Electrochemical Nitration of Aromatic Hydrocarbons in Aprotic Media

Abstract

The electrochemical nitration of anthracene, naphthalene, 1‐nitronaphthalene, and toluene was examined in aprotic solvents. Controlled potential electrolysis of anthracene in acetonitrile containing tetra‐n‐butylammonium nitrite resulted in low yields of 9‐nitroanthracene. Oxidation of naphthalene in acetonitrile containing at potentials insufficient to oxidize resulted in high yields of 1‐nitronaphthalene, while electrolysis of naphthalene at potentials sufficient to oxidize resulted in moderate yields of dinitronaphthalenes. Similar experiments involving cooxidation of and toluene gave moderate yields of 2‐ and 4‐nitrotoluene in both acetonitrile and nitromethane. Nitronium ion was electrogenerated and used to effect nitration of toluene and 1‐nitronaphthalene in acetonitrile. The nitrotoluene isomer distributions obtained were similar to those observed during nitration of toluene with nitronium salts. The results obtained during coelectrolysis of either 1‐nitronaphthalene or toluene with were interpreted in terms of electrophilic attack by nitronium ion solvated via eiectrolytically generated acid. Coelectrolysis of tetra‐n‐butylammonium nitrate and toluene in acetonitrile and nitromethane did not produce nitrated products. However, electrolysis of solutions of and toluene in nitromethane gave low yields of mononitrotoluenes. Rotating disk measurements of the oxidation half‐wave potentials of several nitroaromatic hydrocarbons are presented.