Electron exchange polymers. XI. Oxidation potentials and spectra of water‐soluble hydroquinones and polymeric hydroquinones

Abstract

AbstractReproducible potentiometric titrations of water soluble electron exchange polymers have been obtained. Sulfonated polyvinylhydroquinone homopolymers and a sulfonated copolymer of vinylhydroquinone with α‐methylstyrene were prepared by treatment of the corresponding dibenzoates with concentrated sulfuric acid. Oxidative titrations with ceric sulfate and bromine water are described. It was found that the apparent standard oxidation potential depends on the degree of reduction and is independent of molecular weight, for large molecular weight. These experimental facts are in agreement with a recent theoretical analysis. The standard oxidation (midpoint) potentials of the polymers are somewhat higher than similarly treated isopropylhydroquinone dibenzoate, model monomer. Some effects of salt and pH on the polymer titration behavior are described. Although the polymer potentials are established slowly on platinum electrodes, ultraviolet absorption studies have shown that the oxidation reaction itself is rapid. A pink‐colored intermediate was observed. The effects of sulfonation of two hydroquinones on their oxidation potentials and ultraviolet absorption spectra are described.