142-29-0Relevant articles and documents
Probing Ensemble Effects in Surface Reactions. 1. Site-Size Requirements for the Dehydrogenation of Cyclic Hydrocarbons on Pt(111) Revealed by Bismuth Site Blocking
Campbell, C. T.,Campbell, J. M.,Dalton, P. J.,Henn, F. C.,Rodriguez, J. A.,Seimanides, S. G.
, p. 806 - 814 (1989)
Catalytic reactions on bimetallic surfaces are often thought to be controlled by ensemble effects, whereby a side reaction requiring a large ensemble of active sites can be selectively suppressed by diluting the active metal with a second, inert metal.Unfortunately, the lack of knowledge of surface structure and the complications due to coexisting electronic effects have, until now, precluded accurate determinations of ensemble requirements for surface reactions.We analyze here applications of a new method for determining ensemble sizes that partially overcomes these obstacles and allows for semiquantitative assessment of ensemble effects.The method involves the controlled blocking of sites on a well-defined transition-metal surface with a dispersed overlayer of inert bismuth adatoms.The interactions of five cyclic hydrocarbones (cyclopentane, cyclohexane, cyclopentene, cyclohexene, and benzene) with Pt(111) have been studied in this way in an accompanying series of papers.In particular, the influence of Bi upon the competing dehydrogenation and desorption kinetics of these adsorbed molecules has been qualitatively measured.This present paper correlates the results for those five molecules and fits them with a simple kinetic model to extract the absolute ensemble requirements for the surface dehydrogenation reactions.The method and model may have applicability to a broad range of surface reactions.In addition, an effective ensemble requirement is defined, whose value is useful in predicting ensemble effects in catalysis.Trends in the value of kinetic parameters and the ensemble requirements with hydrocarbon character are discussed. The absolute ensemble requirements for the dehydrogenation of these adsorbed hydrocarbons are surprisingly large and indicate in some cases that at least six additional free Pt atoms are necessary for dehydrogenation (beyond those required for adsorption).Mechanistic implications of these results are discussed.
Structural distortions and dynamic behavior of the elusive "L"-shaped cis-bicyclo[3.3.0]octenyllithium: X-ray crystallographic and NMR studies
Fraenkel, Gideon,Chen, Xiao,Gallucci, Judith,Lu, Yan
, p. 4961 - 4965 (2007)
(Chemical Equation Presented) Substituted cis-bicyclo[3.3.0]octenyllithium prepared by addition of t-BuLi to 3-methylene-1,4-cyclooctadiene in the presence of TMEDA crystallizes as a dimer with one unsolvated Li+ sandwiched between the external faces of two allyl anions in a triple ion, and external to it the second Li+ is bidentately complexed to TMEDA, 8. Within each allyl unit, the allyl bonds have different lengths, and all four rings deviate from coplanarity which relieves strain in the rings despite introducing partial localization of the allyl anions. A similar structure prevails in solution as shown by 7Li NMR and the results of 7Li{1H} HOESY and 1H, 1H NOESY experiments. Carbon-13 NMR line shape changes indicate that the system undergoes a fast allyl bond shift concerted with conformation shifts of the out of plane carbons, ca. ΔG? = 9 kcal·mol-1. Cyclopentyllithium prepared by CH3Li cleavage of the trimethylstannyl derivative slowly undergoes an allowed ring opening to pentadienyllithium as well as deprotonating the solvent. The different behavior of dienylic lithium species is attributed to the relative separation of their termini.
An unusual cleavage of an energetic carbene [1]
Xu, Guopin,Chang, Tsong-Ming,Zhou, Jinglan,McKee, Michael L.,Shevlin, Philip B.
, p. 7150 - 7151 (1999)
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Freidlin,Polkownikow
, p. 1502; engl. Ausg. S. 1547 (1956)
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Allen et al.
, p. 3588 (1950)
SELECTIVE HYDROGENATION OF CYCLOPENTADIENE TO CYCLOPENTENE USING COLLOIDAL PALLADIUM SUPPORTED ON CHELATE RESIN.
Hirai,Komatsuzaki,Toshima
, p. 488 - 494 (1984)
Cyclopentadiene was hydrogenated to cyclopentene selectively by using colloidal palladium supported on chelate resin with iminodiacetic acid moieties as a catalyst. The hydrogenation rate was correlated to the polarity parameter, E//T(30) values, of the solvents used in the reaction, except in the case of dimethyl sulfoxide. The equilibrium constant for complex formation between cyclopentadiene and the catalyst, K//D, was estimated to be over 400 times larger than that between cyclopentene and the catalyst, K//E. A mechanism, including the coordination of olefins to the catalyst and the subsequent hydrogenation of the coordinated complexes, was proposed.
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Halberstadt,Chesick
, p. 2688 (1962)
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Characterization and reactivity of γ-Al2O3 supported Pd-Ni bimetallic nanocatalysts for selective hydrogenation of cyclopentadiene
Feng, Yi-Si,Hao, Jian,Liu, Wei-Wei,Yao, Yun-Jin,Cheng, Yue,Xu, Hua-Jian
, p. 709 - 713 (2015)
Abstract Several γ-Al2O3 supported Pd-Ni bimetallic nanocatalysts (Pd-Ni (x:y)/Al2O3; where x and y represent the mass ratio of Pd and Ni, respectively) were prepared by the impregnation method and used for selective hydrogenation of cyclopentadiene to cyclopentene. The Pd-Ni/Al2O3 samples were confirmed to generate Pd-Ni bimetallic nanoparticles by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The catalytic activity was assessed in view of the effects of different mass ratios of Pd and Ni, temperature, pressure, etc. Among all the samples, the Pd-Ni (1:1)/Al2O3 (PN-1:1) catalyst showed extremely high catalytic ability. The conversion of cyclopentadiene and selectivity for cyclopentene can be simultaneously more than 90%.
