- Method for simultaneously synthesizing methyl-ethylbenzene and diethylbenzene by virtue of one-step method
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The invention relates to a method for simultaneously synthesizing methyl-ethylbenzene and diethylbenzene by virtue of a one-step method. Ethylene, benzene and methylbenzene are taken as raw materials to perform an alkylation reaction so as to synthesize methyl-ethylbenzene and diethylbenzene in one step. The method comprises a pretreatment stage, a reaction stage and an aftertreatment stage. In the method, one reaction system is adopted, and alkylation reaction and aftertreatment are sequentially performed so as to separate components, so that target products are obtained, and thus one-step simultaneous synthesis of methyl-ethylbenzene and diethylbenzene is realized; the problem that two independent devices are respectively used for production in a traditional production process is avoided, and the whole reaction process is convenient and rapid; the yields of different components can be effectively adjusted by adjusting different proportions of raw materials, and unreacted benzene and methylbenzene and the ethylbenzene generated in a reaction process are separated and recycled to serve as raw materials once again, so that the production cost is greatly saved, and meanwhile, the method can adapt to variations of the market to the greatest extent.
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Paragraph 0051-0065
(2016/12/22)
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- Temperature-controlled phase-transfer hydrothermal synthesis of MWW zeolites and their alkylation performances
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MWW zeolites have been synthesized with hexamethyleneimine/aniline as the structure-directing/ promoting agent. As structure-promoting agent, aniline contributes to the crystallization of MWW zeolites without being trapped within zeolites. Meanwhile the t
- Xing, Enhui,Shi, Yanchun,Xie, Wenhua,Zhang, Fengmei,Mu, Xuhong,Shu, Xingtian
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p. 29707 - 29717
(2018/06/04)
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- Synthesis, characterization and application of MCM-22 zeolites via a conventional HMI route and temperature-controlled phase transfer hydrothermal synthesis
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With less environmental and economical impact, temperature-controlled phase transfer hydrothermal synthesis of MWW zeolites was realized with hexamethyleneimine as a structure-directing agent and aniline as a structure-promoting agent. MCM-22 zeolite, synthesized via temperature-controlled phase transfer hydrothermal synthesis, is nearly identical concerning chemical composition and structure, and possesses nearly identical properties with respect to porosity, Si/Al ratio, thermal behavior and catalytic activity at 200°C, compared with that made from conventional synthesis with hexamethyleneimine as the only template.
- Xing, Enhui,Shi, Yanchun,Xie, Wenhua,Zhang, Fengmei,Mu, Xuhong,Shu, Xingtian
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p. 8514 - 8522
(2015/03/05)
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- Enhancing activity without loss of selectivity - Liquid-phase alkylation of benzene with ethylene over MCM-49 zeolites by TEAOH post-synthesis
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As-synthesized and calcined MCM-49 zeolites were post-synthesized by tetraethylammonium hydroxide to tailor their morphology, texture properties, acid sites and catalytic performances. With post-synthesis by tetraethylammonium hydroxide, both as-synthesiz
- Shi, Yanchun,Xing, Enhui,Xie, Wenhua,Zhang, Fengmei,Mu, Xuhong,Shu, Xingtian
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p. 135 - 144
(2015/09/28)
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- Size-controlled synthesis of MCM-49 zeolites and their application in liquid-phase alkylation of benzene with ethylene
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Size-controlled synthesis of MCM-49 zeolites was achieved via topology reconstruction from NaY zeolites with different sizes. SEM images showed that the sizes of the reconstructed H-MCM-49 zeolites were controlled by those of the parent NaY zeolites. Smal
- Shi, Yanchun,Xing, Enhui,Xie, Wenhua,Zhang, Fengmei,Mu, Xuhong,Shu, Xingtian
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p. 13420 - 13429
(2015/02/19)
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- Phosphate modified ZSM-5 for the shape-selective synthesis of para-diethylbenzene: Role of crystal size and acidity
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Pore engineered ZSM-5 zeolite in extrudate form was prepared and used as shape-selective catalyst for vapor phase ethylation of ethylbenzene to selectively form para-diethylbenzene. The physico-chemical properties of the catalyst were established by XRD, N2 sorption, FTIR, FESEM, NH 3-TPD and 31P MAS NMR. Alkylation of ethylbenzene with ethanol was carried out in a continuous, down-flow, tubular reactor, at atmospheric pressure and H2 as a carrier gas in vapor phase. Effect of silica to alumina ratio (SAR), crystal size, acidity of phosphate modified ZSM-5, stepwise phosphate modification and reaction conditions were studied in detail. ZSM-5 with SAR 187 was found to contain optimum acidity for phosphate modification to achieve good conversion and high selectivity for p-diethylbenzene. Under optimized reaction conditions, viz. temperature = 380 °C, ethylbenzene:ethanol mole ratio = 4:1, WHSV = 3 h-1, H 2/reactants = 2, 5PZSM-5 W catalyst gave 22.8% of ethylbenzene conversion with ~98% selectivity for para-diethylbenzene.
