Secondary radicals in the autoxidation of hydroquinones and quinones

The autoxidation of hydroquinones and quinones in strongly alkaline solution gives rise to radical intermediates other than the expected semiquinones. These ‘secondary’ radicals, which are derived from 1,2,4-trihydroxybenzene, can be characterised by means of e.s.r. spectroscopy. Different isomeric radicals may be formed, depending on the solvent, and apparently these may reduce any excess of quinone present to the corresponding semiquinone.