Organic Chemistry of Explosives

Chemical stability of polynitroaliphatic compounds 51

Bachmann and Biermann^339 reported the synthesis of nitroalkanes from the thermolysis

of acyl nitrates. The thermolysis of nitrite and nitrate esters over an asbestos catalyst is also

reported to yield nitroalkanes.^340

Olah and co-workers^341 reported the synthesis of nitroalkanes and nitroalkenes from the

nitrodesilylation of alkylsilanes and allylsilanes, respectively, with nitronium salts.

Nitroacetylenes are generally unstable and very explosive and so they have been little

studied. Schmitt and co-workers^342 used the nitrodesilylation of trialkylsilylacetylenes with

both nitronium salts and nitryl fluoride to obtain nitroacetylenes. Dinitrogen pentoxide has

also been used for the nitrodesilylation of trialkylsilylacetylenes.^343 Nitrodestannylation of

allylsilanes has also been reported.^344

Diels–Alder reactions using highly reactive polynitroalkenes have been reported. These

include cycloaddition reactions with 1,1-dinitroethene,^106 ,^345 1,1,2,2-tetranitroethylene^346 and

various fluoro-1,2-dinitroethylenes.^347

1.12.3 Selective reductions

NO 2

NO 2

196

O 2 N

OH

NO 2

NO 2

O 2 N

NO 2

O 2 N NO 2

NO 2 NO 2 NO 2

194

197

NaBH^195

4 , THF,

MeOH (aq)

Figure 1.93

Reagents like lithium aluminium hydride and hydrogen over palladium readily reduce the

aliphatic nitro group to the corresponding amino group. Sodium borohydride will reduce many

functional groups but leaves both aromatic and aliphatic nitro groups intact. Sodium borohy-

dride has been used for the selective reduction of polynitroaliphatic aldehydes,^348 ketones,^348

esters^349 and acid chlorides^310 to the corresponding polynitroaliphatic alcohols. Sodium boro-

hydride has been used for the reduction of the aromatic rings of 1,3,5-trinitrobenzene (194)

and picric acid (196) to yield 1,3,5-trinitrocyclohexane^350 (195) and 1,3,5-trinitropentane^351

(197) respectively.

1.13 Chemical stability of polynitroaliphatic compounds

The stability of polynitroaliphatic compounds to acids, bases and nucleophiles is often linked

to the presence of an acidicα-proton(s) which may allow various resonance structures to lead

to rearrangement or decomposition. Additionally, the presence of two or more nitro groups

on the same carbon atom greatly increases the susceptibility of the carbon–nitrogen bonds to

nucleophilic attack.