Transformation of phenolic compounds upon UVA irradiation of anthraquinone-2-sulfonate.
This paper studies the transformation of phenol and of 3,5-dichlorophenol (3,5-DCP) upon UVA irradiation of anthraquinone-2-sulfonate (AQ2S). Light-excited AQ2S is able to oxidise phenol, 3,5-DCP, and AQ2S. Transformation reactions do not proceed at a significant extent in the absence of molecular oxygen, in which case recombination reactions of initially formed oxidised and reduced radical species (and/or radical ions) would yield back the initial substrates. AQ2S hydroxyderivatives are the main transformation intermediates, while the phenoxyl radicals arising upon oxidation of phenol and of 3,5-DCP react with the substrates to yield dihydroxybiphenyls and phenoxyphenols. Very small amounts of catechol and of 3,5-dichlorocatechol were observed, indicating a possible minor role of the hydroxyl radicals in the reactivity of the system. Interesting results from an environmental point of view are the formation of 2-hydroxydibenzofuran from phenol and of various tetrachlorinated dihydroxybiphenyls and phenoxyphenols from 3,5-DCP, suggesting that quinone photochemistry can be an important pathway for the formation of hazardous secondary pollutants in the environment.
Maurino
Valter
V
Dipartimento di Chimica Analitica, Università di Torino, Via P. Giuria 5, 10125, Torino, Italy.
Borghesi
Daniele
D
Vione
Davide
D
Minero
Claudio
C
D000880:Anthraquinones / Q000737:chemistry / Q000528:radiation effects*; D002733:Chlorophenols / Q000737:chemistry / Q000528:radiation effects*; D007700:Kinetics; D010084:Oxidation-Reduction; D019800:Phenol / Q000737:chemistry / Q000528:radiation effects*; D010636:Phenols / Q000737:chemistry / Q000528:radiation effects; D013997:Time Factors; D014466:Ultraviolet Rays
D000880:Anthraquinones; D002733:Chlorophenols; D010636:Phenols; C023554:anthraquinone sulfonate; C042329:phenoxy radical; D019800:Phenol; C116190:3,5-dichlorophenol