Photochemical reaction of superoxide radicals with 1-naphthol

The photochemical reactions between 1-naphthol (1-NP) and the superoxide anion radical ([O.sub.2.sup.*-]) were investigated in detail by using 365 nm UV irradiation. The results showed that the conversion rate of 1-NP decreased with the increase of the initial concentration of 1-NP, whereas by increasing the pH and riboflavin concentration, the photochemical reaction was accelerated. The second-order reaction rate constant was estimated to be (3.64 [+ or -] 0.17) * [10.sup.8] L [mol.sup.-1] [s.sup.-1]. The major photolysis products identified by using gas chromatography--mass spectrometry (GC-MS) were 1,4-naphquinone and 2,3-epoxyresin-2,3-dihydro-1,4-naphquinone, and their reaction pathways were also discussed. An atmospheric model showed that both the bulk water reaction and the heterogeneous surface reaction deserve attention in atmospheric aqueous chemistry. Key words: superoxide radicals, 1-naphthol, photolysis kinetics, reaction mechanism, thermodynamics model. Nous avons etudie en detail les reactions photochimiques entre le 1naphtol (1NP) et le radical anionique superoxyde ([O.sub.2.sup.*-]) par irradiation UV a 365 nm. Les resultats ont montre que le taux de conversion du 1naphtol diminuait avec l'augmentation de la concentration initiale de ce dernier, tandis que l'augmentation du pH et de la concentration de la riboflavine accelerait la reaction photochimique. Nous avons estime que la constante de vitesse de reaction, de second ordre, etait de (3,64 [+ or -] 0,17) * [10.sup.8] L [mol.sup.-1] [s.sup.-1]. Les principaux produits de photolyse que nous avons identifies en utilisant la chromatographie en phase gazeuse couplee a la spectrometrie de masse (GC-MS) etaient la 1,4naphtoquinone et la 2,3-epoxyresine-2,3-dihydro-1,4-naphtoquinone. Nous discutons egalement des mecanismes de reaction. A l'aide d'un modele atmospherique, nous avons montre que la reaction dans un volume d'eau et la reaction sur une surface heterogene presentait un interet dans le domaine de la chimie atmospherique de l'eau. [Traduit par la Redaction] Mots-cles: radicaux superoxide, 1-naphtol, cinetique de la photolyse, mecanisme de reaction, modele thermodynamique.
Introduction Polycyclic aromatic hydrocarbons (PAHs, also known as poly-nuclear aromatic hydrocarbons or PNAs) are complex chemical substances with two or more aromatic rings. (1) They are important environmental pollutants and [...]