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Photochemistry of Water‐soluble Quinones. Production of a Water‐derived Spin Adduct
Author(s) -
Alegria Antonio E.,
Ferrer Amaris,
Sepulveda Elsa
Publication year - 1997
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1997.tb03170.x
Subject(s) - chemistry , adduct , anthraquinone , electron paramagnetic resonance , photochemistry , sulfonate , spectroscopy , nitrogen , inorganic chemistry , sodium , organic chemistry , physics , nuclear magnetic resonance , quantum mechanics
— The photolyses of phosphate‐buffered (pH 7) air‐ and nitrogen‐saturated solutions containing the water‐soluble quinones, 1,4‐benzoquinone (BQ), 2‐methyl‐l,4‐ben‐zoquinone (MBQ), sodium 1,4‐naphthoquinones‐sulfonate (NQ2S), 9,10‐anthraquinone‐2‐sulfonate (AQ2S) or 9,10‐anthraquinone‐l,5‐disulfonate (AQDS), and the spin trap 5,5‐dimethylpyrroline‐l‐oxide (DMPO) produce a DMPO‐OH adduct. Electron paramagnetic resonance spectroscopy of the photolyzed samples in 17 0‐enriched water demonstrates that this adduct derives almost exclusively from water. With the exception of BQ, quantum yields for the formation of DMPO‐OH are larger in air than in nitrogen‐saturated samples, thus supporting the idea of the formation of air‐oxidized intermediates that enhance the DMPO hydroxylation reaction rate. Evidence has been obtained which suggests that BQ and MBQ, but not AQDS, are able to photoox‐idize water, with the consequent production of the free OH radical.