- Hodala, Janardhan L.,Halgeri, Anand B.,Shanbhag, Ganapati V.
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- Synthesis and optical reactivity of 6,13-α-diketoprecursors of 2,3,9,10-tetraalkylpentacenes in solution, films and crystals
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Tetraalkylpentacenes having alkyl chains at 2,3,9,10-positions (Et-PEN, Pr-PEN and Hex-PEN) were prepared from their precursors Et-PDK, Pr-PDK and Hex-PDK, respectively. Photoreactions proceeded both in solutions, thin-films, and crystals, thus the properties of Et-PDK in films can be studied despite the instability of the pentacenes in solution. Et-PEN showed significantly different aggregation-nature compared with the parent pentacene. The hole mobilities of Et-PEN and Pr-PEN in films were 3.4 × 10-6 and 8.1 × 10-7 cm2 V-1 s-1, respectively, determined by space-charge-limited current measurement, comparable with the order 10-6 cm2 V-1 s-1 of the electron mobility of Alq3.
- Katsuta, Shuhei,Saeki, Hiroyuki,Tanaka, Katsuki,Murai, Yuki,Kuzuhara, Daiki,Misaki, Masahiro,Aratani, Naoki,Masuo, Sadahiro,Ueda, Yasukiyo,Yamada, Hiroko
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p. 986 - 993
(2014/02/14)
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- Platinum(II)-catalyzed ethylene hydrophenylation: Switching selectivity between alkyl- and vinylbenzene production
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The series of PtII complexes [(xbpy)Pt(Ph)(THF)] [BAr′4] (xbpy =4,4′-X-2,2′-bipyridyl, X = OMe, tBu, H, Br, CO2Et, NO2; Ar′ = 3,5-bis(trifluoromethyl)phenyl) are catalyst precursors for ethylene hydrophenylation. The bipyridyl substituent provides a tunable switch for catalyst selectivity that also has significant influence on catalyst activity and longevity. Less electron donating 4,4′-substituents increase the propensity toward styrene formation over ethylbenzene.
- McKeown, Bradley A.,Gonzalez, H. Emanuel,Friedfeld, Max R.,Brosnahan, Anna M.,Gunnoe, T. Brent,Cundari, Thomas R.,Sabat, Michal
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p. 2857 - 2865
(2013/06/26)
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- PtII-catalyzed ethylene hydrophenylation: Influence of dipyridyl chelate ring size on catalyst activity and longevity
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Expansion of the dipyridyl ligand from a five- to six-membered chelate for PtII-catalyzed ethylene hydrophenylation provides an enhancement of catalyst activity and longevity. Mechanistic studies of [(dpm)Pt(Ph)(THF)] [BAr′4] [dpm = 2,2′-dipyridylmethane, and Ar′ = 3,5-(CF3)2C6H3] attribute the improved catalytic performance at elevated temperatures to a favorable change in entropy of activation with an increase in chelate ring size. The Pt II catalyst precursor [(dpm)Pt(Ph)(THF)][BAr′4] is among the most active catalysts for ethylene hydrophenylation by a non-acid-catalyzed mechanism.
- McKeown, Bradley A.,Gonzalez, Hector Emanuel,Gunnoe, T. Brent,Cundari, Thomas R.,Sabat, Michal
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p. 1165 - 1171
(2013/07/26)
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- Control of olefin hydroarylation catalysis via a sterically and electronically flexible platinum(II) catalyst scaffold
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PtII complexes supported by dipyridyl ligands have been demonstrated to catalyze olefin hydroarylation. Herein, studies on the influence of dipyridyl motif variation are reported. Increasing the chelate ring size of dipyridyl-ligated PtII complexes from five- to six-membered rings by replacing 4,4′-di-tert-butyl-2,2′-bipyridine with 2,2′-dipyridylmethane has been shown to increase catalytic activity and longevity for catalytic ethylene hydrophenylation. For 2,2′-dipyridyl ligands, the presence of methyl groups in the 6/6′-positions of the pyridyl rings reduces the extent of dialkylation to produce diethylbenzenes but also increases the rate of catalyst decomposition. Substituting the methylene spacer between the pyridyl rings of 2,2′-dipyridylmethane with more electron-withdrawing groups also reduces catalytic efficiency. The steric profile of PtII complexes with increased chelate ring size or substituents in the 6/6′-positions of the pyridyl rings provides a marked change in regioselectivity for ethylene hydroarylation using ethylbenzene as well as the linear to branched selectivity for the hydrophenylation of propylene.
