- Hydrogen Bonding in α-Phenylethyl Hydroperoxide
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The H-bonded associates of α-phenylethyl hydroperoxide (HROOH) were investigated in CCl4, at various concentrations (0.788 X 1E-3 - 960 X 1E-3 M) and temperatures (22-75 deg C), by using IR spectroscopic methods.A very stable intramolecular OH..? bond was observed with a low enthalpy value.Above a concentration of 50 X 1E-3 M cyclic dimers and trimers were found, the latter with the lowest thermal stability.The corresponding thermodynamic parameters have been calculated.
- Danoczy, E.,Holly, S.,Jalsovszky, G.,Gal, D.
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- Temperature effect on the rate of formation of free radicals in CTAB-catalyzed decomposition of hydroperoxides
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The temperature effect on the rate of the decomposition of hydroperoxides and the rate of the formation of free radicals in the oxidation of ethylbenzene with molecular oxygen in the presence of α-phenylethyl hydroperoxide-cetyltrimethylammonium bromide (CTAB) as a catalytic system for free radical generation was studied by kinetic methods (from the oxygen consumption and hydroperoxide decomposition rates) and the inhibition method involving different acceptors of free radicals.
- Pisarenko,Maksimova,Kartasheva,Kasaikina
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- Photooxidation of ethylbenzene with TiO2 and metal coated TiO2 and its kinetics
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Photooxidation of ethylbenzene with oxygen to give ethylbenzene hydroperoxide has been achieved in a stirred photochemical reactor that was cooled by a water system by irradiation with a 400 W high-pressure mercury lamp and using TiO2 powder and metal coated TiO2. The effects of the amount of copper or silver coated on TiO2 and of the temperature on the rate of oxidation have been investigated. It is suggested that thermal cleavage of the O-O bond and photochemically generated singlet oxygen should be considered as the initiating step in a radical chain mechanism. An optimum loading of 6% Ag or 4-5% Cu was observed for photooxidation of ethylbenzene. Springer-Verlag 2004.
- Habibi, Mohammad H.,Isfahani, A. Zeini,Mohammadkhani,Montazerozohori
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- Selective side-chain oxidation of alkyl aromatic compounds catalyzed by cerium modified silver catalysts
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Silver supported on silica effectively catalyzes the aerobic side-chain oxidation of alkyl aromatic compounds under solvent-free conditions. Toluene, p-xylene, ethylbenzene and cumene were investigated as model substrates. Typically, the reaction was performed at ambient pressure; only for toluene an elevated pressure was required. Carboxylic acids, such as benzoic acid or p-toluic acid, additionally increased the reaction rate while CeO2 could act both as a promoter and an inhibitor depending on the substrate and the reaction conditions. Silver catalysts were prepared both by standard impregnation and flame spray pyrolysis. Addition of a Ce precursor to the FSP catalyst resulted in significantly smaller silver particles. Ce-doped FSP catalysts in general exhibited a superior catalytic performance with TONs up to 2000 except for cumene oxidation that appeared to proceed mainly by homogeneous catalysis. In addition, flame-made catalysts were more stable against silver leaching compared to the impregnated catalysts. The structure of the silver catalysts was studied in detail both by X-ray absorption spectroscopy and transmission electron microscopy suggesting metallic silver to be required for catalytic activity. Catalytic studies point to a radical mechanism which differs depending on the type of substrate.
- Beier, Matthias J.,Schimmoeller, Bjoern,Hansen, Thomas W.,Andersen, Jens E.T.,Pratsinis, Sotiris E.,Grunwaldt, Jan-Dierk
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- Inhibition of the oxidation of styrene epoxide by potassium iodide and bromide in an acidic solution
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The inhibiting action of potassium iodide and bromide on the oxidation of the binary system of styrene epoxide + p-toluenesulfonic acid and on the hydroperoxide decomposition in the presence of the binary system was revealed. The inhibition mechanism is complex. During the course of the inhibition, the active form of the inhibitor is regenerated, which interacts, according to the kinetic data, with the transient species formed in the binary mixture.
- Petrov,Solyanikov
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- In situ formed Co clusters in selective oxidation of Α-C–H bond: Stabilizing effect from reactants
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Aerobic oxidation of α-C–H bond of organic compounds to valuable chemicals is widely investigated in both fundamental research and industry. Due to the good stability of molecular oxygen, severe reaction conditions are generally required. Herein, by in situ synthesis we used molecular oxygen to induce cobalt nanoclusters with the sensitive catalysis in mild selective oxidation. The cobalt containing clusters with an average diameter around 0.9 nm are in situ prepared in the presence of cis-cyclooctene epoxidation and cyclooctene dimer oxide is formed at the interface to stabilize Co clusters with electron donation as an oil-soluble surfactant. The soluble clusters exhibit high activity in selective oxidation of α-C–H bond of ethylbenzene into acetophenone and turnover number (TON) reaches about 7 × 104 during 50 h’ reaction at 373 K, which is around 960 times more active than the one using CoCl2 salt as the catalyst, resulting from efficient mass transportation, π bond interaction and oxygen gas activation. Extended work based on this understanding demonstrates that cobalt nanoclusters also effectively catalyze aerobic oxidation of cyclohexene.
