Copper reduction potential

Divalent copper, cobalt, nickel, and vanadyl ions promote chemiluminescence from the luminol—hydrogen peroxide reaction, which can be used to determine these metals to concentrations of 1—10 ppb (272,273). The light intensity is generally linear with metal concentration of 10 to 10 M range (272). Manganese(II) can also be determined when an amine is added to increase its reduction potential by stabili2ing Mn (ITT) (272). Since all of these ions are active, ion exchange must be used for deterrnination of a particular metal in mixtures (274). 

Copper compounds, which represent only a small percentage of ah copper production, play key roles ia both iadustry and the biosphere. Copper [7440-50.8] mol wt = 63.546, [Ar]3/°4.t is a member of the first transition series and much of its chemistry is associated with the copper(II) ion [15158-11-9] [Ar]3i5. Copper forms compounds of commercial iaterest ia the +1 and +2 oxidation states. The standard reduction potentials, for the reasonably attainable valence states of copper are... 

Oxidation-reduction potential Because of the interest in bacterial corrosion under anaerobic conditions, the oxidation-reduction situation in the soil was suggested as an indication of expected corrosion rates. The work of Starkey and Wight , McVey , and others led to the development and testing of the so-called redox probe. The probe with platinum electrodes and copper sulphate reference cells has been described as difficult to clean. Hence, results are difficult to reproduce. At the present time this procedure does not seem adapted to use in field tests. Of more importance is the fact that the data obtained by the redox method simply indicate anaerobic situations in the soil. Such data would be effective in predicting anaerobic corrosion by sulphate-reducing bacteria, but would fail to give any information regarding other types of corrosion. 

Fig. 3. Evans-diagram for the cementation of Cu2+ and Pb2 with zinc amalgam of different zinc content. If the zinc concentration in the mercury employed for this special extraction technique is low, the anodic zinc-dissolution current density may be diffusion controlled and below the limiting cathodic current density for the copper reduction. The resulting mixed potential will lie near the halfwave potential for the reaction Cu2+ + 2e j Cu°(Hg) and only Cu2 ions are cemented into the mercury.

A student was given a standard Cu(s) Cu2+(aq) half-cell and another half-cell containing an unknown metal M immersed in 1.00 M M(NO,)2(aq). When the copper was connected as the anode at 25°C, the cell emf was found to be —0.689 V. What is the reduction potential for the unknown M2+/M couple ... 

The table of standard reduction potentials assists in the determination as to whether species can react with each other, or not. This can be substantiated by considering the reaction of hydrogen with two metals, copper and zinc. In order to determine whether or not a reaction takes place spontaneously under standard conditions, one calculates the standard potential using hydrogen ions and the metal as reactants. 

We focus here on the use of oxygenases, particularly the blue copper oxygenases, such as laccase and bilirubin oxidase, which can biocatalytically reduce oxygen directly to water at relatively high reduction potentials under mild conditions. First, however, we will briefly consider reports on the use of hydrogen peroxide as an oxidant in biocatalytic fuel cells. 

Co-immobilization of this redox polymer with a fungal laccase from Trametes versicolor, possessing a Tl copper site reduction potential of +0.57 V vs Ag/AgCl ( +0.77 vs NHE), was achieved using a diepoxide cross-linker, in an approach... 

When water is electrolyzed with copper electrodes or using other common metals, the amount of 02(g) is less than when Pt electrodes are used, but the amount of H2(g) produced is independent of electrode material. Why does this happen In electrolysis, the most easily oxidized species is oxidized and the most easily reduced species is reduced. If we compare Cu and H20 by looking on the standard reduction potentials chart (data given below), we see that Cu is a stronger reducing agent than H20, because 0.337 V is less than 0.828 V. This means that Cu is more easily oxidized than water. 

Type II copper enzymes generally have more positive reduction potentials, weaker electronic absorption signals, and larger EPR hyperfine coupling constants. They adopt trigonal, square-planar, five-coordinate, or tetragonally distorted octahedral geometries. Usually, type II copper enzymes are involved in catalytic oxidations of substrate molecules and may be found in combination with both Type I and Type III copper centers. Laccase and ascorbate oxidase are typical examples. Information on these enzymes is found in Tables 5.1, 5.2, and 5.3. Superoxide dismutase, discussed in more detail below, contains a lone Type II copper center in each of two subunits of its quaternary structure. 

Reduction always occurs at the cathode. Note that H°ed for silver is +0.7991 volt, according to the Table of Standard Reduction Potentials. E°ed for copper is +0.337. This means that the copper metal is higher in the activity series than the silver metal, so copper metal will reduce the silver ion. The equation that describes reduction (or the cathode reaction) is therefore... 

For a Daniell cell, you know that copper is the cathode and zinc is the anode. The relevant half-reactions and standard reduction potentials from Table 11.1 are as follows. 

Blue copper proteins, 36 323, 377-378, see also Azurin Plastocyanin active site protonations, 36 396-398 charge, 36 398-401 classification, 36 378-379 comparison with rubredoxin, 36 404 coordinated amino acid spacing, 36 399 cucumber basic protein, 36 390 electron transfer routes, 36 403-404 electron transport, 36 378 EXAFS studies, 36 390-391 functional role, 36 382-383 occurrence, 36 379-382 properties, 36 380 pseudoazurin, 36 389-390 reduction potentials, 36 393-396 self-exchange rate constants, 36 401-403 UV-VIS spectra, 36 391-393 Blue species... 

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