- McKeown, Bradley A.,Gonzalez, Hector Emanuel,Michaelos, Thoe,Gunnoe, T. Brent,Cundari, Thomas R.,Crabtree, Robert H.,Sabat, Michal
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p. 3903 - 3913
(2013/08/23)
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- Liquid-phase alkylation of benzene with ethylene over postsynthesized MCM-56 analogues
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MCM-56 analogues were postsynthesized via a mild acid treatment technique from hydrothermally synthesized MCM-22 lamellar precursors with Si/Al ratios of 15-45. The physicochemical properties of MCM-56 were characterized by XRD, SEM, N2 adsorption, XPS, 29Si and 27Al MAS NMR, NH3-TPD and pyridine adsorption IR techniques. In comparison to MCM-22 with 3-dimensional MWW topology, the postsynthesized MCM-56 showed a broad X-ray diffraction of emerged 1 0 1 and 1 0 2 reflections and possessed a structural disorder along the layer stacking direction. Composed of partially delaminated MWW nanosheets, MCM-56 analogues had a larger external surface than MCM-22. The MCM-56 and MCM-22 catalysts were employed in the liquid-phase alkylation of benzene with ethylene. MCM-56 analogues exhibited a higher yield of ethylated benzenes and a higher catalytic stability than MCM-22, proving to serve as promising solid-acid catalysts for processing bulky molecules in petrochemical industry.
- Zhang, Bin,Ji, Yongjun,Wang, Zhendong,Liu, Yueming,Sun, Hongmin,Yang, Weimin,Wu, Peng
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p. 103 - 110
(2012/11/07)
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- Catalytic dehydroaromatization of n-alkanes by pincer-ligated iridium complexes
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Aromatic hydrocarbons are among the most important building blocks in the chemical industry. Benzene, toluene and xylenes are obtained from the high temperature thermolysis of alkanes. Higher alkylaromatics are generally derived from arene-olefin coupling, which gives branched products-that is, secondary alkyl arenes-with olefins higher than ethylene. The dehydrogenation of acyclic alkanes to give alkylaromatics can be achieved using heterogeneous catalysts at high temperatures, but with low yields and low selectivity. We present here the first catalytic conversion of n-alkanes to alkylaromatics using homogeneous or molecular catalysts-specifically 'pincerg'-ligated iridium complexes-and olefinic hydrogen acceptors. For example, the reaction of n-octane affords up to 86% yield of aromatic product, primarily o-xylene and secondarily ethylbenzene. In the case of n-decane and n-dodecane, the resulting alkylarenes are exclusively unbranched (that is, n-alkyl-substituted), with selectivity for the corresponding o-(n-alkyl)toluene.
- Ahuja, Ritu,Punji, Benudhar,Findlater, Michael,Supplee, Carolyn,Schinski, William,Brookhart, Maurice,Goldman, Alan S.
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experimental part
p. 167 - 171
(2012/03/27)
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- Mechanistic studies of ethylene hydrophenylation catalyzed by bipyridyl Pt(II) complexes
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Cationic platinum(II) complexes [(tbpy)Pt(Ph)(L)]+ [tbpy =4,4′-di-tert-butyl-2,2′-bipyridyl; L = THF, NC5F5, or NCMe] catalyze the hydrophenylation of ethylene to generate ethylbenzene and isomers of
- McKeown, Bradley A.,Gonzalez, Hector Emanuel,Friedfeld, Max R.,Gunnoe, T. Brent,Cundari, Thomas R.,Sabat, Michal
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experimental part
p. 19131 - 19152
(2012/01/12)
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- Zeolite SSZ-53: An extra-large-pore zeolite with interesting catalytic properties
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(Figure Presented) Wide pores for wide applications: The catalytic properties of SSZ-53, an extra-large-pore high-silica zeolite, were explored by using ethylbenzene disproportionation and the isomerization and hydrocracking of n-decane as test reactions. High activity together with a very open channel system render this zeolite an attractive candidate as catalyst for applications in petroleum refining.
- Tontisirin, Supak,Ernst, Stefan
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p. 7304 - 7306
(2008/09/18)
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- Polymerizations initiated by diradicals from cycloaromatization reactions
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Four cycloaromatization substrates each produce diradicals that lead to the initiation of polymerization of vinyl monomers. All the initiators produce significant amounts of polymer, especially with methacrylate monomers. Intramolecular termination of short diradical chains produces oligomeric byproducts and limits the amount of high polymer that is formed. The polymer yield can be increased through the addition of a chain transfer agent by presumably converting unproductive diradicals into pairs of monoradicals. The enediynes that contain terminal acetylenes are less effective initiators because they retard radical polymerization. Bergman cyclization substrates are better initiators than Myers cyclization substrates.
