urbaf2

NITRO DERIVATIVES OF HALOGENOBENZENES^455

When using chlorodinitrobenzene in the manufacture of explosives, the products
obtained from it (e.g. dinitroanisole, dinitrodiphenylamine) are nearly always
subjected to further nitration. Both the 1,2,6- and 1,2,4-isomers then yield the same

trinitro derivative, 1-chloro-2,4,6-trinitrobenzene. In such cases separation of the

isomers and the preparation of highly pure 1,2,4-isomer is not necessary.

There are cases, however, where the presence of the two isomers makes process

control difficult, i.e. when the process is controlled by determining the melting

point of the product. Then o- and p- chlorodinitrobenzenes are separated, and only

the latter is nitrated, pure l- chloro-2,4-dinitrobenzene being obtained.

Toxicity. The chlorodinitrobenzene isomers are highly toxic. Contact with the

skin is especially harmful and provokes eczema. Smiriagin and Shapiro report (see

Lazarev [16]) that out of 54 women working with their hands dipped in a liquid

containing as little as 0.003% of 1-chloro-2,4-dinitrobenzene, all but 2 suffered

from acute eczema after a month of exposure, and were unable to work for 8-23

days or even longer. Grave injuries may also be caused by inhaling the vapours

of the hot substance or its dust. The maximum allowable concentration of chloro-

dinitrobenzene in the air is 0.001 mg/l, according to Lazarev.

Apart from skin injuries the symptoms of poisoning by chlorodinitrobenzene

are similar to those produced by dinitrobenzene, namely general bodily weakness,

cyanosis, a decrease of the number of red blood cells, disturbances in the functioning

of digestive organs and heart failure. Treatment and recovery sometimes prove

most difficult especially with regard to the digestive tract and the heart, whereas

skin lesions are relatively easier to heal.

1-Chloro-2,4-dinitrobenzene is converted in the living body into m- nitroaniline

and nitroaminophenol :

(6)

Both compounds can be determined colorimetrically, by diazotization followed

by conjugation with β− naphthol.

The nitration reaction of chlorobenzene is usually accompanied by oxidation

reactions, resulting in the formation of phenols, as for example, l-chloro-4-nitro-

5-hydroxybenzene (2-nitro-5-chlorophenol) :

in the proportion of about 0.1%.