M. Millet et al., INVESTIGATION OF THE PHOTOCHEMISTRY OF UREA HERBICIDES (CHLOROTOLURONAND ISOPROTURON) AND QUANTUM YIELDS USING POLYCHROMATIC IRRADIATION, Environmental toxicology and chemistry, 17(2), 1998, pp. 258-264
This paper presents the investigation of the photochemical reaction of
chlorotoluron (3-(3-chloro-4-methyl-phenyl)-1,1-dimethylurea) in CH3C
N, hexane, and aqueous and buffered solutions (pH = 4, 7, and 9) and o
f isoproturon (3-(4-isopropylphenyl)-1,1-dimethylurea) in aqueous and
buffered solutions using a polychromatic light source at a temperature
of 22 degrees C. For chlorotoluron, isosbestic points were found (wit
h the exception of hexane as solvent) and ultraviolet spectroscopy was
used to obtain kinetic data. The main photoproduct for the photolysis
of chlorotoluron in aqueous solutions was identified as 3-(3-hydroxy-
4-methyl-phenyl)-1,1 dimethylurea. Quantum yields found in aqueous and
buffered solutions were comparable (about 0.07) and 2 times lower and
10 times higher in CH3CN and hexane, respectively. No isosbestic poin
ts were found for isoproturon, and quantum yields of about 0.004 were
calculated in all solutions. Chlorotoluron and isoproturon present ver
y low molar extinction coefficients above 290 nm, and they can be assu
med to be photostable with respect to direct irradiation by sunlight.