Catalysis/catalytic

Catalysis. Catalytic properties of the activated carbon surface are useful in both inorganic and organic synthesis. For example, the fumigant sulfuryl fluoride is made by reaction of sulfur dioxide with hydrogen fluoride and fluorine over activated carbon (114). Activated carbon also catalyzes the addition of halogens across a carbon—carbon double bond in the production of a variety of organic haUdes (85) and is used in the production of phosgene... 

Catalytic Oxidization. A principal technology for control of exhaust gas pollutants is the catalyzed conversion of these substances into innocuous chemical species, such as water and carbon dioxide. This is typically a thermally activated process commonly called catalytic oxidation, and is a proven method for reducing VOC concentrations to the levels mandated by the CAAA (see Catalysis). Catalytic oxidation is also used for treatment of industrial exhausts containing halogenated compounds. 

Catalysis Catalytic reagents (as selective as possible) are superior to stoichiometric reagents. 

J.M. Hermann, in F. Jansen, R.A. van Santen, Eds., Water Treatment by Hetemgeneous Photocatalysis in Envimnmental Catalysis, Catalytic Science Series, Vol. 1, Imperial College Press, London, 1999, chap. 9, pp. 171-194. 

The combined use of the modem tools of surface science should allow one to understand many fundamental questions in catalysis, at least for metals. These tools afford the experimentalist with an abundance of information on surface structure, surface composition, surface electronic structure, reaction mechanism, and reaction rate parameters for elementary steps. In combination they yield direct information on the effects of surface structure and composition on heterogeneous reactivity or, more accurately, surface reactivity. Consequently, the origin of well-known effects in catalysis such as structure sensitivity, selective poisoning, ligand and ensemble effects in alloy catalysis, catalytic promotion, chemical specificity, volcano effects, to name just a few, should be subject to study via surface science. In addition, mechanistic and kinetic studies can yield information helpful in unraveling results obtained in flow reactors under greatly different operating conditions. 

Chirality plays a central role in the chemical, biological, pharmaceutical and material sciences. Owing to the recent advances in asymmetric catalysis, catalytic enantioselective synthesis has become one of the most efficient methods for the preparation of enantiomer-ically enriched compounds. An increased amount of enantiomerically enriched product can be obtained from an asymmetric reaction using a small amount of an asymmetric catalyst. Studies on the enantioselective addition of dialkylzincs to aldehydes have attracted increasing interest. After the chiral amino alcohols were developed, highly enantioselective and reproducible —C bond forming reactions have become possible. 

Specificity of conventional protein enzymes is provided by precise molecular fit. The mutual recognition of an enzyme and is substrate is the result of various intermolecular forces which are almost always strongly dominated by hydrophobic interaction. In contrast, specificity of catalytic RNAs is provided by base pairing (see for example the hammerhead ribozyme in Figure 1) and to a lesser extent by tertiary interactions. Both are the results of hydrogen bond specificity. Metal ions too, in particular Mg2+, are often involved in RNA structure formation and catalysis. Catalytic action of RNA on RNA is exercised in the cofolded complexes of ribozyme and substrate. Since the formation of a ribozyme s catalytic center which operates on another RNA molecule requires sequence complementarity in parts of the substrate, ribozyme specificity is thus predominantly reflected by the sequence and not by the three-dimensional structure of the isolated substrate. 

Thus, the accumulation of chemical energy of the reaction in the form of highly active intermediate compounds happens with the energy consumption. For this purpose photosensibilization, light exposure (photochemical reactions), catalysis (catalytic decay) and chemical induction (couples processes) are used. 

Shilov devoted his review [12] to the development of selective and non-waste processes. He discusses the questions of organized molecular system (or ensembles) construction. Note that in the case of usual catalysis, catalytic sites freely interact with substrate molecules. This process is characterized by the absence of complementary activity. This is the reason for the relatively low selectivity of catalytic reactions. However, from positions of applied catalysis, such a catalytic system possesses clear advantages ... 

