Reduction of peroxides

Sodium cyclopentadienide, 41, 96 Sodium dichromate for oxidation of alkylarcncs to aromatic carboxylic acids, 43, 80 Sodium iodide, in conversion of 2,4-di-nitrochlorobenzene to 2,4-dinitro-iodobenzene, 40, 34 reduction of peroxide with, 41,... 

Iron(II) complexes of flavonoids like quercetin could, however, be involved in the reduction of peroxides ... 

The following analytical procedure for the accurate estimation of hydroperoxides was proposed [61], The reduction of peroxide occurs in a solution of isopropanol saturated with Nal in the presence of acetic acid and C02 atmosphere at 373 K (in water bath). The reaction ceases after 15 min. The relative standard deviation equals 0.2%. 

Kinetic Parameters of Reduction of Peroxides by Ketyl and Alkyl Radicals [68]... 

Enthalpies, Activation Energies, and Rate Constants of the Reduction of Peroxides by Ketyl, Semiquinone, and Hydroperoxyl Radicals Calculated by the I PM Model [68]... 

Comparison of the Thermodynamic and the Kinetic Characteristics of Substitution and Reduction of Peroxides by Alkyl Radicals... 

The detailed mechanism of P aeruginosa CCP has been studied by a combination of stopped-flow spectroscopy (64, 65, 84, 85) and paramagnetic spectroscopies (51, 74). These data have been combined by Foote and colleagues (62) to yield a quantitative scheme that describes the activation process and reaction cycle. A version of this scheme, which involves four spectroscopically distinct intermediates, is shown in Fig. 10. In this scheme the resting oxidized enzyme (structure in Section III,B) reacts with 1 equiv of an electron donor (Cu(I) azurin) to yield the active mixed-valence (half-reduced) state. The active MV form reacts productively with substrate, hydrogen peroxide, to yield compound I. Compound I reacts sequentially with two further equivalents of Cu(I) azurin to complete the reduction of peroxide (compound II) before returning the enzyme to the MV state. A further state, compound 0, that has not been shown experimentally but would precede compound I formation is proposed in order to facilitate comparison with other peroxidases. 

More abundant are reductions with sodium sulfite which is applied in aqueous solutions (solubility 24%). Its specialties are reduction of peroxides to alcohols [257], of sulfonyl chlorides to sulfinic acids [252], of aromatic diazonium compounds to hydrazines [253], and partial reduction of geminal polyhalides [254] Procedure 43, p. 216). 

Radical-anion complexes Scope of this review 91 Thermodynamic and kinetic methodologies Voltammetric methods 92 Homogeneous redox catalysis 94 Convolution analysis 98 Laser flash photolysis 102 Photoacoustic calorimetry 103 Thermochemical estimates 105 Fleduction of C—O and O O bonds 106 Reduction of ethers 107 Reduction of peroxides and endoperoxides Reduction of S—S and C—S bonds 136 Reduction of disulfides 137 Reduction of sulfides 150 Concluding remarks 157 Fleferences 160... 

CIEEL mechanism was originally proposed by Schuster for intense luminescence (or bioluminescence) in the decomposition of endoperoxides and dioxetanes. The relevance and importance of ET in the latter has recently been discussed. While the mechanism of reduction of peroxides in these early studies was described essentially as a concerted dissociative process, little insight into the fine detail of the mechanism could be provided. 

ET rate constants can also be determined using solution donors. Indirect reduction of peroxides and endoperoxides was accomplished by homogeneous... 

Reduction of carboxylic acids 9-42 Reduction of carboxylic esters 9-43 Reduction of carboxylic esters with titanocene dichloride 9-44 Reduction of anhydrides 9-45 Reduction of acyl halides 9-53 Reduction of nitriles 9-57 Reduction of hydroperoxides 9-60 Reduction of peroxides 9-69 Reaction between aldehydes and base (Cannizzaro)... 

Reductive alkylation of alcohols 9-40 Reduction of carboxylic esters 9-60 Reduction of peroxides... 

Selenium is an essential element for humans and is a constituent of selenoamino acids contained in selenoenzymes, such as glutathione peroxidases. This group of enzymes catalyzes the reduction of peroxides and thereby takes part in the anti-oxidative defense of the body. A severely low Se intake may cause heart disease (Keshan s disease). Therefore, possible adverse health effects are associated with a low intake of this element and justify the focus on the low percentile Se intake in the population. The food groups that contribute the most to the Se intake are meat (including offal) followed by bread and cereals, and fish, as shown in Figure 9.8. 

Peroxidases belong to the class of oxidoreductases containing iron (111) and protoporphyrin IX as the prosthetic groups. Peroxidases catalyze the reduction of peroxides and the oxidation of many organic and inorganic compounds. These enzymes are widely used for the removal of phenolic compounds, decolorization of synthetic dyes, deodorization of swine manure, in enzyme immunoassays, for biofuel production and organic and polymer synthesis (Hamid and Rehman, 2009). Peroxidases have also been used for the surface modification of poly-p-phenylene-2,6-benzo-bisthiazole (PBO), polyethylene, and grafting of acrylamide onto kevlar fibers. 

---