PARAMAGNETIC RADICAL SPECIES FORMED DURING THE PHOTOOXIDATION OF PHENOLIC-COMPOUNDS - AN EPR STUDY

Photolysis of benzene solutions of di-tert-butyl peroxide and phenols, having at least one of the ortho and para positions free of substitue nts, frequently leads to the formation of persistent secondary radical s arising from dimerisation or polymerisation of the primary phenoxyl radicals. The structure of the observed dimeric and polymeric aroxyls, the majority of which results from oxygen-to-carbon coupling at the p ara position, has been identified by EPR spectroscopy. These aroxyls s how a peculiar conformational behaviour essentially determined by ster ic rather than by conjugative effects.