urbaf2

450 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

tive effect which opposes substitution is felt most strongly at the ortho position.

Ingold [5] summarized his experiments on the rate of substitution. Some rates

of nitration which were calculated relative to the total rate for benzene, taken as

unity, are given in Table 101.

TABLE 101

Benzene 1 Fluorobenzene 0.15

Toluene 24.5 Chlorobenzene 0.033

Ethyl benzoate 0.00367 Bromobenzene 0.030

Benzyl chloride 0.302 Iodobenzene 0.18

NITRO DERIVATIVES OF CHLOROBENZENE

Chloronitro compounds are nearly always obtained by nitration of the corre-

sponding chlorinated hydrocarbons. Picryl chloride, for example, a trinitro derivative

of chlorobenzene, may be prepared by direct nitration. This possibility has in the

past aroused some interest in picryl chloride as an explosive. It was indeed manu-

factured and used in small quantities in Germany during World War I but in the

long run did not achieve any importance as a high explosive, mainly because of

its high reactivity and its readiness to yield picric acid and, with metals, picrates.

Picryl chloride may be a useful starting material in the preparation of several higher

nitrated derivatives of diphenyloxide (p. 549) and diphenylamine. Nitro derivatives

of p- dichlorobenzene (p. 466) were also used during World War I as high explosives.

The nitration of chlorobenzene was first mentioned in 1862 by Riche [6]. Later

the reaction was studied by Sokolov [7] and Holleman and de Bruyn [8]. Junglleisch

[9] was the first to describe the method of preparation of chlorodinitrobenzene

from o- or p- chloronitrobenzene. Laubenheimer [10] investigated the products

of the nitration of m- chloronitrobenzene, and Ostromyslenskii [11] determined the

structure of the products obtained by Jungfleisch, i.e. of 1,2,4- and 1,2,6-chloro-

dinitrobenzenes. Finally in 1894 the Griesheim factory reported [12] on a method

of preparing chlorotrinitrobenzene by direct nitration of chlorobenzene.

MONONITRO DERIVATIVES OF CHLOROBENZENE

There are three chloronitrobenzene isomers known: ortho, meta and para:

m. p. 32.5°C m. p. 46°C

b. p. 245°C b. p. 235°C

m. p. 83°C

b. p. 242°C