Energetic materials, synthesis

The chemical properties of the nitro group have important implications for the synthesis of more complex and useful polynitroaliphatic compounds and so these issues are discussed in relation to energetic materials synthesis. 

Oxidation of aliphatic nitroso functionality is usually facile but is not widely used in energetic materials synthesis. The following reagents have been used in these conversions oxygen,hydrogen peroxide, nitrous oxide, " dinitrogen tetroxide, ... 

Formaldehyde is the most important aldehyde used in Henry reactions in relation to energetic materials synthesis. Nitroform (112) reacts with formaldehyde in the form of trioxane or formalin to yield 2,2,2-trinitroethanol (159). The Henry reaction of nitroform with aldehydes other than formaldehyde gives products which are not isolable. 

A number of routes to aliphatic nitro compounds are not used for energetic materials synthesis but are included here for completeness. 

The effect which amino functionality has on the thermal and impact sensitivity of polyni-troarylenes (Section 4.8.1.4) makes amination by VNS a method with much future potential for energetic materials synthesis. Other carbon, nitrogen, oxygen and sulfur nucleophiles can displace aromatic hydrogen examples with 1,3-dinitrobenzene and 1,3,5-trinitrobenzene are extensive. 

There are four important groups of A-nitro compounds which are relevant to energetic materials synthesis. These are primary nitramines, secondary nitramines, secondary nitramides (including A-nitroureas and A, A -dinitroureas) and nitrimines. The synthesis and incorporation of these A-nitro functionalities into organic compounds is the focus of this chapter. 

J., and Endsor, R. (2003) Energetic materials synthesis in UK, in Theory and Practice of Energetic Materials (eds H. 

Lobbecke, S., Antes, )., Turcke, T., Marioth, E., Schmid, K., Krause, H., The potential of microreactors for the synthesis of energetic materials, in Proceedings of the 31st Int. Annu. 

Derivatives of furozan and furoxan have a wide spectrum of applications. First of all they are used as starting materials in organic synthesis and pharmaceuticals. Particular attention has been focused on furoxans as sources of NO in biological studies, biological markers, fluorescent and energetic materials. 

The fact that the 3,5-dimethylpyrazol-l-yl moieties of 1,2,4,5-tetrazine 63 are good leaving groups in nucleophilic displacements has been used for the synthesis of azotetrazine 66, a novel high-nitrogen energetic material <00AG(E)1791>. 

Olah, G.A. Malhotra, R. und Narang, S.C. Nitration, Methods and Mechanisms, VCH-Verlagsges., Weinheim 1989 Nitro Compounds, Recent Advances in Synthesis and Chemistry, Hrsg. Feuer, H. und Nielsen, A. 77, VCH-Verlagsges., Weinheim 1990 Chemistry of Energetic Materials, Hrsg. Olah, G.A. und Squire, D.R., Academic Press, London 1991... 

Lewis, B. und Elbe, G. von Combustion, Flames and Explosives of Gases, 3. Aufl., Academic Press, Orlando, Florida 1987 Energetic Materials New Synthesis Routes, Ignition, Propagation and Stability of Detonation, Hrsg. Field, J.E. und Gray, R, The Royal Society, London 1992... 

A comprehensive discussion of the synthetic methods used to introduce the nitro group into aliphatic compounds, and its diverse chemistry, would require more space than available in this book. While every effort has been made to achieve this, some of these methods are given only brief discussion because they have not as yet found use for the synthesis of energetic materials, or their use is limited in this respect. The nature of energetic materials means that methods used to introduce polynitro functionality are of prime importance and so these are discussed in detail. Therefore, this work complements the last major review on this subject. ... 

The Ter Meer reaction has not been widely exploited for the synthesis of m-dinitroaliphatic compounds. This is partly because the Kaplan-Shechter oxidative nitration (Section 1.7) is more convenient, but also because of some more serious limitations. The first is the inability to synthesize internal em-dinitroaliphatic compounds functionality which shows high chemical stability and is found in many cyclic and caged energetic materials. Secondly, the em-nitronitronate salts formed in the Ter Meer reactions often need to be isolated to improve the yield and purity of the product. Dry em-nitronitronate salts are hazardous to handle and those from nitroalkanes like 1,1,4,4-tetranitrobutane are primary explosives which can explode even when wet. Even so, it is common to use conditions that lead to the precipitation of gem-nitronitronate salts from solution, a process that both drives the reaction to completion and also provides isolation and purification of the product salt by simple filtration. Purification of em-nitronitronate salts by filtration from the reaction liquors, followed by washing with methanol or ethanol to remove occluded impurities, has been used, although these salts should never be allowed to completely dry. 

Polynitroaliphatic alcohols are invaluable intermediates for the synthesis of energetic materials (see Section 1.11). The most important route to /i-nitroalcohols is via the Henry reaction where a mixture of the aldehyde and nitroalkane is treated with a catalytic amount of base, or the nitronate salt of the nitroalkane is used directly, in which case, on reaction completion, the reaction mixture is acidified with a weak acid. Reactions are reversible and in the presence of base the salt of the nitroalkane and the free aldehyde are reformed. This reverse reaction is known as demethylolation if formaldehyde is formed. 

R. J. Spear and W. S. Wilson, Recent Approaches to the Synthesis of High Explosive and Energetic Materials , J. Energ. Mater., 1984, 2, 61-149. 

J. C. Bottaro, R E. Penwell and R. J. Schmitt, "Synthesis of Cubane Based Energetic Materials, Final Report, December 1989 , SRI International, Menlo Park, CA [AD-A217 147/8/XAB]. 

Despite the amount of research focused on the iV-nitration of amines with nonacidic reagents, the use of conventional acidic reagents based on nitric acid and acid anhydrides has been far more extensive for the synthesis of energetic materials. 

The nitrolysis of A,A-disubstituted amides is one of the key tools for the synthesis of nitramine containing energetic materials. The present synthesis of the high performance explosive HMX is via the nitrolysis of hexamine (Section 5.15). This is an inefficient reaction requiring large amounts of expensive acetic anhydride. An alternative route to HMX (4) is via the nitrolysis of either l,3,5,7-tetraacetyl-l,3,5,7-tetraazacyclooctane (79) (79%) or 1,5-dinitro-3,7-diacetyl-l,3,5,7-tetraazacyclooctane (80) (98 %) with dinitrogen pentoxide in absolute nitric acid. These reactions are discussed in more detail in Section 5.15. 

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