- Reactivity and Product Analysis of a Pair of Cumyloxyl and tert-Butoxyl Radicals Generated in Photolysis of tert-Butyl Cumyl Peroxide
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Alkoxyl radicals play important roles in various fields of chemistry. Understanding their reactivity is essential to applying their chemistry for industrial and biological purposes. Hydrogen-atom transfer and C-C β-scission reactions have been reported from alkoxyl radicals. The ratios of these two processes were investigated using cumyloxyl (CumO?) and tert-butoxyl radicals (t-BuO?), respectively. However, the products generated from the pair of radicals have not been investigated in detail. In this study, CumO? and t-BuO? were simultaneously generated from the photolysis of tert-butyl cumyl peroxide to understand the chemical behavior of the pair of radicals by analyzing the products and their distribution. Electron paramagnetic resonance and/or transient absorption spectroscopy analyses of radicals, including CumO? and t-BuO?, provide more information about the radicals generated during the photolysis of tert-butyl cumyl peroxide. Furthermore, the photoproducts of (3-(tert-butylperoxy)pentane-3-yl)benzene demonstrated that the ether products were formed in in-cage reactions. The triplet-sensitized reaction induced by acetophenone, which is produced from CumO?, clarified that the spin state did not affect the product distribution.
- Oyama, Ryoko,Abe, Manabu
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p. 8627 - 8638
(2020/07/21)
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- Liquid phase oxidation of alkanes by tert-butyl hydroperoxide catalyzed by a manganese(III) pyridine amide complex
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Oxidation of alkanes by tert-butyl hydroperoxide in acetonitrile solution at room temperature has been performed in the presence of catalytic amounts of [Mn(bpc)OAc]MeOH, where bpc=4, 5-dichloro-1, 2-bis(pyridine- 2- carboxamido)benzene. Cyclohexane, adamantane, toluene; ethylbenzene and cumene give corresponding oxygenated products in moderate to high yields. A mechanism predominantly involving radical chain pathway is proposed.
- Tembe, Gopal L.,Ganeshpure, Pralhad A.
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p. 611 - 613
(2007/10/03)
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- Copper-catalyzed homolytic and heterolytic benzylic and allylic oxidation using tert-butyl hydroperoxide
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Allylic and benzylic alcohols were oxidized in good yields to the respective ketones by tert-butyl hydroperoxide (TBHP) in the presence of copper salts under phase-transfer catalysis conditions. This dehydrogenation was found to proceed via a heterolytic mechanism. CuCl2, CuCl, and even copper powder were equally facile as catalysts, as they were all transformed in situ to Cu(OH)Cl which was extracted into the organic phase by the phase-transfer catalyst (PTC). Deuterium labeling experiments evidenced the scission of the benzylic C-H bond in the rate-determining step. Nonproductive TBHP decomposition was not observed in the presence of the alcohol substrates. Conversely, the oxygenation of π-activated methylene groups in the same medium was found to be a free radical process, and the major products were the appropriate tert-butyl peroxides. Catalyst deactivation, solvent effects, and extraction effects are discussed. By applying Minisci's postulations concerning the relative reactivity of TBHP molecules towards tert-butoxyl radicals in protic and nonprotic environments, the coexistence of the homolytic and the heterolytic pathways can be explained. A complete reaction mechanism is proposed, wherein the free-radical oxidation obeys Kochi's mechanism, and the heterolytic dehydrogenation is based on either a high-valent CuIV=O species or a [Cu(OH)Cl]2 species.
- Rothenberg, Gadi,Feldberg, Liron,Wiener, Harold,Sasson, Yoel
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p. 2429 - 2434
(2007/10/03)
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- Steric and Electronic Substituent Effects in Tertiary Alkyl Peroxide Decompositions
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Rate constants for the homolysis of aryl- substituted α-cumyl tert-butyl peroxides (X-PhCMe2OOCMe3) produce a Hammett plot with a ρ value of -0.22 +/- .04.Both steric and electronic parameters influence the decomposition rate constants of tertiary alkyl peroxides with bulky substituents: log krel = (-0.40 +/- .08)Σ?* - (0.43 +/- .02)ΣEsc.
- Hendrickson, William H.,Nguyen, Chi C.,Nguyen, Jackie T.,Simons, Kim T.
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p. 7217 - 7220
(2007/10/02)
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- New Syntheses of Mixed Peroxides under Gif-Barton Oxidation of Alkylbenzenes, Conjugated Alkenes and Alkanes; a Free-radical Mechanism
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Syntheses of mixed peroxides are performed under Gif oxidation of alkylaromatics, electron-rich conjugated alkenes (styrene, α-methylstyrene) or cyclohexane and acrylonitrile; chemical and kinetic evidence support a free-radical redox chain mechanism.
