Electron spin resonance studies of photo-oxidation by metal ions in rigid media at low temperatures. Part 1.—Ce(IV) photo-oxidation of alcohols

Photolysis of deoxygenated solutions of ceric perchlorate and ceric ammonium nitrate in alcoholic, aqueous alcoholic and water + alcohol + acetonitrile solutions at 77 K by light of wavelength >300 nm leads to formation of radicals derived from the alcohol identified by electron spin resonance (e.s.r.) spectroscopy. Primary alcohols RCH₂OH yield RĊHOH but secondary alcohols R₂CHOH yield R· in addition to, and sometimes to the exclusion of R₂ĊOH. Tertiary alcohols always give an alkyl fragment, e.g. C₂H₅· from tert-amyl alcohol. Allylic alcohols produce the corresponding hydroxyallyl radical and 1,2-diphenylethanol gives a spectrum of benzyl radical, indicating C—C cleavage. The mode of photo-oxidation by Ce(IV) clearly parallels that of the corresponding thermal oxidation.