The Chemistry of Powder and Explosives - Sciencemadness Dot Org

170 AROMATIC NITRO COMPOUNDS
acid and trinitrocresol, but it contains no hydroxyl group and
docs not attack metals readily with the formation of dangerously
explosive salts. In actual use, however, it reacts slowly with
moisture and yields some picric acid. It has been colloidcd with
nitrocellulose in the form of a strip powder, flashless and of low
hygroscopicity, but the powder in the course of time developed
enough picric acid to stain the fingers and to give a yellow solution
with water. Its relatively low melting point, 67-68°, gives it
an advantage over picric acid for certain purposes. Methyl alcohol
is needed for its synthesis, and the present availability of
this substance cheaply from high-pressure synthesis further
commends it. While anisol is an expensive raw material, and has
the further disadvantage that its direct nitration is dangerous,
trinitroanisol may be prepared, without it, economically and
easily from benzene through the use of dinitrochlorobenzene.
Trinitroanisol was prepared by Cahours 88 in 1849 by the direct
nitration of anisol, and the same process has been studied more
recently by Broadbent and Sparre. 04 The strongly ortho-para
orienting methoxy group promotes substitution greatly, the first
products of the nitration are explosive, and the temperature of
the reaction mixture during the first stages ought never to be
allowed to rise above 0°. A small drop of anisol, or of phenetol
or other aromatic-aliphatic ether, added to 10 cc. of nitric acid
(d. 1.42) in a test tube and shaken, causes a remarkable series of
color changes; the liquid turns yellow, then green, then blue, and
finally reddish purple. A batch of anisol which was being nitrated
at ordinary temperature in the author's laboratory detonated
without warning and without provocation while showing a bluishpurple
color. Small pieces of the 2-liter flask which had contained
the mixture were propelled so violently that they punctured the
plate-glass windows of the laboratory without, however, breaking
or cracking them.
Trinitroanisol may also be prepared by the interaction of
methyl iodide and silver picrate, and by the nitration of anisic
acid, during which the carboxyl group is lost, but the most convenient
method appears to be that of Jackson 70 and his collaborators
by which a methoxy group is substituted for chlorine in a
nucleus already nitrated. A methyl alcohol solution of picryl
68 Ann., 69, 236 (1849).
69 Eighth Intern. Congr. Appl. Chem., 4, 15 (1912).
70 Am. Chem. J., 20, 448 (1898); 23, 294 (1901).