Dialkyl peroxides induced decomposition

As a peroxide class, dialkyl peioxydicaibonates are very susceptible to ladical-induced decompositions ... 

This is basically the same type of induced decomposition that occurs with other peroxide classes, eg, the dialkyl peioxydicaibonates and diacyl peroxides. Table 8. Commercial rerf-Alkyl Hydroperoxides ... 

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. 

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). 

Thermal or photo-induced decompositions of dialkyl peroxides in the presence of suitable substrates yield various products. For example, with nitric oxides, alkyl nitrites or nitrates are formed and, with carbon monoxide, Z fZ-alkyl esters are obtained (44) ... 

The use of monomers that do not homopolymerize, eg, maleic anhydride and dialkyl maleates, reduces the shock sensitivity of tert-huty peroxyesters and other organic peroxides, presumably by acting as radical scavengers, that prevent self-accelerating, induced decomposition (246). 

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... 

Radiation-induced decomposition, 5,6-dihydrothymine, 930 Radiation stress, polymers, 685 Radical polymerization dialkyl peroxides, 707 peroxycarboxylic esters, 697 Radicals... 

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. 

For further examples of dichotomous solvent-influenced radical/ionic perester decompositions, see the base-catalyzed perester fragmentation shown in Eq. (5-39) in Section 5.3.2 [110], as well as the decomposition of t-butyl heptafluoroperoxybutyrate, C3p7-C0-0-0-C(CH3)3 [691]. The relative extent of monomolecular and induced thermal decomposition of disubstituted dibenzyl peroxydicarbonate, ArCH2-0-C0-0-0-C0-0-CH2Ar, is also substantially influenced by the reaction medium [692]. The thermolysis of suitable dialkyl peroxides can also proceed by two solvent-dependent competitive reaction pathways (homolytic and electrocyclic reaction), as already shown by Eq. (5-59) in Section 5.3.4 [564]. 

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. 

Peroxide decomposers react with peroxides to form stable products. Their low reactivity toward dialkyl and mainly polymer peroxides limits their domain of application [13]. The induced hydroperoxide decomposition may be generally given by [51]... 

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