The Reaction of Electrogenerated Superoxide Ion with Nitroaromatic Amines

Abstract

The reaction of electrogenerated superoxide ion with 2‐, 3‐, and 4‐nitroaniline and N,N‐dimethyl‐4‐nitroaniline was studied as a function of temperature in N,N‐dimethylformamide containing tetra‐n‐butylammonium perchlorate as the supporting electrolyte. Techniques used for the investigation were cyclic voltammetry, chronoamperometry, and absorption spectroscopy. The results obtained indicate that superoxide ion behaves as a strong base, effecting proton transfer from the amino group of 2‐ and 4‐nitroaniline. No reaction of superoxide ion was observed with 3‐nitroaniline or N,N‐dimethyl‐4‐nitroaniline on the time scale of voltammetry. Pseudo‐first‐order rate constants for the chemical step in the ECE mechanism involving deprotonation of 2‐ and 4‐nitroaniline by superoxide ion were estimated from chronoamperometric data to be 0.14 and 0.13 sec−1, respectively, at 25.0°C and 0.46 and 0.30 sec−1, respectively, at 40.0°C.