Copper, catalytic action

The excess magnetite problem has been associated with the catalytic action of copper ions on the Schikorr reactionHence, inhibitors that will... 

The enzymes are protein molecules having globular structure, as a rule. The molecular masses of the different enzymes have values between ten thousands and hundred thousands. The enzyme s active site, which, as a rule, consists of a nonproteinic organic compound containing metal ions of variable valency (iron, copper, molybdenum, etc.) is linked to the protein globule by covalent or hydrogen bonds. The catalytic action of the enzymes is due to electron transfer from these ions to the substrate. The protein part of the enzyme secures a suitable disposition of the substrate relative to the active site and is responsible for the high selectivity of catalytic action. 

The additional protection given to nylon by antioxidants has already been mentioned. Since the need is to protect against oxidation by free radicals, antioxidants are essentially of two types peroxide decomposers and radical scavengers. Reviews of these products are available [409,410,413] these should be consulted for details of the mechanisms involved. Peroxide decomposer types include compounds of manganese (II) or copper(I) and copper(II) complexes, such as azomethine bridge derivatives of the type represented by 10.160, of which numerous water-soluble or water-insoluble variants are possible [409]. These products have a catalytic action and are therefore used in very small amounts. 

For the copper-induced decomposition of diazodiphenylmethane in acetonitrile, a fundamental difference in the catalytic action of Cu C104 and Cu ClO was detected. Whilst with CuC104, intermediary copper carbenoids are believed to be responsible for the mainly formed benzophenone azine402, CufClO initiates a chain reaction, promoted by radical cations and yielding mainly tetraphenylethene... 

The following kinetic scheme was suggested to explain these results on the catalytic action of the copper surface in the presence of antioxidant InH [12]. 

Synthesis of organosilanes from silicon and RC1 is facilitated if a silicon-copper alloy is employed 96 The catalytic action of the copper is due to the formation of CuCl, which then reacts with silicon to form SiCl2 ... 

In 1884, Sandmeyer, however, made the important discovery that in the presence of the corresponding cuprous salt chlorine and bromine are also directed to the nucleus. This catalytic action has not yet been explained. Perhaps a double salt is formed, or else a complex salt in which the halogen is more firmly bound than in the simple halide. According to Gattermann, the cuprous salt may be replaced by copper powder. In general, the decomposition of labile diazo-compounds, by elimination of elementary nitrogen, is accelerated by copper. 

Conventionally, organometallic chemistry and transition-metal catalysis are carried out under an inert gas atmosphere and the exclusion of moisture has been essential. In contrast, the catalytic actions of transition metals under ambient conditions of air and water have played a key role in various enzymatic reactions, which is in sharp contrast to most transition-metal-catalyzed reactions commonly used in the laboratory. Quasi-nature catalysis has now been developed using late transition metals in air and water, for instance copper-, palladium- and rhodium-catalyzed C-C bond formation, and ruthenium-catalyzed olefin isomerization, metathesis and C-H activation. Even a Grignard-type reaction could be realized in water using a bimetallic ruthenium-indium catalytic system [67]. 

In this special field, earlier work had been done in other laboratories, such as by the Schering Company, Berlin (36), and by Ipatieff (37) in connection with his work on the hydrogenation of camphor and of other organic compounds. At both places, the favorable effect of alkali oxides and earth alkali oxides on nickel, cobalt and copper has been investigated. Similarly, Paal and his coworkers (38) have used a palladium-aluminum hydroxide catalyst in 1913 for the hydrogenation of double bonds. Bedford and Erdman (39) had reported that the catalytic action of nickel oxide is enhanced by the oxides of aluminum, zirconium, titanium, calcium, lanthanum, and magnesium. 

Infrared spectra of propene and isobutene on different catalysts were measured by Gorokhovatskii [143]. Copper oxide, which converts olefins to butadiene and aldehydes, shows adsorption complexes different from structures on a V2Os—P2Os catalyst which produces maleic acid anhydride. Differences also exist between selective oxidation catalysts and total oxidation catalysts. The latter show carbonate and formate bands, in contrast to selective oxides for which 7r-allylic species are indicated. A difficulty in this type of work is that only a few data are available under catalytic conditions most of them refer to a pre-catalysis situation. Therefore it is not certain that complexes observed are relevant for the catalytic action. 

