Organic Chemistry of Explosives

232 Synthetic Routes toN-Nitro

(CH 2 )n (CH

2 )n

(CH 2 )n

NH 2. HCl

NH 2. HCl

H 2 NNH 2

N

NO 2

C NHNO 2

N

N

H

N

N

CO

NO 2

NO 2

O 2 NHN(CH 2 )nNHNO 2

+

15

n = 3, 93 %

n = 4, 92 %

excess

HNO 3 , Ac 2 O

2, n = 2

174, n = 3

175, n = 4

n = 2, 3 or 4

Hydrolysis

Condensation

171 172

173

Figure 5.72

decompose in the presence of primary alkylamines with the loss of ammonia and the formation

of 3-alkyl-substituted nitroguanidines.^140 The same reaction in the presence of a linear diamine

(171) forms a 2-nitramino-1,3-diazacycloalk-2-ene (172), which is readily nitrated to the cor-

responding cyclicN, N′-dinitrourea (173) with an excess of nitric acid in acetic anhydride.

N

C

NH

NHNO 2

H 3 C

(CH 2 )n (CH 2 )n

N

C

N

O

H 3 C

NO 2

NO 2

176, n = 0

177, n = 1

n = 0, 76 %

n = 1, 93 %

n = 0, 82 %

n = 1, 97 %

excess

HNO 3 , Ac 2 O Hydrolysis

n = 0 or 1

O 2 NHN NHNO 2

CH 3

n

Figure 5.73

McKay and co-workers^141 ,^142 prepared a number of cyclicN, N′-dinitroureas via the ni-

troguanidine route; hydrolysis to the parent linear dinitramines was effected with boiling

water or aqueous sodium hydroxide. This route was used to synthesize: ethylenedinitramine

(2), 1,2-dinitraminopropane (176), 1,3-dinitraminopropane (174), 1,3-dinitraminobutane (177)

and 1,4-dinitraminobutane (175).

5.11 Dehydration of nitrate salts

The dehydration of the nitrate salts of some primary and secondary amines can yield the corre-

sponding nitramine. Dimethylnitramine has been prepared in 65 % yield from the dehydration

of dimethylamine nitrate in acetic anhydride to which 4 mole % of anhydrous zinc chloride

has been added.^4 The same reaction in the absence of chloride ion only generates a 5 % yield

of dimethylnitramine.^4 Some arylnitramines derived from weakly basic amines have been

prepared via the addition of the amine nitrate salts to acetic anhydride.^143