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88 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

(3) Any alkyl group present in the paraffin can be replaced by a nitro group,

i.e. chain fission takes place. Thus, isopentane yields nine nitroparaffins. The

fission reaction increases as the temperature rises.

(4) Oxidation always accompanies nitration, resulting in the formation of

nitro compounds and a mixture of acids, aldehydes, ketones, alcohols, nitrites,

nitroso compounds, nitroolefins, polymers, carbon monoxide and carbon dioxide.

Catalysts such as copper, iron, platinum oxide, etc., accelerate oxidation rather

than nitration.

When considering the mechanism of nitration of paraffin hydrocarbons with

nitric acid Titov [34] assumed in his papers dating from 1937 to 1948 that nitrogen

oxides, NO 2 and NO, were the nitrating agents for aliphatic chains. The role of

nitric acid would consist in regeneration of nitrogen oxide by oxidation of the

lower nitrogen oxides formed during the reaction. Moreover, Titov assumed the

nitration reaction to be a free radical one. In the first stage, a hydrocarbon is con-

verted into a free radical under the influence of a nitrating agent:

RH + NO 2 -> R. + HNO 2 (8)

Subsequently, a free radical reacts with nitrogen oxides, also in the form of free

radicals to form a nitro compound, nitroso compound or nitrite:

R. + .N=O -> RNO

Nitroso compound

R. + .NO 2 -> RNO 2

Nitro compound

(9)

R.+ .ONO -> RONO

Nitrite

Since Titov believed that the NO 3 radical might also be present in the vapour

phase, he gave the following overall scheme for the reaction of NO 2 and NO 3 with

a hydrocarbon RH, and for the reactions of NO, NO 2 , N 2 O 4 , N 2 O 3 , N 2 O 5 , HNO 3

and O 2 with a free radical R:

It can be seen that nitrites and nitrates, peroxides and alcohols are formed
along with nitroso and nitro compounds. The nitroso compounds (secondary)