Organic Chemistry of Explosives

Nitrolysis 213

and Suri^89 used the same system, which probably involves trifluoroacetyl nitrate as the active

nitrating agent, for theN-nitration of some cyclic amides, imides and ureas (66). For this

purpose, ammonium nitrate–TFAA in nitromethane was used. A comprehensive study of this

nitrating system in relation to amides was subsequently conducted, including optimization of

conditions and exploring other related nitrating agents.^90

NHHN

O

NN

O

O 2 N NO 2

n-Bu 4 N NO 3 , Tf 2 O,

CH 2 Cl 2 , 33 %

66 67

or

NH 4 NO 3 , TFAA,

CH 3 NO 2 , 41 %

Figure 5.40

A reagent composed of tetra-n-butylammonium nitrate and TFAA in methylene chloride

has been used to nitrate a series ofN-alkyl andN-aryl amides (40–90 %).^91 The formation of

significant amounts ofN-nitrosamides was noted. Tetra-n-butylammonium nitrate and triflic

anhydride in methylene chloride has been used to successfully nitrate a variety of heterocyclic

amides, imides and ureas (66).^92

5.6 Nitrolysis

‘Nitrolysis’ is a term originally used for the rupture of a N–C bond leading to the formation

of the N–NO 2 group. A prime example is the nitrolysis of the N–CH 2 bonds of hexamine to

form the important military explosives RDX and HMX. Nitrolysis is the most important route

available to polynitramine energetic materials.

The scope of nitrolysis is huge, with examples of nitramine formation from the cleavage

of tertiary amines, methylenediamines, carbamates, ureas, formamides, acetamides and other

amides. The definition of nitrolysis must be extended to the nitrative cleavage of other nitrogen

bonds because sulfonamides and nitrosamines are also important substrates for these reactions.

The nitrative cleavage of silylamines and silylamides is also a form of nitrolysis (Section 5.7).

The range of reagents used for nitrolysis is also vast and includes absolute nitric acid, acid

anhydride–nitric acid, mixed acid, dinitrogen pentoxide–nitric acid, nitronium salts and many

more.

5.6.1 Nitrolysis of amides and their derivatives

R^1 N

O

R

R

R^1 N

O

R

NO 2

R^1 COOH+R 2 NNO 2

77

+ROH

nitrolysis

Path A

Path B

78

76

Figure 5.41

Substrates containingN, N-disubstituted amide functionality (76) can undergo nitrolysis by

two pathways leading to different products – a secondary nitramine (77) can be formed from