- Wang, Zhijie,Guan, Anxiang,Kung, Mayfair C.,Peng, Anyang,Kung, Harold H.,Lv, Ximeng,Zheng, Gengfeng,Qian, Linping
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- An Improved Catalytic Performance of Fe(III)-promoted NHPI in the Oxidation of Hydrocarbons to Hydroperoxides
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Abstract: N-hydroxyphthalimide (NHPI) is a promising catalyst in aerobic oxidation of hydrocarbons to corresponding hydroperoxides. We have found that a trace amount of Fe(benz)3 or Fe(acac)3 (in concentration of less than 10?1 mmol/l and with the ratio of Fe(III): NHPI = 1:500) considerably accelerates the oxidation of cyclohexene and ethylbenzene, while retaining the selectivity to hydroperoxides at a level of 90%. As a consequence, the reaction temperature could be lowered down to 50–60?°C. The promoting effect of the additives was attributed to the ability of Fe(III) complexes to generate phthalimido-N-oxyl radicals (PINO) without participation in any transformations of hydrocarbon intermediates and hydroperoxides, thus ensuring selective formation and stability of the hydroperoxides.
- Kuznetsova,Kuznetsova,Yakovina,Karmadonova,Bal’zhinimaev
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- An experimental and theoretical study of the catalytic effect of quaternary ammonium salts on the oxidation of hydrocarbons
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The enhancement in the autoxidation of ethylbenzene by molecular oxygen in the presence of quaternary ammonium salts (QAS) was investigated from the experimental and theoretical points of view. The primary effect of the addition of QAS to the reaction medium was an increase in ethylbenzene conversion. Quantum chemical calculations, using B3LYP hybrid functional, revealed a weakening of C-O and O-H bonds of the hydroperoxide. These effects favor the formation of ethylbenzenyl and peroxyl radicals, respectively, both of which are involved in the propagation reaction that leads to the formation of hydroperoxide, the desired final product. Analysis of the electronic properties of the structures formed between reactants and catalysts offers a better understanding of the mechanism of ethylbenzene oxidation reactions. The atoms-in-molecules approach enables a rigorous description of atomic charges and bond properties that can be qualitatively related to the experimental data.
- Barrio,Toribio,Campos-Martin,Fierro
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- New Understanding of Selective Aerobic Oxidation of Ethylbenzene Catalyzed by Nitrogen-doped Carbon Nanotubes
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Selective aerobic oxidation of hydrocarbons undergoes a free-radical chain reaction to yield corresponding value-added products is the significant process in the chemical industry. Nanocarbons with heteroatoms doping as free-metal catalysts have been prov
- Su, Yongzhao,Li, Yuhang,Chen, Zhicheng,Huang, Jiangnan,Wang, Hongjuan,Yu, Hao,Cao, Yonghai,Peng, Feng
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p. 646 - 655
(2020/12/04)
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- Mixed hetero-/homogeneous TiO2/N-hydroxyimide photocatalysis in visible-light-induced controllable benzylic oxidation by molecular oxygen
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Homogeneous and heterogeneous types of catalysis are frequently considered as separate disciplines or even opposed to each other. In the present work, a new type of mixed hetero-/homogeneous catalysis was demonstrated for the case of selective alkylarene
- Krylov, Igor B.,Lopat'eva, Elena R.,Nikishin, Gennady I.,Subbotina, Irina R.,Terent'ev, Alexander O.,Yu, Bing
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p. 1700 - 1711
(2021/06/28)
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- Room Temperature Aerobic Peroxidation of Organic Substrates Catalyzed by Cobalt(III) Alkylperoxo Complexes
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Room temperature aerobic oxidation of hydrocarbons is highly desirable and remains a great challenge. Here we report a series of highly electrophilic cobalt(III) alkylperoxo complexes, CoIII(qpy)OOR supported by a planar tetradentate quaterpyridine ligand that can directly abstract H atoms from hydrocarbons (R′H) at ambient conditions (CoIII(qpy)OOR + R′H → CoII(qpy) + R′?+ ROOH). The resulting alkyl radical (R′?) reacts rapidly with O2to form alkylperoxy radical (R′OO?), which is efficiently scavenged by CoII(qpy) to give CoIII(qpy)OOR′ (CoII(qpy) + R′OO?→ CoIII(qpy)OOR′). This unique reactivity enables CoIII(qpy)OOR to function as efficient catalysts for aerobic peroxidation of hydrocarbons (R′H + O2→ R′OOH) under 1 atm air and at room temperature.
- Chen, Yunzhou,Shi, Huatian,Lee, Chi-Sing,Yiu, Shek-Man,Man, Wai-Lun,Lau, Tai-Chu
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supporting information
p. 14445 - 14450
(2021/09/18)
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- Solvent-Free Aerobic Oxidation of Ethylbenzene Promoted by NHPI/Co(II) Catalytic System: The Key Role of Ionic Liquids
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The synergistic action between imidazolium based ionic liquid (IL) [bmim][OcOSO3] and Co(II)/N-hydroxyphthalimide (NHPI) systems in the catalytic aerobic oxidation of ethylbenzene under solvent-free conditions have been here demonstrated by reaching a 35 % conversion with 83 % of selectivity in acetophenone at 80 °C. This highly performing catalytic system have been selected after screening several different IL and Co(II) salt combinations, and making sure that the complete solubilization of the polar NHPI in the lipophilic medium, without thus requiring any chemical modification of the organic catalyst, could be attained. This solubilizing effect can be ascribed to a direct interaction between [bmim][OcOSO3] IL and NHPI as revealed by a detailed NMR investigation which also allowed to exclude the formation of higher IL aggregates in the form of micelles or vesicles.