- Rule, Joseph D.,Moore, Jeffrey S.
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p. 7266 - 7273
(2007/10/03)
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- Ethylation of ethylbenzene over AFI type molecular sieves
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Magnesium, manganese and zinc incorporated aluminophosphate molecular sieves, MgMnAPO-5 and MnZnAPO-5, have been prepared by hydrothermal methods. The samples have been characterised by the techniques of XRD, FT-IR, 31P and 27Al MAS-NMR spectroscopy, BET-surface area, n-butylamine-TPD and ICP-MS. The cataiytic performance of these materials has been examined for ethylation of ethylbenzene with ethanoi in the vapour phase. MnZnAPO-5 has been found to be more active than MgMnAPO-5. The products are PDEB (1,4-diethylbenzene), MDEB (1,3-diethylbenzene), ODEB (1,2-diethylbenzene), PAB [(1,2,4 and 1,3,5-triethylbenzene) and (1,2,4,5-tetraethylbenzene)]. Maximum conversion (20.1%) has been noted at 350°C over MnZnAPO-5.
- Raj, K. Joseph Antony,Vijayaraghavan
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p. 254 - 257
(2007/10/03)
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- Catalytic ring-attachment isomerization and dealkylation of diethylbenzenes over halide clusters of group 5 and group 6 transition metals
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A molybdenum halide cluster, (H3O)2[(Mo 6Cl8)Cl6]·6H2O, possessing an octahedral metal framework was used as a catalyst in a gas flow reactor under 1 atm of hydrogen. On reaction of p-diethylbenzene, dehydrogenation to ethylstyrene proceeded selectively at 300°C. At 400°C, mutual interconversion of o-, m-, and p-diethylbenzenes proceeded selectively. The ethyl group migrated by an intramolecular 1,2-shift mechanism without yielding disproportionation products. Niobium and tungsten chloride clusters with the same metal framework were also active catalysts for the isomerization of p-diethylbenzene. All the reactions resulted in appreciable yields of dealkylation products. The catalytic activity for isomerization can be ascribed to acid sites on the cluster surface, and the catalytic activity for dealkylation, to the metallic nature of the framework metal.
- Kamiguchi, Satoshi,Kondo, Kunihiko,Kodomari, Mitsuo,Chihara, Teiji
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- Kinetics and Mechanisms of Transalkylation and Disproportionation of meta-Diethylbenzene by Triflic Acid Catalyst
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The kinetics of transalkylation and isomerization of meta-diethylbenzene in the presence of benzene using triflic acid as a catalyst has been investigated. High catalytic activity of the triflic acid catalyst was observed in homogeneous liquid-phase reactions. On the basis of the product distribution obtained, transalkylation, disproportionation, and isomerization reactions have been considered and the main product of the reaction was ethylbenzene. These reactions are conducted in a closed liquid batch reactor with continuous stirring under dry nitrogen and atmospheric pressure over the temperature range of 288-308 K. The main transalkylation, disproportionation, and isomerization reactions occurred simultaneously and were considered as elementary reactions. The apparent activation energy of the transalkylation reaction was found to be 35.5 kj/mol, while that of disproportionation reaction was 42.3 kj/mol. The reproducibility of the experimental product distribution occurred with an average relative error of ±2%.
- Al-Zahrani,Al-Kinany,Al-Humaizi,Al-Khowaiter
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p. 555 - 563
(2007/10/03)
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- Cobalt(I)-catalyzed neutral Diels-Alder reactions of oxygen-functionalized acyclic 1,3-dienes with alkynes
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The cobalt-catalyzed Diels-Alder reaction of alkoxy-substituted 1,3-butadienes with terminal and internal alkynes is described. While the reaction of 1-alkoxy derivatives gave the aromatic hydrocarbons upon elimination of alcohol from the alkoxy-substituted dihydroaromatic intermediates, the reactions with 2-alkoxy derivatives generated stable dihydroaromatic enol ethers in good to excellent chemical yields and good to high regioselectivities for unsymmetrical starting materials. The enol ethers can be easily hydrolysed to the corresponding β,γ-unsaturated ketones in a one pot reaction sequence or used in cyclopropanation or other subsequent chemical transformations.
- Hilt, Gerhard,Smolko, Konstantin I.,Lotsch, Bettina V.
