Lead anodic oxidation

The reaction is the electrochemical version of the well-known transmetallation with lead salts, and becomes significant when the lead anode oxidizes. The very high current yields (Ca 170-180%) imply that formation of R4Pb by nonelectrodic reactions takes place as well ... 

A variation of the anode bag technology is the anode skirt, as shown in Figure 3, which is a bag type that is open at the bottom and does not require a separate anolyte extraction system. The anode skirt does not collect gas but is useful for suppressing mist in cathode bag nickel EW systems. The skirt is made of hydrophilic polyester that collects the acid mist droplets and drains them back to the electrolyte while allowing air/oxygen mixture to escape [11]. Lead anode oxide corrosion product falls to the bottom of the cell to be cleaned and so the skirts do not have to be cleaned of lead sludge. 

Tetravalent lead is obtained when the metal is subjected to strong oxidizing action, such as in the electrolytic oxidation of lead anodes to lead dioxide, Pb02 when bivalent lead compounds are subjected to powerful oxidizing conditions, as in the calcination of lead monoxide to lead tetroxide, Pb O or by wet oxidation of bivalent lead ions to lead dioxide by chlorine water. The inorganic compounds of tetravalent lead are relatively unstable eg, in the presence of water they hydrolyze to give lead dioxide. 

The purple permanganate ion [14333-13-2], MnOu can be obtained from lower valent manganese compounds by a wide variety of reactions, eg, from manganese metal by anodic oxidation from Mn(II) solution by oxidants such as o2one, periodate, bismuthate, and persulfate (using Ag" as catalyst), lead peroxide in acid, or chlorine in base or from MnO by disproportionation, or chemical or electrochemical oxidation. 

Other approaches to the generation of the azallyl cation have been found. One of the most useful involves the use of lead tetraacetate (73TL2143). The anodic oxidation of aziridines also leads to the azallyl cation intermediate (75JA1600). 

Ruetschi, P. and Angstadt, R. T., Anodic Oxidation of Lead at Constant Potential , J. Elec-trochem. Soc., Ill, 1323 (1964)... 

A further difficulty arises during preparative electrolyses in aprotic solvents because of the bulk pH change which commonly occurs. Thus cathodic reductions often require proton abstraction from the solvent in order to yield stable products, while many anodic oxidations, mcluding those of aromatic and aliphatic hydrocarbons, give rise to a quantitative yield of proton and the consequent changes in the pH. of the electrolysis media would be expected to lead to a variation in the products with the duration of the electrolysis. Unfortunately, the pH can be a very difficult parameter to control in aprotic solvents and most work reported in the literature has been carried out in unbuffered conditions. In the case of oxidations, organic bases, e.g. pyridine, have... 

Meincke H, Ebling DG, Heinze J, Tacke M, Bbttner H (1999) A photoelectrochemical study of anodic oxides on lead selenide surfaces in alkaline solutions. Fresenius J Anal Chem 365 147-149... 

Anodic processes can also be used for tetraethyllead electrosynthesis. Here solutions of organometallic compounds are used the overall reaction is replacement of the metal in these compounds by another metal, lead. One such process uses a melt of the compound NaAl(C2H5)4, from which radicals QHj are produced anodically. The process is highly efficient, but it is not easy to isolate the TEL produced from the melt. More convenient is a commercial process involving the anodic oxidation of the Grignard reagent C2H5MgCl ... 

C—Lead Lead anode Lead oxide Secondary Lead—add batteries used for starting, lighting, and ignition (SLI)... 

Studies of cathodic reduction have been few. Amusingly, attempted anodic oxidation of the furyl ketone 123 actually resulted in cathodic reduction to the dimer 124 the corresponding ester was oxidized normally, however.301 Sometimes the dimethoxydihydrofurans formed in oxidation processes are reduced in a side reaction leading to the tetrahydrofuran derivatives.302 By using dimethylformamide as solvent instead of the protic solvents used formerly, a Czech group has demonstrated that the cathodic reductions of furans can produce fairly stable anion radicals having ESR spectra which agree well with theory.3023... 

Heterogeneous route, at the electrode surface. The lead anode is attacked and yields tetraethyllead as the main product. For this stage, several reaction routes are possible, e.g. diethylcadmium may be oxidized on the lead anode to produce ethyl radicals which, in turn, may oxidize metallic lead. Partially alkylated lead compounds thus formed are alkylated to tetraethyllead by ethyl iodide. 

Electrochemical etching is one way of controlling the etch rate and determine a clear etch stop layer when bulk micromachining Silicon. In this case, the wafer is used as anode in an HF-Electrolyte. Sufficiently high currents lead to oxidation of the silicon. The resulting oxide which is dissolved by the HF-solution. Since lowly doped silicon material is not exhibiting a notable etch rate, it can be used as an etch stop. 

Plates of lead, each coated with lead dioxide, are immersed in fairly concentrated sulphuric acid. Lead is oxidized at the lead anode during discharge ... 

Recently, Germain et al. have also shown that the indirect anodic oxidation in fluorosulfuric add of fluorocarbon derivatives of the type RfCF2X (X — H, COOH, S03H, CH2OH, Br), which are not directly oxidizable, leads to fluorosulfates of the type FSG3CF3Rf (Eqs. 18 and 19) [37, 38], in these reactions, the peroxide (FS03)2, partially dissociated in its free radicals, is the in-situ electrochemically produced reactive intermediate as shown in Scheme 5.1. 

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