- Dobras, Gabriela,Sitko, Magdalena,Petroselli, Manuel,Caruso, Manfredi,Cametti, Massimo,Punta, Carlo,Orlińska, Beata
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p. 259 - 266
(2019/11/14)
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- Palladium aminopyridine complexes catalyzed selective benzylic C-H oxidations with peracetic acid
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Four palladium(ii) complexes with tripodal ligands of the tpa family (tpa = tris(2-pyridylmethyl)amine) have been synthesized and X-ray characterized. These complexes efficiently catalyze benzylic C-H oxidation of various substrates with peracetic acid, affording the corresponding ketones in high yields (up to 100%), at 1 mol% catalyst loadings. Complex [(tpa)Pd(OAc)](PF6) with the least sterically demanding ligand tpa demonstrates the highest substrate conversions and ketone selectivities. Preliminary mechanistic data provide evidence in favor of metal complex-mediated rate-limiting benzylic C-H bond cleavage by an electron-deficient oxidant.
- Bryliakov, Konstantin P.,Lubov, Dmitry P.,Lyakin, Oleg Yu.,Rybalova, Tatyana V.,Samsonenko, Denis G.,Talsi, Evgenii P.
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supporting information
p. 11150 - 11156
(2020/09/02)
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- Hydrophobic Modification of Microenvironment of Highly Dispersed Co3O4 Nanoparticles for the Catalytic Selective Oxidation of Ethylbenzene
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Microenvironments in enzymes play crucial roles in controlling the activities of active centers. Here, hexagonal mesoporous silicas (HMS) with hydrophobic microenvironment was used to mimic the enzymes on the hydrocarbon oxidation with cobalt oxides incor
- Zhao, Li,Shi, Song,Liu, Meng,Chen, Chen,Zhu, Guozhi,Gao, Jin,Xu, Jie
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p. 903 - 910
(2019/12/03)
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- Preparation method of arylethyl hydrogen peroxide (by machine translation)
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The invention discloses a preparation method of arylethyl hydrogen peroxide. The aromatic ethane is used as a starting material, the raw materials are easy to obtain; the product obtained by the method is wide in application, and can be conveniently converted into aryl ethanone. In addition, the method disclosed by the invention is carried out in illumination air, is mild in reaction condition, high in target product yield, simple, and suitable for industrial production, and the reaction operation and the post-treatment process are simple. (by machine translation)
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Paragraph 0020-0021
(2019/09/05)
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- Aliphatic amines modified CoO nanoparticles for catalytic oxidation of aromatic hydrocarbon with molecular oxygen
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The surface modification of metal oxides using organic modifiers is a potential strategy for enhancing their catalytic performances. In this study, a hydrophobic surface amine-modified CoO catalyst with a water contact angle of 143° was fabricated. The catalyst was characterized by XRD, TGA, FT-IR, HR-TEM, and XPS. The results showed that the fabricated catalyst performed better than the hydrophilic commercial CoO nanoparticle in the process of aromatic hydrocarbon oxidation. After the amines modification, commercial CoO also became hydrophobic and improved conversion of ethylbenzene was achieved. The surface modification of CoO with amines induced the hydrophobicity property, which could serve as a reference for the design of other hydrophobic catalysts.
- Liu, Meng,Shi, Song,Zhao, Li,Chen, Chen,Gao, Jin,Xu, Jie
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p. 1488 - 1493
(2019/09/09)
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- Indium-Mediated Synthesis of Benzylic Hydroperoxides
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An indium(0)-metal-mediated efficient synthesis of benzylic hydroperoxides is described. The reaction proceeds efficiently with a broad range of benzyl bromides under aerobic conditions at room temperature to afford benzyl hydroperoxides in good to excellent yields. In addition, the tandem hydroperoxidation-Michael addition of (E)-1-(bromomethyl)-2-(2-nitrovinyl)benzene was also demonstrated.
- Hou, Yuxuan,Hu, Jinjin,Xu, Ruigang,Pan, Shulei,Zeng, Xiaofei,Zhong, Guofu
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supporting information
p. 4428 - 4432
(2019/06/17)
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- Effective Utilization of in Situ Generated Hydroperoxide by a Co-SiO2@Ti-Si Core-Shell Catalyst in the Oxidation Reactions
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A core-shell catalyst (Co-SiO2@Ti-Si) with cobalt-based SiO2 nanocomposite (Co-SiO2) as the core and Ti-doped mesoporous silica as the shell was designed to catalyze a one-pot reaction of sulfide oxidation with in situ generated hydroperoxide. The catalyst was characterized by SEM, TEM, UV-vis spectroscopy, and XPS, among other methods. Compared to Co-SiO2 and the physical mixture of the two components (Co-SiO2 + Ti-Si), the core-shell catalyst significantly enhanced the reaction rate of the sulfide oxidation. The utilization efficiency of the hydroperoxide was an important factor responsible for the differences in the reaction rates. A further mechanism study showed that the improvement of the efficiency was due to the existence of a coordination pathway. The core-shell structure of a bifunctional catalyst represents a strategy for improving the utilization efficiency of hydroperoxide.
- Liu, Meng,Shi, Song,Zhao, Li,Wang, Min,Zhu, Guozhi,Zheng, Xi,Gao, Jin,Xu, Jie
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p. 683 - 691
(2018/01/17)
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- Catalytic Systems Based on Magnesium and Zinc Compounds in the Oxidation Reactions of Alkylarenes and the Decomposition Reactions of the Corresponding Hydroperoxides
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The oxidation of aromatic hydrocarbons in the presence of magnesium and zinc 2-ethylhexanoates and a mixed catalyst based on these compounds is studied. It is shown that magnesium and zinc carboxylates are active catalytic systems which catalyze the decomposition of hydroperoxides representing the primary alkylarene oxidation products alongside with activation of oxygen.
- Kharlampidi, Kh. E.,Nurullina,Batyrshin,Usmanova, Yu. Kh.
