126 Synthetic Routes to AromaticC-Nitro Compounds
4.2 Polynitroarylenes as explosives
Polynitroarylenes hold a central position in the field of explosives and for many years they
have been an important class of explosives for military use. 2,4,6-Trinitrotoluene (TNT) (1)
was first synthesized in 1863 and has found wide use as a secondary high explosive. It is by
no means a high performance explosive (VOD∼6940 m/s,d= 1 .64 g/cm^3 ), but it has a
combination of properties, such as relatively high chemical stability, moderate insensitivity to
impact and friction, and a low enough melting point (80.8◦C) to permit melt casting of charges,
which makes it suitable for mass use in munitions. Equally important, TNT is synthesized from
readily available and cheap raw materials. The high oxygen deficiency of TNT (−74 %) has
meant that melt-cast mixtures with ammonium nitrate, known as amatols, have found wide
use in the past. The brisance of such mixtures is relatively low and so the powerful nitramine
explosives RDX and HMX are currently the most widely used military explosives. TNT still
finds use as a practical explosive but in mixtures where it is effectively an energetic binder
for cast compositions. The cyclotols (RDX/TNT), Torpex (RDX/TNT/Al), pentolite (PETN/
TNT) and PTX-1 (RDX/tetryl/TNT) are all secondary high explosive compositions based
on TNT.
1,3,5-Trinitrobenzene (TNB) (2) is a more powerful explosive than TNT. However, the
direct synthesis of TNB from benzene is not practical and the need for an indirect route for its
synthesis makes its manufacture too expensive for use as a practical high explosive.
NO 2NO 2NO 2NO 2NO 2
NO 2O 2 NO 2 N O 2 N O 2 N O 2 NO 2 NO 2 N O 2 NCH 3 OHOHOHNO 2 NO 2NO 2 NO 2CH 3CH 3OCH 3 OC 2 H 5
NO 2 NO 2 NO 2NO 2 NO 2 NO 2OHCH 32,4,6-trinitrotoluene
(TNT)1
1,3,5-trinitrobenzene
(TNB)2
2,4,6-trinitrophenol
(picric acid)42,4,6-trinitro-
resorcinol
(styphnic acid)53
2,4,6-trinitroxylene
(TNX)7
2,4,6-trinitroanisole
(methyl picrate)8
2,4,6-trinitrophenetole6
2,4,6-trinitrocresolFigure 4.1During the first half of the last century a large number of aromatic nitro compounds
found limited use as secondary explosives. These included: 2,4,6-trinitroxylene (TNX)
(3), 2,4,6-trinitrophenol (picric acid) (4), 2,4,6-trinitrocresol (6), 2,4,6-trinitroanisole (7),
2,4,6-trinitrophenetole (8), trinitronaphthalene (mixture of 1,3,5-, 1,4,5- and 1,3,8-isomers)
(9), 2,2′,4,4′,6,6′-hexanitrodiphenylsulfide (10), 2,2′,4,4′,6,6′-hexanitrocarbanilide (11) and
2,2′,4,4′,6,6′-hexanitrodiphenylamine (hexyl) (12) amongst others. The use of such compounds