Fentons Reagent

FIGURE 1.13 Transformation products from (a) chlorobenzene, (b) 2,4-dichlorophenoxyacetate, (c) pentachlorophenol. 

These are complexes formed between tungstates and molybdates, and silicate or phosphate, and have been used to generate hydroxyl radicals photochemically. The tungstates PWj204q and SiWj204o have been used most frequently. 

They have also been used to bring about photochemical reduction of Hg + via Hg2 to Hg° (Troupis et al. 2005). 

The mechanism involves photochemical production of a free electron in the conduction band (e b ) nd a corresponding hole (h b ) in th valence band. Both of these produce H2O2 and thence hydroxyl radicals. 

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Combinations of H2O2 and Fe(II) salts, generally known as Fenton reagents, have for many years been used in organic and polymer chemistry, Medalia and Kolthoff [77] summarized the principal features of this reaction. 

It is concluded that zeoHte beta can be simultaneously detemplated and Fe-exchanged without FeO formation by treating the parent zeoHte with a Fenton reagent. The catalyst shows good performance on N2O decomposition. This one-pot process simplifies its preparation protocol and can be extended to other systems. Indeed, our approach was followed by Liu et al. [170], for preparing Fe-S BA-15 for benzylation of benzene with interesting results. 

Panzella, L, Manini, P, Napolitano, A, and d Ischia, M, 2004. Free radical oxidation of (E)-retinoic acid by the Fenton reagent Competing epoxidation and oxidative breakdown pathways and novel products of 5,6-epoxyretinoic acid transformation. ChemRes Toxicol 17, 1716-1724. 

Entezari Mohammad H, Christian P, Pierre D (2003) Degradation of azo dyes by hybrid ultrasound-Fenton reagent. Ultrason Sonochem 10(2) 103-108... 

Tai Li Ji, Ya-Li S (2009) Degradation of AR 97 aqueous solution by combining ultrasound and Fenton reagent. Environ Prog Sustain Energy 29(1) 101-106... 

Goi A, Trapido M (2002) Hydrogen peroxide photolysis, Fenton reagent and photo-Fenton for the degradation of nitrophenols a comparative study. Chemosphere 46 913-922... 

Chamarro E, Marco A, Esplugas S (2001) Use of Fenton reagent to improve organic chemical biodegradability. Water Res 35 1047-1051... 

The oxidation of organic compounds by Fenton reagent is associated, as it is clear now, with the generation of hydroxyl radicals. For example, the oxidation of tartaric acid includes the following reactions as key steps [16] ... 

Walling, C. 1975. Fenton reagent revisted. Accounts of Chemical Research 8 125-131. 

A three-channel approach was developed by Lee et al. (1993) to distinguish H202 from hydroxymethyl hydroperoxide and total peroxides. In this approach, one channel is used to scrub the air sample into a POPHA solution to obtain total peroxides. In a second channel, the air sample is scrubbed into Fenton reagent solution at a pH of 3. This converts the H202 into OH radicals ... 

Demethylation of methylated sugars by means of hydrogen peroxide in the presence of ferrous ions (the Fenton reagent) has been re-... 

A principally different approach for the indirect electrochemical oxidation of aromatic compounds goes via the formation of hydroxyl radicals from cathodically generated hydrogen peroxide and from reductively formed iron(II) ions. The thus in situ formed Fenton reagent can lead to side-chain as well as nuclear oxidations of aromatic compounds. Side-chain oxidations to form benzaldehydes according to Eqs. (18)—(24) can also be initiated by the redox pairs and Cu instead of... 

A developed gel electrophoresis of DNA following oxidative damage by the Fenton reagent. 

On the basis of differences in the product distributions in oxidations by the Fenton reagent, and by the Udenfriend reagent a different mechanism for the latter was suggested. In aprotic solvents, however, the Fenton reagent gives results similar to those in enzymatic hydroxylations. It was observed that the hydrogen displaced... 

The kinetics of oxidation of aldehydes by the Fenton reagent [Fe(II)-H202-0H-] have been studied.89 It has been suggested that different reactivities of PhIO in iron(III)-porphyrin-catalysed alkene epoxidation may be due to the formation of a more reactive iron(IV)-0-IPh complex.90 The iron(m) complex of tetrakis(3,5-disulfonato-mesityl)porphyrin catalyses the oxidative degradation of 2,4,6-trichlorophenol to 2,6-dichloro-l,4-benzoquinone with KHSO5 as the oxygen atom donor a peroxidase-type oxidation is thought to be involved.91... 

Table 3.7. Hydroxylation of salicylic acid (5 x 10-3 mol dm-3 product 2,3-dihydroxyben-zoicacid, 2,3-DHB 2.13 x 10-5 mol dm-3 in the absence of a scavenger) and phenylalanine (5 x 10-3 mol dm-3 product p-tyrosine, 7.3 x 10 s mol dm-3 in the absence of a scavenger, total tyrosines 2.21 x 10-5 mol dm-3 by the Fenton reagent (Fe(lll) 5 x 10-s mol dm-3, EDTA 1.5 x 10 5 mol dm-3, H2O2 5 x 10-5 mol dm-3, ascorbate 5 x 10-5 mol dm-3, phosphate buffer pH 7.4) (Kauret al. 1997). Calculations are based on competition kinetics using established rate constants. (Buxton et al. 1988)...

Matsufuji H, Shibamoto T (2004) The role of EDTA in malonaldehyde formation from DNA oxidized by Fenton reagent systems. J Agric Food Chem 52 3136-3140 Matsunga T, Hieda K, Nikaido O (1991) Wavelength dependent formation of thymine dimers and (6-4)photoproducts in DNA by monochromatic ultraviolet light ranging from 150 to 365 nm. Photochem Photobiol 54 403-410... 

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