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Free radicals dialkyl peroxide decomposition

Primary and secondary dialkyl peroxides undergo thermal decompositions more rapidly than expected owing to radical-induced decompositions (73). Such radical-induced peroxide decompositions result in inefficient generation of free radicals. [Pg.107]

Because di-/ fZ-alkyl peroxides are less susceptible to radical-induced decompositions, they are safer and more efficient radical generators than primary or secondary dialkyl peroxides. They are the preferred dialkyl peroxides for generating free radicals for commercial appHcations. Without reactive substrates present, di-/ fZ-alkyl peroxides decompose to generate alcohols, ketones, hydrocarbons, and minor amounts of ethers, epoxides, and carbon monoxide. Photolysis of di-/ fZ-butyl peroxide generates / fZ-butoxy radicals at low temperatures (75), whereas thermolysis at high temperatures generates methyl radicals by P-scission (44). [Pg.107]

Dialkyl peroxydicarboaates are used primarily as free-radical iaitiators for viayl monomer po1ymeri2ations (18,208). Dialkyl peroxydicarboaate decompositioas are accelerated by certaia metals, coaceatrated sulfuric acid, and amines (44). Violent decompositions can occur with neat or highly concentrated peroxides. As with most peroxides, they Hberate iodine from acidified iodides. In the presence of copper ions and suitable substrates, dialkyl peroxydicarbonates have been used to synthesi2e alkyl carbonates (44) ... [Pg.124]

The reaction follows a free-radical mechanism and gives a hydroperoxide, a compound of the type ROOH. Hydroperoxides tend to be unstable and shock-sensitive. On standing, they form related peroxidic derivatives, which are also prone to violent decomposition. Air oxidation leads to peroxides within a few days if ethers are even briefly exposed to atmospheric oxygen. For this reason, one should never use old bottles of dialkyl ethers, and extreme care must be exercised in then- disposal. [Pg.674]

Catalysis (initiation) by a free radical, on the other hand, is fairly conclusive evidence of a radical reaction, provided it is known that the catalyst is indeed a free radical and that it does not have pronounced polar properties as well. Many classes of compound once thought to decompose exclusively into ions or exclusively into radicals are now known to do both. Peroxides are one well-known example, AT-halo-amides are another. Catalysis by benzoyl peroxide probably does indicate a radical reaction since there is no evidence that this particular peroxide tends to give ions even under the most favorable conditions. But many other peroxides are known to decompose into ions, or at least ion pairs, as well as into radicals. The decomposition of azo compounds can also be either radical or ionic, the dialkyl azo compounds tending to give radicals, the diazonium compounds either radicals or ions. Catalysis by a borderline example of an azo compound would therefore be dubious evidence of either kind of mechanism. The initiation of the polymerization of octyl vinyl ether by triphenylmethyl chloride in polar... [Pg.247]

Methods for detecting whether peroxy compound have been used for cross-linking elastomers have been reviewed. An important application of dialkyl peroxides is as initiators of cross-linking and graft polymerization processes. The success of both processes depends on the ability of the peroxide to produce free radicals and the ability of the free radicals for H-abstraction from a relevant donor substrate. A method for evaluating this ability consists of inducing thermal decomposition of the peroxide dissolved in a mixture of cyclohexane and MSD (225). The free radical X" derived from the... [Pg.706]

Because di-tert-alkyl peroxides are less susceptible to radical-induced decompositions, they tire safer and more efficient radical generators Ilian primary or secondary dialkyl peroxides. They are the preferred clialkyl peroxides for generating free radicals for commercial applications. [Pg.1232]

Dialkyl peroxydicarbonates are used primarily as free-radical initiators for vinyl monomer polymerizations. Dialkyl peroxydicarbonate decompositions are accelerated by certain metals, concentrated sulfuric acid, and amines. Violent decompositions can occur with neat or highly concentrated peroxides. [Pg.1238]

Oxidation reactions of hydrocarbons have a typical course. From the low rates, the reaction accelerates successively due to the consecutive formation of another source of free radicals which increases the rate of the primary initiation reaction. The amplification of the number of reactive free radicals is caused mainly by the decomposition of alkyl hydroperoxides, dialkyl and diacyl peroxides and peracids which are formed as intermediates in the oxidation reaction. [Pg.209]

Kinetics of thermal decomposition of dialkyl peroxides in solution as well as the gas phase have been reviewed by Molyneux and Frost and Pearson . The decomposition of dialkyl peroxides is moderately free from induced decomposition, compared to other types of peroxides. As seen from Table 65, the first-order rate coefficient increases by about 16 % when the initial peroxide concentration is increased about 5 fold at reasonably high peroxide concentrations. The increase in the rate coefficient is attributed to an induced decomposition where hydrogen atom abstraction generates the radical (I). Further reaction of (I) produces isobutylene oxide and the f-butoxy radical, viz. [Pg.488]

Peroxides are the most important initiators for free-radical polymerization. Among them, dialkyl or diaryl peroxides, peroxyesters, diacyl peroxides, and per-oxycarbonates are of particular relevance. For a large number of such peroxides, the temperature and pressure dependence of the decomposition rate coefficient. [Pg.57]

Most frequently the polymerization process is initiated by free radicals obtained through the decomposition of hydroperoxides, alkyl peroxides, dialkyl peroxides, acyl peroxides, carboxylic ester peracids, salts of (tetraoxo)sulphuric acid, hydrogen peroxide, aliphatic azo compounds and bifunctional azobenzoin initiators. The rate of decomposition of different initiators into free radicals depends on their stmcture and on temperature. A measure of the efficiency of the initiator in the pol5mierization process is the half-decomposition period. [Pg.257]


See other pages where Free radicals dialkyl peroxide decomposition is mentioned: [Pg.1473]    [Pg.124]    [Pg.47]    [Pg.653]    [Pg.47]    [Pg.935]    [Pg.95]    [Pg.21]    [Pg.330]    [Pg.330]    [Pg.47]    [Pg.177]    [Pg.375]    [Pg.38]    [Pg.360]    [Pg.73]    [Pg.827]    [Pg.299]    [Pg.7589]    [Pg.345]    [Pg.1312]   


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Decomposition radical

Dialkyl peroxides

Dialkyl peroxides, decomposition

Peroxide decomposition

Radical, peroxides

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