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p. 328 - 332
(2018/06/11)
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- Pd-Catalyzed Aerobic Oxidation Reactions: Strategies to Increase Catalyst Lifetimes
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The palladium complex [(neocuproine)Pd(μ-OAc)]2[OTf]2 (1, neocuproine = 2,9-dimethyl-1,10-phenanthroline) is an effective catalyst precursor for the selective oxidation of primary and secondary alcohols, vicinal diols, polyols, and carbohydrates. Both air and benzoquinone can be used as terminal oxidants, but aerobic oxidations are accompanied by oxidative degradation of the neocuproine ligand, thus necessitating high Pd loadings. Several strategies to improve aerobic catalyst lifetimes were devised, guided by mechanistic studies of catalyst deactivation. These studies implicate a radical autoxidation mechanism initiated by H atom abstraction from the neocuproine ligand. Ligand modifications designed to retard H atom abstractions as well as the addition of sacrificial H atom donors increase catalyst lifetimes and lead to higher turnover numbers (TON) under aerobic conditions. Additional investigations revealed that the addition of benzylic hydroperoxides or styrene leads to significant increases in TON as well. Mechanistic studies suggest that benzylic hydroperoxides function as H atom donors and that styrene is effective at intercepting Pd hydrides. These strategies enabled the selective aerobic oxidation of polyols on preparative scales using as little as 0.25 mol % of Pd, a major improvement over previous work.
- Ho, Wilson C.,Chung, Kevin,Ingram, Andrew J.,Waymouth, Robert M.
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supporting information
p. 748 - 757
(2018/01/26)
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- Noncatalytic Liquid Phase Air Oxidation of Ethylbenzene to 1-Phenyl Ethyl Hydroperoxide in Low Oxygen Volume Fraction
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The catalyst- and solvent-free liquid phase air oxidation reaction of ethylbenzene (EB) to 1-phenyl ethyl hydroperoxide (PEHP) was investigated at scheduled temperature and pressure with a separate deacidifying zone. The oxidation reaction was done in the
- Roohi, Hossein,Rajabi, Mehrdad
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p. 136 - 146
(2018/02/23)
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- Thioether oxidation method
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The invention discloses a thioether oxidation method. The method comprises the following steps: (1-1), ethylbenzene and oxygen are subjected to a contact reaction, and the content of EBHP in a reaction mixture obtained by the contact reaction under contact reaction condition is more than 1 weight%; optional (1-2), the reaction mixture in the step (1-1) is mixed with inorganic acid; (2), under condition that thioether is oxidized, a raw material mixture containing the reaction mixture obtained in the step (1-1) and thioether is subjected to a contact reaction with a titanium silicon molecular sieve, or a raw material mixture containing the mixture in the step (1-2) and thioether is subjected to the contact reaction with the titanium silicon molecular sieve. The method is in favor of increasing effective processing amount of equipment, and can obtain high thioether conversion rate and target oxidation product selectivity. The method can directly install a thioether oxidation reaction apparatus at a material outlet end of a current ethylbenzene oxidation apparatus, and is easy to carry out.
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Paragraph 0093; 0094; 0130; 0143
(2017/08/29)
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- AuNP@TiO2 catalyzed peroxidation of Ethyl- and N-Propylbenzene: Exploring the interaction between Radical species and the nanoparticle surface
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Ethyl- and n-propylbenzene peroxidation has been studied in the presence of supported gold nanoparticles on TiO2 (AuNP@TiO2). The decomposition products obtained from Fentoninduced cumene hydroperoxide decomposition, as well as the oxidation products of ethyl- and n-propylbenzene, implicate the participation of reactive oxygen species adsorbed on the AuNP surface. This surface intermediate is believed to be a fundamental participant in hydrogen abstraction reactions required to facilitate the formation of the observed carbonyl derived product.
- Crites, Charles-Oneil L.,Netto-Ferreira, José Carlos,Hallett-Tapley, Geniece L.,Scaiano, Juan Cesar
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p. 334 - 340
(2016/03/19)
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- Light-active azaphenalene alkoxyamines: Fast and efficient mediators of a photo-induced persistent radical effect
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Here we report the first example of an alkoxyamine derived from an azaphenalene nitroxide, which when exposed to UV-light, readily undergoes homolysis to efficiently and cleanly re-form a nitroxide. This process selectively cleaves the C-O bond of the alkoxyamine and occurs orders of magnitude more rapidly than any other alkoxyamine homolysis previously described in the literature. We demonstrate the use of light to generate a persistent radical effect (PRE) and apply this to undertake radical insertion, radical exchange and proof of concept polymerization reactions.
- Bottle, Steven E.,Clement, Jean-Louis,Fleige, Mirco,Simpson, Emily M.,Guillaneuf, Yohann,Fairfull-Smith, Kathryn E.,Gigmes, Didier,Blinco, James P.
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p. 80328 - 80333
(2017/04/04)
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- Efficient metal-free oxidation of ethylbenzene with molecular oxygen utilizing the synergistic combination of NHPI analogues
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Abstract A metal- and initiator-free catalytic system comprising N-hydroxyquinolinimide (NHQI) and 4-carboxyl-N-hydroxyphthalimide (Car-NHPI) was developed for the oxidation of ethylbenzene using molecular oxygen as the terminal oxidant. The catalytic activity of Car-NHPI/NHQI catalytic system was higher than that of Car-NHPI or NHQI alone. The high catalytic performance of Car-NHPI/NHQI catalytic system could be attributed to the dual interactions of radical exchange and acid-base neutralization, which resulted in the increment of the conversion of ethylbenzene up to 70% and the selectivity of acetophenone up to 66% at 120 C under 1 atm O2 for 15 h.
