- Catalytic Oxidation of 2,6-Di-t-butyl-4-methylphenol by a Supported Iron Complex
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The catalytic oxidation of 2,6-di-t-butyl-4-methylphenol using a catalyst of K4 supported on acid-modified τ-Al2O3 is reported.
- Homs, Narcis,Piscina, Pilar Ramirez de la,Borrull, Francesc
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- Synthesis of 4-(ω-hydroxyalkyl)-2,6-di-tert-butylphenols and the properties of related sulfides
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Reaction of 2,6-di-tert-butylphenol with aliphatic linear and branched diols in an alkaline medium at a temperature of 180-220°C leads to the formation of 4-(ω-hydroxyalkyl)-2,6-di-tert-butylphenols. The increase in the product yield and reducing the reaction temperature was reached at the catalysis of this reaction with zinc oxide. The structure of the diphenylalkane derivatives generated in side reaction was proved and the structural influence of the length of the aliphatic residue on the antioxidant effectiveness of the sulfides derived from the corresponding hydroxyalkylphenols was examined.
- Krysin,Pustovskikh,Koptyug
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experimental part
p. 2001 - 2006
(2011/02/18)
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- Practical process for the air oxidation of cresols: Part A. Mechanistic investigations
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The catalytic air oxidation of p-cresol and 2,6-di-tert-butyl-4- methylphenol to the corresponding benzaldehydes was investigated to determine the mechanism at work in these oxidation reactions. A number of intermediates and byproducts, mainly in the form of dimers, were observed during the course of the reactions, and their structures were elucidated by spectroscopic and chromatographic methods. The existence of these compounds in the reaction mixtures, and their proposed methods of formation, provided further insight into the mechanism involved in these oxidations.
- Barton, Benita,Logie, Catherine G.,Schoonees, Barbara M.,Zeelie, Bernard
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- Thermal decomposition of 2,6-di-tert-butyl-4-dimethylaminomethylphenol
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Products of thermolysis of 2,6-di-tert-butyl-4-dimethylaminomethylphenol were determined qualitatively and quantitatively by GLC, UV, and 1H NMR methods. The kinetics of the reaction was studied. The thermolysis products were studied as the inhibitors in thermopolymerization of monomers.
- Zakharova,Khismatullina,Ivanov
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p. 1787 - 1789
(2007/10/03)
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- Oxidative Dehydrogenation of Sterically Hindered para-Substituted Phenols with 3,3′,5,5′-Tetra-tert-butyl-4,4′-diphenoquinone
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The reactivity of 4-methyl-, 4-mercapto-, and 4-methoxymethyl-2,6-di-tert-butylphenols in oxidative dehydrogenation with 3,3′,5,5′-tetra-tert-butyl-4,4′-diphenoquinone was studied, and the structure of products was determined.
- Mukmeneva,Bukharov,Kadyrova,Zharkova,Gorshunova,Fazlieva
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p. 1486 - 1489
(2007/10/03)
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- Stabilizer of isoprene rubber and thermoplastic compositions on its base
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The stabilizing efficiency was studied of the products of oxidative dehydration of 4-methyl-2,6-di-tert-butylphenol with 3,3′,5,5′-tetra-tert-butyl-4,4′-diphenoquinone in SKI-3 synthetic isoprene rubber and a thermoplastic composition based on SKI-3 and polypropylene.
