tetryl,
either acetone or benzene is commonly used.
Preparation of Tetryl. Twenty grains of dimethylaniline is dissolved
in 240 grams of concentrated sulfuric acid (d. 1.84}, the temperature
being kept below 25°, and the solution is allowed to run from a separatory
funnel drop by drop into 160 grams of 80 per cent nitric acid
(d. 1.46), previously warmed to 55° or 60°, while this is stirred continuously
and kept at a temperature between 65° and 70°. The addition
requires about an hour. After all has been added, the stirring is continued
while the temperature of the mixture is maintained at 65° to 70°.
The material is allowed to cool; the solid matter is collated on an asbestos
filter, washed with water, and boiled for an hour with 240 cc. of
water while further water is added from time to time to replace that
which boils away. The crude tetryl is filtered off, ground under water to
pass a 150-mesh sieve, and boiled twice for 4 hours each time with 12
times its weight of water. The solid is dried and treated with benzene
sufficient to dissolve all readily soluble material. The solution is filtered
and allowed to evaporate spontaneously, and the residue is recrystal-
80 Davis and Allen, J. Am. Chem. Soc, 46, 1063 (1924).
81 Z. ges. Schiess- u. Sprengstoffw., 7, 445 (1912).
62 Rec. trav. chim., 37, 111 (1917).
83 /. Ind. Eng. Chem., 12, 247 (1920).
84 Arms and Explosives, 1920, 6.
s5 Mem. poudres, 19, 217 (1922).
86 Army Ordnance, 6, 435 (1926).