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104 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

The nitro compound, nitrosyl chloride, and basic aluminium chloride formed

a number of addition products, which are in equilibrium:

RH + N 2 O 4 + 2AlC1 3 <-> RNO 2 .AlCl 3 + AlCl 2 OH.NOCl <->

(33a)

and then

<-> RNO 2 .AlCl 2 OH + AlC1 3 .NOCl

RNO 2 .AlCl 3 + N 2 O 4 + RH -> AlCl 2 (OH).(2RNO 2 )(NOCl) (33b)

AlC1 2 OH.NOCl + N 2 O 4 + RH + AlCl(OH) 2 (RNO 2 )(2NOCl) (33c)

When heated, the complexes dissociated into their components.

Titov explained the activating action of aluminium chloride by the fact that alu-

minium chloride is coordinatively unsaturated and strongly polarizes the molecule

of the compound being nitrated:

(34)

The hydrogen atom attached to the carbon atom linked to the nitro group is readily

split off to form nitrobenzene.

Titov used the following technique for the nitration. A mixture of hydrocarbon

and aluminium chloride was saturated with nitrogen dioxide. An exothermic re-

action took place, AlCl 3 being dissolved. The intensity of the reaction diminished

after all the aluminium chloride had been dissolved. The saturation of the mixture

with NO 2 was stopped at 95% of the theoretical amount. Then the unreacted

nitrogen dioxide was expelled by passing CO 2. The liquid nitro compound phase was

separated from the solid aluminium salt. The yield of the nitro derivatives

of toluene and chlorobenzene was 88% and 96% of theoretical for toluene and

chlorobenzene respectively.

Bogdanov [90] investigated the nitration of aromatic compounds with nitro-

gen dioxide in the presence of ferric chloride. He assumed that in the first stage

of the reaction a complex was formed:

FeC1 3

Chlorine introduced into the mixture activated the nitration reaction by promoting

the decomposition of the complex into nitrobenzene and ferric chloride, the latter

again taking part in the reaction.
Among more recent work Topchiev’s experiments [60] should be mentioned,

in which boron fluoride was used as a catalyst for the nitration with nitrogen
dioxide. At a temperature of 55-50°C and with an N 2 O 4 to benzene molar ratio

0.5:1 he obtained 18% of the theoretical yield.