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NITRATION THEORIES 75

nitrating toluene. Since the phenolic group thus introduced then promotes the

introduction of the nitro groups, the number of the latter may be relatively large.

Thus, in the nitration of naphthalene to nitronaphthalene, 0.5-3.5% of 2,4-dinitro-

α− naphthol is formed (Fierz-David and Sponagel [80]). Titov [39] found dinitro-

phenol and picric acid in the products resulting from the nitration of benzene,

trinitro-m-cresol in the products of the nitration of toluene and trinitro-m-chloro-

phenol in the products of nitrating chlorobenzene.

Titov believes that phenols are formed from hydrocarbons under the influence

of the nitrosyl ion, NO+ A nitroso compound forms first, which then undergoes

a rearrangement :

(37)

Another scheme of Titov [32,39] suggests that the mechanism of oxidation

operates through the formation of an aryl nitrate, which is the result of attaching

NO 2 + through the oxygen atom:

Ar-H + O=N+=O -> Ar-O-N=O + H+ (38a)

Ar-O-N=O + H+ -> Ar-OH + NO+ (38b)

A similar hypothesis was suggested by Bennett [35] in 1945.

Oxidation followed by decomposition of the molecule may result in the formation

of nitrated aliphatic compounds, as for example tetranitromethane and chloro-

picrin in the nitrations of toluene or chlorobenzene respectively.

Along with nitration processes, isomerization processes may take place which

in turn may lead to various fairly complex reactions. As a result such products

as CO 2 , CO, NH 3 are formed. Such reactions are particularly notable in the nitration

of phenols. Their mechanism has been explained by Seyevetz [81] in the following

way. A phenol undergoes nitrosation under the influence of nitrous acid present
in the nitrating acid. Nitrosophenol isomerizes to quinone oxime, which oxidizes

at the double bonds to form mesoxalic acid and its oxime: