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236 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

Three-component systems with m- dinitrobenzene have been studied by Khai-

bashev and Bogush [12a]. They found ternary eutectics:

(1) 9% trinitro-m-xylene, 9% tetryl, 82% m-dinitrobenzene, m.p. 80.6%.

(2) 18.5% 1,8-dinitronaphthalene, 7% tetryl, 74.5 m- dinitrobenzene, m.p. 74.5°C.

(3) 8.5% trinitro-m-xylene, 16% pentaerythritol tetranitrate, 75% m- dinitrobenzene.

m.p 79.5%.

(4) 16.5% 1,8-dinitronaphthalene, 12.5% pentaerythritol tetranitrate, 71% m- dinitroben-

zene, m.p. 69°C.

(5) 5% trinitro-m-xylene, 43% picric acid, 52% m- dinitrobenzene, m.p. 57.6°C.

m- Dinitrobenzene can be separated from the o- isomer by paper-chromato-

graphy (Franc [13]), the mobile phase being composed of ethyl alcohol, water and

acetic acid.

The thermochemical properties of dinitrobenzene are given on pp. 259-262

(Fig. 50).

CHEMICAL PROPERTIES

m- Dinitrobenzene is the least reactive of the three isomeric forms of dinitro-

benzene, because its nitro groups are in the meta position to each other.

Like most nitro compounds all three isomers are resistant to concentrated

acids, and fairly sensitive to alkalis.

When treated with alkalis, o- and p- dinitrobenzenes are slowly converted to

o- and p- nitrophenols, while with ammonia they form o- and p- nitroaniline. These

reactions proceed slowly at room temperature, and more rapidly on heating.

(1)

m- Dinitrobenzene does not undergo this reaction. This property was utilized

in the past for separating m- dinitrobenzene from its isomers. Crude dinitrobenzene

was shaken up with a 0.5-1.0% NaOH solution at about 80°C and the o- and

p- isomers were partly extracted as corresponding nitrophenates. However, this
method was not very efficient as the purified dinitrobenzene had a low melting point
(80°C). It has now been replaced by sodium sulphite method.