WagnerMeerwein Rearrangements of radical Cations Generated by Triphenylpyrylium Tetrafluoroborate Photosensitized Electron Transfer of Azoalkanes
Adam, Waldemar,Doerr, Markus
, p. 1570 - 1572 (1987)
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Mechanism of Formation of Grignard Reagents. Rate of Reaction of Cyclopentyl Bromide with a Rotating Disk of Magnesium
Root, Karen S.,Deutch, John,Whitesides, George M.
, p. 5475 - 5479 (1981)
Careful studies of the dependence of the rate of reaction (k) of cyclopentyl bromide in diethyl ether with the surface of rotating disk as a function of the angular lelocity (ω) of the disk confirm the relation k * ω1/2 expected for a mass-transfer limited reaction.More limited studies also indicate that the variations in this rate with other parameters are compatible with those expected for a mass-transfer limited reaction: k * (η)-5/6(ρ)1/6 (η is the shear viscosity of the solution and ρ is its density); k * D2/3 (D is the diffusion coefficient of the alkyl halide).
Diastereotopically Distinct. Secondary Deuterium Kinetic Isotope Effects on the Thermal Isomerization of Vinylcyclopropane to Cyclopentene
Baldwin, John E.,Villarica, Karla A.
, p. 7905 - 7908 (1994)
The (2'-deuterioethenyl)cyclopropanes isomerize to 3-deuteriocyclopentene at 341 deg C with kH/kD = 1.08 and 1.15 for the Z and E isomers, respectively.These normal effects are consistent with 2Z-penten-1,5-diyl diradical transition structures for the isomerization.
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Stock,Gunning
, p. 2295 (1960)
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Brown,H.C.,Knights,E.F.
, p. 4439 - 4444 (1968)
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Lepley
, p. 322 (1962)
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The thermal rearrangement of 6-methyl-6-vinylbicyclo[3.2.0]heptane
Glass, Timothy E.,Leber, Phyllis A.
, p. 1085 - 1088 (1990)
Gas-phase pyrolysis of theendo-vinyl epimer (1A) of the title compound at 275°C affords predominantly 3-(2-methyl-2-butenyl)cyclopentene (presumably the Z isomer), a direct [1,5]-hydrogen shift product, whereas the exo-vinyl epimer (IB) favors the fragmentation products, cyclopentene and isoprene.
Beck et al.
, p. 678 (1954)
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Steel et al.
, p. 679 (1964)
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GROUP 1 METAL ION CONTENT OF MICROPOROUS MOLECULAR SIEVE CATALYSTS
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Paragraph 0046-0047, (2020/05/28)
A catalyst comprising a microporous crystalline aluminosilicate having a Constraint Index less than or equal to 12, a Group 1 alkali metal or a compound thereof and/or a Group 2 alkaline earth metal or a compound thereof, a Group 10 metal or a compound thereof, and optionally a Group 11 metal or a compound thereof; wherein the total amount of Group 1 and/or Group 2 metal is present at a ratio that is optimized for the desirable chemical conversion process.
Preparation of Highly Active Monometallic Rhenium Catalysts for Selective Synthesis of 1,4-Butanediol from 1,4-Anhydroerythritol
Wang, Tianmiao,Tamura, Masazumi,Nakagawa, Yoshinao,Tomishige, Keiichi
, p. 3615 - 3626 (2019/07/15)
1,4-Butanediol can be produced from 1,4-anhydroerythritol through the co-catalysis of monometallic mixed catalysts (ReOx/CeO2+ReOx/C) in the one-pot reduction with H2. The highest yield of 1,4-butanediol was over 80 %, which is similar to the value obtained over ReOx–Au/CeO2+ReOx/C catalysts. Mixed catalysts of CeO2+ReOx/C showed almost the same performance, giving 89 % yield of 1,4-butanediol. The reactivity trends of possible intermediates suggest that the reaction mechanism over ReOx/CeO2+ReOx/C is similar to that over ReOx–Au/CeO2+ReOx/C: deoxydehydration (DODH) of 1,4-anhydroerythritol to 2,5-dihydrofuran over ReOx species on the CeO2 support with the promotion of H2 activation by ReOx/C, isomerization of 2,5-dihydrofuran to 2,3-dihydrofuran catalyzed by ReOx on the C support, hydration of 2,3-dihydrofuran catalyzed by C, and hydrogenation to 1,4-butanediol catalyzed by ReOx/C. The reaction order of conversion of 1,4-anhydroerythritol with respect to H2 pressure is almost zero and this indicates that the rate-determining step is the formation of 2,5-dihydrofuran from the coordinated substrate with reduced Re in the DODH step. The activity of ReOx/CeO2+ReOx/C is higher than that of ReOx–Au/CeO2+ReOx/C, which is probably related to the reducibility of ReOx/C and the mobility of the Re species between the supports. High-valent Re species such as Re7+ on the CeO2 and C supports are mobile in the solvent; however, low-valent Re species, including metallic Re species, have much lower mobility. Metallic Re and cationic low-valent Re species with high reducibility and low mobility can be present on the carbon support as a trigger for H2 activation and promoter of the reduction of Re species on CeO2. The presence of noble metals such as Au can enhance the reducibility through the activation of H2 molecules on the noble metal and the formation of spilt-over hydrogen over noble metal/CeO2, as indicated by H2 temperature-programmed reduction. The higher reducibility of ReOx–Au/CeO2 lowers the DODH activity of ReOx–Au/CeO2+ReOx/C in comparison with ReOx/CeO2+ReOx/C by restricting the movement of Re species from C to CeO2.
