Copper hydrogens from

It can be prepared by the reduction of hot concentrated sulphuric acid by a metal. Copper is used since it does not also liberate hydrogen from the acid ... 

Apparently the alkoxy radical, R O , abstracts a hydrogen from the substrate, H, and the resulting radical, R" , is oxidized by Cu " (one-electron transfer) to form a carbonium ion that reacts with the carboxylate ion, RCO - The overall process is a chain reaction in which copper ion cycles between + 1 and +2 oxidation states. Suitable substrates include olefins, alcohols, mercaptans, ethers, dienes, sulfides, amines, amides, and various active methylene compounds (44). This reaction can also be used with tert-huty peroxycarbamates to introduce carbamoyloxy groups to these substrates (243). 

In metallurgy, hydrogen sulfide is used to precipitate copper sulfide from nickel—copper-containing ore leach solutions in Alberta, Canada, or to precipitate nickel and cobalt sulfides from sulfuric acid leaching oflaterite ores in Moa Bay, Cuba (120) (see Metallurgy, extractive metallurgy). 

Another method to hydrogenate butadiene occurs during an oxidation—reduction reaction in which an alcohol is oxidi2ed and butadiene is reduced. Thus copper—chromia or copper—2inc oxide cataly2es the transfer of hydrogen from 2-butanol or 2-propanol to butadiene at 90—130°C (87,88). 

The zinc metal is active enough to replace the hydrogen from the acid. Bubbles of hydrogen gas can be seen rising to the surface, and the piece of zinc is consumed. On the other hand, if the less active metal, copper, is placed into a hydrochloric acid solution, no reaction will take place. 

Marino, F. J. Cerrella, E. G. Duhalde, S. Jobbagy, M. Laborde, M. A., Hydrogen from steam reforming of ethanol. Characterization and performance of copper-nickel supported catalysts. International Journal of Hydrogen Energy 1998,23(12), 1095-1101. 

Extending partial copper passivation from one and two hydrogen atoms to three, one expects to obtain a fully passivated (Cu,H3) center. Strong support for the formation of such an electrically inactive center stems from hydrogenation experiments that have shown that the concentrations of all copper-related levels are reduced. Prolonged annealing in a vacuum regenerates the various level (Pearton, 1982). 

In the Cu/Ru system, ruthenium may function as a reservoir for atomic hydrogen, which is accessible via spillover to neighboring copper. Kinetically controlled spillover of hydrogen from ruthenium to copper (5) is consistent with the observed optimum reaction rate at an intermediate copper coverage. 

Worked Example 5.2. During the reductive formation of copper metal (from an aqueous solution of Cu " ), it is noticed that hydrogen gas is formed at the negative cathode, that is, in addition to the formation of a layer of fresh, pink copper metal. The volume of the gas at STP is 2.24 dm, and the overall electrochemical charge passed was 1.40 x 10 C. What is the electrolytic efficiency ... 

The metal is not strong enough to reduce H+ from acids to H2. Therefore, under ordinary conditions, copper metal does not liberate hydrogen from mineral acids. Copper can reduce Ag" ", Au6+, and Hg + ions that have greater positive E° values for reduction half reactions, thus displacing these metals from their aqueous solutions. 

All the internal monooxygenases that have so far been purified and characterized contain flavin coenzymes. The external hydrogen donors include reduced NAD, reduced NADP, ascorbic acid and sulfhydryl compounds. Cofactors required for the external monooxygenases are flavin, pteridine, copper, nonheme iron and heme as cytochrome P-450. In some monooxygenase reactions, enzymes and/or electron carrier systems other than monooxygenase itself are involved in the transfer of an electron or hydrogen from the external hydrogen donor to the cofactor involved. 

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