Phototransformation of linuron and chlorbromuron in aqueous solution

Faure, Valérie; Boule, Pierre

doi:10.1002/(sici)1096-9063(199712)51:4<413::aid-ps671>3.0.co;2-9

Cited by 27 publications

(20 citation statements)

References 13 publications

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“…The photoreaction of polyhalogenated aromatics is more complicated. The 4-OH derivatives of diuron 137) and linuron 138) were mainly produced by irradiation at 365 nm, while the predominant formation of 3-OH derivatives was observed at 254 nm. Dicamba 141) and pentachlorophenol 140) mainly underwent the photosubstitution of Cl by OH, while the radical mechanism was most likely for methoxychlor 141) and DDE.…”

Section: Dehalogenation 3151 Dechlorinationsupporting

confidence: 72%

Direct photolysis mechanism of pesticides in water

Katagi

2018

Journal of Pesticide Science

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Photodegradation is one of the most important abiotic transformations for pesticides in the aquatic environment, and the high energy of sunlight causes characteristic reactions such as bond scission, cyclization, and rearrangement, which are scarcely observed in hydrolysis and microbial degradation. This review deals with direct photolysis via excitation of a pesticide by absorbing natural or artificial sunlight in order to know its basic photochemistry, and indirect photolysis meaning either sensitization by dissolved organic matters or oxidation by reactive oxygen species is basically excluded. Several experimental approaches including spectroscopic techniques together with theoretical calculations are first discussed from the viewpoint of the reaction mechanisms in direct photolysis. Then, the typical photoreactions of pesticides are summarized by chemical classes and/or functional groups and discussed as far as possible in relation to their mechanisms.

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Section: Dehalogenation 3151 Dechlorinationsupporting

confidence: 72%

Direct photolysis mechanism of pesticides in water

Katagi

2018

Journal of Pesticide Science

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“…It is explained by a Norrish-type II reaction. The formation of formaldehyde has been experimentally proved [24]. It was reported by Soley et al [25] that the photoproducts initially formed in the photodegradation of MCPA (4-chloro-2-methylphenoxyacetic acid) irradiated with a mercury lamp HPK 125 or in simulated sunlight in the presence of a photosensitizer, are 4-chloro-2-methylphenol and 4-chloro-2-methylphenyl formate.…”

Section: Chloroaromatic Herbicidesmentioning

confidence: 83%

Phototransformation of halogenoaromatic derivatives in aqueous solution

Boule

Othmen

Richard

et al. 1999

International Journal of Photoenergy

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Abstract. The photochemical behaviour of monohalogeno-phenols and -anilines is highly dependent on the position of the halogen on the ring, but most often it is not significantly influenced by the nature of the halogen (Cl, Br, F). Photohydrolysis is the main reaction observed with 3-halogenated and it is almost specific. With 2-halogenated, photohydrolysis and photocontraction of the ring compete, the latter being very efficient with 2-halogeno-phenolates.The photochemical behaviour of 4-halogeno-phenols and -anilines is more complex. It depends on both concentration and oxygenation. It was rationalized when it was experimentally proved by laser flash photolysis that the first step is the formation of a carbene (in the cationic form in the case of 4-halogenoaniline). p-Benzoquinone is the product of photooxidation of 4-halogenophenols, whereas the photooxidation of 4-chloroaniline leads to 4-amino-4 -chlorodiphenylamine.Chlorohydroquinone behaves differently, the formation of the main photoproducts involving a radical mechanism.With dihalogenoanilines photohydrolysis is initially almost quantitative whatever the position of halogen atom on the ring. It occurs more easily in meta than in ortho position and in ortho than in para position. In the case of 2,4-and 2,6-dichloroanilines aminophenoxazones are formed as secondary photoproducts. This reaction involves the intermediate formation of o-benzoquinone monoimine.Several halogenoaromatic herbicides were also studied (bromoxynil, chlorpropham, propanil, diuron, linuron, chlorbromuron, MCPA). The most frequent reaction is photohydrolysis. However some other reactions such as photoreduction and photo-demethoxylation were observed. In some cases a wavelength effect was observed particularly with MCPA and halogenophenylureas.

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“…The quantum yield of the direct photodegradation of monolinuron was evaluated as 0.13€0.01 at 254 nm but was found to progressively decrease by increasing excitation wavelength (0.11, 0.06 and 0.03, all €0.01) at 270, 290 and 300 nm, respectively. This excitation wavelength dependence has also been reported for chlorophenylureas like diuron (Jirkovsky et al 1997) and linuron (Faure and Boule 1997), and tentatively explained as resulting from the "keto-enolic" equilibrium of the urea function.…”

Section: Quantum Yields and Kineticsmentioning

confidence: 99%

Nitrite and nitrate induced photodegradation of monolinuron in aqueous solution

et al. 2004

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Here we evidenced the photo-induced degradation of monolinuron, a phenylurea herbicide, through the 300-450 nm light excitation of nitrite and nitrate species. The degradation pathways were compared to those obtained under direct photolysis at 254 nm. When using NO 3 and NO 2 as photoinducers, hydroxyphenylsubstituted photodegradation products were found to be formed specifically through the involvement of OH radicals. NO and NO 2 -phenyl substituted compounds were also observed as a result of the production of NO and NO 2 radicals. Half-lives of monolinuron in aqueous solutions were measured in various conditions of concentrations of substrate and inducer, oxygen content and pH.

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Phototransformation of linuron and chlorbromuron in aqueous solution

Cited by 27 publications

References 13 publications

Direct photolysis mechanism of pesticides in water

Direct photolysis mechanism of pesticides in water

Phototransformation of halogenoaromatic derivatives in aqueous solution

Nitrite and nitrate induced photodegradation of monolinuron in aqueous solution

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