Polynitroarylenes as explosives

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. 

6-trinitro- 2,4,6-trinitrocresol 2,4,6-trinitroanisoie 2,4,6-trinitrophenetole resorcinoi (methyi picrate) 

During 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-trinitroanisoie (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 

6- Trinitrophenol (4), commonly known as picric acid (VOD 7350 m/s, d = 1.71 g/cm ), was once used as a military explosive although its highly acidic nature enables it to readily corrode metals. This kind of reaction has led to many fatal accidents, a consequence of some metal picrates being very sensitive primary explosives. The lead salt of picric acid is a dangerous explosive and should be avoided at all cost. In contrast, the ammonium (Explosive D, VOD 7050 m/s, d = 1.60 g/cm ) and guanidine salts of picric acid are unusually insensitive to impact and have been used in armour piercing munitions. 

6- Trinitroresorcinol (5) (styphnic acid) has also seen limited use as an explosive because of its acidic properties and the relatively high cost of resorcinol. However, the lead salt of styphnic acid has found use as a primary explosive in detonators and primers. 

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While we believe our discussions of nitramine and nitrate ester synthesis to be comprehensive, it would be quite impossible to have a comprehensive discussion of aromatic nitration in this short chapter - published studies into aromatic nitration run into many tens of thousands. The purpose of this chapter is primarily to discuss the methods used for the synthesis of polynitroarylene explosives. Undoubtedly the most important and direct method for the synthesis of polynitroarylenes involves direct electrophilic nitration of the parent aromatic hydrocarbon. This work gives an overview of aromatic nitration but the discussion doesn t approach mechanistic studies in detail. Readers with more specialized interests in aromatic nitration are advised to consult several important works published in this area which give credit to this important reaction class.The use of polynitroarylenes as explosives and their detailed industrial synthesis has been expertly covered by Urbanski in Volumes 1 and 4 of Chemistry and Technology of Explosives ... 

The reactivity of nitro groups positioned olp- 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 (a-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... 

The acidity of polynitrophenols is a direct consequence of the negative inductive effect of the nitro groups. This has implications for other polynitroarylenes as practical explosives. 

Interest in polynitroarylenes has resumed over the past few decades as the demand for thermally stable explosives with a low sensitivity to impact has increased. This is mainly due to advances in military weapons technology but also for thermally demanding commercial applications i.e. oil well exploration, space programmes etc. Explosives like 1,3-diamino-2,4,6-trinitrobenzene (DATB) (13), l,3,5-triamino-2,4,6-trinitrobenzene (TATB) (14), 3,3 -diamino-2,2, 4,4, 6,6 -hexanitrobiphenyl (DIPAM) (15), 2,2, 4,4, 6,6 -hexanitrostilbene(HNS, VOD 7120 m/s, = 1.70 g/cm ) (16) and A,A -bis(l,2,4-triazol-3-yl)-4,4 -diamino-2,2, 3,3, 5,5, 6,6 -octanitroazobenzene (BTDAONAB) (17) fall into this class. TATB is the benchmark for thermal and impact insensitive explosives and finds wide use for military, space and nuclear applications. 

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