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Autoxidation sulfoxide

The sulfenic acids have been found to be extremely active radical scavengers showing rate constants of at least 107 m"1 s 1 for the reactions with peroxyl radicals at 333 K17. It has also been suggested that the main inhibiting action of dialkyl sulfoxides or related compounds in the autoxidation of hydrocarbon derives from their ability to form the transient sulfenic acids on thermal decomposition, i.e.17... [Pg.1083]

The Pacman catalyst selectively oxidized a broad range of organic substrates including sulfides to the corresponding sulfoxides and olefins to epoxides and ketones. However, cyclohexene gave a typical autoxidation product distribution yielding the allylic oxidation products 2-cyclohexene-l-ol (12%) and 2-cyclohexene-1-one (73%) and the epoxide with 15% yield [115]. [Pg.98]

Figure 7. First derivative ESR spectra of radical anions observed in dimethyl sulfoxide solutions of potassium tert-butoxide. Top, autoxidation product of diphenylamine. No signal was observed in the absence of oxygen. Middle, autoxidation of 4-hydroxy-diphenylamine. Bottom, spontaneous reduction product of mono-anil of p-benzoquinone. Figure 7. First derivative ESR spectra of radical anions observed in dimethyl sulfoxide solutions of potassium tert-butoxide. Top, autoxidation product of diphenylamine. No signal was observed in the absence of oxygen. Middle, autoxidation of 4-hydroxy-diphenylamine. Bottom, spontaneous reduction product of mono-anil of p-benzoquinone.
At atmospheric pressure, autoxidation of thioethers occurs primarily by abstraction of the a-hydrogen and sulfoxides are produced in low yields by reaction of the unreacted thioethers with intermediate a-hydroperoxides (36,37). [Pg.535]

Sulfoxides form complexes with hydroperoxides and can inhibit a partially oxidized substrate, but their inhibiting activity is destroyed by the simultaneous addition of an acidic substance such as stearic acid. The "activity of sulfur compounds cannot be wholly accounted for by their peroxide-decomposing action, and although they suppress peroxide-initiated autoxidation, they do not suppress oxidations initiated by free radical sources such as azobisisobutyronitrile (10). [Pg.224]

Air, the cheapest oxidant, is used only rarely without irradiation and without catalysts. Examples of oxidations by air alone are the conversion of aldehydes into carboxylic acids (autoxidation) and the oxidation of acyl-oins to a-diketones. Usually, exposure to light, irradiation with ultraviolet light, or catalysts are needed. Under such circumstances, dehydrogenative coupling in benzylic positions takes place at very mild conditions [7]. In the presence of catalysts, terminal acetylenes are coupled to give diacetylenes [2], and anthracene is oxidized to anthraquinone [3]. Alcohols are converted into aldehydes or ketones with limited amounts of air [4, 5, 6, 7], Air oxidizes esters to keto esters [3], thiols to disulfides [9], and sulfoxides to sulfones [10. In the presence of mercuric bromide and under irradiation, methylene groups in allylic and benzylic positions are oxidized to carbonyls [11]. [Pg.1]

Autoxidation of cyclohexene is mediated by 812(804)3 to give 1-cyclopentene-l-carboxylic acid in 90-92% yield [232], The selective oxidation of sulfides to sulfoxides is accomplished by Bi(NO3)3, both stoichiometrically [233] and catalytically with air [234]. [Pg.784]

It has been found possible to construct the 1,4-benzothiazine ring by direct interaction of bis-(2-aminobenzene) disulfide (96) with carbonyl compounds.139,140 The reaction is most efficient when conducted under a nitrogen atmosphere with a 1 1 ratio of reactants otherwise, the principle products are benzothiazoles. While reduction of the benzothiazine 97 with sodium borohydride gives a stable dihydro derivative, the unsaturated benzothiazines themselves were prone to autoxidation, giving rise to benzothiazoles and benzothiazine sulfoxides.141... [Pg.163]

There are two ways in which stabilizers can function to retard autoxidation and the resultant degradation of polymers. Preventive antioxidants reduce the rate of initiation, e.g., by converting hydroperoxide to nonradical products. Chain-breaking antioxidants terminate the kinetic chain by reacting with the chain-propagating free radicals. Both mechanisms are discussed and illustrated. Current studies on the role of certain organic sulfur compounds as preventive antioxidants are also described. Sulfenic acids, RSOH, from the decomposition of sulfoxides have been reported to exhibit both prooxidant effects and chain-breaking antioxidant activity in addition to their preventive antioxidant activity as peroxide decomposers. [Pg.220]


See other pages where Autoxidation sulfoxide is mentioned: [Pg.1540]    [Pg.182]    [Pg.761]    [Pg.86]    [Pg.1780]    [Pg.949]    [Pg.292]    [Pg.154]    [Pg.173]    [Pg.626]    [Pg.228]    [Pg.50]    [Pg.110]    [Pg.305]    [Pg.171]    [Pg.85]    [Pg.235]    [Pg.591]    [Pg.1312]   
See also in sourсe #XX -- [ Pg.18 , Pg.324 ]




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Autoxidation, dimethyl sulfoxide

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