PHOTOCHEMICAL BEHAVIOR OF THE IRON(III) 2,6-DIMETHYLPHENOL SYSTEM/

The photoinduced degradation of 2,6-dimethylphenol (DMP) by iron(lll) in aqueous solution has been investigated under monochromatic excitati on (lambda = 365 nm). Depending on the nature of the iron(lll) species (monomeric, dimeric...) present in the solution, there are two differ ent mechanisms that can induce DMP disappearance. When the monomeric s pecies Fe(OH)(2+) is present, an attack by (OH)-O-. radicals coming fr om an intramolecular photoredox process accounts for half of the degra dation; the second process involves a quenching between iron(lll) spec ies in the excited state and DMP leading to 2,6-dimethyl-phenoxyl radi cal. in the absence of monomeric species only the second mechanism is present. The major photoproduct is 2-hydroxy-3,5-dimethylbenzoquinone, which comes from a further hydroxylation of 2,6-dimethylbenzoquinone, whose formation was evidenced only by Rash photolysis-HPLC experiment s. For prolonged irradiations, the total degradation of DMP is observe d.