Hydrogenations and Reductions

Some further reductions and hydrogenations leading to ring-opened products are mentioned in Sections VII.B. 1 and VII.B.5. 

Sljukic B, Bank CE, Compton RG (2004) The search for stable and efficient sonoelectroca-talysts for oxygen reduction and hydrogen peroxide formation azobenzene and derivatives. Phys Chem Chem Phys 6 4034-4041... 

A. A. Tsygankov, L. T. Serebryakova, K. K. Rao, D. O. Hall (1998) Acetylene reduction and hydrogen photoproduction by wild type and mutant of Anabaena at different CO2 and O2 concentrations.FEMS Microbiol. Lett., 167 13-17. 

F. Fischer and H. Tropsch, Reduction and hydrogenation of carbon monoxide, Brennst-ojf-Chem., 1926, 7, 299-300. 

Figure 15.8 Oxygen reduction and hydrogen oxidation electrode reactions (standard conditions, on shiny platinum).

The compound 77 proved to be a key intermediate for further synthesis in this field. Indeed, ( )-y-lycorane (87) was obtained from 77 through the acid lactam 80. The latter, on treatment with acetic anhydride, gave the imide 86 readily converted upon LiAlH4 reduction and hydrogenation into 87 (10). 

In an alkaline medium, oxygen reduction and hydrogen oxidation involve OH- ions. The OH-species formed by the cathodic reduction of oxygen move through the electrolyte to the anode, where recombination with hydrogen, oxidized at the anode, produces water. 

Electrochemical studies of the oxygen reduction and hydrogen oxidation were conducted using the P-5848 potentiostate in a 0.5 M solution of sulphuric acid in an oxygen- or hydrogen-saturated atmosphere [1, 3, 5]. 

Rodriguez MM, Bill E, Brennessel WW, Holland PL. N(2) reduction and hydrogenation to ammonia by a molecular iron-potassium complex. Science. 2011 334 780-3. 

Dissimilar metals. Galvanic corrosion occurs when two metals with different electrochemical potentials are in contact in the same solution [Figures 6.7 and 6.8]. In both cases, the corrosion of iron (steel) is exothermic and the cathodic reaction is controlling the corrosion rate. The more noble metal, copper increases the corrosion through cathodic reaction of hydrogen ion reduction and hydrogen evolution A passive oxide film on stainless steel for example can accelerate hydrogen reduction reaction. 

For fuel-cell technology development, it has been important to understand the characteristics and operation of highly dispersed platinum and platinum alloy electrocatalysts. A series of papers on platinum crystallite size determinations in acid environments for oxygen reduction and hydrogen oxidation was published together by Bert, Stonehart, Kinoshita and co-workers.5 The conclusion from these studies was that the specific activity for oxygen reduction on the platinum surface was independent of the size of the platinum crystallite and that there were no crystallite size effects. 

Reductions of chalcogenopyrylium ions that are not the result of a nucleophilic attack, such as one-electron reductions and hydrogenation reactions, are discussed in this section. 

A mixed electrochemical reaction with a mixed potential difference, inevitably of reduced output. Detailed consideration of the breakdown of the oxygen reduction and hydrogen oxidation paths would be involved in a calculation, including any chemically irreversible cul-de-sacs, such as platinum particles insulated from the electrode, which catalyse irreversible combustion rather than reversible electrochemical oxidation. 

Coking, widely experienced in the catalysis of hydrocarbon conversion (7), can deactivate both metallic and acid catalytic sites for hydrocarbon reactions (2). Accumulation of such carbonaceous deposits affects selectivity in hydrocarbon conversion (5). Adsorbed ethene even inhibits facile o-p-Hj conversion over Ni or Pt (4 ), the surface of which it appears is very nearly covered at lower temperatures in such deposits. H spillover may enhance hydrocarbonaceous residue formation (6). Accumulated carbonaceous residues can be removed by temperature programmed oxidation, reduction and hydrogenation TPO, TPR, TPH, etc (7) as part of catalyst regeneration. 

To investigate the effect of micropores, we conducted electrolyses using the following catalysts, unmodified ACF, iron and nickel catalysts supported on non-activated carhon fibers (CF/Fe, CF/Ni), iron catalyst supported on activated carhon fibers (ACF/Fe) and two types of nickel catalysts supported on activated carbon fibers (ACF/Ni-1, ACF/Ni-2). Table 1 shows the reduction product distributions for the various catalysts at -1.8V vs. SCE. The ACF catalyst itself has very fittle activity for CO2 reduction, and hydrogen evolution was the principal reaction. The CF/Fe and CF/Ni catalysts showed very little activity as well. 

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