Organic Chemistry of Explosives

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JWBK121-09 October 11, 2006 21:24 Char Count= 0

Synthesis of the high performance 363

O

50

H 3 C CH 2 ONO 2

3 C CH

CH 2 ONO 2

CH 2 ONO 2

42

3 C CH

CH 2 ONO 2

CH 2 ONO 2

52

HNO 3

ONO 2

O O 2 NO ONO 2

ONO 2

38

HO ONO 2

ONO 2

51

N 2 O 5

N 2 O 5

HNO 3

49

CH 2 OH CH 2 ONO 2

Figure 9.23

It is interesting to note that the nitration of HMMO (41) to NIMMO (50) in a batch reactor

cannot be scaled-up above 1 mole because of competing ring cleavage leading to the produc-

tion of metriol dinitrate (52) and trinitrate (42) as impurities. The nitration of glycidol (37)

to glycidyl nitrate (49) under batch reactor conditions is unworkable, producing significant

amounts of glycerol-1,2-dinitrate (51) and nitroglycerine (38).

9.11 SYNTHESIS OF THE HIGH PERFORMANCE AND

ECO-FRIENDLY OXIDIZER – AMMONIUM DINITRAMIDE

Most composite propellants in wide use today use ammonium perchlorate as the oxidizer

component. While such propellants benefit from high specific impulse and a lower vulnerability

than double-base propellants based on nitroglycerine, they have a significant environmental

impact, the exhaust fumes being rich in corrosive hydrogen chloride leading to acid rain after

the launch of missiles/rockets.

The dinitramide anion is one of the most significant recent discoveries in the field of

energetic materials. Ammonium dinitramide (ADN) (55) is of particular interest as a chlorine-

free alternative to ammonium perchlorate. This is a high-energy oxidizer with a large amount of

available oxygen for combustion. Propellants based on ammonium dinitramide exhibit higher

specific impulse^74 than conventional propellants and the exhaust gases are rich in nitrogen,

and so tactically reducing the exhausts radar signature.^75

NH 2 CO 2 Et

53

HN(NO 2 ) 2

54

NH 4 N(NO 2 ) 2

55

(ADN)

N 2 O 5 , HNO 3 , CH 3 CN i-PrOH, NH 3

-20 °C, 1 h

Figure 9.24

Both Russian^76 and American^77 chemists have reported numerous routes to the dinitramide

anion but many are generally not feasible for large scale production. One route involves treating

ethyl or ammonium carbamate with nitronium tetrafluoroborate, followed by treatment with

ammonia if ethyl carbamate (53) is used.^77 However, nitronium salts are not widely available

because of the harsh conditions and reagents needed for their preparation. The same reaction

is achieved with high efficiency with dinitrogen pentoxide–nitric acid reagent in acetonitrile

at subambient temperature.^77 The industrial availability of this reagent has fuelled increased