Hydrogen peroxide and persulfates

TFE is a colorless, tasteless, odorless, and nontoxic gas. To avoid any undesired reactions during storage, inhibitors must be added. The polymerization is carried out by an addition-type reaction in an aqueous emulsion medium and in the presence of initiators such as benzoyl peroxide, hydrogen peroxide, and persulfates. The monomer is fed into a cooled emulsion medium and then heated to a temperature of 70-80°C, at which the polymerization takes place. 

Tin/Nickel and Nickel Tin/nickel ahoy (65 percent Sn, 35 percent Ni) and nickel plate, used as is or overplated with gold, solder, or tin, are also capable metal resists for etching copper in alkahne ammonia, sulfuric acid-hydrogen peroxide, and persulfates. 

Method 1. Free-Radical Initiation Intra-intermolecular polymerizations can be initiated by free radicals in several ways. Typical free-radical initiators like peroxides, peracids, azobis-(isobutyronitrile), oxygen, ferrous ion/hydrogen peroxide, and persulfate can... 

Bleaches of the simple ammoniacal peroxide type give limited lightening, which can be increased with bleach accelerators or boosters, including one or more per salts such as ammonium, potassium, or sodium persulfate or their combinations. These salts, which are susceptible to decomposition in aqueous solution, are packaged as dry powders and added just before use. In the absence of hydrogen peroxide, however, persulfates do not have any bleaching effect (41). 

Inorganic peroxides [hydrogen peroxide (63), persulfate (41), peroxymonosulfate and peroxydiphosphate (64)] generally have limited usefulness as initiators in bulk or solution polymerization due to their poor solubility in... 

Vinyl monomers may be polymerized at favorable rates in an aqueous medium containing an emulsifier and a water-soluble initiator. A typical simple Tecipe would consist of the following ingredients with their proportions indicated in parts by weight 100 of monomer, 180 of water, 2 to 5 of a fatty acid soap, and 0.1 to 0.5 of potassium persulfate. Cationic soaps (e.g., dodecylamine hydrochloride) may be used instead of the fatty acid soap, and various other initiators may replace the persulfate (e.g., hydrogen peroxide and ferrous ion, or a water-soluble organic hydroperoxide). 

Polymerization of vinyl chloride occurs through a radical chain addition mechanism, which can be achieved through bulk, suspension, or emulsion polymerization processes. Radical initiators used in vinyl chloride polymerization fall into two classes water-soluble or monomer-soluble. The water-soluble initiators, such as hydrogen peroxide and alkali metal persulfates, are used in emulsion polymerization processes where polymerization begins in the aqueous phase. Monomer-soluble initiators include peroxides, such as dilauryl and benzoyl peroxide, and azo species, such as 1,1 -azobisisobutyrate, which are shown in Fig. 22.2. These initiators are used in emulsion and bulk polymerization processes. 

The initiators used in emulsion polymerization are water-soluble initiators such as potassium or ammonium persulfate, hydrogen peroxide, and 2,2 -azobis(2-amidinopropane) dihydrochloride. Partially water-soluble peroxides such a succinic acid peroxide and f-butyl hydroperoxide and azo compounds such as 4,4 -azobis(4-cyanopentanoic acid) have also been used. Redox systems such as persulfate with ferrous ion (Eq. 3-38a) are commonly used. Redox systems are advantageous in yielding desirable initiation rates at temperatures below 50°C. Other useful redox systems include cumyl hydroperoxide or hydrogen peroxide with ferrous, sulfite, or bisulfite ion. 

Acridinium derivatives can be oxidized with hydrogen peroxide " and other peroxides , persulfates or molecular oxygen ° in neutral or alkaline media, resulting... 

The most common initiators are acyl peroxides, hydroperoxides, or azo compounds. Hydrogen peroxide, potassium persulfate, and sodium perborate are popular in aqueous systems. Ferrous ion in some cases enhances the catalytic effectiveness. 

