Oxygen-hydrogen peroxide

Conversion of Aromatic Rings to Nonaromatic Cyclic Structures. On treatment with oxidants such as chlorine, hypochlorite anion, chlorine dioxide, oxygen, hydrogen peroxide, and peroxy acids, the aromatic nuclei in lignin typically ate converted to o- and -quinoid stmctures and oxinane derivatives of quinols. Because of thein relatively high reactivity, these stmctures often appear as transient intermediates rather than as end products. Further reactions of the intermediates lead to the formation of catechol, hydroquinone, and mono- and dicarboxyhc acids. 

The aromatic ring of a phenoxy anion is the site of electrophilic addition, eg, in methylolation with formaldehyde (qv). The phenoxy anion is highly reactive to many oxidants such as oxygen, hydrogen peroxide, ozone, and peroxyacetic acid. Many of the chemical modification reactions of lignin utilizing its aromatic and phenoHc nature have been reviewed elsewhere (53). 

Wet Oxidation (WO) The oxidation of oxidizable substances in water using the oxygen in air, pure or enriched oxygen, hydrogen peroxide, nitric acid or some other oxidizing agent as the source of the oxidant. The oxidation process is conducted at subcritical temperatures (<374°C). 

A wide variety of enzymes have been used in conjunction with electrochemical techniques. The only requirement is that an electroactive product is formed during the reaction, either from the substrate or as a cofactor (i.e. NADH). In most cases, the electroactive products detected have been oxygen, hydrogen peroxide, NADH, or ferri/ferrocyanide. Some workers have used the dye intermediates used in classical colorimetric methods because these dyes are typically also electroactive. Although an electroactive product must be formed, it does not necessarily have to arise directly from the enzyme reaction of interest. Several cases of coupling enzyme reactions to produce an electroactive product have been described. The ability to use several coupled enzyme reactions extends the possible use of electrochemical techniques to essentially any enzyme system. 

The most common sources as oxygen supply are air, pure oxygen, hydrogen peroxide, or possibly ozone. Table 18.3 summarizes the advantages and disadvantages of these oxygen supply alternatives. 

Biocompatible nanosized polyamidoamine (PAMAM) dendrimer films provided a suitable microenvironment for heme proteins to transfer electron directly with underlying pyrolytic graphite electrodes. The Mb-PAMAM film can catalytically reduced oxygen, hydrogen peroxide, and nitrite, indicating that the potential applicability of the film can be used to fabricate a new type of biosensor or bioreactor based on the direct electron transfer of Mb [234],... 

Biopolymers such as agarose hydrogel can also be used to immobilize HRP and to reduce oxygen, hydrogen peroxide and nitric oxide [231], For an HRP-agarose/EPG in a pH 7.0 PBS, a reduction peak at -0.30V was observed after addition of H2Q2. 

Oxidation of aliphatic nitroso functionality is usually facile but is not widely used in energetic materials synthesis. The following reagents have been used in these conversions oxygen,hydrogen peroxide, nitrous oxide, " dinitrogen tetroxide, ... 

Perfluoropropene (1) can be directly oxidized to perfluoro-1,2-epoxypropane (2) by a variety of oxidizing reagents, e.g. oxygen, hydrogen peroxide.50 s2 Pcrfluoro-1,2-epoxypropane (2) can fluorinate carboxylic acids to their corresponding acid fluorides in the presence of tertiary amines.52 55... 

Formation of oxygen Hydrogen peroxide Fe3+. Fe(lllf-phdiolocyunine chelate... 

The most reliable technique for the analysis of superoxides is that developed by Seyb and Kleinberg. In this method the superoxide sample is treated with a mixture of glacial acetic acid and diethyl or dibutyl phthalate. The superoxide reacts with the acetic add to yield oxygen, hydrogen peroxide, and potassium acetate. The amount of superoxide in the sample is related to the amount of oxygen evolved which is measured with a gas buret. The stoichiometry of the analytical reaction is ... 

Transition metal peroxides, particularly peroxo (2), alkylperoxo (7) and hydroperoxo (8) complexes, are extremely important reactive intermediates in catalytic oxidations involving molecular oxygen, hydrogen peroxide and alkyl hydroperoxides as the oxygen source. Representative peroxo complexes are listed in Table 3, and alkylperoxo and hydroperoxo complexes are listed in Table 4 together with their reactivities. 

Although unstable with respect to water and oxygen, hydrogen peroxide decomposes only very slowly at room temperature because the reaction has a high activation energy (76 kj/mol). In the presence of iodide ion, however, the reaction is appreciably faster (Figure 12.16) because it can proceed by a different, lower-energy pathway ... 

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