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576 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

DINITRO DERIVATIVES

More vigorous nitration with nitric acid of specific gravity 1.48 and at tempera-

tures up to 100°C results in the formation of 2,6-dinitroazoxybenzene (III) (Va-

lori [6]).

III

m. p. 172°C

TRINITRO DERIVATIVES

Even more vigorous nitration, with boiling nitric acid of specific gravity 1.51,

leads to the formation of a mixture of trinitroazoxybenzenes: 2,4,2’- (IV); 2,4,3’-

(V) and 2,4,4’- (VI):

IV

m. p. 192°C

V

m. p. 178°C

VI

m. p. 135-136°C

All the compounds are formed in the nitration of azobenzene (Werner and Stiasny

[1]).

The 2,4,4’-isomer may also be obtained either by the nitration of azobenzene

or of 4,4’-dinitroazoxybenzene with nitric acid sp. gr. 1.51 Klinger and Zuurdeeg

[7]). 4,4’-Dinitroazoxybenzene may be obtained by the action of alkalis on p- di-

nitrobenzene (Lobry de Bruyn [8]; Lobry de Bruyn and Blanksma [9]; Lobry

de Bruyn and Greuns [10]) or by the oxidation of p- nitroaniline with persulphuric

acid (Bamberger and Hübner [11]).

TETRANITRO DERIVATIVES

To obtain higher nitrated azoxybenzenes, indirect nitration methods must be

applied. 3,5,3’,5’-Tetranitroazoxybenzene (VII), for example, may be prepared

from sym-trinitrobenzene either by boiling with a dilute sodium carbonate solution

(Lobry de Bruyn and Leent [12]) or by partial reduction (Blanksma [13]).