- Fazlieva,Mukmeneva,Bukharov,Vol'fson
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p. 1252 - 1253
(2007/10/03)
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- Antioxidant Synergism Between Butylated Hydroxyanisole and Butylated Hydroxytoluene
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Decay of the 2,6-di-tert-butyl-4-methylphenoxy radical in the presence of butylated hydroxyanisole (BHA) was investigated in 1,2-dimethoxyethane with or without triethylamine.BHT-radical was conveniently generated by dissociation of its unstable dimer in solution.The products were BHT, 3,3'-di-tert-butyl-5,5'-dimethoxy-2,2'-dihydroxybiphenyl (BHA-dimer), 2,6-di-tert-butyl-p-quinone methide (QM), 1,2-bis(3,5-di-tert-butyl-4-hydroxyphenyl)ethane, and 3,3',5,5'-tetra-tert-butyl-4,4'-stilbenequinone.The reaction without added triethylamine gave larger quantities of the last two products and BHA (recovery), whereas the reaction with it provided larger quantities of the first two products.The marked difference in the product distribution can be accounted for by a series of reactions including reversible dehydrogenation of BHA with BHT-radical, which generates 2-tert-butyl-4-methoxyphenoxy radical (BHA-radical) and BHT, reversible dimerization of BHA-radical, which affords an intermediary bis(cyclohexadienone), and spontaneous and base-catalysed prototropic rearrangement of the intermediate into BHA-dimer.Products of coupling between BHT-radical and BHA-radical were not obtained.BHA was found to undergo facile acid-catalyzed addition to QM, providing two isomeric bis(hydroxyphenyl)methanes.The results help to elucidate the mechanism of antioxidant synergism between BHA and BHT and may suggest that the synergism can be affected by base or acid. - Key words: Antioxidant synergism; butylated hydroxyanisole; butylated hydroxytoluene; effect of acid; effect of base; fate of phenoxy radicals involved.
- Omura, Kanji
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p. 1565 - 1570
(2007/10/03)
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- SYNTHESIS OF 2,6-DI-tert-BUTYL-4-(3,5-DI-tert-BUTYL-4-HYDROXYBENZYLIDENE)-2,5-CYCLOHEXADIENONE
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2,6-Di-tert-butyl-4-(3,5-di-tert-butyl-4-hydroxybenzylidene)-2,5-cyclohexadienone has been prepared in 63-92percent yield by oxidative dehydrogenation of 4,4'-methylenebis(2,6-di-tert-butylphenol) with various quinones.The products of quinone reduction have been isolated.
- Mukmeneva, N. A.,Bukharov, S. V.,Kadyrova, V. Kh.,Zharkova, V. M.
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p. 1350 - 1351
(2007/10/02)
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- Chemical evidence for peroxy radicals intermediacy in copper(II) reaction with hydroperoxides
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Two unprecedented decompositions of tertiary hydroperoxides by Cu(II) in CH3CN have been encountered : deoxygenation of 4- hydroperoxy cyclohexa 2,5- dienones 1 and 2 brings chemical support to the existence of intermediate peroxy radicals R-OO· 1′ and 2′.
- Maumy, Michel,Capdevielle, Patrice
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p. 7455 - 7462
(2007/10/02)
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- Reinvestigation on the Reaction of 2,6-Di-tert-butylbenzoquinone Methide and 2,6-Di-tert-butylphenol
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The reaction of quinone methide 1 and phenol 2 in equimolar amounts was investigated in pentane at 30 deg C.Products were isolated by means of column chromatography on SiO2.There was a marked difference in product distribution between the reactions in the presence and absence of added Et3N.Dienones 3 and 10 were obtained only from the former reaction, while formation of 1,2-bis(4-hydroxyphenyl)ethane 18 and 4,4'-dihydroxybiphenyl 20 was overwhelming in the latter reaction.Other products from both reactions were relatively small quantities of 4,4'-stilbenequinone 17, 4,4'-diphenoquinone 21, and bis(4-hydroxyphenyl)methane 24, but dienone 4 was not obtained.Compounds 20 and 24 obtained from the latter reaction were formed by isomerization of dienones 19 and 23, respectively, during chromatography.The reaction is initiated by dimerization of 1 to generate biradical 11.Subsequent processes involving hydrogenation-dehydrogenation, coupling-dissociation, and dienone-phenol rearrangement account for the formation or the lack of formation of the products.The difference in product distribution is ascribed to capability of Et3N to catalyze the isomerization.Quinone methide 1 also adds to 2 to give 23.The decay of 1 in the presence of both 2 and phenol 6 gave dienone 8 additionally.The formation of 24 and 4 was facilitated by conducting the reaction of 1 and 2 in DMSO.Dehydrogenation of 10 and 3 with PbO2 afforded spirodienones 27 and 28, respectively.Compounds 27 and 28 were unstable, and their decay in solution was investigated in the presence or absence of added 2.The results show that the decay is initiated by homolytic scission of the C-C bond connecting the dienone rings in the cyclopentane (in 27) and cyclohexane (in 28) rings.Compound 28 is novel in that it bears two kinds of such C-C bonds.Reversibility of the dimerization of 1 is suggested.
