Time evolution and competing pathways in photodegradation of trifluralin and three of its major degradation products

MARTÍN G. SARMIENTO TAGLE; MARÍA LAURA SALUM; ELBA I. BUJÁN; GUSTAVO A. ARGÜELLO

PHOTOCHEMISTRY AND PHOTOBIOLOGY

The Royal Society of Chemistry and Owener Societies

Año: 2005 vol. 4 p. 869 - 875

0031-8655

The herbicide trifluralin (I) (N,N-di-n-propyl-2,6-dinitro-4-trifluoromethylaniline) decomposes, by the action of UV-Vis light (k > 300 nm), to several products, the most important (because they give subsequent photochemical reactions) being N-n-propyl-2,6-dinitro-4-trifluoromethylaniline (VI), 2-ethyl-7-nitro-5-trifluoromethyl-1Hbenzimidazole 3-oxide (VII) and 2,6-dinitro-4-trifluoromethylaniline (XII). The time evolution of degradation of trifluralin (I) and the aforementioned three main photoproducts was studied in water and acetonitrile as solvents. The pseudo-first order rate constants allow one to calculate the branching ratios for some of the reactions involved. The preference for either N-dealkylation or cyclization depends on the solvent employed. Dissolved oxygen accelerates the photodegradation, especially the dealkylation.