Catalysi, Raney nickel

Even though zeolites and porous glasses are materials that allow coveting two orders of magnitude in pore diameter, they remain silica based. A complete description of the role of the confining material in radiolysis would require the access to alternative porous materials. The development of metallic porous frameworks has been studied for catalysis (Raney Nickel), electrochemistry and heat dissipation. 

Rigorous hydrogenating conditions, particularly with Raney Nickel, remove the sulfur atom of thiophenes. With vapor-phase catalysis, hydrodesulfurization is the technique used to remove sulfur materials from cmde oil. Chemically hydrodesulfurization can be a valuable route to alkanes otherwise difficult to access. 

P. Gallezot, P.J. Cerino, B. Blanc, G. Fleche and P. Fuertes, Glucose Hydrogenation on Promoted Raney-Nickel Catalysts, Journal of Catalysis 146 (1994) 93. 

The enantioselective hydrogenation of prochiral substances bearing an activated group, such as an ester, an acid or an amide, is often an important step in the industrial synthesis of fine and pharmaceutical products. In addition to the hydrogenation of /5-ketoesters into optically pure products with Raney nickel modified by tartaric acid [117], the asymmetric reduction of a-ketoesters on heterogeneous platinum catalysts modified by cinchona alkaloids (cinchonidine and cinchonine) was reported for the first time by Orito and coworkers [118-121]. Asymmetric catalysis on solid surfaces remains a very important research area for a better mechanistic understanding of the interaction between the substrate, the modifier and the catalyst [122-125], although excellent results in terms of enantiomeric excesses (up to 97%) have been obtained in the reduction of ethyl pyruvate under optimum reaction conditions with these Pt/cinchona systems [126-128],... 

Source Compiled from S.R. Montgomery, Functional group activity of promoted Raney nickel catalysts, in Catalysis of Organic Reactions, W.R. Moser, Ed., Marcel Dekker, New York, 1981, pp. 383-409. 

Moderate to good enantioselectivities were obtained for nearly all examples, but the products from 83a-c could be recrystallized to higher enantiomeric purity. Addition of iodine was critical for catalysis as was the use of a ligand with electron-poor para-fluorophenyl groups on the phosphorous atom. Substitution at the 3 position of the pyridine ring was described as being difficult for both the quinolines and pyridine systems. The resulting hydrazine derivatives could be easily converted to piperdines by reduction with Raney nickel or under Birch conditions. 

Another major industrial use of nickel is in catalysis. Nickel and raney nickel are used in catalytic hydrogenation or dehydrogenation of organic compounds including olefins, fats, and oils. 

Izumi, Y, Akabori, S., Fukawa, H., Tatumi, S., Imaida, N, Fukuda, T, Komatu, S. Asymmetric Hydrogenation with Modified Raney Nickel. Proc. Third Intern. Congr. Catalysis. Volume II, p. 1364. Amsterdam North Holland Publ. Comp. 1965. 

Surface area, pore size, and pore volume are among the most fundamentally important properties in catalysis because the active sites are present or dispersed throughout the internal surface through which reactants and products are transported. The pores are usually formed by drying or calcining precipitates of hydrous oxides however, some materials possess porosity naturally, as in the case of carbons, natural zeolites, and others. Raney nickel catalysts... 

The transformations that use asymmetric heterogeneous catalysis will be highlighted P-keto esters and diketone reductions by Raney nickel catalyst modified with R,R-tartaric acid and NaBr. a-Keto acid reductions with cinchona modified Pt catalysts are discussed in Chapter 18. 

Heterogeneous catalysis The heterogeneous catalyst, either the finely dispersed metal itself or the metal adsorbed onto a support, remains in a separate phase during the course of reaction. Examples of hydrogenation of alkenes given below include reduction of oleic acid (6.1) with H2 and Pd-C to octadecanoic acid (6.2) and cinnamyl alcohol (6.3) and Raney nickel in ethanol to 3-phenyl-l-propanol (6.4). 

Scheme 10.8 Quantitative analysis of the product ee-values obtained by the hydrogenation of P-ketoesters over the tartaric acid-NaBr-modified Raney nickel. Factor-/ indicates the intrinsic enantioselective ability of the tartaric acid-modified sites, and E and N indicate the contribution of the enantioselective catalysis sites and nonenantioselective hydrogenation sites, respectively.

Dianhydrides react with other nucleophilic or electrophilic reagents in a steric course similar to that operating with water under basic or acid catalysis, to give amino, halogeno, and thio derivatives (see Sects. VI and VII). Catalytic reduction in the presence of Raney nickel,540,746 or with lithium aluminum hydride,155 331 affords the mono-155 331 746 and di-746 deoxy derivatives of 1,6-anhydrohexoses (see Sect. VII,3,a,ii). 

Substances such as X are called catalysts, and the process of lowering the activation energy of a reaction is catalysis. Catalysis is a pretty common phenomenon in chemistry and finds much application, both in the laboratory and in commerce. Catalytic cracking of oil to give petrol and other derivatives, or the use of Raney nickel as a catalyst in the reduction of oils, saturating their double bonds and turning them into fats such as margarine, are well-known processes. 

F. Hochard, H. Jobic, G. Clugnet, A.J. Renouprez J. Tomkinson (1993). Catalysis Letters, 21, 381-389. Inelastic neutron scattering study of acetonitrile adsorbed on Raney nickel. 

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