Constitution and properties of the coatings formed in situ by anodic oxidation of azophenols

Three different azophenols were oxidized by both the system CuCl/O2 in pyridine and electrochemically (as coherent films) on Fe and Cu anodes in water/methanol mixtures. Products of the chemical and anodic oxidative coupling process are in any case very near each other. Poly(oxy-4-phenylazo-1,2-phenylene) and its 3-allyl derivative are obtained from 4-hydroxyazobenzene (1) and 3-allyl-4-hydroxyazobenzene (2), respectively. The polymerization of 4-hydroxy-3,5-dimethylazobenzene (3) mainly proceeds through elimination of the phenylazo group and formation of poly(oxy-2,6-dimethyl-1,4-phenylene). By oxidation of 2 at Cu anodes thin, adherent films having very good protective features are obtained in short electrolysis times.