Concerning the mechanism of displacement of nitro groups from activated aromatic systems

Abstract

The photostimulated reactions of p-nitrobenzophenone and p-nitrobenzonitrile with a variety of nucleophiles have been investigated. Displacement of the nitro group is observed in all cases. The rates of the reactions were measured by FT-IR. The rates were slowed by substances such as sulfur, air, Galvinoxyl and p-benzoquinone. In several cases rates of loss of starting material were monitored by quenching the reaction mixtures and isolating product and starting material. These reactions also showed inhibition of their rates in the presence of inhibitors. These results indicate that the reactions are chain processes. It is concluded that the substrates are converted into their corresponding radical anions which then react with the nucleophiles in a bimolecular displacement reaction. The alternate mechanism, which involves dissociation of the radical anions, is precluded because they are known not to dissociate.