Reactions of NO2 with Aromatic Compounds

The attachment of NO to organic molecules is successfully applied to the industrial production of nitroalkanes, but in the case of nitroarenes this method is frequently unsuitable because of the low affinity of NO radicals toward aromatic nuclei. Under the same conditions, NO reacts to produce a complicated mixture of products arising 

In accordance with the radical mechanism, the reaction in benzene yields trinitrobenzene, p- and w-dinitrobenzenes, 2,4-di- and 2,4,6-trinitrophenol and oxalic acid. The formation of w-dinitrobenzenes, and trinitrobenzene is accounted for by the addition of three and five NO radicals to the primary nitrocyclohexadienyl radical followed by an abstraction of two or three nitrous acid (HNO ) molecules from the adducts. For the trinitrobenzene formation, this process can be represented as follows [4]  

Study of the interaction of toluene, nitrobenzene, dimethylaniline, phenol, anisole, and chlorobenzene with pernitrous acid (HOONO) at 8-98 C enabled formulation of the reaction mechanism [22]. HOONO is an important intermediate in the interconversion of nitrogen-containing species [23]. It forms upon reaction between hydrogen peroxide and nitrous acid. HOONO undergoes homolytic detachment  

The hydroxyl radical enters the aromatic nucleus almost exclusively in the o- and the p-position  

By reaction between the cyclohexadienyl radicals and NO, for which the activation energy will be practically zero, the nitro group is attached with the formation, for example, of the following nitro compounds  

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