Electron spin resonance studies of photo-oxidation by metal ions in rigid media at low temperatures. Part 5.—Photo-oxidation by the iron(III) ion

Abstract

Iron(III), both as its perchlorate and chloride salts, is an effective photo-oxidant for a wide range of organic compounds to give radical species readily trapped and detected by e.s.r. spectroscopy at 77 K. Its general behaviour parallels that of cerium(IV) photo-oxidation in that C—C fission processes are prominent with tertiary alcohols and carboxylic acids, although with simple alcohols, amides and certain other types of molecule, abstraction of a hydrogen atom from an activated C—H bond is found. The closely similar behaviour of the two salts towards the compounds we have examined suggests that Cl atoms are not essential intermediates in Fe^III photo-oxidations, as has been previously suggested, although there are photo-oxidations by FeCl₃ in which chlorine is incorporated into the isolable product.