Dialkyl peroxides autoxidation

Secondary alcohols, such as isopropyl alcohol, j -butyl alcohol, 2-pentanol, 3-pentanol, cyclopentanol, and cyclohexanol, have been autoxidized to hydroxyaLkyl hydroperoxides (1, X = OH R = H) (10,44). These autoxidations usually are carried out at ca 20°C with uv radiation in the presence of a photosensitizer, eg, benzophenone. a-Oxygen-substituted dialkyl peroxides (2, X = Y = OH and X = Y = OOH), also are formed and sometimes they are the exclusive products (10). 

The kinetic results are summarized in Table II. The autoxidation products in general are similar to those observed by Van Sickle at lower temperatures and conversions. Table III summarizes analyses made by Van Sickle at conditions approximating our levels of conversion and temperature. The polymeric dialkyl peroxides are included in the residue. 

Any oxidation that proceeds spontaneously using oxygen in the air. Autoxidation of ethers gives hydroperoxides and dialkyl peroxides, (p. 641)... 

Epoxidation of methyl 7,8-dihydroretinoate (114) with monoperphthalic acid gave three main products (115)-(117). In the presence of acid (115) gave the spiro-derivative (118). The autoxidation of solid all-frans-retinyl acetate and palmitate, tra 5-axerophtene (82), and ll-cw-retinol has been studied. From amorphous samples dialkyl peroxides and carbonyl and hydroxy-compounds were formed, but in the crystalline state carbonyl compounds were the only products. ... 

Dialkyl peroxides ROOR are often obtained as the principal product or as by-product of autoxidation of organic compounds, but almost always as a result of secondary reactions of alkyl hydroperoxides. Direct union of relatively long-lived radicals with oxygen is of minor importance and occurs only in exceptional cases, e.g., in the formation of bis(triphenylmethyl) peroxide from triphenylmethyl 343... 

In most cases dialkyl peroxides arise from the alkyl hydroperoxides formed as primary products this is so in autoxidation of isochroman,333 phthalan,334 2-methyl-l,3-dioxolane,344 and tetrahydroacenaphthacene.345 Formation of dialkyl peroxides from alkyl hydroperoxides can occur under the influence of acids, and in this ionic dimerization 333,334 hydrogen peroxide is also formed ... 

When ethers are stored in the presence of atmospheric oxygen, they slowly oxidize to produce hydroperoxides and dialkyl peroxides, both of which are explosive. Such a spontaneous oxidation by atmospheric oxygen is called an autoxidation. 

Radical reactions may play an important role in the biological chemistry of phosphines. As discussed in Sects. 4.1 and 4.2, under certain conditions phosphines can react with dialkyl peroxides, disulphides and thiols by radical pathways rather than ionic mechanism. The autoxidation of phosphines also appears to involve a radical mechanism. For all of these examples the intermediate species is a phosphoranyl radical R4P which contains... 

The dialkyl denomination also includes cyclic peroxides (endoperoxides). The most significant route for peroxide formation is probably that of autoxidation of organic materials, leading to their gradual degradation. Although hydroperoxides are the main products of this process, also peroxyesters are formed, as is the case, for example, of isoprostane bicyclic endoperoxides (25) mentioned in Section II.A.2.C. 

The inhibition of hydrocarbon autoxidation by zinc dialkyl dithiophosphates was first studied by Kennerly and Patterson (13) and later by Larson (14). In both cases the induction period preceding oxidation of a mineral oil at 155 °C. increased appreciably by adding a zinc dialkyl dithiophosphate. In particular, Larson (14) observed that zinc salts containing secondary alkyl groups were more efficient antioxidants than those containing primary groups. In these papers the inhibition mechanism was discussed only in terms of peroxide decomposition. 

Peroxide Decomposition Mechanism. Since virtually no work has been reported which concerns only the mechanism by which zinc dialkyl di-thiophosphates act as peroxide decomposers, it is pertinent to discuss metal dialkyl dithiophosphates as a whole. The mechanism has been studied both by investigating the products and the decomposition rates of hydroperoxides in the presence of metal dithiophosphates and by measuring the efficiency of these compounds as antioxidants in hydrocarbon autoxidation systems in which hydroperoxide initiation is significant. 

The t-butylsulphinyl radical has been identified in the photolysis product of di-t-butyl peroxide and t-butylsulphenic acid, in toluene or isopentane at -40 to -60 °C, and the powerful anti-oxidant action of dialkyl sulphoxides on the autoxidation of hydrocarbons has been ascribed to radicalscavenging properties of the sulphenic acid produced from the sulphoxide on thermolysis. "... 

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