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NITRO DERIVATIVES OF HALOGENOBENZENES 467

( o- and m- chloronitrobenzenes were also obtained in the reaction). The crude pro-

duct contains traces of chloropicrin as an impurity.

Dinitro derivatives of p- dichlorobenzene

Three isomeric p- dichlorodinitrobenzenes α (m. p. 106°C), β (m. p. 101°C;

b. p. 318°C) and γ (m, p. 119°C) are known, with the nitro groups in the positions
2,6- (3,5-), 2,3- and 2,5- (3,6-) respectively.

α β γ

The 2,6-isomer is the principal product of nitration of p- dichlorobenzene, the

2,3-isomer being formed in a smaller quantity, and the 2,5-isomer to a still smaller

extent.

The melting point of the crude nitration product ranges between 60°C and

80°C. Traces of chloropicrin can be detected in the product.

MacLeod, Pfund and Kilpatrick [40] believed that the 2,6- and 2,5-isomers

formed an addition compound (in a 3:2 ratio), melting at 81°C. The isomers are

very poisonous (Voegtlin [41]).

1,4-Dichloro-2,6-dinitrobenzene is difficult to dissolve in water and cold alcohol,

though it dissolves readily in hot alcohol and in most organic solvents.

One of the chlorine atoms (adjacent to the nitro groups) is very reactive and can

easily be substituted by some other group. In consequence, on boiling the compound

with, for example, an aqueous solution of sodium carbonate, chlorodinitrophenol

can be obtained:

(14)

With ammonia or amines it yields the corresponding amines, the reactions

being characteristic of such chloronitro compounds.

Holleman [38] obtained very pure 1,4-dichloro-2,6-dinitrobenzene in the follow-

ing way: