Oxidation by hydrogen peroxide

In the presence of acid, solutions of iodide are oxidized by hydrogen peroxide... 

Glycohc acid also undergoes reduction or hydrogenation with certain metals to form acetic acid, and oxidation by hydrogen peroxide ia the presence of ferrous salts to form glyoxylic acid [298-12A], HCOCOOH, and ia the presence of ferric salts ia neutral solution to form oxaHc acid, HOOCCOOH formic acid, HCOOH and Hberate CO2 and H2O. These reduction and oxidation reactions are not commercially significant. 

Oxidation by Hydrogen Peroxide. This reaction produces amine oxides (qv) (1,7,33,34,36). 

Methylthioquinoxaline is oxidized by hydrogen peroxide in acetic acid at room temperature mainly to 2-methylsulfonylquinoxa-line (88) at 55°C, 2-methylsulfonylquinoxaline 4-oxide (89) and quinoxaline-2,3-dione are formed. 

Taking E H202 = +1.763 V, determine which of the following species will be oxidized by hydrogen peroxide (use Table 18.1 to find E values). 

Propyl gallate is an antioxidant. It protects against oxidation by hydrogen peroxide and oxygen free radicals in a catalytic manner similar to superoxide dismutase. 

Figure 4.90 Scheme of test facility for ethanol oxidation by hydrogen peroxide [51. ... 

A mixture of sodium peroxide and diethyl ether combusts when water is present. This accident is caused by ether oxidation by hydrogen peroxide, which is formed by the effect of water on alkaline peroxide. 

Answers to these questions were initiated over a decade ago during our studies on catalase (CAT) and horseradish peroxidase (HRP) (30). Both native enzymes are ferric hemoproteins and both are oxidized by hydrogen peroxide. These oxidations cause the loss of two electrons and generate active enzymatic intermediates that can be formally considered as Fe + complexes. 

Oxidation of secondary amines into nitrones has been extensively studied and a variety of well-known efficient oxidants and catalysts which can be employed in this process are available. Catalytic oxidation by hydrogen peroxide at room temperature is carried out by using sodium tungstate (Fig. 2.1) (28-47). 

There is as yet no known enzyme that breaks the C—F bond in fluoroacetic acid, FCH2COOH, or in related compounds. It is interesting to note, however, that in the course of our investigations2 on peroxidase-catalysed oxidations, we have effected an enzymic cleavage of the C—F bond in p-fluoroaniline.3 In acetate buffer (pH 4-5) and at room temperature, the amine was oxidized by hydrogen peroxide and peroxidase to give mainly the red crystalline 2-amino-5-p-fluoroanilinobenzoquinone di-p-fluoroanil (XX). 

Phenols (p-cresol, guaiacol, pyrogallol, catechol) and aromatic amines (aniline, p-tolidine, o-phenyldiamine, o-dianisidine) are typical substrates for peroxidases [90 -109]. These compounds are oxidized by hydrogen peroxide or hydroperoxides under peroxidase catalysis to generate radicals, which after diffusion from the active center of the enzyme react with further aromatic substrates to form dimeric, oligomeric or polymeric products. 

The second reaction achieved notoriety as a possible source of hydroxyl radicals, but the reaction proceeds extremely slowly. Iron(III) complexes may catalyze this reaction in this case, Fe(III) would first be reduced by the superoxide, followed by oxidation by hydrogen peroxide. See also Fenton Reaction... 

Rhenium is attacked by neither hydrochloric acid nor by cold sulfuric or hydrofluoric acid. However, oxidizing acids, such as nitric acid or hot sulfuric acid, vigorously react with the metal forming perrhenic acid, HRe04. The metal is oxidized by hydrogen peroxide in ammoniacal solution forming ammonium perrhenate, NH4Re04. 

Technetium dissolves in dilute or concentrated nitric acid to form nitrate, Tc(N03)2. Reaction with concentrated sulfuric acid yields the sulfate TCSO4. Technetium is oxidized by hydrogen peroxide in alkaline solution to form soluble pertechnetate, Tc04 anion. Such pertechnatate anion forms complexes with tertiary or quarternary amines, pyridine and its methyl-substituted derivatives. 

In 1948 Maxted and Walker studied the detoxification of catalyst poisons in the hydrogenation of aromatic hydrocarbons and found that the isomeric thienothiophenes 1 and 2 could be converted into the sul-fones of fully hydrogenated thienothiophenes 1 and 2, which do not poison the catalysts. This conversion is performed by brief preliminary hydrogenation and subsequent oxidation by hydrogen peroxide or per-molybdic acid. However, no data on the isolation or foe properties of these disulfones are available. It has been reported that direct oxidation of thienothiophenes 1 and 2 does not produce sulfones. 

Scheme 28) Quantum yields of lucigenin oxidation by hydrogen peroxide in alkaline media are comparable with the values obtained in luminol oxidation (1.24 x 10 E mol ) ° . However, the use of other peroxides, such as tcrt-butyl hydroperoxide, results in a decrease of chemiluminescence quantum yields of two orders of magnitude, confuming the hypothesis that a 1,2-dioxetane is the HEI, since its formation would be impossible with alkyl peroxides . 

Lagrange, J., C. Pallares, G. Wenger, and P. Lagrange, Kinetics of SulphuKIV) Oxidation by Hydrogen Peroxide in Basic Aqueous Solution, Atmos. Environ., 30, 1013-1018(1996). 

---