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p. 1081 - 1084
(2007/10/03)
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- Novel organoborane Lewis acids via selective boron-tin exchange processes - Steric constraints to electrophilic initiation by the boron halide
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With the purpose of preparing novel mono- and bidentate organoboron Lewis acids, the scope and limitations of synthesizing the requisite organoboranes by the boron-tin exchange between a boron halide and the appropriate organostannane have been examined in detail. The following organotin derivatives have been obtained either from the corresponding RMgBr or RLi reagent and MenSnCl4-n or from a Barbier procedure using the organic halide, Me3SnCl and magnesium metal: 1,2-bis(trimethylstannyl)ethyne, o-, m-, and p-bis(trimethylstannyl)benzenes, α,o-bis(trimethylstannyl)toluene, α,α-bis(trimethylstannyl)-o-xylene, and 2,2-dimethyl-2-stannaindane. The individual interaction of the 1,2-bis(trimethylstannyl)ethyne and the isomeric bis(trimethylstannyl)benzenes with Et2BBr produced the corresponding bis(diethylboryl)-derivatives. By contrast, with Et2BCl the α,o-bis(trimethylstannyl)toluene gave only o-diethylboryl-α-trimethylstannyltoluene and with BCl3 the α,α′-bis(trimethylstannyl)-o-xylene formed only α,α′-bis-(chlorodimethylstannyl)-o-xylene. Furthermore, in the attempted double boron-tin exchange between o-bis(trimethylstannyl)benzene and BCl3, an unprecedented rearrangement of the 1-(dichloroboryl)-2-(trimethylstannyl)benzene intermediate into its 1-[chloro(methyl)boryl]-2-(chlorodimethylstannyl) isomer was observed. Likewise, o-bis(trimethylstannyl)benzene with PhBCl2 produced by a similar rearrangement 1-[methyl(phenyl)boryl]-2-(chloro-dimethylstannyl)benzene. The thermolysis of such boranes led variously to definite dimers or ill-defined oligomers. Preliminary studies of the properties of these organoboranes have identified the heightened Lewis acidity of 1,2-bis(diethylboryl)ethyne and the π-electron delocalization involving the 2pΖ-boron orbitals in the 9,10-dihydro-9,10-diboraanthracene system. Finally, an electronic mechanism for the boron-tin exchange has been developed to account for the selectivity of the boron halide's attack at unsaturated carbon-tin bonds.
- Eisch, John J.,Kotowicz, Boguslaw W.
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p. 761 - 769
(2007/10/03)
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- The influence of the external acidity of H-ZSM-5 on its shape selective properties in the disproportionation of ethylbenzene
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The shape selectivity of H-ZSM-5 in the disproportionation of ethylbenzene was investigated, using a set of samples with the same Si/Al ratio, but different particle sizes in the range from 0.1 to 80 μm. The number of external acid sites of each sample was measured gravimetrically by the adsorption of 2,6-dimethylpyridine. The data were correlated with the results of catalytic experiments. Conversion and product distribution are strongly dependent on the external acidity which in turn correlates well with the particle size. An estimate for the diffusion coefficient could be obtained by fitting the effectiveness factor for the different particle sizes.
- Melson, Sabine,Schueth, Ferdi
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- Selective Mono-Alkylation and Arylation of Dichlorobenzenes by Palladium-Catalyzed Grignard Cross-Coupling
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Palladium(II)-phosphine complexes, especially PdCl2(dppf) where dppf stands for 1,1'-Bis(diphenylphosphino)ferrocene, are effective catalysts for the cross-coupling of Grignard reagents with dichlorobenzenes to produce selectively mono-alkylated and arylated benzenes.The addition of ligands is also effective for the cross-coupling of Grignard reagents containing a β-hydrogen(s).
- Katayama, Tatsuo,Umeno, Masayuki
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p. 2073 - 2076
(2007/10/02)
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- Shape Selectivity of ZSM-5 Type Zeolite for Alkylation of Ethylbenzene with Ethanol
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The alkylation of ethylbenzene with ethanol on ZSM-5 zeolites was studied at 673 K.The primary product in this alkylation on HZSM-5 catalyst was only p-diethylbenzene because of the transition-state selectivity.Therefore, the isomerization of p-diethylbenzene has to be restrained for the selective formation of p-diethylbenzene.The modified HZSM-5 catalysts with oxide of magnesium, phosphorus or boron showed much higher para-selectivity than the parent HZSM-5.The modification reduced not only the effective pore dimension of HZSM-5 but also the amount of strong acid sites.We claim that the absence of strong acid sites is necessary rather than the narrowness of pores for the suppression of the isomerization of p-diethylbenzene produced as a primary product.
- Kim, Jong-Ho,Namba, Seitaro,Yashima, Tatsuaki
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p. 1051 - 1056
(2007/10/02)
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- Process for separation of substituted benzene isomers
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A substituted benzene isomer mixture containing a meta-substituted benzene or 1,3,5-substituted benzene is contacted with an adsorbent of a faujasite type zeolite containing a Ag cation and/or a Cu cation, whereby the meta-substituted benzene or 1,3,5-substituted benzene is separated and recovered as a raffinate component.
