The photolysis of 1,4-benzoquinone, duroquinone, and 1,4-naphthoquinone in isopropanol and in dioxane leads to the observation of e.s.r. spectra of the corresponding semiquinone radicals. The rates of the selfdisproportionation of these radicals were measured by the rotating-sector technique. In the case of 1,4-naphthoquinone, unexpected e.s.r. emission was initially observed by photochemically induced dynamic electron polarization of the semiquinone radicals. Photolysis of anthraquinone in isopropanol gives e.s.r. spectra of the anthrasemiquinone radical anions. Their rate of decay was measured and a mechanism for the decay was suggested. The neutral anthrasemiquinone radical, however, was observed when photolyzed in dioxane.La photolyse de la benzoquinone-l,4,duroquinone et naphtoquinone-1,4 dans I'isopropanol et dans le dioxane, permet d'observer les spectres r.p.e. des radicaux semiquinone correspondants. Les vitesses d'autodismutation de ces radicaux ont kt6 mesurees par la technique du secteur tournant. Dans le cas de la naphtoquinone-1,4, on a observe initialement un spectre d'emission r.p.e. inattendu explique par une polarisation electronique dynamique, induite par voie photochimique, des radicaux semiquinone. La photolyse de l'anthraquinone dans l'isopropanol donne des spectres r.p.e. des radicaux anions anthrasemiquinone. Leur duree de vie a ete mesuree et un mecanisme de leur extinction suggere. Cependant, le radical neutre anthrasemiquinone a ete observe par photolyse dans le dioxane.[Traduit par le journa(] Canadian Journal of Chemistry, 50,3052 (1972)

The photochemical reactions of tetraphenyldiphosphine, triphenylphosphine, and diphenylphosphine in alcohol were studied by flash photolysis and product analysis. The primary photochemical process of all three phosphines studied appeared to be the formation of diphenylphosphinyl radicals which subsequently abstract a-H atoms from the solvent alcohol. The relationship between the rate constants of the abstraction and the a-H bond energies of various alcohols was examined.Les reactions photochimiques de la tktraphknyldiphosphine et des di-et triphknylphosphines ont kt6 ttudiks, dans l'alcool, par photolyse "flash" et par analyse des produits. Le processus photochimique prirnaire pour les trois phosphines semble &tre la formation de radicaux diphknylphosphinyles qui arrachent subs6quemment des atomes d'hydrogkne-a de I'alcool utilisk cornrne solvant. Une relation entre les constantes de vitesse d'abstraction et les energies de liaison des hydrogenes-a de divers alcools a etk examink.