Alkyl peroxo radical

The fate of the alkyl radical R is combined with O2 to form the alkyl peroxo radical RO2 (R—O—O ) ... 

It has been proposed that the crucial step of the oxidation by the reagent O2 - H2O2 - VOj"- pyrazine-2-carboxylic acid is the very efficient generation of HO radicals [15]. These radicals abstract a hydrogen atom from the alkane, RH, to generate the alkyl radical, R. The latter reacts rapidly with an O2 molecule affording the peroxo radical, ROO. This radical is then transformed simultaneously into three products alkyl hydroperoxide, ketone, and alcohol. The relative content of the last two products is increased if the reaction temperature is higher. 

Cobalt(III)-alkylperoxo complexes find use in the oxidation of hydrocarbons.1342,1343 Since they release ROO and RO radicals upon mild heating in solution, they are effective oxidants under mild conditions, and produce catalytic systems in the presence of excess ROOH. Aliphatic C—11 bond oxidation by ConOOR (R = Con, alkyl, H) complexes including a hydrotris(pyrazolyl) borate ligand have also been reported, with homolysis of the peroxo O—O bond believed to be important in oxygenation of the C—H bond.1344... 

The obvious candidates for the two competing reactions are those shown in Eqs. (24) and (25). The mechanisms of the two reactions are probably similar, although it was not possible to show whether reaction 25 produced isobutene. The expected chemistry is shown in more detail in Eq. (32). In a less appealing possibility, the tentative peroxo intermediate would cleave homolytically to yield alkyl and alkoxyl radicals, a route that is thermodynamically much less favorable than reaction 32. 

The data seem to support an alternative mechanism compared with the so-called Lyons mechanism in which O2 is activated forming a metal-oxo (M=0) species.1831 Via reaction of a second metalloporphyrin with a primarily formed superoxo (Me-OO0) or peroxo species, a metal-oxo is formed, reacting eventually with an alkane according to the oxygen rebound mechanism. Alternatively, radicals present in solution, upon reaction with dioxygen, may form alkyl hydroperoxides that are decomposed by metalloporphyrins.[83]... 

In this section we present a short overview of the polymerization of VC. The most common method is polymerization by free radicals [305]. According to the ease of homolytic splitting of the n bond in the monomer, radical polymerization takes place in the presence of suitable initiation systems. In general, there are three methods for producing radicals available for the polymerization of VC (A) thermal cleavage of azo or peroxo compounds, (B) oxidation-reduction processes, and (C) metal alkyls in connection with oxygen. After the initiation step, chain growth takes place rapidly ... 

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