Functional monomers and polymers. XXXV. Oxidation of hydroquinone catalyzed by Cu(II)–polyelectrolyte complexes

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Abstract
Oxidation of hydroquinone catalyzed by copper(II) complexes of poly‐1‐vinylimidazole, vinylamine‐vinylacetamide copolymer, and polyethyleneimine was studied in aqueous solution at 25°C. The rate of oxidation was determined spectrophotometrically over several pH values. The rate of copper(II) reduction was evaluated from copper(I)–cuproin complex formation, and the reoxidation of copper(I) to copper(II) was observed by visible spectroscopy. Among the copper(II) complexes, poly‐1‐vinylimidazole complex exhibited excellent catalytic activity, which amounted to over 20 times that of aqueous copper(II) ion solution, while the reduction of copper(II) in the former system was slower than that in the latter system. The reoxidation of copper(I) to copper(II) was found to be completed immediately in the presence of polymer ligands such as poly‐1‐vinylimidazole, while copper(I) ion was only slowly reoxidized. The discussion of the reaction mechanism emphasizes the importance of the reoxidation process.