- Omura, Kanji
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p. 306 - 312
(2007/10/02)
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- The Reaction of the 2,6-Di-tert-butyl-4-methylphenoxy Radical with Phenols
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Dimer 3 dissociates in solution to give the phenoxy radical 4.When solid 3 is dissolved in a solution of phenol 11a, radical 4 dehydrogenates the phenol to afford phenol 5 and phenoxy radical 12.Radical 12 couples with more 4 to afford principally bis(cyclohexadienone) 16a and a minor amount of the dimeric bis(cyclohexadienone) 13.The preferential formation of 16a over 13 is explained as the result of a solvent-cage reaction.Compounds 13 and 16a are isomerized in the presence of silica gel or triethylamine to 4,4'-dihydroxybiphenyl 14 and phenolic dienone 17a, respectively.Compound 13 is relatively stable in hexane at 30 deg C, while 16a slowly dissociates under these conditions to afford parent radicals 4 and 12.If 11a is present, radical 4 either recombines with 12 or dehydrogenates the phenol.Two radicals of 12 generated by the dissociation of 16a and the subsequent dehydrogenation of 11a couple to give 13.Therefore, dissolving 3 in hexane containing excess 11a and keeping the resulting solution at 30 deg C results in the preferential formation of 13.Dissolving 3 in triethylamine containing phenols 11 or 21 similarly affords dienones 17 or 23.The yields of these dienones increase with increasing electron-donating capability of the substituent of the phenol ring.
- Omura, Kanji
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p. 921 - 927
(2007/10/02)
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- Electroorganic Reactions. 31. Quinonemethide Radical-Anions and Dianoins: Their Cathodic Generation and Reactivity
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The cathodic reactions of a number of relatively stable quinonemethides have been examined in detail by cyclic voltammetry, controlled potential coulometry, and rigorous product analysis following preparative-scale electrolyses.The results of cyclic voltammetric experiments differ in some respects from those of earlier polarographic work.The lifetimes of the electrogenerated radical-anions and dianions, in the absence of added electrophile, are governed by steric hindrance.Hindered intermediates are relatively long-lived yet hydrogenate in the presence of proton donor and alkylate in the presence of methyl iodide.Less hindered analogue efficiently and rapidly dimerize, at carbon, with concomitant protonation or O-methylation depending on added electrophile.The ambident cathodically generated nucleophiles alkylate at both carbon and oxygen, and the competition is crucially dependent on the cation (Bu4N+ or Li+).Fuchsone 3 gives reduction products which vary with initial concentration and on the presence, or otherwise, of oxygen.Efficient reaction between oxygen and triarylmethyl radicals generated, e.g., from 3 has been demonstrated.
- Goulart, Marilia O. F.,Utley, James H. P.
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p. 2520 - 2525
(2007/10/02)
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- Oxidation of Phenols with Iodine in Alkaline Methanol
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The use of iodine as an oxidizing agent for phenolic compounds has been explored.The reaction has been conducted in methanol containing such alkali as potassium hydroxide and, depending on the nature of the substituents and on the amount of iodine employed, leads to iodination, oxidation to give a stable phenoxy radical, oxidative dimerization, or benzylic oxidation.In general the reaction proceeds smoothly at room temperature, and under appropriate conditions yields of products are good to excellent.Oxidative dimerization of 2,4- and 2,6-di-tert-butylphenols invol-ves iodination followed by iodine-catalyzed dimerization.The oxidation of 4-methylphenols with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone in methanol has been carried out for comparison.
- Omura, Kanji
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p. 3046 - 3050
(2007/10/02)
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- Electrolytic oxidative methyl-methyl coupling of cresol salts
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Electrolytic oxidation of cresol salts substituted with non-interfering, blocking substituents at least at the 2,4,6-positions relative to the phenolic oxyanion where at least one of the substituents is the cresolic methyl leads to methyl-methyl coupled dehydrodimeric cresols.
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