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CHAPTER VII

NITRO DERIVATIVES OF BENZENE

ONE or two nitro groups can be introduced by the direct nitration of benzene.

The introduction of a third can be accomplished only with great difficulty and the

yield obtained is relatively poor. For this reason trinitro derivatives of benzene

are prepared by indirect methods. Higher nitrated derivatives of benzene-tetra- and

hexanitrobenzene-are also known; they can be obtained by special methods. Di-

nitrobenzene is the most important of them as an explosive. It was the most used

substitute for trinitrotoluene.

NITROBENZENE

PHYSICAL PROPERTIES

Nitrobenzene is a highly toxic, pale, yellow liquid, having a specific smell

of bitter almonds. It melts at +5.7°C, and boils at 210.9°C. It was first obtained

by Mitscherlich [l] in 1834. The compound is widely used in organic industry as

a starting material for the preparation of aniline, benzidine and other intermediates

TABLE 29

SOLUBILITY OF NITROBENZENE IN SULPHURIC ACID ALONE, AND IN

THE PRESENCE OF HNO 3 , AT 43°C

Concentration of

H 2 SO 4 , containing

0.2% HNO 3 , %

C 6 H 5 NO 2 content in

the solution, %

H 2 SO 4 concentration C 6 H 5 NO 2 content in

% the solution, %

1-6

40

50

60

70

80

0.02 - -

0.015 -.

0.02 40-50 ca. 0.015

0.03 60 ca. 0.02

0.04 75 completely soluble

completely soluble - -

for the manufacture of dyes, medicinals, etc. It is also used for the preparation

of dinitrobenzene and as a component of liquid explosives.

The solubility of nitrobenzene in water and in spent nitrating acid is its most

important property, which should be borne in mind in its manufacture on account

of the possible loss of the product and the toxicity of the waste water.

The relevant data, reported by Groggins [2] are tabulated above (Table 29).