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- CATALYTIC PROPERTIES OF DECATIONATED HTsVM AND H-MORDENITE ZEOLITES.
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A comparison was made of the catalytic properties of decationated HTsVM zeolites (Soviet zeolites of the pentasil family) and of H-mordenite (HM) in conversions of m-xylene and ethylbenzene under elevated hydrogen pressures, under conditions tending to improve the stability of operation of zeolite catalysts. It is found that in conversions of m-xylene and ethylbenzene on decationated mordenite under hydrogen pressure (at 400 degree , total pressure 1. 5 MPa, mass feed rate 15-60 h** minus **1) the yields of products of disproportionation of xylenes and ethylbenzene are equal. In conversions of m-xylene and ethylbenzene on a decationated zeolite of the pentasil family, HTsVM (molar ration SiO//2:Al//2O//3 equals 40:1) under the conditions studied the yields of products of disproportionation of xylenes and ethylbenzene are different: lower than on H-mordenite in the case of xylenes, and higher than on H-mordenite in the case of ethylbenzene.
- Bursian,Martynov,Nikitina,Zhemchugova
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p. 2498 - 2502
(2007/10/02)
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- Alkylation of Arenes with Ethylene over H-ZSM-5 and Modernite-H Catalysis
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Attempts were made to alkylate acetophenone, benzene, benzonitrile, bromobenzene, chlorobenzene, ethylbenzene, fluorobenzene, iodobenzene, methoxybenzene, nitrobenzene, toluene and α,α,α-trifluorotoluene with ethylene over H-ZSM-5 and mordenite-H catalysts at 400 and 250 deg C, respectively.Over H-ZSM-5 benzene, bromobenzene, chlorobenzene, ethylbenzene and toluene gave monoethylarenes as the major product (95-100percent) with the para product as the dominant isomer (87-95percent).Over mordenite-H benzene, bromobenzene, chlorobenzene and toluene reacted.The monoethylarenes were again the major product (85-95percent) but the isomer distributions were close to the thermodynamically controlled ones due to isomerization of the initially formed products.Over H-ZSM-5 the results indicated the reaction to be of a Friedel-Crafts type.It was proposed that the product composition was determined by the chemical reaction, not by the rate of diffusion of the products.
- Akervold, Idar,Bakke, Jan M.,Steinsvik, Eirik
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p. 437 - 444
(2007/10/02)
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- INTERMOLECULAR HYDROGEN TRANSFER IN UNSATURATED HYDROCARBONS INDUCED BY DIMERIC TITANOCENE
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μ-(η5:η5-Fulvalene)-di-μ-hydrido-bis(η5-cyclopentadienyltitanium) and μ-(η5:η5-fulvalene)-μ-chloro-μ-hydrido-bis(cyclopentadienyltitanium) form a thermally stable complex which catalyzes the intermolecular hydrogen transfer in unsaturated hydrocarbons, in addition to isomerizations and cyclizations.Cyclic hydrocarbons disproportionate under catalysis to saturated and aromatic hydrocarbons, while linear olefins yield predominantly linear alkanes and high molecular weight tar.The catalyst enables the hydrocarbon system to approach the thermodynamicequilibrium through a series of substitution reactions between alkyl- and allyltitanocene-like species and olefins and dienes.The catalytic complex was characterized by UV and ESR spectra.About one half of overall titanium content could be converted to mononuclear η3-allyltitanocene-like species, stable up to 400 deg C.This exceptional thermal stability is ascribed to a firmly bound allyl containing ligand.
