R e~u le 5 mars 1980 LOUISE-MARIE COULANGEON, GILLES PERBET, PIERRE BOULE et JACQUES LEMAIRE. Can. J. Chem. 58,2230Chem. 58, (1980. En solution aqueuse, 1'0-phknyl-phenol prksente une double fluorescence qui traduit un Cquilibre de deprotonation dans I'Ctat excite singulet. Cette propriCtC permet d'interprkter I'influence de I'oxygene sur la production photochimique primaire des radicaux phknoxy. On montre que, seul I'etat excite singulet de la forme phenolate donne lieu a la photo-kjection d'electrons. L'oxygene inhibe la recombinaison des electrons eject& avec les radicaux phknoxy. D'autres capteurs d'ilectrons comme les Cd2+ ou NO3-sont tgalement susceptibles d'accroitre le rendement quantique de disparition de 1'0-phenyl-phenol en solution dtgazee. L'effet de I'oxygene au niveau du processus primaire permet d'interprkter les resultats acquis en photo-oxydation d e derives phCnoliques donnant naissance a des radicaux phenoxy inoxydables.LOUISE-MARIE COULANGEON, GILLES PERBET, RERRE BOULE, and JACQUES LEMAIRE. Can. J. Chem. 58,2230Chem. 58, (1980. The dual fluorescence observed in aqueous solution of o-phenyl-phenol is attributed to a deprotonation equilibrium in the excited singlet state. The effect of oxygen on the primary photochemical process of formation of phenoxy radicals can be explained in a parallel study of the variations of fluorescence and photo-oxidation quantum yields of this phenolic compound at different pH. It is shown that photoionisation occurs only from the excited singlet state of the phenolate form. Oxygen inhibits recombination of the solvated electron and phenoxy radical. Increase of quantum yield for the disappearance of irradiated o-phenyl-phenol in degased solution also is observed in the presence of electron scavengers like Cd2+ or NO3-ions. Even when the phenoxy radicals are not able to react with oxygen, quantum yield for the disappearance of the phenolic compounds is higher in an aerated than in a degassed solution; the oxygen effect on the primary photochemical step may explain this difference.

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