A Fourier Transform Infrared Spectroscopy Study of the Passive Film Produced during Aqueous Acidic Phenol Electro‐oxidation

In this work Fourier transform infrared spectroscopy was used to analyze samples of the passivating film produced on the anode during phenol electrolysis. Work by other researchers with p‐tertbutyl‐phenol was extended to the acidic region where the main product was found to be a 1,2,4 substituted ether‐linked polymer. The films produced by the oxidation of p‐cresol, o,o'‐biphenol, and phenol were also studied. As the monomers became less sterically hindered polymerization was found to occur more through direct carbon‐carbon coupling of the aromatic rings as opposed to ether linkages. Because the carbon‐carbon coupled monomers retain their hydroxyl groups, and so remain reactive, there is a tendency to form completely reacted 1,2,4,6 substituted structures resulting in highly branched and cross‐linked products. Some quinone‐type structures were also observed in the film spectra. The films were also found to easily fluoresce indicating significant delocalization of electrons within the films.