Peroxidative hydroxylation

Ca.ta.lysis by Protons. The discovery of hydrogen peroxide hydroxylation of phenol in the presence of strong acids such as perchloric, trifluoromethane-sulfonic, or sulfuric acids allows suppression of all previous drawbacks of the process (18,19). This mode of hydroxylation gives high yields (85% based on H2O2 at phenol conversion of 5—6%). It can be mn without solvents and does not generate resorcinol. Its main advantage rehes on... 

The direct conversion of aniline into aminophenols may be achieved by hydrogen peroxide hydroxylation in SbE —HE at —20 to —40° C. The reaction yields all possible aminophenols via the action of H20" 2 on the anilinium ions the major product is 3-aminophenol (64% yield) (70,71). This isomer may also be made by the hydrolysis of 3-aminoaniline [108-45-2] in dilute acid at 190°C (72). Another method of limited importance, but useful in the synthesis of derivatives, is the dehydrogenation of aminocyclohexenones (73). 

Wang S Y and Jiao HJ. 2000. Scavenging capacity of berry crops on superoxide radicals, hydrogen peroxide, hydroxyl radicals, and singlet oxygen. J Agric Food Chem 48 5677-5684. 

The primary ozonation by-products of atrazine (15 mg/L) in natural surface water and synthetic water were deethylatrazine, deisopropylatrazine, 2-chloro-4,6-diamino-s-triazine, a deisopropylatrazine amide (4-acetamido-4-amino-6-chloro-5-triazine), 2-amino-4-hydroxy-6-isopropylamino-5-triazine, and an unknown compound. The types of compounds formed were pH dependent. At high pH, low alkalinity, or in the presence of hydrogen peroxide, hydroxyl radicals formed from ozone yielded 5-triazine hydroxy analogs via hydrolysis of the Cl-Cl bond. At low pH and low alkalinity, which minimized the production of hydroxy radicals, dealkylated atrazine and an amide were the primary byproducts formed (Adams and Randtke, 1992). 

While some phenol is produced by the nucleophilic substitution of chlorine in chlorobenzene by the hydroxyl group (structure 17.17), most is produced by the acidic decomposition of cumene hydroperoxide (structure 17.18) that also gives acetone along with the phenol. Some of the new processes for synthesizing phenol are the dehydrogenation of cyclohexanol, the decarboxylation of benzoic acid, and the hydrogen peroxide hydroxylation of benzene. 

By the action of adds upon bario peroxide, hydroxyl is formed (p. 4d). 

Oxygen Superoxide Hydrogen peroxide Hydroxyl radical Water... 

Dehmlow and coworkers used quaternary ammonium salt 3 [8d] for the peroxidative hydroxylation of 2-ethyl-l-tetralone (Scheme 7.15), which was originally introduced by Shioiri et al. [49]. 

Therefore, the sequential addition of a single electron results in the formation of superoxide anion, hydrogen peroxide, hydroxyl radical, and water. 

To produce radicals the cellulose substrate can be saturated with potassium persulfate. Another method includes impregnation of cellulose with ferrous salts followed by treatment with a monomer solution in the presence of hydrogen peroxide. Hydroxyl radicals are produced in this system according to the following reaction ... 

Keywords Absorption cross section Hydrogen peroxide Hydroxyl radical ... 

A18. Aruoma, O. I., Halliwell, B., Hoey, B. M., and Butler, J., The antioxidant action of N-acetylcysteine Its reaction with hydrogen peroxide, hydroxyl radical, superoxide, and hypochlorous acid. Free Radicals Biol. Med. 6, 593-597 (1989). 

Many of the classical electrolytic reactions occur at a potential which is either more negative (reduction) or more positive (oxidation) than the decomposition potentials of the media. The mechanism of such reactions must be investigated in each case, but it can usually be classified as one of the following three cases (1) a direct electron transfer from electrode to substrate (A2), (2) a formation of solvated electrons which, in turn, reduoe the substrate (Bl), or (3) a formation of an active species in the electrochemical step (adsorbed hydrogen, active metals, hydrogen peroxide, hydroxyl radicals, halogens, etc.) which reacts chemically with the substrate (B2). 

Laughton, M. J., Halliwell, B., Evans, P. J., and Hoult, J. R. (1989). Antioxidant and prooxidant actions of the plant phenolics quercetin, gossypol and myricetin. Effects on lipid peroxidation, hydroxyl radical generation and bleomycin-dependent damage to DNA. Biochem. Pharmacol. 38, 2859-2865. 

This procedure has been applied to the determination of organic peroxides hydroxyl amine chromium(VI) cerium(IV) molybdenum(VI) nitrate, chlorate, and perchlorate ions and numerous other oxidants (see, for example. Problems 20-37 and 20-39). 

Tea polyphenols show profound antioxidative effects in various systems they are strong scavengers of superoxide, hydrogen peroxide, hydroxyl radicals, nitric oxide, and peroxynitrite, the products of various chemical reactions and biological systems. 

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