Cadmium cathodes

Adiponitrile is readily hydrogenated catalytically to hexamethylenediamine, which is an important starting material for the prodnction of nylons and other plastics. The electrochemical production of adiponitrile was started in the United States in 1965 at present its volume is about 200 kilotons per year. The reaction occurs at lead or cadmium cathodes with current densities of np to 200 mA/cm in phosphate buffer solutions of pH 8.5 to 9. Salts of tetrabntylammonium [N(C4H9)4] are added to the solution this cation is specihcally adsorbed on the cathode and displaces water molecules from the first solution layer at the snrface. Therefore, the concentration of proton donors is drastically rednced in the reaction zone, and the reaction follows the scheme of (15.36) rather than that of (15.35), which wonld yield propi-onitrile. 

These are well known nonelectrodic reactions38. The electrochemical processes are meant to take care of the large amount of elemental lead set free in transmetallation, and has been devised to confine all the reactions to a single-compartment cell process. The cell in the present example is undivided, with Cd and Pb electrodes in DMF or DMSO solutions containing TBAP and Etl(10%) with Nal(5%). A sacrificial cadmium cathode is oxidized to diethylcadmium by ethyl iodide or, less readily, with ethyl bromide. 

Polyfluorobenzyl alcohols are one class of fluorinated starting materials for medicinal and agricultural usage. Practical electrochemical methods for the product-selective synthesis of polyfluorobenzyl alcohols have been developed [79, 80], 2,3,4,5,6-Pentafluorobenzoic acid is reduced selectively to 2,3,4,5,6-pentafluorobenzyl alcohol at amalgamated lead, zinc and cadmium cathodes in aqueous sulfuric acid solutions, while 2,3,5,6-tetrafluorobenzyl alcohol can also be obtained selectively by using the non-amalgamated cathodes in solutions containing small amounts of a quartemary ammonium salt [79],... 

The most efficient system devised by Monsanto uses electrodes fabricated from carbon steel plate, electro-coated on one face with cadmium. These are stacked in parallel so that the electrolyte can be pumped through the gap between successive plates. Overall tire system forms a series of electrochemical cells with a cadmium cathode and a carbon steel anode. Each plate of metal forms the cathode of one cell and the anode of the next in the stack. Electric current is passed across the stack. The electrolyte contains phosphate and borate salts as corrosion inhibitors, EDTA to chelate any cadmium and iron ions generated by corrosion together with hex-amethylenebis(ethyldibutylammonium) phosphate to provide the necessary telraal-kylammonium ions. This electrolyte circulates through the cell from a reservoir and there is provision for the introduction of acjylonitrile and water as feedstock. The overall cell reaction is ... 

Electrochemical reduction of 4-benzylidene-2-methyl-5(47/)-oxazolone to produce racemic Al-acetylphenylalanine has been accomplished using lead and cadmium cathodes. ... 

Uozumi, lizuka, and coauthors have published several studies on the electrochemical behavior of Pu at liquid cadmium cathodes in LiCl—KCl eutectic melts [128-130]. In one account [130] the authors studied the reduction of Pu " " to Pu° at the LiCl— KCl melt and liquid Cd interface and compared the results to those obtained at a solid Mo cathode surface. The electrode reaction at liquid Cd was found to be close to fully reversible with rapid. 

Emulsion with aq. phosphate buffer, lead alloy, or steel anode/lead or cadmium cathode, 55°C Yield 90%... 

X-ray spectroscopy (DRON-3, cadmium cathode) showed the presence of different forms of iron (a-Fe, b-Fe), amorphous carbon, possibly iron carbide and dense forms of carbon, as well as Fe2C>3 (Figure 5). The spectrum shows signals which are characteristic for Fe-C bonds and for a hexagonal symmetry of carbon. Small angle measurements also indicated the presence of amorphous iron. The presence of amorphous iron and iron carbide may explain the low oxidation of the adsorbent particles in water. 

Aromatic carboxylic esters may be reduced to produce the corresponding primary alcohol by electrolysis at a mercury, lead or cadmium cathode. - For example, methyl benzoate is readily reduced to benzyl alcohol (91%) at a mercury cathode in MeOH containing Me4NCl. Ring substituents in the ben-... 

In a reaction similar to that shown above for aliphatic esters [Eq. (13)], it has been reported that aromatic esters may also be reduced to the corresponding diketone provided the reduction is carried out using a cadmium cathode and magnesium anode [60]. Earlier work demonstrated that phenyl benzoate anion radical cleaves to form phenolate in good yield and presumably benzoyl radical, which leads to dibenzoyl [16]. Nitro-substituted phenyl benzoates are similarly cleaved on reduction to give phenolate [62,63]. 

A galvanic cell consists of a cadmium cathode immersed in a CdS04 solution and a zinc anode immersed in a ZnS04 solution. A salt bridge connects the two half-cells. 

Lead and Cadmium— The hydrogen overvoltage on Pb and Cd is high, and they are easy to work mechanically. For many reactions, a lead or cadmium cathode yields the same chemical products as mercury. 

Electrolytic reduction is also sometimes used. For instance, electrolysis of l-butyl-3-pyrrolidone in 30% sulfuric acid at 60° and at a cadmium cathode with a current density of 0.053-0.073 A/cm2 opens the ring, affording dibutyl-amine in 64% yield.543... 

When the actinide products are removed from electrorefiners, the electrorefiner salts cover the metal. The cathodes are processed to distill adhering salt and to consolidate the actinide metals. These salts are recycled to the electrorefiner for further use (Westphal and Mariani, 2000 Westphal et al., 2002). In the case of the liquid cadmium cathode, the cadmium is... 

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