Although the accelerator compounds can form copper complexes at sufficiently high pH values,167 171 it is unlikely that the catalytic action operates by a simple exchange mechanism such as... 

Organic Catalysts. III. The Catalytic Action of Copper-Iron Polyphthalocyanine... 

The noble metals and their oxides, especially palladium, are used chiefly as promoters of other catalysts. Small amounts of palladium, less than 1%, greatly increase the catalytic action of copper oxide for the combustion of CO near room temperature (58). Hurst and Rideal (59) found that a copper catalyst activated by Pd showed increased adsorption of CO and also increased the ratio of oxidized CO to oxidized H2 when the combustion was carried out in a mixture of these gases containing 02. 

An interesting observation has been made by Palmer 9 in connexion with the catalytic action on ethyl alcohol and isopropyl alcohol of metallic copper. When produced by the reduction of copper oxide, the metal was found to be active in promoting catalysis of ethyl alcohol to acetaldehyde but electrolytic copper was without effect on either alcohol. 

The decarboxylation of copper perfluorobenzoate in quinoline gives (CuQF5) . The catalytic action of copper or copper salts on decarboxylation reactions of carboxylic acids presumably involves organo intermediates. 

Prior to the hydrolysis of the ester mentioned above, Hatano, Nozawa, Ikeda and Yamamoto (29) studied the catalytic action of poly(S-lysine) (PEL) - copper(II) complex for the oxidation of 3,4-dihydroxyphenylalanine (DOPA) to the corresponding quinone. 

Potassium chlorate begins to decompose at about 70 0 by the catalytic action of metal oxides manganese dioxide, copper oxides etc. produce oxygen. The reaction actively progresses over 100 C. FeClj, CUCI2, Cr Oj and KiCriOy also promote the reaction. 

Summary The question of the nature of the catalytically active copper species in Rochow contact masses has been investigated using the SEM/EDX technique. The results do not support the hypothesis of active ri-CusSi, but they provide more direct evidence for the existence and the catalytic action of X-ray amorphous Cu-Si surface species, i.e., extremely dispersed particles or even two-dimensional species like Cu Si surface compounds, which we proposed recently. The investigation of zinc-promoted and non-promoted contact masses on basis of the pure and technical-grade silicon showed that the mode of operation of the famous Rochow promoter zinc can be understood rather as a moderation than as a real acceleration. By moderating the initial reaction rate, the promoter enables a sufficiently high stationarity of the reaction. 

Introduction. In the preceding experiment it was shown that an aqueous solution of a diazonium salt treated with a solution of an alkali iodide gives iodobenzene. The replacement of the diazo group, N2X, by chlorine or bromine atoms involves the catalytic action of copper salts. Thus, benzenediazonium chloride warmed with a solution of cuprous chloride and hydrochloric acid gives chlorobenzene with cuprous bromide, bromobenzene is formed. The use of the cuprous salt is known as the Sandmeyer method. Instead of cuprous salts, finely divided copper may be used according to Gatterman s method. 

The catalytic action of the cuprous salts is assumed to depend on the formation of addition compounds which aid in the elimination of nitrogen and direct the halogen to the nucleus. In the Sandmeyer method the diazonium salt solution is added to a freshly prepared solution of the cuprous halide at a temperature below 10°. The mixture is then warmed until the evolution of nitrogen ceases. In some cases better yields are obtained if the diazonium solution is added slowly to a boiling solution of the cuprous salt. In the Gatterman method the desired diazonium salt is prepared. In the case of bromide and iodide, the diazonium sulfate is prepared and is mixed with an excess of potassium bromide or iodide. Finely divided copper is added and the mixture is warmed until the evolution of nitrogen ceases. The finely divided copper may be prepared by adding zinc dust to copper sulfate solution. The object of this experiment is to illustrate both methods. For semimicro work either chlorobenzene or o-chlorotoluene may be used. 

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