- Mach, Karel,Petrusova, Lidmila,Antropiusova, Helena,Hanus, Vladimir,Turecek, Frantisek,Sedmera, Petr
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p. 2924 - 2936
(2007/10/02)
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- Alkylation Reactions over Ion-exchanged Molecular Sieve Zeolite Catlysts. Part 3. Alkylation of Toluene and Benzene with Ethanol: Consideration of the Effects of Initial Coke Formation on para Selectivity
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The ethylation of toluene and benzene with ethanol at 423 K over a wide range of exchanged NaNH4Y catalysts and also over a NH4Y-91.5 sample calcined at 11 different temperatures between 523 and 875 K has been studied.Alkylation with ethanol was found not
- Coughlan, Brendan,Carroll, William M.,Nunan, John
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p. 311 - 326
(2007/10/02)
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- Catalytic Hydrogenation of Some Hydrocarbons with Spiroanellated Bicyclopropyl Units
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The spirocyclopropyl groups of dispirodec-8-ene (1) and dispirohexane-3',1''-cyclopropane> (11) both upon catalytic hydrogenation are ringopened to ethyl groups rather than gem-dimethyl groups as would be expected
- Kaufmann, Dieter,Meijere, Armin de
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p. 833 - 837
(2007/10/02)
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- FORMATION OF SULPHUR COMPOUNDS IN THE HYDRODENITROGENATION OF 2-METHYLQUINOLINE, 2-METHYLPIPERIDINE, INDOLE, AND ISOQUINOLINE ON A NICKEL-TUNGSTEN CATALYST IN THE PRESENCE OF HYDROGEN SULPHIDE
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2-Methylquinoline, 2-methylpiperidine, indole, and isoquinoline were subjected to hydrodenitrogenation (HDN) on a sulphidized nickel-tungsten catalyst in an autoclave at 300 and 350 deg C using pure hydrogen or a hydrogen-hydrogen sulphide mixture.The neutral fraction from the HDN of 2-methylquinoline and 2-methylpiperidine contained 40 and 90percent sulphur compounds, respectively.The presence of hydrogen sulphide in the HDN of isoquinoline resulted in an enhanced fraction of the neutral moiety.A reaction mechanism is suggested for the HDN of 2-methylquinoline and 2-methylpiperidine in the presence of hydrogen sulphide, in which the latter contributes to the higher degree of conversion due to the formation of corresponding sulphur compounds.
- Cerny, Mirko,Trka, Antonin
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p. 3413 - 3420
(2007/10/02)
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- The Metallation-Elimination Reaction, II. Monocyclic Anions and Polyanions
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Equimolar mixtures of n-butyllithium and potassium tert-amyloxide effect metallation and metal hydride elimination of cyclic olefins directly to give conjugated anions and polyanions in a single operation. 1-Methyl-1-cycloalkenes or methylenecycloalkanes are particularly well suited and give highly unsaturated products.Odd-membered rings eliminate better than their even-membered counterparts, and eight-membered rings eliminate particularly slowly.Reactions with methyl iodide and trimethylsilyl chloride proceed smoothly in high yield.
- Wilhelm, Dieter,Clark, Timothy,Friedl, Thomas,Schleyer, Paul von Rague
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p. 751 - 760
(2007/10/02)
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- Studies in Trifluoromethanesulfonic Acid. 3. Kinetics and Mechanism of Transalkylation Reactions
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Rates of disproportionation of ethylbenzene and m-diethylbenzene have been measured in the solvent trifluoromethanesulfonic acid (triflic acid).Ethylbenzene disproportionates very rapidly, whereas m-diethylbenzene reacts at a conveniently measurable rate.The reactions obey first-order kinetics over a wide range of concentration, and the results are interpreted as involving ethyl transfer to the triflate anion followed by alkylation via the ethyl triflate formed.
- Bakoss, H. J.,Roberts, R. M. G.,Sadri, A. R.
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p. 4053 - 4055
(2007/10/02)
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- 78. Ueber den Anteil sigmatroper 1,5-Wanderung von Kohlenwasserstoffgruppen bei der thermolytischen Skelettisomerisierung 5,5-disubstituierter 1,3-Cyclohexadiene
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The uncatalyzed skeletal isomerization of 5,5-disubstituted 1,3-cyclohexadienes was investigated with the aim to establish the extent to which sigmatropic 1,5-shifts of hydrocarbon groups are participating in these reactions.Gas phase pyrolysis of 5,5-diethyl-1,3-cyclohexadiene (7) at 460 deg C followed by chloranil aromatization yields only 4percent of 1,3-diethylbenzene resulting from 7 through a 1,5-ethyl migration in the primary reaction step 2,3-Dimethylethylbenzene (56percent) and 1,4-diethylbentene (4percent) are obtained as other C10-compounds.This shows that isomerization proceeds mainly through a sequence of electrocyclic and 1,7-shift reactions.Ethylbenzene (24percent) and other aromatic C8- and C9-hydrocarbons are formed to a considerable extent, indicating that C,C-bond cleavage is a major competing process and that the 1,3-diethylbenzene found is the result of a radical recombination reaction and not of a concerted sigmatropic shift of the ethyl group. 5-Methyl-5-phenyl-1,3-cyclohexadiene (12) yields 3-methylbiphenyl (14) and biphenyl upon thermolysis and aromatization.Through 13C-substitution of the methyl group in 12 it is shown that in solution at 300 deg skeletal isomerization proceeds through electrocyclic and 1,7-H-shift reactions exclusively.In the gas phase at 500 deg 4percent of the isomerization product is formed by a 1,5-shift of a substituent, presumably of the methyl group, through a dissociative mechanism.Thermolysis of 5,5-diphenyl-1,3-cyclohexadiene (22) at 560 deg in the gas phase leads to 1,1-diphenyl-1,3,5-hexatriene (23) and 1-vinyl-4-phenyl-1,2 dihydronaphthalene (24) through electrocyclic reaction steps.In addition a small amount of m-terphenyl is obtained at high conversion of 22.This indicates that sigmatropic 1,5-phenyl migration can participate in product formation only at high temperature and in the absence of other irreversible pathways to stable products.
