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排序方式: 共有142条查询结果,搜索用时 0 毫秒
1.
Josep Castells Elisabet Duñach Fernando Geijo Francisco López-Calahorra Margarita Prats Olga Sanahuja Laura Villanova 《Tetrahedron letters》1980,21(23):2291-2294
Triethylamine catalyzed Michael additions of benzoins to chalcone can prevail over the expected Michael-Stetter additions when certain thiazolium ion conjugate bases - prepared from the pertinent thiazolium salts and triethylamine- are used as catalysts. 相似文献
2.
Gunnarsson M Abbas Z Ahlberg E Nordholm S 《Journal of colloid and interface science》2004,274(2):563-578
Statistical mechanics has been used to derive a model for the charging of a spherical particle in a salt solution to complement our experimental studies and gain a deeper understanding of the processes involved in surface complexation. Our chosen model goes beyond the equilibrium constants and the Gouy-Chapmann theory currently used in surface complexation models. The proton adsorption is taken to occur at a harmonic potential well on the surface characterized by a frequency v and a well depth u(0). Outside the particle surface there is a capacitor layer of width w(c) which is impenetrable to the salt ions. The diffuse screening of the charged particle is described by a corrected Debye-Hückel analysis accounting for ion size in the ion-ion interactions. To account also for nonlinear electrostatic response a layer of condensed counterions has been introduced. The criterion for the onset of ion condensation is that the electrostatic field exceeds a linear response criterion. Ion size effects are accounted for in terms of hole-corrected electrostatic energies and excluded volume. The model has been applied to titrated surface charge data on goethite (alpha-FeOOH) at various background concentrations and good agreement between the experimental data and the model was obtained. Both the size of the screening ions and the central particle size were shown to be of importance for the surface charge. 相似文献
3.
Metal‐Triflate‐Catalyzed Synthesis of Polycyclic Tertiary Alcohols by Cyclization of γ‐Allenic Ketones 下载免费PDF全文
Ilhem Diaf Dr. Gilles Lemière Dr. Elisabet Duñach 《Angewandte Chemie (International ed. in English)》2014,53(16):4177-4180
It has been established that bismuth(III) triflate catalyzes the cyclization of γ‐allenic ketones under mild reaction conditions. This reaction allows the selective formation of polycyclic tertiary alcohols from cyclic ketone derivatives. The resulting dienols can engage in stereoselective cycloadditions to efficiently afford complex polycyclic systems. 相似文献
4.
Elisabet Öberg Andreas Orthaber Marie-Pierre Santoni Fredrick Howard Sascha Ott 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-3):152-158
Abstract Attempts to utilize C-ethylenic phosphaalkenes in metathesis reactions are discussed. Unprecedented reactivity is observed where the vinylphosphaalkene undergoes the first step of the catalytic cycle and cross-metathesis with the phenylmethylene moiety of Grubbs 2nd generation catalyst. However, homo-metathesis reaction to form 1,6-diphosphahexa-1,3,5-triene is not observed, presumably due to steric constraints. 相似文献
5.
MaxwellD. Cummings Jimmy Lindberg Tse‐I Lin Herman deKock Oliver Lenz Elisabet Lilja Sara Fellnder Vera Baraznenok Susanne Nystrm Magnus Nilsson Lotta Vrang Michael Edlund sa Rosenquist Bertil Samuelsson Pierre Raboisson Kenneth Simmen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2010,122(9):1552-1552
6.
Jirkovský JS Panas I Ahlberg E Halasa M Romani S Schiffrin DJ 《Journal of the American Chemical Society》2011,133(48):19432-19441
A novel strategy to direct the oxygen reduction reaction to preferentially produce H(2)O(2) is formulated and evaluated. The approach combines the inertness of Au nanoparticles toward oxidation, with the improved O(2) sticking probability of isolated transition metal "guest" atoms embedded in the Au "host". DFT modeling was employed to screen for the best alloy candidates. Modeling indicates that isolated alloying atoms of Pd, Pt, or Rh placed within the Au surface should enhance the H(2)O(2) production relative to pure Au. Consequently, Au(1-x)Pd(x) nanoalloys with variable Pd content supported on Vulcan XC-72 were prepared to investigate the predicted selectivity toward H(2)O(2) production for Au alloyed with Pd. It is demonstrated that increasing the Pd concentration to 8% leads to an increase of the electrocatalytic H(2)O(2) production selectivity up to nearly 95%, when the nanoparticles are placed in an environment compatible with that of a proton exchange membrane. Further increase of Pd content leads to a drop in H(2)O(2) selectivity, to below 10% for x = 0.5. It is proposed that the enhancement in H(2)O(2) selectivity is caused by the presence of individual surface Pd atoms surrounded by gold, whereas surface ensembles of contiguous Pd atoms support H(2)O formation. The results are discussed in the context of exergonic electrocatalytic H(2)O(2) synthesis in Polymer Electrolyte Fuel Cells for the simultaneous cogeneration of chemicals and electricity, the latter a credit to production costs. 相似文献
7.
8.
Elisabet Öberg Sascha Ott 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-3):164-167
Abstract Bis(trimethylsilyl)-terminated C,C-diacetylenic phosphaalkene was prepared from Mes*PCl2 and a propargylic Grignard reagent that in turn was formed from 3-bromo-1,5-bis(trimethylsilyl)penta-1,4-diyne and Rieke-Mg. 相似文献
9.
Maxwell D. Cummings Jimmy Lindberg Tse‐I Lin Herman de Kock Oliver Lenz Elisabet Lilja Sara Felländer Vera Baraznenok Susanne Nyström Magnus Nilsson Lotta Vrang Michael Edlund Åsa Rosenquist Bertil Samuelsson Pierre Raboisson Kenneth Simmen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2010,122(19):3320-3320
10.
Alexander Björling Elisabet Ahlberg Juan M. Feliu 《Electrochemistry communications》2010,12(3):359-361
Electrochemical oxygen adsorption/desorption below monolayer level leads to a disordering of platinum single-crystal surfaces vicinal to the (1 1 1) plane. The kinetics can be described by means of a consecutive reaction from (1 1 1)-terrace sites to (1 1 0)-defect sites, in which (1 0 0)-defects act as intermediates. The first oxidation of the electrode reflects independent contributions from terrace and step sites, the latter being structure sensitive. Oxygen adsorption charges amount to a mean value of one electron per step site. 相似文献