Nitration Nitrosobenzene

The conversion may consist simply in oxidation or be the result of a more complex reaction. For example, nitrosotoluene can be converted into diazonium nitrate under the influence of nitrous acid. Bamberger [132] found in 1918 that nitrosobenzene could be converted into benzenediazonium nitrate under the influence of nitrous acid. According to Bamberger [133] and Nesmeyanov [134], mercury-aromatic compounds also give nitrates of corresponding diazonium compounds under the influence of N203, presumably also through nitroso compounds. 

Thus ferricyanide hydrolyzes photochemically to aquopentacyanoferrate which is a slightly better catalyst for decomposition than ferricyanide. On addition of ferrocyanide the ferrate is reduced to the ferrite which is more active. Some confirmation of these reactions is given by the observations that addition of the ferrate to ferricyanide increases the dark rate, and also that cyanide, nitrate, and nitrosobenzene inhibit this as well as the catalysis induced by irradiation of ferricyanide. 

The benzene is initially converted to phenylmercuric nitrate which reacts with nitrogen dioxide to yield nitrosobenzene Each of these intermediates has been isolated from the reaction mixture. The nitrosobenzene can react in two wajrs. In nitric acid weaker than 50 per cent, it reacts with 2 moles of nitric oxide to form phenyldiazonium nitrate, a reaction first discovered by Bamberger. The diazonium salt is converted by water to phenol, which is nitrated in steps to the final products. In nitric acid of greater than 50 per cent concentration, the nitrosobenzene is converted directly to p-nitro-phenol without going through the diazonium compound. The p-nitro-phenol is then nitrated further to give the dinitrophenol and picric acid. 

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