- Zhao, Qiming,Chen, Kexian,Zhang, Wensong,Yao, Jia,Li, Haoran
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- Enhancing the catalytic activity of carbon nanotubes by filled iron nanowires for selective oxidation of ethylbenzene
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Iron nanowire filled carbon nanotubes (Fe@CNTs) were synthesized by chemical vapor deposition method and employed as heterogeneous catalysts for selective oxidation of ethylbenzene to acetophenone with molecular oxygen. The results showed that filled iron
- Luo, Jin,Yu, Hao,Wang, Hongjuan,Peng, Feng
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- Superhydrophobic SiO2-based nanocomposite modified with organic groups as catalyst for selective oxidation of ethylbenzene
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A surface organic modification strategy is utilized to design and prepare a series of superhydrophobic SiO2-based nanocomposites with cobalt ions in the bulk phase and different organic groups on the surface. Physical properties such as BET sur
- Chen, Chen,Shi, Song,Wang, Min,Ma, Hong,Zhou, Lipeng,Xu, Jie
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p. 8126 - 8134
(2014/05/20)
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- Mesoporous strong base supported cobalt oxide as a catalyst for the oxidation of ethylbenzene
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A mesoporous solid strong base was applied to support cobalt oxide to obtain a strong base-type catalyst, which showed good performance in the heterogeneous oxidation of ethylbenzene under solvent-free conditions in the temperature range of 373-403 K. It
- Shi, Song,Chen, Chen,Wang, Min,Ma, Jiping,Gao, Jin,Xu, Jie
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p. 3606 - 3610
(2015/04/14)
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- Homogeneous liquid-phase oxidation of ethylbenzene to acetophenone in continuous flow mode
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The oxidation of ethylbenzene with hydrogen peroxide and molecular oxygen catalyzed by cobalt and bromide ions in acetic acid as solvent was studied. The oxidation of ethylbenzene with hydrogen peroxide provided a mixture of ethylbenzene hydroperoxide, ac
- Gutmann, Bernhard,Elsner, Petteri,Roberge, Dominique,Kappe, C. Oliver
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p. 2669 - 2676
(2014/01/06)
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- Oxidizing properties of the tert-butyl hydroperoxide-tetra-tert- butoxychromium system
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tert-Butyl hydroperoxide reacts with the tetra-tert-butoxychromium by oxidizing the latter to chromyl CrV=O (C6H6, 20 C). At t-BuOOH-Cr(OBu-t)4 ratio of 2: 1 or higher, oxygen is released. The occuring processes include the formation of chromium-containing peroxides and peroxytrioxydes. The t-BuOOH-Cr(OBu-t)4 system oxidizes aromatic hydrocarbons of various structures (anthracene, 9,10-dimethylanthracene, 1,1-diphenylethylene, alkylarenes), as well as primary and secondary alcohols. Depending on the structure of the substrate, the oxidants are: in situ generated oxygen including that in the singlet state, peroxy radicals, or chromium-containing peroxides.
- Stepovik,Potkina,Poddelskii
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p. 2005 - 2017
(2014/01/17)
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- Preparation of enantiomerically pure p-substituted phenylethyl hydroperoxides by kinetic resolution and their use as enantioselective oxidants in the asymmetric Weitz-Scheffer epoxidation of E-chalcone
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The kinetic resolution of a variety of secondary para-substituted phenylethyl hydroperoxides by Raphanus sativus L. (black radish peroxidase) in the presence of guaiacol is reported. The peroxidase enzyme recognized (R)-configured alkyl aryl hydroperoxides, which furnished optically active (S)-hydroperoxides and (R)-alcohols. Kinetic resolution of tertiary hydroperoxides by the enzyme was unsuccessful. This study also shows how the optically active p-substituted (S)-hydroperoxides obtained can be employed as enantioselective oxidants in the asymmetric Weitz-Scheffer epoxidation of E-chalcone in the presence of KF-Al2O3 as a base. In all cases, a chalcone epoxide with the (αS,βR)-configuration was obtained as the major isomer. Under the optimized reaction conditions, the enantiomeric excess of the chalcone epoxide was obtained in up to 49% in CH3CN at -40 °C.
- Zilbeyaz, Kani,Kilic, Hamdullah,Sisecioglu, Melda,Ozdemir, Hasan,Guengoer, Azize Alayli
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experimental part
p. 594 - 601
(2012/08/13)
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- Highly active mesoporous chromium silicate catalysts in side-chain oxidation of alkylaromatics
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We approach a green method in the production of alkylaromatic ketones over hexagonally ordered mesoporous CrSBA-15 catalysts, which were used, in green routes, in the liquid-phase oxidation of alkylaromatics. A promising chemical treatment method was used with ammonium acetate solution to remove the toxic nature of non-framework chromium oxides deposited on the surface of calcined CrSBA-15(8), and the obtained green mesoporous CrSBA-15(8) catalyst was used to find its catalytic activity while the recyclability of mesoporous CrSBA-15 catalysts was also studied. Particularly, the mesoporous CrSBA-15 catalysts synthesized with a variety of chromium contents were extensively used in the production of acetophenone (APO) with various reaction parameters. On the basis of all catalytic results, the mesoporous CrSBA-15(8) catalyst produced a higher selectivity of alkylaromatic ketones (76-100%) as compared to other CrSBA-15 catalysts and was found to be a highly active, recyclable and promising heterogeneous catalyst for selective synthesis of alkylaromatic ketones. The Royal Society of Chemistry 2012.
