Organic Chemistry of Explosives

N-Nitration of amides and related compounds 211

N

NN

N

O

O 2 N

O 2 N

NO 2

69 NO^2

(TNGU)

N

NN

N

O

14 NO^2

(DINGU)

N

H

H

N

H

N

N

H

OOOO

68

or

HNO 3 , H 2 SO 4

H

H

O 2 N

100 % HNO 3 HNO 3 , N 2 O 5

Figure 5.37

Glycouril (68) is converted to its dinitro derivative (14) (DINGU) on treatment with either

absolute nitric acid or strong mixed acid. Further nitration to the tetranitro derivative (69)

(TNGU) requires the use of a more powerful nitrating agent in the form of a 20 % solution

of dinitrogen pentoxide in absolute nitric acid.^75 The latter reagent has only fairly recently

found wide use for the synthesis of energetic materials, but the number of examples of its

use for nitrolysis (Section 5.6) is already extensive. In the laboratory a solution of dinitrogen

pentoxide in nitric acid is readily synthesized by the addition of phosphorous pentoxide^76 to

absolute nitric acid or from the anodic oxidation of dinitrogen tetroxide^77 in absolute nitric

acid (Chapter 9).

O

H

H

H

NN

NN

O

NN

NN

O

O

(^7071)
CH
CH 2
CH NN
NN
OC CO
72
H
NO 2
NO 2
O 2 N
O 2 N
H H
HH
CH
CH 2
CH NN
NN
OC CO
73
(TNPDU)
O 2 N NO 2
O 2 NNO 2
Figure 5.38
The tricycle (71) has been synthesized in 97 % yield via the nitration of the corresponding
urea (70) with dinitrogen pentoxide in nitric acid.^78 The high performance bicyclicN, N′-
dinitrourea known as TNPDU (73) is synthesized from the reaction of propanediurea (72) with
acetic anhydride–nitric acid.^79
N, N′-Dinitrourea (DNU) has been prepared by the nitration of urea with a mixture of 98 %
nitric acid and 20 % oleum between− 10 ◦C and− 15 ◦C.N, N′-Dinitrourea is unstable at room
temperature. However, the diammonium and dipotassium salts are more stable and decompose
at 110◦C and 135◦C respectively.^80 N, N′-Dinitrourea may find future use for the synthesis of
bicyclic and caged heterocyclicN, N′-dinitroureas.
The synthesis, properties and potential uses of high performanceN-nitroureas andN, N′-
dinitroureas are discussed in more detail in Chapter 6.

5.5.2 Nitration with nonacidic reagents

TheN-nitration of amides and related compounds with nonacidic nitrating agents has received

far less attention for the synthesis of energetic materials compared to the use of acidic reagents

employing nitric acid and its mixtures. Even so, reagents like dinitrogen pentoxide in chlori-

nated solvents and nitronium salts, are efficient and mild nitrating agents for amides and ureas.