Identification of sensitized photooxidation products of bromacil in water

Acher, A. J.; Dunkelblum, E.

doi:10.1021/jf60226a027

Cited by 20 publications

(17 citation statements)

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“…This type of dimerization differs from the usual dimerization reactions as observed in different halogen uracils (Feneslau and Wang, 1969;Wang, 1976). The fact that a similar compound was not obtained from VI (Acher and Dunkelblum, 1979) is due to the more facile homolitic cleavage of the tert-butyl group as compared to that of the sec-butyl group. The formation of V, which is an oligomer, although its exact structure has not yet been elucidated, implies probably a radical reaction mechanism, initiated by RF (Oster, 1954).…”

Section: Discussionmentioning

confidence: 99%

“…Pure I1 (white needle crystals) was obtained by recrystallization (ether-hexane, 15) of the crude material eluted from a silica gel column after elution of I: TLC RI = 0.85 and RnI = 1.5; mp 104-106 "C. The chemical structure of I1 was established by comparison with VI (Acher and Dunkelblum, 1979 (2) 3-tert-Butyld-hydroxyhydantoin (110. This compound was obtained only in the photoreaction of I carried out at pH 17.8 and a temperature >15 "C. Experiments showed that under such conditions this compound may also be obtained from I1 in the dark and without sensitizers.…”

Section: (C) Photodegradation Products (Table I; Scheme I) (I) 3-termentioning

confidence: 99%

“…Recent studies of the photodecomposition of bromacil (3-sec-butyl-5-bromo-6-methyluracil, VI) showed that aerated aqueous solutions H R XI R=-CH-CzHs I C"3 exposed to sunlight in the presence of dye sensitizers resulted in rapid and complete degradation. The major photooxidation product was identified as a mixture of diastereoisomers of 3-sec-butyl-5-acetyl-5-hydroxyhydantoin (VII) (Acher and Saltzman, 1980;Acher and Dunkelblum, 1979). Compound I differs from VI in the halogen substituent at C-5 as well as in the N-alkyl group (C1 and tert-butyl instead of Br and sec-butyl, respectively).…”

mentioning

confidence: 99%

“…The sensitizers methylene blue (MB), rose bengal (RB), riboflavin (RF), and humic acids (HA), the specifications of which were given in a previous work (Acher and Saltzman, 1980), were used as 0.1% aqueous solutions.…”

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confidence: 99%

“…The apparatus used for the irradiations and identification of I and its reaction produds were described previously (Acher and Dunkelblum, 1979;Acher and Saltzman, 1980). Laboratory Lamp Photodegradation Procedure.…”

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confidence: 99%

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Photosensitized decomposition of terbacil in aqueous solutions

Acher¹,

Saltzman²,

Brates³

et al. 1981

J. Agric. Food Chem.

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The dye-sensitized photolysis of aerated aqueous solutions of terbacil (3-tert-5-chloro-6-methyluracil, I) exposed to solar irradiation was investigated under different reaction conditions. After 2 h of exposure to sunlight, in the presence of methylene blue (3 ppm) or riboflavin (10 ppm), the major photodegradation product in the pH range of 3.0-9.2 was 3-tert-butyl-5-acetyl-5-hydroxyhydantoin (11). In alkaline reaction mixtures (pH 8.0 or 9.2), this product undergoes deacylation, giving 3-tert-5-hydroxyhydantoin (111). In experiments carried out under neutral or acidic conditions (PH 6.8 or 3.0) with riboflavin, two additional products were isolated a mono-N-dealkylated terbacil dimer (IV) and a nonidentified water-insoluble product (V). The structures of 11,111, and IV were determined by using proton and carbon-13 nuclear magnetic resonance, infrared, ultraviolet, and mass spectroscopy.Terbacil (3-tert-butyl-5-chloro-6-methyluracil,

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Section: Discussionmentioning

confidence: 99%

Section: (C) Photodegradation Products (Table I; Scheme I) (I) 3-termentioning

confidence: 99%

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Photosensitized decomposition of terbacil in aqueous solutions

Acher¹,

Saltzman²,

Brates³

et al. 1981

J. Agric. Food Chem.

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Removal of the phytotoxicity of uracil herbicides in water by photodecomposition

et al. 1982

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The efficiency of a photo‐oxidation procedure for the detoxication of water containing herbicides of the uracil group was tested by bioassay. Treated herbicide solutions were checked for their inhibiting effect on germination and photosynthesis in sorghum (Sorghum bicolor). The treated solutions, and the main photodegradation products of bromacil and terbacil did not inhibit significantly either germination or seedling development at concentrations of up to 200 and 10 mg litre−1, respectively. Preliminary tests with industrial waste effluents containing added uracil compounds showed that these compounds were rendered non‐phytotoxic by the photo‐oxidation procedure.

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Photocatalytic degradation of pesticides and bio‐molecules in water

Muszkat

Feigelson

Bir

et al. 2002

Pest Management Science

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Two approaches are suggested for the acceleration of the photocatalytic oxidation of organic contaminants of water: acceleration by oxidants and photo-enhancement by dyes. These processes were examined with several substances: two widely applied herbicides, bromacil (a uracil) and metribuzin (a triazine), and three proteins, studied as models of biocontaminated waters. The effects of oxygen and hydrogen peroxide indicated two different reaction patterns of photo-oxidation of the herbicides. With metribuzin, oxygen had a pronounced effect on the rate of photo-oxidation, while the influence of hydrogen peroxide was quite moderate; with bromacil, oxygen had a limited effect on the rate of photo-oxidation, which however was considerably enhanced by hydrogen peroxide. Acceleration of the photo-catalytic oxidation of colourless refractory contaminants by photo-excited dye was observed. Both UV and visible light were required for the enhanced decomposition. The mechanism of the reaction seems to involve a combination of oxidation by hydroxyl radicals, via the hole-electron semiconductor route, with subsequent oxidation of photo-intermediates by singlet oxygen formed by dye sensitization. The TiO2-photocatalyzed oxidation of proteins (albumin, ovalbumin and gamma-globulin) showed the susceptibility of proteins to photocleavage and of the amino acids to photocatalytic degradation. Tyrosine was the most sensitive, while the degradation of the aliphatic amino acids Gly and Asp was slow.

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Identification of sensitized photooxidation products of bromacil in water

Cited by 20 publications

References 13 publications

Photosensitized decomposition of terbacil in aqueous solutions

Photosensitized decomposition of terbacil in aqueous solutions

Removal of the phytotoxicity of uracil herbicides in water by photodecomposition

Photocatalytic degradation of pesticides and bio‐molecules in water

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