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NITRO DERIVATIVES OF NAPHTHALENE^431

Gorst and Khlebnikov [31] reported that the colour of the solution of dinitro-
naphthalene in 84.5% H 2 SO 4 did not change appreciably when kept at room

temperature. When the concentration of sulphuric acid was 98% the solution dark-

ened after 24 hr. Darkening occurs even more quickly when the sulphuric acid

concentration is higher. The darkening is probably due to reactions similar to (2).
Application. A mixture of the dinitronaphthalene isomers is used in explosive

compositions with picric acid and ammonium nitrate for military and mining

explosives (Vol. III). The mixture is often referred to as “Dinal”. It is also designated by

the symbols DN or DNN. It is an explosive very difficult to detonate. The highest rate

of detonation of Dinal, when using a very powerful detonator, is about 5100 m/sec

(Calvet [32]).

TRINITRO DERIVATIVES OF NAPHTHALENE

There are three isomers of trinitronaphthalene known, which can be obtained

by direct nitration of a-nitronaphthalene, viz. : the α− (1,3,5-), β− (1,3,8-), and γ−
(1,4,8-) or 1,4,5-isomers. The δ− isomer (1,2,5-) does not exist, according to Dimroth

and Ruck [18a]. It is probably a mixture of the isomers.

α

m. p. 123°C

(119.5°C [18a])

β

m. p. 218°C

γ

m. p. 147°C

They are very fine crystalline, light brownish-grey products, sparingly soluble

in organic solvents.

The crude product of the nitration of naphthalene or α− nitro- or commercial

dinitro-naphthalene is a mixture of the four isomers. It melts at 115-160°C, the

melting point depending on the nitration conditions.

Separation of the isomers can be achieved by taking advantage of their different

solubility in alcohol. Thus, the 1,3,5-isomer dissolves in alcohol only with great

difficulty. The 1,4,8-isomer does not dissolve in 70% alcohol, while the 1,3,8-iso-

mer dissolves in the hot solution and may be precipitated from the solution either
by cooling or by dilution (Pascal and Garnier [33]).
The conversion of dinitro- into trinitro-naphthalene may be achieved by using
nitrating mixtures of varying compositions :

HNO 3 15-100%

H 2 SO 4 0-70%

H 2 O 0-15%