Organic Chemistry of Explosives

286 Nitramines and Their Derivatives

Ammonium dinitramide (152) is synthesized by treating a solution of ammonium ni-

trourethane (150) with nitronium tetrafluoroborate or dinitrogen pentoxide in methylene chlo-

ride at –30◦C, followed by ammonolysis of the resulting ethylN,N-dinitrourethane (151).^75

Ammonium dinitramide can be prepared from the nitration of ethyl carbamate and ammonium

carbamate with the same reagents. This is currently the most efficient route to ammonium

dinitramide and is used for its manufacture (Section 9.11).

NH 2 NO 2

153

1. NO 2 X, CH 3 CN


2. NH 3
   X = BF 4 - or HS 2 O 7 -

NH 4 N

NO 2

NO 2

152

Figure 6.48

The nitration of nitramine (153) with nitronium tetrafluoroborate, followed by neutralization

of the resulting dinitraminic acid with ammonia, also generates ammonium dinitramide (152).^75

Neutralization of this reaction with alkylamines, instead of ammonia, yields the corresponding

alkylammonium salts of dinitramide. The nitration of ammonia with dinitrogen pentoxide

(15 %) or nitronium salts like the tetrafluoroborate (25 %) yield ammonium dinitramide (152)

through the initial formation of nitramine.

NH 3 + NO 2 X

excess NH 3 X = NO^3 , 15 %

X = BF 4 - , 25 %

X = HS 2 O 7 - , 20 %

NH 4 N

NO 2

NO 2

152

Figure 6.49

Ammonium dinitramide has been synthesized from the nitration of ammonium sulfamate

with strong mixed acid at−35 to− 45 ◦C followed by neutralization of the resulting dinitraminic

acid with ammonia.^76 The yield is∼45 % when the mole ratios of sulfuric acid to nitric acid is

2:1 and ammonium sulfamate to total acid is 1:6. The nitration of other sulfonamide derivatives,

followed by hydrolysis with metal hydroxides, also yields dinitramide salts.^77

6.11.2 AlkylN,N-dinitramines

AlkylN,N-dinitramines belong to a class of highly energetic materials. However, their use is

limited by poor thermal stability and a high sensitivity to shock and impact. These undesirable

properties result from the high electron deficiency on the central nitrogen atom of theN,N-

dinitramino group which makes the N–N bonds highly susceptible to cleavage.

R

NO 2

NO 2

RNO 2 NR 4 NR

NO 2 F, CH 3 CN NO 2 BF 4 , CH 3 CN

155

154

M = NH (^4156)
N R = alkyl N +, K+ or Li+
NO 2 M
Figure 6.50