Organic Chemistry of Explosives

Energetic nitrate esters 115

(114) (pentryl), 1,3-bis(2-nitroxyethylnitramino)-2,4,6-trinitrobenzene (115) and 1,3,5-tris

(2-nitroxyethylnitramino)-2,4,6-trinitrobenzene (116) have been prepared by condensing

picryl chloride, styphnyl chloride and 1,3,5-trichloro-2,4,6-trinitrobenzene respectively with

ethanolamine, followed by nitration with mixed acid. All three explosives were found to exhibit

respectable performance [calculated VOD – 8100 m/s (114), 8500 m/s (115) and 8650 m/s

(116)].

R

N

NO 2

ONO 2

R = alkyl

117

Figure 3.51

Br

H 2 N OH

90 %

N

H

OH N ONO 2

NO 2

HNO 3 , Ac 2 O,

ZnCl 2

80 %

(^118119)
(Bu-NENA)
Figure 3.52
Nitroxyethylnitramines of general structure (117) are known as NENAs and are conveniently
prepared from the nitrative cleavage ofN-alkylaziridines with dinitrogen pentoxide in chlori-
nated solvents or from the nitration of the parent aminoalcohol. These compounds find use as
energetic plasticizers in explosives and propellants; Bu-NENA (R=n-Bu) is a component of
some LOVA (low vulnerability ammunition) propellants.^119 ,^162 Bu-NENA (119) is synthesized
in high yield from the chloride-catalyzed nitration ofN-butylethanolamine (118).^163
HO
ONO 2
ONO 2
OH
m n-m
121
(NHTPB)
HO OH
n
120

1. CH 3 CO 3 H, CH 2 Cl 2
   2. N 2 O 5 , CH 2 Cl 2

Figure 3.53

A number of energetic polymers containing nitrate ester functionality have received attention

for use as binders in high performance propellant and explosive formulations. Nitrated hydroxy-

terminated polybutadiene (121) (NHTPB) is synthesized from the epoxidation of the double

bonds of HTPB (120) oligomers with peroxyacetic acid, followed by ring-opening nitration of

the resulting epoxide functionality with dinitrogen pentoxide in methylene chloride.^76 Nitrated

HTPB with 10 % of the double bonds converted to dinitrate ester functionality is a usable

pre-polymer with a viscosity significantly low enough to permit easy processing and high

solids loading. Such pre-polymers can be cured with aliphatic or aromatic diisocyanates to

give energetic binders. The number of double bonds converted to dinitrate ester functionality

depends on the epoxide content of the intermediate polymer. The epoxidation step must be

conducted with care to avoid oxidative side-reactions and chain cleavage.