Organic Chemistry of Explosives

5 Synthetic Routes toN-Nitro Functionality

5.1 Introduction

Aromatic and aliphatic nitro compounds are of huge industrial importance and are invaluable

intermediates in organic synthesis. This has in part fuelled the enormous amount of research

into nitration. Compounds resulting from the nitration of nitrogen are of far less use for main-

stream organic synthesis. However, the N–NO 2 (N-nitro) group is an important ‘explosophore’

and is present in many energetic materials. Consequently, research intoN-nitration has been

exclusively driven by the use of the products as energetic materials. Some of these compounds

are in wide use today as high explosives and ingredients of propellants and are manufactured

on an enormous scale.

R NHNO 2

R N R

NO 2 N

NO 2 NO 2

O

R'

1 ° nitramine 2 ° nitramine 2 ° nitramide nitrimine

R R

N

Figure 5.1

There are four important groups ofN-nitro compounds which are relevant to energetic ma-

terials synthesis.^1 These are primary nitramines, secondary nitramines, secondary nitramides

(includingN-nitroureas andN, N′-dinitroureas) and nitrimines. The synthesis and incorpora-

tion of theseN-nitro functionalities into organic compounds is the focus of this chapter.

The replacement of amine and amide hydrogen with a nitro group via direct nitration is

an important route toN-nitro functionality. However, the cleavage of other bonds is also

important. In the case of C–N bond cleavage the process is known as ‘nitrolysis’ and is an

invaluable route to many energetic materials (Section 5.6). The nitrolysis of hexamine and the

syntheses of the important explosives HMX and RDX are discussed in Section 5.15. This area

of chemistry could easily demand a separate chapter of its own and is the most complex and

diverse in the field of nitramine chemistry.

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5 Synthetic Routes toN-Nitro Functionality