It was also shown that the ratio of oxidized alcohol to oxidized Fe2+ could be greater then one. Baxendale and Wilson (1957) showed that hydroxyl radical initiating the chain polymerization of olefins by hydrogen peroxide was the same process as the rapid oxidation of glycolic acid. Merz and Waters (1947) confirmed that simple water-soluble alcohols are oxidized rapidly by Fenton s reagent. The primary alcohols are oxidized to aldehydes, which are further oxidized at comparable rates by exactly the same mechanism. Merz and Waters proposed a mechanism of chain oxidation of alcohols and aldehydes by sodium persulfate, hydrogen peroxide, and an excess of ferrous salt as follows ... 

Redox reactions occur with hydroperoxides, peroxides, peresters, persulfates, hydrogen peroxide, and other peroxides. A wide variety of metal ions may be used as reducing agents. Ions which are commonly used include Co +, Fe +, Cr ", and Cu+. 

Significant enhancement effects of electron acceptors (additives) such as hydrogen peroxide, ammonium persulfate, potassium bromate, and potassium peroxymono-sulfate (oxone) on the Ti02 photocatalytic degradation of various organic pollutants were observed already in early investigations [376]. The results showed that these additives markedly improved the degradation rate of 2,4-dichlorophenol. The enhanced photocatalytic oxidation of sulfide ions on phthalocyanine modified titania was ascribed [377] to the additional formation of superoxide radicals. 

Main group elements such as Se, B, As, Al, and C carry out epoxidations with hydrogen peroxide and other oxidants such as persulfates. In this case, the oxygen atom transferred is the distal oxygen atom. 

The most widely used chemical oxidants have been ammonium persulfate, (Nn4)2S208, and FeCl3, although hydrogen peroxide and a range of transition metal salts (e.g., Fe3+, Cc4+, Cu2+, Cr6+, andMn7+) have also been employed. The use of H202 (with Fe3+catalyst) is attractive environmentally, as the only by-product is water. For the metal-based oxidants considered by Chao and March,72 infrared (IR) spectroscopy confirmed that similar PPy backbones were formed in each case. 

Water soluble peroxides and persulfates, in combination with a reducing agent such as ferrous (Fe ) and thiosulfate (8203 ) ions, are a common source of radicals in aqueous and emulsion systems. An example of such a redox system has hydrogen peroxide as the oxidant and Fe as the reductant ... 

Inii/ioHon-. Any material which decomposes spontaneously or under external stimidus into free radicals may be used as an initiator for polymerization at the double bond A variety of peroxides satisfy this condition, such as, for instance, benzoyl peroxide and tertiary butylhydroper-oxide in systems where the initiator is dissolved in the monomer itself or in a monomer solution also hydrogen peroxide and potassium persulfate in emulsion polymerizations where the initiator is dissolved in an aqueous medium. Benzoyl peroxide decomposition occurs by Unimolecular reao tion ... 

Alkanes can be oxidized in the presence of some transition metal complexes in aqueous and acidic media For example, in concentrated sulfuric acid the oxidative properties of the complexes are enhanced. Solutions of derivatives of palladium(II), platinum(III), manganese(III) and mercury(II) as well as some other compounds (hydrogen peroxide, ammonium persulfate, nitric acid and even concentrated sulfuric acid itself) can be used as oxidants. In the cases of metal-free oxidants the active species are apparently electrophiles such as NO2 or SO3I-C (for nitration of aromatics, see, for example, recent publication [40] and references therein). 

The classical electrochemical production of hydrogen peroxide uses the electrolytic production of persulfate from sulfuric acid and hydrolyzes the persulfate in a second step into hydrogen peroxide and sulfuric acid. Hydrogen peroxide is always a by-product for the anodic production of oxidants in dilute solutions (Fig. 22.3). 

Production of persulfate, ozone, hydrogen peroxide, and oxygen 1 Ah.h, 200 mA.cm ... 

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