Attempts to support models of the catalytic activity and the operative mechanism with results of theoretical considerations have been reported for the oxygen reduction [iii] and hydrogen oxidation [iv]. Electrocatalytic electrodes are indispensable parts of fuel cells [v]. A great variety of electrocatalytic electrodes has been developed for analytical applications [vi]. See also electro catalysis, catalytic current, -> catalytic hydrogen evolution, catalymetry. 

Such studies, when well designed, provide for a more fundamental understanding of catalysis. Catalytic concepts and models are thereby developed and "catalysts by design" come within the realm of reality. This area of catalyst characterization is exciting, complex and requires researchers of many talents. This is where the issue of true fundamental interest, the structure and associated energetics of the transition state should be identified as a major challenge. 

Photo-assisted catalysis Catalytic reaction involving production of a catalyst by absorption of light. 

These hydroxy-1,1 -binaphthyl functionalised NHC ligands can be used in asynunetric catalysis. Catalytic reagents performed with transition metal catalysts carrying these ligands include olefin metathesis [19,80,86], allylic alkylation [17,18,88] and hydrosilylation of ketones [85]. 

Matros, Y. S. (Ed.), Studies in Surface Science and Catalysis Catalytic Processes under Unstoady-Stato Conditions, Vol. 43. Elsevier. Amsterdam, 1989. 

The use of CeOs-based materials in catalysis has attracted considerable attention in recent years, particularly in applications like environmental catalysis, where ceria has shown great potential. This book critically reviews the most recent advances in the field, with the focus on both fundamental and applied issues. The first few chapters cover structural and chemical properties of ceria and related materials, i.e. phase stability, reduction behaviour, synthesis, interaction with probe molecules (CO. O2, NO), and metal-support interaction — all presented from the viewpoint of catalytic applications. The use of computational techniques and ceria surfaces and films for model catalytic studies are also reviewed. The second part of the book provides a critical evaluation of the role of ceria in the most important catalytic processes three-way catalysis, catalytic wet oxidation and fluid catalytic cracking. Other topics include oxidation-combustion catalysts, electrocatalysis and the use of cerium catalysts/additives in diesel soot abatement technology. 

See also catalysis catalytic coefficient intramolecular catalysis pseudocatalysis specific catalysis. 

Silva, A.L. Bordado, J.C. Recent developments in pol)airethane catalysis catalytic mechanisms review. Catal. Rev. 2004, 46 (1), 31-51. 

By comparison with the intensively investigated syntheses of low molecular weight compounds by biphasic catalysis, catalytic polymerization in aqueous systems has received less attention. This is somewhat surprising, as polymerization in aqueous systems offers unique advantages, as illustrated by the large-scale applications of free-radical emulsion and suspension polymerization. 

The catalytic reactions of interest in organic synthesis can conveniently be divided into five categories solid-acid catalysis, solid-base catalysis, catalytic hydrogenation and dehydrogenation, catalytic oxidation, and catalytic C-C bond formation. 

C. Zerner, Michael J. Scott and C. Russell Bowers. He then joined Michael B. Hall s research group at Texas A M University and is currently an Assistant Research Scientist. His research focuses on using theoretical and computational chemistry to research and answer questions in a variety of areas, including biological enzyme catalysis, catalytic and stoichiometric mechanisms of bond activation and functionalization of organic molecules by organometallic transition metal complexes, and the elucidation of structure and bonding of various compounds of interest. 

This section is not concerned with transition metal catalysis. Catalytic activation of organic reactions by Lewis acids is a wide field of investigation [6]. It is usually preferred to other activation modes merely for commodity reasons. The idea of simultaneous use of pressure and traditional Lewis acid catalysts has been recognized for some time [7]. Curiously, the method was only developed in the last decade [8]. It was observed that coupling of both activation methods was beneficial in all [4 + 2] cycloadditions examined. However, most classical hard Lewis acids (AICI3, TiCU, SnCU, ZnCl2. ..) present a number of inherent problems such as... 

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