- Selvaraj,Park,Kim,Kawi,Ha
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p. 14204 - 14210
(2013/01/15)
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- Selective catalytic aerobic oxidation of substituted ethylbenzenes under mild conditions
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Ethylbenzene is oxidized to the corresponding hydroperoxide (PEHP) with high selectivity, under mild conditions, by means of a metal-free catalytic system consisting of an aldehyde and N-hydroxyphthalimide (NHPI). The process occurs via a free radical mechanism by in situ generation of the phthalimido-N-oxyl (PINO) radical. The protocol is applied with success on a wide range of substituted ethylbenzenes (ETBs). The competitive experiments carried out on few couples of ETBs revealed a marked polar effect, this proving the key role that PINO plays as real hydrogen abstracting species, at least at low conversion. At higher conversion, the formation of highly reactive OH radicals from PEHP reduces the differences in the reactivity of selected couples of ETBs. The study of the reaction mechanism, including the investigation on aldehyde and catalyst percentage amounts, and temperature and concentration effects, allows to achieve the final PEHPs products with good yields.
- Melone, Lucio,Prosperini, Simona,Gambarotti, Cristian,Pastori, Nadia,Recupero, Francesco,Punta, Carlo
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experimental part
p. 155 - 160
(2012/03/09)
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- Pyrazolate-based cobalt(II)-containing metal-organic frameworks in heterogeneous catalytic oxidation reactions: Elucidating the role of entatic states for biomimetic oxidation processes
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Crystal structures of two metal-organic frameworks (MFU-1 and MFU-2) are presented, both of which contain redox-active CoII centres coordinated by linear 1,4-bis[(3,5-dimethyl)pyrazol-4-yl] ligands. In contrast to many MOFs reported previously, these compounds show excellent stability against hydrolytic decomposition. Catalytic turnover is achieved in oxidation reactions by employing tert-butyl hydroperoxide and the solid catalysts are easily recovered from the reaction mixture. Whereas heterogeneous catalysis is unambiguously demonstrated for MFU-1, MFU-2 shows catalytic activity due to slow metal leaching, emphasising the need for a deeper understanding of structure-reactivity relationships in the future design of redox-active metal-organic frameworks. Mechanistic details for oxidation reactions employing tert-butyl hydroperoxide are studied by UV/Vis and IR spectroscopy and XRPD measurements. The catalytic process accompanying changes of redox states and structural changes were investigated by means of cobalt K-edge X-ray absorption spectroscopy. To probe the putative binding modes of molecular oxygen, the isosteric heats of adsorption of O2 were determined and compared with models from DFT calculations. The stabilities of the frameworks in an oxygen atmosphere as a reactive gas were examined by temperature-programmed oxidation (TPO). Solution impregnation of MFU-1 with a co-catalyst (N-hydroxyphthalimide) led to NHPI@MFU-1, which oxidised a range of organic substrates under ambient conditions by employing molecular oxygen from air. The catalytic reaction involved a biomimetic reaction cascade based on free radicals. The concept of an entatic state of the cobalt centres is proposed and its relevance for sustained catalytic activity is briefly discussed.
- Tonigold, Markus,Lu, Ying,Mavrandonakis, Andreas,Puls, Angela,Staudt, Reiner,Moellmer, Jens,Sauer, Joachim,Volkmer, Dirk
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experimental part
p. 8671 - 8695
(2011/10/04)
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- Superhydrophobic materials as efficient catalysts for hydrocarbon selective oxidation
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A new type of superhydrophobic material, FP-Co-SiO2 was prepared with organic groups immobilized on the surface of the SiO2-based nanocomposite. This material showed much higher catalytic activity for selective oxidation of hydrocarbons than an equivalent hydrophilic catalyst.
- Chen, Chen,Xu, Jie,Zhang, Qiaohong,Ma, Yinf,Zhou, Lipeng,Wang, Min
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supporting information; scheme or table
p. 1336 - 1338
(2011/03/22)
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- Catalytic activity of iron-substituted polyoxotungstates in the oxidation of aromatic compounds with hydrogen peroxide
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The tetrabutylammonium (TBA) salts of Keggin-type polyoxotungstates of the general formula [XW11FeIII(H2O)O39] n-, where X = P, B or Si, were evaluated as catalysts in the oxidation, under mild conditions, of ethylbenzene, cumene, p-cymene and sec-butylbenzene with aqueous H2O2 in CH3CN at 80 °C. The influence of various factors, such as the substrate/catalyst molar ratio, the amount of oxidant added or the reaction time, was investigated in a systematic way. Generally, the system exhibited moderate conversion, with good selectivity towards the corresponding acetophenone and hydroperoxide. In order to understand the reaction pathways, the oxidation of several products and presumed intermediates was also carried out in the presence of TBA 4[PW11Fe(H2O)O39]?2H 2O. Under the conditions used, the oxidation of styrene and styrene derivatives gave rise mainly to carbon-carbon double-bond cleavage, affording the corresponding products in very high yields (81-87%). Possible reaction pathways are presented.
- Estrada, Ana C.,Simoes, Mario M. Q.,Santos, Isabel C. M. S.,Neves, M. Graca P. M. S.,Cavaleiro, Jose A. S.,Cavaleiro, Ana M. V.
