168 Synthetic Routes to AromaticC-Nitro Compounds
Highly nitrated derivatives of benzene readily react with water to form phenols. 1,2,3,5-
Tetranitrobenzene (54) is readily converted to picric acid on reaction with hot water.^252 This
type of reaction has practical concerns if such an explosive is used in a military context –
picric acid forms dangerous picrates if allowed to come into contact with a metal surface
i.e. the inside of a munition’s shell. Other explosives like 2,3,4,6-tetranitrophenol (121) and
2,3,4,6-tetranitrotoluene react with water to form 2,4,6-trinitroresorcinol (styphnic acid) and
2,4,6-trinitro-m-cresol respectively. Some hindered nitro groups are displaced smoothly even
at room temperature, and hexanitrobenzene (55), although a powerful explosive, is readily
hydrolyzed to 2,4,6-trinitrophloroglucinol on reaction with water;^253 the latter is also formed
from the reaction of water with 2,3,4,5,6-pentanitrophenol.^240
The reactions of hexanitrobenzene^153 (55) and 2,3,4,5,6-pentanitroaniline^143 (31) with
ammonia have been used to synthesize the thermally stable explosive 1,3,5-triamino-2,4,6-
trinitrobenzene (TATB). Holmes and Fl ̈urschiem^140 have studied the reactions of 2,3,4,5,6-
pentanitroaniline with nucleophiles.
OH
NO 2NO 2
NO 2OH
NO 2Cl
NO 2O 2 N O 2 NOH
NO 2I
NO 2O 2 N122 12312140 % HI, heat
64 %conc. HCl, heat
75 %Figure 4.50Orlova and co-workers^254 reacted 1,2,3,5-tetranitrobenzene with hydrochloric and hydro-
bromic acids to form picryl chloride and picryl bromide respectively. The same chemists
treated 2,3,4,6-tetranitroaniline and 2,3,4,6-tetranitrophenol (121) with aqueous solutions of
hydrogen halides to form 3-halo-2,4,6-trinitroanilines and 3-halo-2,4,6-trinitrophenols (122
and 123) respectively.
CH 3
NO 2NO 2
124O 2 NO 2 NCH 3 CH 3 CH 3
NO 2 NO 2 NO 2NO 2
NO 2
125NO 2
126NO 2
127NaO 3 SSO 3 NaCH 3NO 2NO 2CH 3
NO 2SO 3 NaO 2 N128 129Na 2 SO 3 (aq) Na 2 SO 3 (aq)Na 2 SO 3 (aq)Figure 4.51The reactivity of nitro groups positionedo/p- to other nitro groups has implications for the
use of other polynitroarylenes as explosives. For example, of the numerous possible isomers
of trinitrotoluene, only the symmetrical 2,4,6-isomer (α-TNT) is chemically stable enough for
use as an explosive. Only in the case of the 2,4,6-isomer are the three nitro groups positioned
m- to one another; all other isomers of trinitrotoluene contain either one or two nitro group in