Electron-transfer oxidations of organic compounds. Part II. The oxidation of phenol and 2,6-dimethylphenol by the hexachloroiridate(IV) anion

Abstract

Kinetic and product studies have been made of the oxidation of phenol and 2,6-dimethylphenol by hexachloroiridate(IV) in acid aqueous solutions. The kinetic studies indicate that the initial step involves the actual transfer of an electron from the phenol or its anion to the iridium complex. The back reaction can become important, and the kinetics then demonstrate that the free phenoxy-radical initially formed may either dimerise, attack a further phenol molecule, or be further oxidised to a phenoxy-cation. The products from the oxidation of 2,6-dimethylphenol with excess of iridate are 3,3′,5,5′-tetramethyl-4,4′-diphenoquinone (probably from radical dimerisation and substitution), and 2,6-dimethylbenzoquinone (probably from solvolysis of the phenoxy-cation).