Mechanism of the photochemical transformation of naphthalene in water

Upon irradiation in air-saturated aqueous solution, naphthalene is mainly c onverted into 7-hydroxy-1,4-naphthoquinone, 2-formylcinnamaldehyde and 2-ca rboxycinnamaldehyde. The quantum yield of photolysis is equal to 0.0025+/-0 .0005. Naphthalene is likely to be phototransformed via monophotonic ioniza tion that occurs with a quantum yield equal to 0.02. The radical cations fo rmed after the electron ejection can deprotonate or react with water yieldi ng radicals that are oxidized by molecular oxygen. Finally, 2-formylcinnama ldehyde and 2-carboxycinnamaldehyde are yielded. The production of 7-hydrox y-1,4-naphthoquinone is consistent with the intermediary formation of photo labile 1,4-naphtoquinone. (C) 1999 Elsevier Science S.A. All rights reserve d.