Side reactions in the nitration process

A nitration reaction is always accompanied by side reactions which depend on such different factors as the nature of the substance being nitrated, the composition of the nitrating acid and the general nitration conditions. 

oxidation reactions occurring along with a nitration reaction are particularly strong, whenever the aromatic ring is liable to such a reaction (e.g. oxidation of phenol to oxalic acid, oxidation of methyl groups in benzene homologues to hydroxymethyl and carboxyl group, oxidation of naphthalene to phthalic acid etc.). 

According to Nightale [79] the action on poly alky lbenzene of concentrated nitric acid (d = 1.5) leads to oxidation of an alkyl group to yield an alcohol and possibly a nitrate, e.g.  

An aromatic nucleus not yet substituted with the nitro group is also readily oxidized to form phenols. That is the reason why certain quantities of nitrophenols are formed when nitrating benzene to nitrobenzene, and certain nitrocresols when 

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  

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