176 Synthetic Routes to AromaticC-Nitro Compounds
CH 2 Cl
O 2 N NO 2
O 2 NO 2 NNO 2 O 2 N
145CH CHNO 2NO 2NO 2THF, MeOH,
1 eq NaOH, 50 %
or
THF, MeOH
2.4 eq Et 3 N, 70 % 16
(HNS)Figure 4.642,4,6-Trinitrobenzyl chloride is isolated in 85 % yield if a reaction mixture composed of
TNT and 5 % aqueous sodium hypochlorite in methanol at 0◦C is quenched into dilute acid after
1 minute; longer reaction times at ambient temperature lead to the isolation of the heat resistant
explosive 2,2′,4,4′,6,6′-hexanitrostilbene (HNS) in 42 % yield.^288 HNS (16) is also formed in
50 % yield from the reaction of 2,4,6-trinitrobenzyl chloride (145) with sodium hydroxide
in THF–methanol.^288 ,^289 Sollot^290 later found that the yield of 2,2′,4,4′,6,6′-hexanitrostilbene
(16) could be increased to 70 % by treating the same substrate with 2.4 mole equivalents of
triethylamine in the same solvent mixture.
The oxidative coupling of TNT with hypochlorite was shown to involve 2,2′,4,4′,6,6′-
hexanitrodibenzyl as an intermediate, which can be isolated in 79 % yield by stopping the
reaction at an early stage.^288 ,^291 Treating TNT with a mixture of anhydrous copper (II) sulfate–
pyridine complex in the presence of potassium hydroxide in ethanol–triglyme is also reported to
yield 2,2′,4,4′,6,6′-hexanitrodibenzyl in 56 % yield.^292 Golding and Hayes^293 later investigated
the oxidative coupling of TNT in the presence of base, oxygen and various transition metal
catalysts.
TNT has been used as a starting material for the synthesis of 2,3,4,5,6-pentani-
troaniline^143 ,^282 (see Section 4.8.4), and hence, for the synthesis of hexanitrobenzene^39 ,^139 ,^153
via oxidation with peroxydisulfuric acid, and 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) via
nucleophilic displacement with ammonia.^140 ,^143
4.10 Conjugation and thermally insensitive explosives
Some high-molecular weight aromatic nitro compounds have been recognized for their high
thermal stability. The effect on thermal stability of having amino functionality adjacent to nitro
groups is discussed in Section 4.8.1.4. Conjugation between aromatic rings is also known to
increase thermal stability in explosives.^251
CH CHNO 2NO 2NO 2XXO 2 NO 2 NO 2 NO 2 NO 2 NO 2 NNNNO 2NO 2NO 216, X = H (HNS)
146, X = NH 2 (DAHNS)90
(HNAB)Figure 4.65