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experimental part
p. 1223 - 1235
(2011/09/12)
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- Metal-Free: An efficient and selective catalytic aerobic oxidation of hydrocarbons with oxime and N-Hydroxyphthalimide
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A non-metal catalytic system consisting of dimethylglyoxime (DMG) and N-hydroxyphthal-imide (NHPI) for the selective oxidation of hydrocarbons with dioxygen is described. The synergistic effect of DMG and NHPI ensures its efficient catalytic ability: 82.1% conversion of ethylbenzene with 94.9% selectivity for acetophenone could be obtained at 80°C under 0.3 MPa of dioxygen in 10h. Several hydrocarbons were efficiently oxidized to their corresponding oxygenated products under mild conditions. aerobic oxidation; catalyst design; dimethylglyoxime ; hydrocarbons ; N-hydroxyphthalimide
- Zheng, Gengxiu,Liu, Chunhong,Wang, Qiufen,Wang, Mingyu,Yang, Guanyu
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scheme or table
p. 2638 - 2642
(2009/12/30)
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- CATALYTIC PROCESS FOR THE PREPARATION OF HYDROPEROXIDES OF ALKYLBENZENES BY AEROBIC OXIDATION UNDER MILD CONDITIONS
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Process for the preparation of hydroperoxides of alkylbenzenes characterized by the fact that the alkyibenzene reacts with oxygen in the presence of a catalytic system consisting of an N-hydroxyimide associated with a peroxide activator having a peracid or dioxyrane structure, possibly generated in situ.
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Page/Page column 10
(2009/10/22)
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- Kinetic resolution of hydroperoxides with enantiopure phosphines: Preparation of enantioenriched tertiary hydroperoxides
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An efficient reductive kinetic resolution strategy capable of accessing optically active tertiary hydroperoxides is reported. Readily accessible tertiary hydroperoxides are resolved with commercially available (R)- or (S)-xylyl-PHANEPHOS with selectivity factors as large as 37. The resulting bis(phosphine oxide) can be recycled in high yields. The isolated mono(phosphine oxide) intermediate resolved hydroperoxides with the same selectivity as the parent bisphosphine. Copyright
- Driver, Tom G.,Harris, Jason R.,Woerpel
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p. 3836 - 3837
(2008/02/13)
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- High activity of Mn-MgAl hydrotalcite in heterogeneously catalyzed liquid-phase selective oxidation of alkylaromatics to benzylic ketones with 1 atm of molecular oxygen
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Mn-MgAl hydrotalcite, surface-enriched with Mn, was prepared by thermal decomposition of MgAl hydrotalcite followed by reconstruction of its structure in the presence of Mn(II) cations and atmospheric CO2 as a guest inorganic anion through contacting the decomposed mass with aqueous Mn(II) nitrate solution. The Mn-MgAl hydrotalcite showed very high catalytic activity, stability, and reusability in the liquid-phase selective oxidation of a wide range of alkylaromatics to their corresponding benzylic ketones, using atmospheric pressure of molecular O2 as a sole oxidant under solvent-free and mild reaction conditions. The catalytic performance of Mn-MgAl hydrotalcite was found to be much higher than that of Mn-containing hydrotalcites prepared by different methods or MgAl hydrotalcite catalysts containing various other transition metals and synthesized through similar procedures.
- Jana, Suman K.,Kubota, Yoshihiro,Tatsumi, Takashi
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p. 214 - 222
(2008/03/12)
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- Catalytic investigations of calix[4]arene scaffold based phase transfer catalyst
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Calix[4]arene scaffold based quaternary ammonium salts as multi-site phase transfer catalysts were prepared and their catalytic activities were investigated for Darzens condensation, O/N-alkylation reactions and ethyl benzene oxidation. These calix[4]arene based multi-site phase transfer catalysts showed significant high catalytic activity as compared to single-site phase transfer catalysts.
- Srivastava, Pallavi,Srivastava, Rajendra
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p. 4489 - 4493
(2008/02/03)
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- Autoxidation of ethylbenzene: The mechanism elucidated
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(Chemical Equation Presented) Using a combined experimental and theoretical approach, we elucidated the mechanism of ethylbenzene autoxidation, at about 420 K. The generally accepted literature mechanism indeed fails to explain basic experimental observat
- Hermans, Ive,Peeters, Jozef,Jacobs, Pierre A.
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p. 3057 - 3064
(2008/02/08)
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- Benzylic oxidation and photooxidation by air in the presence of graphite and cyclohexene
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Graphite is introduced as a convenient catalyst for cyclohexene-promoted photooxidation of p-xylene, ethylbenzene, and cumene by air. Availability of the reagent (air), lack of chemical waste, low toxicity, and reusability of the catalyst make the process a good green alternative of oxidation of these industrially important hydrocarbons.
- Sereda, Grigoriy,Rajpara, Vikul
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p. 3417 - 3421
(2008/02/10)
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- PROCESS FOR PREPARING AN ORGANIC HYDROPEROXIDE, INDUSTRIAL SET-UP THEREFORE AND PROCESS WHEREIN SUCH ORGANIC HYDROPEROXIDE IS USED IN THE PREPARATION OF AN ALKYLENE OXIDE
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Process for preparing an organic hydroperoxide, which process comprises: a) oxidizing of an organic compound to obtain a organic reaction product containing organic hydroperoxide; b) mixing at least part of the organic reaction product of step (a) with a basic aqueous solution to obtain a mixture of basic aqueous solution and the organic reaction product; c) separating the mixture of step (b) to obtain a separated organic phase, containing organic hydroperoxide, and a separated aqueous phase; d) mixing at least part of the separated organic phase of step (c) with water to obtain a mixture of an aqueous phase and the organic phase; and e) separating the mixture of step (d) to obtain a separated organic phase, containing organic hydroperoxide, and a separated aqueous phase; in which process the separation to a separated organic phase and a separated aqueous phase in step (e) is carried out with the help of a coalescer containing glass fibers . Process for the preparation of alkylene oxide wherein the above prepared organic hydroperoxide is used, and industrial set-up for carrying out the above process .
