Organic Chemistry of Explosives

6 Synthetic Routes to AliphaticC-Nitro

At temperatures between 0◦C and 25◦C thevic-dinitrate ester is often observed in the

product mixture and can be the major product in some cases.45c−eThe synthesis ofvic-dinitrate

esters via this route is discussed in Section 3.6.2. Fischer^46 has given a comprehensive review

of work relating to the mechanism of dinitrogen pentoxide addition to alkenes.

n

N 2 O 5 , CH 2 Cl 2

m

ONO 2

NO 2

OH

HO HO

n-m

OH

8

9

Figure 1.6

Hydroxy-terminated polybutadiene (8) (HTPB) has been treated with dinitrogen pentoxide

in methylene chloride. The product (9) is an energetic oligomer but is unlikely to find application

because of the inherent instability ofβ-nitronitrates.^47 Initial peroxyacid epoxidation of some

of the double bonds of HTPB followed by reaction with dinitrogen pentoxide yields a product

containingvic-dinitrate ester groups and this product (NHTPB) is of much more interest as an

energetic binder (see Section 3.10).^47

1.4.4 Nitrous oxide and dinitrogen trioxide

R

RR

R NO or N 2 O 3

CC

NO 2 NO 2

RR

R +

5a

R CC

NO 2 NO

RR

R

10

R

Figure 1.7

The addition of nitrous oxide (NO) or dinitrogen trioxide (N 2 O 3 ) across the double

bond of an alkene usually generates a mixture of dinitro (5a) and nitro-nitroso (10)

alkanes.^48 ,^49 The reaction of tetrafluoroethylene with dinitrogen trioxide is reported to give

1,2-dinitrotetrafluoroethane and 1-nitro-2-nitrosotetrafluoroethane in 8 % and 42 % yield

respectively;^48 the same reaction with nitrous oxide leading to increased yields of 15 % and

68 % respectively.^49 When an excess of nitrous oxide or dinitrogen trioxide is used in these

reactions thevic-dinitroalkane is usually the main product.^49

1.4.5 Other nitrating agents

Alkenes react with nitryl chloride to giveβ-nitroalkyl chlorides,β-chloroalkyl nitrites andvic-

dichloroalkane products.^50 Nitryl chloride reacts with enol esters to giveα-nitroketones.32b

A process known as alkene nitrofluorination has been extensively used for the synthesis

ofβ-nitroalkyl fluorides. Reagents used generate the nitronium cation in the presence of

fluoride anion, and include: HF/HNO 3 ,^51 HF/HNO 3 /FSO 3 H,^52 NO 2 F,^53 SO 2 /NO 2 BF 454 and

HF/pyridine/NO 2 BF 4.^55

A mixture of silver nitrite and iodine reacts with alkenes to giveβ-nitroalkyl iodides,^56 and

therefore, provides a convenient route toα-nitroalkenes.^5 Treatment of alkenes with ammo-

nium nitrate and trifluoroacetic anhydride in the presence of ammonium bromide, followed by