- Schiess, Peter,Dinkel, Rolf
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p. 801 - 812
(2007/10/02)
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- Kinetic Evidence for the Formation of Discrete 1,4-Dehydrobenzene Intermediates. Trapping by Inter- and Intramolecular Hydrogen Atom Transfer and Observation of High-Temperature CIDNP
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Upon being heated, alkyl-substituted cis-1,2-diethynyl olefins undergo cyclization to yield reactive 1,4-dehydrobenzenes; the products isolated may be derived from either unimolecular or bimolecular reactions of the intermediate. (Z)-4,5-Diethynyl-4-octene (4) undergoes rearrangement to yield 2,3-di-n-propyl-1,4-dehydrobenzene (17).Solution pyrolysis of 4 in inert aromatic solvent produces three unimolecular products, (Z)-dodeca-4,8-diyn-6-ene (7), benzocyclooctene (9), and o-allyl-n-propylbenzene (10), in high yield.When 1,4-cyclohexadiene is added to the pyrolysis solution as a trapping agent, high yields of the reduced product o-di-n-propylbenzene (12) are obtained.The kinetics of solution pyrolysis of 4 in the presence and absence of trapping agent establish that 2,3-di-n-propyl-1,4-dehydrobenzene is a discrete intermediate on the pathway leading to products.When the reaction was run in the heated probe of an NMR spectrometer, CIDNP was observed in 10.This observation, along with kinetic and chemical trapping evidence, indicates the presence of two additional intermediates, formed from 17 by squential intramolecular hydrogen transfer, on the pathway to products.The observation of CIDNP, coupled with the reactivity exhibited by 17 and the other two intermediates, implicates a biradical description of these molecules.Biradical 17 has been estimated to have a lifetime of about 10-9 s at 200 deg C and to lie in a well of about 5 kcal per mole with respect to the lowest energy unimolecular pathway ( hydrogen transfer).Ring opening (expected to be the lowest energy process for 1,4-dehydrobenzenes in which intramolecular hydrogen transfer is unlikely) to the isomeric diethynyl olefin 7 appears to have an activation enthalpy of about 10 kcal/mol.Upon thermal reaction in the gas phase (400 deg C) or in solution in inert solvents (Z)-2,3-diethylhexa-1,5-diyn-3-ene (5) rearranges in good yield to the isomeric diethynyl olefin (Z)-deca-3,7-diyn-5-ene (8) again presumably via 2,3-diethyl-1,4-dihydrobenzene 20 (addition of 1,4-cyclohexadiene to the reaction solution leads to a good yield of o-diethylbenzene, the expected trapping product of biradical 20).The absence of products due to intramolecular hydrogen transfer indicates that this process is at least 1 or 2 orders of magnitude slower than hydrogen transfer in 17.At 500 deg C in the gas phase products due to hydrogen transfer begin to appear.
- Lockhart, Thomas P.,Comita, Paul B.,Bergman, Robert G.
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p. 4082 - 4090
(2007/10/02)
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- Alkyltrifluoromethanesulphonates as alkylating reagents for aromatic compounds
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Methyl and ethyl trifluoromethanesulphonates (' triflates '), prepared by conventional routes involving either trifluoromethanesulphonic acid (' triflic acid ') or its anhydride, contain traces of triflic acid as an impurity, which catalyse their alkylation reactions with aromatic compounds. Pure methyl triflate, obtained from reaction between CH3l and CFS03Ag, does not alkylate p-cymene after several hours at 100 °C. Pure ethyl triflate, prepared by a similar method, is thermally less stable under these conditions, and alkylation takes place only after long induction periods during which some breakdown to triflic acid occurs. With aromatic substrates such as p-cymene or mesitylene the onset of alkylation is followed rapidly by the formation of isomerisation and disproportionation products. Benzyl triflate, prepared from PhCH2Br and CF3SO3Ag, alkylates p-cymene even at room temperature. The strong Lewis acids SbF5 and AlCl3 similarly catalyse alkylation reactions of methyl and ethyl triflates, but BF3, FeCl3, and SnCl4 are much less effective.
- Booth, Brian L.,Haszeldine, Robert N.,Laali, Khosrow
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p. 2887 - 2893
(2007/10/02)
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