THE MECHANISM OF NITRATION OF PHENOL AND 4-METHYLPHENOL BY NITROGEN-DIOXIDE IN SOLUTION

The quantitative formation of nitrophenols from phenol by reaction with nitrogen dioxide in solution involves stages, the first being the abstraction of a hydrogen atom from the hydroxyl group by NO2 and the second the reaction of the phenoxy radical formed with NO2. The first stage is rate-limiting at high [NO2]. In the case of 4-methylphenol a similar mechanism leads to both 4-methyl-4-nitrocyclohexa-2-5-dien-1-one and 4-methyl-6-nitrocyclohexa-2,4-dien-1-one intermediates and at high [NO2] the apparent rate of reaction can become the conversion of the latter intermediate into 4-methyl-2-nitrophenol.