Phototransformation of bifenox in aqueous isopropanol

Abstract

Phototransformation of bifenox was studied under UV and sunlight in aqueous isopropanol using TiO2 as photocatalyst. The rate of photodegradation of bifenox in aqueous isopropanol (10 µg mL−1) followed first-order kinetics under UV (T1/2 = 15 h) and sunlight (T1/2 = 28 h). UV-irradiated bifenox solution yielded five metabolites F1, F2, F3, F4, and F5 and sunlight irradiated solution delivered four metabolites F1, F2, F6, and F7. The metabolite F1 was isolated as yellow crystalline solid (m.p. 91–93°C) and characterized as methyl (2,4-dichlorophenoxy) anthranilate by direct comparison with an authentic sample prepared in the laboratory. The other metabolites were identified as 3-carboxymethyl-4-nitrophenol (F2), 2,4-dihydroxy phenoxy aniline (F3), 4-hydroxy hydroxyl-aminobenzene (F4), isopropyl 2,4-dichlorophenolate (F5), 4-isopropyloxy-4′-nitrosodiphenyl ether (F6), and 2,4-di-isopropyloxy hydroxyl aminobenzene (F7) by GC-MS. The relative amounts of the products were found to be 18–20% for F1, 11–17% for F2, and 1–3% for F3–F7. The mechanism of phototransformation involved reduction, dechlorination, hydrolysis as well as nucleophilic displacement reactions.