Photolysis of 3-(4-chlorophenyl)-1,1-dimethylurea in dilute aqueous solution

Reviews of Environmental Contamination and Toxicology

“…Monomethyl monuron (77), fenuron (1,1 ,dimethyl-3-phenylurea) (88), monomethyl fenuron (l-methyl-3-phenylurea) (89), monuron dimer (83) Only dealkylation, coupling and reductive dehalogenation processes were observed in the presence of surfactants. Pbotooxidation products previously observed by Tanaka et al (1977), with aqueous oxygenated solutions of monuron were not detected in Reaction 22. In summary, results show a nonparticipation of oxygen in the photoreaction ofmonuron in the presence of surface-active agents.…”

“…2 trimer 87 were isolated by TLC and identified by mass spectrometry (MS) (Reaction 21). The same sort of photoproducts was obtained with both sources, only the distribution of product yields was slightly different (Tanaka et al 1977). Reaction 21 indicates that photochemical processes occurring were ring hydroxylation, methyloxidation, N-demethylation, decWorination, dimerization, and trimerization.…”

“…Tanaka and coworkers extensively studied the photolysis of herbicide 76 under various conditions; viz., in dilute aqueous solutions (1977), in nonionic surface-active agent solutions (1979), and in aqueous solutions (198Ia, 1982a(198Ia, , 1982b(198Ia, , 1984. Tanaka et al (1977) reported the photolysis of monuron (76) in dilute oxygenated aqueous solutions (200 ppm) using two different environmentally relevant light sources: (1) A Rayonet RPR-204 reactor equipped with RUL-3000 lamps with peak spectral energy distribution at 300 nm, and (2) a 450 W Hanovia high-pressure immersion lamp, with a Pyrex filter to yield a minimum UV-cutoff of approximately 280 nm. Eleven photoproducts, namely 3-(4-chlorophenyl)-I-methylurea (77), 3-(4-cWorophenyl)-I-formyl-I-methylurea (78), 3-(4-chloro-2-hydroxyphenyl)-I, I-dimethylurea (79), 3-(4-hydroxyphenyl)-I,I-dimethylurea (80), 3-(4-hydroxyphenyl)-I-formyl-lmethylurea (81), 4,4'-dichlorocarbanilide (82) HERE R' C-NI CH, !…”

“…Reaction 21 indicates that photochemical processes occurring were ring hydroxylation, methyloxidation, N-demethylation, decWorination, dimerization, and trimerization. For instance, in the case of Rayonet Photoreactor (3 hr) exposure the yields of major products such as compounds 77, 78,80,83,85, and 87 from herbicide 76 were 0.6, trace ( < 0.05), 7.1, 1.5, 1.6, and 1.5%, respectively; while yields of these products were 1.0, 1.0, 2.0, 1.6, 0.4, and 0.3%, respectively, when aqueous solution of 76 was exposed to UV for 25 hr using a Hanovia lamp light source (see Reaction 21) (Tanaka et al 1977). Likewise, quantum yields for the photogeneration of products 77,80, 83,85, and 87 arising from monuron were 0.001,0.01,0.006,0.003, and 0.002, respectively; the starting material being irradiated for 45 min with a Rayonet Reactor.…”

“…Likewise, quantum yields for the photogeneration of products 77,80, 83,85, and 87 arising from monuron were 0.001,0.01,0.006,0.003, and 0.002, respectively; the starting material being irradiated for 45 min with a Rayonet Reactor. According to Tanaka et al (1977), very low quantum yields suggest that direct photodecomposition of monuron under environmental conditions would not be expected to be a major pathway for its degradation. The products shown by Reaction 21 were identified by MS, and alternative struc;.tures for compounds 82-87 can also be considered (see below).…”