Electrochemical Reactions of Organic Compounds in Liquid Ammonia. II. Nitrobenzene and Nitrosobenzene

Abstract

The electrochemical behavior of nitrobenzene and nitrosobenzene in anhydrous liquid ammonia was investigated by cyclic voltammetry and controlled potential coulometry. In the absence of added protonating agents, nitrosobenzene and nitrobenzene are both reversibly reduced in two one-electron transfer steps to yield the stable radical anion and stable dianion species. In the presence of the weak acid isopropyl alcohol, the dianion of nitrosobenzene adds a single proton to form the anionic species, which can be reversibly oxidized back to parent compound. The dianion of nitrobenzene also adds a single proton and then rapidly decomposes with the loss of hydroxyl ion to neutral nitrosobenzene, which undergoes further reduction and protonation. The overall reduction process consists of the addition of a single electron to yield a stable radical anion followed by addition of three electrons and two protons to yield the protonated dianion of nitrosobenzene. In the presence of strong acid (ammonium ion), nitrosobenzene is reduced in a single two-electron reduction process to yield phenylhydroxylamine. Nitrobenzene is reduced in two steps, involving the addition of one and three electrons, to yield the same final product, phenylhydroxylamine. Estimates of the equilibrium or rate constants for several of these reactions associated with the electrode reactions are given. © 1975, American Chemical Society. All rights reserved.