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Page/Page column 17-19; 22-23
(2008/06/13)
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- System vanadium alkoxy compound-tert-butyl hydroperoxide-oxidant of hydrocarbon C-H bonds
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Vanadium alkoxy compounds [(t-BuO)4V, (t-BuO)3VO] react with tert-butyl hydroperoxide (C6H6, 20°C) to liberate oxygen, partly in the singlet form, and to form alkoxyl and peroxyl radicals via the intermediacy of vanadium peroxides and trioxide. These systems are capable of oxidizing hydrocarbon C-H bonds. The process is radical in nature and involves formation of carbon-centered radicals and their reaction with oxygen generated in the systems. Vanadium-containing peroxides, too, take part in the oxidation reaction.
- Stepovik,Gulenova,Tishkina,Cherkasov
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p. 1254 - 1262
(2008/03/12)
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- Solvent-free, heterogeneous photooxygenation of hydrocarbons by Hyflon membranes embedding a fluorous-tagged decatungstate
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Hybrid fluoropolymeric membranes with 25% loading of the fluorous-tagged (RfN)4W10O32 effect the solvent-free photooxygenation of benzylic C-H bonds with up to 6100 TONs in 4 hours. The Royal Society of Chemistry 2006.
- Carraro, Mauro,Gardan, Martino,Scorrano, Gianfranco,Drioli, Enrico,Fontananova, Enrica,Bonchio, Marcella
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p. 4533 - 4535
(2008/09/19)
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- Reaction of zirconium alkoxides with tert-butyl hydroperoxide. Oxidative ability of the Zr(OBu-t)4-t-BuOOH system
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Oxidation of the isopropoxy group in the Zr(i-PrO)4·i- PrOH complex involves both direct reaction with tert-butyl hydroperoxide and intermediate formation of zirconium peroxy compound. Zirconium tetra-tert-butoxide reacts with tert-bytyl hydroperoxide to form metal-containing peroxide and trioxide. Decomposition of the latter leads to oxygen evolution and is accompanied by radical formation. The alkoxyl and peroxyl radicals formed were identified by ESR spectroscopy. The nature of the oxidant (oxygen, zirconium-containing peroxide and-trioxide) in the Zr(OBu-t)4-t-BuOOH system is determined by the structure of the substrate molecule. Pleiades Publishing, Inc., 2006.
- Gulenova,Stepovik,Cherkasov
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p. 980 - 988
(2008/02/03)
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- Ethylbenzene oxidation in the presence of acetic anhydride
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The kinetics of formation and subsequent transformation of the products of ethylbenzene oxidation in the presence of acetic anhydride at 100°C was studied by solution of the inverse kinetic problem.
- Nosacheva,Revkov,Perkel
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p. 443 - 447
(2008/02/02)
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- PROCESS FOR PRODUCING ALKYLENE OXIDE
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A process for preparing an alkylene oxide, which process comprises: (i) oxidizing an alkylebenzene to obtain a stream comprising alkylbenzene hydroperoxide; (ii) contacting at least part of the alkylbenzene hydroperoxide obtained in step (i) with an olefin to obtain a product stream comprising an alkylene oxide; (iii) separating alkylene oxide compound from the product stream of step (ii) to obtain (a) a residual product stream comprising alkylphenyl alcohol, and (b) alkylene oxide; (iv) feeding at least a part of the residual product stream comprising alkylphenyl alcohol to a reactor having a catalytic distillation zone, and concurrently in the reactor: (a) contacting the residual product stream comprising alkylphenyl alcohol with hydrogen in the catalytic distillation zone to convert the alkylphenyl alcohol in the residual product stream to alkylbenzene and from a reaction mixture; and, (b) separating alkylbenze from the reaction mixture by fraction distillation; (v) withdrawing a stream comprising alkybenzene and having a reduced concentration of alkylphenyl alcohol than the feed stream from the reactor at a position upper from the catalytic reaction zone; withdrawing from the reactor at a position lower than the catalytic distillation zone a bottom stream comprising dimer(s) of alkylbenzene; alkylbenze; and. (viii) recycling at least a part of the alkylbenzene produced from (iv)(b) and/or (vi) to step (i).
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Page/Page column 21
(2008/06/13)
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- Highly efficient and metal-free aerobic hydrocarbons oxidation process by an o-phenanthroline-mediated organocatalytic system
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A highly efficient o-phenanthroline-mediated, metal-free catalytic system has been developed for oxidation of hydrocarbons with dioxygen in the presence of N-hydroxyphthalimide; various hydrocarbons were efficiently and high selectively oxidized, e.g., ethylbenzene to acetophenone in 97% selectivity and 76% conversion, under mild conditions.
- Tong, Xinli,Xu, Jie,Miao, Hong
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p. 1953 - 1957
(2007/10/03)
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- Process for preparation of hydroperoxides
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The invention relates to a process for preparing hydroperoxides from their corresponding hydrocarbons which comprises oxidizing said hydrocarbons, particularly ethylbenzene, with an oxygen containing gas in the presence of a catalyst comprising a cyclic i
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Page/Page column 3
(2008/06/13)
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- Titanium(IV) tert-butoxide-tert-butyl hydroperoxide system as oxidant for C-H bonds in hydrocarbons and oxygen-containing compounds
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The system Ti(IV) tetra-tert-butoxide-tert-butyl hydroperoxide in mild conditions (20°C) oxidizes C-H bonds of methyl (toluene), methylene (hexane, ethylbenzene, benzyl ethyl ether), and methine (1, 1-diphenylethane, triphenylmethane) groups. The role of oxidant is played by the oxygen generated by the system. The process involves free radicals and produces hydroperoxides and Ti(IV) peroxides. The latter decompose both with preservation and decomposition of the hydrocarbon skeleton. 2005 Pleiades Publishing, Inc.
- Stepovik,Gulenova,Martynova
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p. 507 - 513
(2007/10/03)
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