Processus primaire de la photolyse et de la photo-oxydation de l'o-phényl-phénol

Abstract

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.

Electron Spin Resonance of Eumelanin From Hair: Photoinduced Radicals in Solid Matrix

“…A similar phenomenon can be observed in the production of phenoxy radicals from simple phenols like phenol (Audureau et al, 1976;Grabner and Getoff, 1982;Mialocq et al, 1980). diphenols (Perbet et al, 1979), and orthophenylphenol (Coulangeon et al, 1980) in aqueous oxygenated solution. In the work of Kalyanaraman et al (1984), photoionization and photohomolysis of the 0-H bond are presented as competitive pathways of the melanin photolysis.…”

Photodegradation of Triclosan on the Kaolinite Surface: Kinetic, Mechanistic, and Molecular Modeling Approach

“…Their elemental composition is C 24 H 12 O 4 Cl 6 , suggesting that their formation occurs via condensation of 2 TCS molecules, with the loss of two hydrogen atoms. The pathway for this condensation can be described as the formation of a cation radical formed via photoejection of an electron in the presence of dioxygen, followed by a reaction between the cation radical and another molecule of TCS, as described in the literature in the case of phenol and chlorophenol irradiation. , Various isomers can be formed by this process, and we could not assign precise structures to P6 and P7 .…”

Utilisation de l’Energie Solaire dans le Traitement des Eaux : Dégradation Photocatalytique de Micropolluants Organiques en Solution Aqueuse

“…Le rendement quantique de la transformation de OPP a été abordé dés 1980 par Coulangeon et al [14] par mesure de la fluorescence, puis repris par Sefar et al [15]. Ce rendement quantique dépend des conditions d'irradiation.…”