- Minisci, Francesco,Fontana, Francesca,Araneo, Silvia,Recupero, Francesco
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p. 1823 - 1824
(2007/10/02)
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Reaction of alkyl hydroperoxides (1(ary), 2(ary) or 3(ary)) upon tertiary alkyl trichloroacetimidates under acidic catalysis yielded unsymmetrical dialkyl peroxides with yields in the range 30-70%.
- Bourgeois,Montaudon,Maillard
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p. 2477 - 2484
(2007/10/02)
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- Radical Intermediates in the Thermal Decomposition of 1,1-Bis(t-butyldioxy)cyclohexane
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The thermolysis mechanism of 1,1-bis(t-butyldioxy)cyclohexane (6) has been studied in solutions.The activation parameters obtained in cumene are ΔH=139.5 kJ mol-1 and ΔS=44.8 J K-1 mol-1, and the volatile products are t-butyl alcohol, t-butyl peroxyhexanoate, and 2,3-dimethyl-2,3-diphenylbutane along with minor products of acetone, cyclohexanone, and t-butyl 1-methyl-1-phenylethyl peroxide.The thermolysis of 6 in benzene gave acetone and t-butyl alcohol as major volatile products.The polyester of 2-hydroxyhexanoic acid was obtained both in cumene and benzene as a non-volatile product, and the yield was as high as 76percent in benzene.These facts indicate that oxyl radical (7) undergoes a facile ring-opening reaction yielding 5-(t-butyldioxycarbonyl)pentyl radical (8).The resulting radicals abstract hydrogen atoms either intra- or intermolecularly.The former reaction is predominant in the absence of good hydrogen donors, affording 2-hexanolide and ultimately the corresponding polyesters.
- Sugihara, Yasushi,Watanabe, Yasumasa,Kumura, Hiromi,Nakamura, Tomoyuki,Suyama, Shuji,Sawaki, Yasuhiko
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p. 664 - 667
(2007/10/02)
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- Simultaneous Generation of t-BuO(radical) and t-BuOO(radical) from the Decomposition of 2,2-Bis(t-butyldioxy)propane. A New Synthetic Method for Introducing a t-BuOO Group into Organic Molecules
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A free-radical synthetic method for introducing a t-BuOO group into various organic substrates has been developed using 2,2-bis(t-butyldioxy)propane (1a) which can efficiently give two oxygen-centered radicals, t-BuO(radical) and t-BuOO(radical), by thermolysis.The thermal reaction of 1a with cumene afforded the desired dialkyl peroxide, t-butyl 1-methyl-1-phenylethyl peroxide, in good yield (53percent based on 1a reacted) together with an appreciable amount of a dimer, 2,3-dimethyl-2,3-diphenylbutane, as a by-product.The addition of t-BuOOH increased the yield of the dialkyl peroxide to as high as 82percent, by suppressing the dimer formation (10percent).Also, reaction with isobutyronitrile and isopropyl methyl ketone gave good yields of dialkyl peroxides.The present method makes it possible to prepare unsymmetrical dialkyl peroxides containing functional groups, if the substrates are good hydrogen donors.
- Watanabe, Yasumasa,Ohta, Kenjiro,Suyama, Shuji
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p. 2063 - 2066
(2007/10/02)
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- Polymerization Mechanism of Styrene Initiated by 2,2-Bis(t-butyldioxy)alkanes
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The radical polymerization mechanism of styrene initiated by 2,2-bis(t-butyldioxy)alkanes (1) has been studied in benzene.The decomposition products of 1 are acetone, alkyl methyl ketone, t-butyl alcohol, and t-butyl peracetate.Styrene monomer converts to polystyrene along with styrene oxide.The peroxides 1 cleave homolytically at one of dioxy bonds to yield intermediate alkoxy radicals with α-t-butyldioxy group, which undergo β-scission to afford t-butyldioxy or alkyl radicals.The resulting t-butyldioxy radical reacts with styrene to form 2-(t-butyldiox)-1-phenylethyl radical, which decomposes subsequently to styrene oxide and t-butoxyl radical via γ-scission.Alternatively, a part of t-butyldioxy radical adds to styrene to afford polystyrene containing dioxy bond.
- Watanabe, Yasumasa,Ishigaki, Hideyo,Okada, Hiroshi,Suyama, Shuji
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p. 1231 - 1234
(2007/10/02)
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