Current yield electrosynthesis

Electrosynthesis by anodic dissolution of the metal in absolute alcohol appears for many elements to be a promising, inexpensive way to obtain large amounts of metal alkoxides [54]. The process goes smoothly and has good current yields for metals, such as scandium and lanthanides, and early transition metals (Ti, Zr, and Nb) using tetrabutylammonium bromide as an electrolyte. Oxo or hydroxo compounds are obtained for more electropositive metals (Mg and alkaline-earth metals), however, probably as a result of alcohol dehydration reactions. 

Another example of the use of ion-exchange membranes in electrosynthesis is cathodic dehalogenation. Dichloroacetic acid has been obtained with almost quantitative current yields from trichloroacetic acid by elimination of chlorine at controlled potential [21]. The overall reaction which takes place in the electrolyzer can be written as follows ... 

Details of many synthetic processes are never reported and, hence, as noticed by Pletcher and Walsh [10], any contribution of electrosynthesis remains speculative. Crucial factors are generally the availability and costs of the starting materials, the material yield, a simple product isolation, the stability of the electrolysis medium and acceptable current densities. 

These syntheses were carried out in methanol medium at azole concentration from 0.002 to 0.4mol/L the yields were 12-75% (on azoles) and 15-95% (on current) [567,568]. Further, the electrosynthesis was used to produce complexes of methyl-pyrazoles 788 with yields (on ligands) 18-100%, depending on the solvent and metal nature [551,569]. The highest yield was observed in alcohols (especially in methanol Cd, 75% Fe, 84% Ni, 96.7% Co, 99% Zn, 100%), the lowest one in acetonitrile (Zn, 18% Co, 20% Cd, 30% Ni, 74%). The chelates with five-member metal-cycles 789 and 790 [567,568] were isolated in analogous conditions such compounds cannot be obtained from ligands and metal salts ... 

It is recommended that organic electrosynthesis be carried out at a constant current at first, since the setup and operation are simple. Then the product selectivity and yield can be improved by changing current density and the amoimt of electricity passed [current (A) x time (i) = electricity (C)]. However, the electrode potential changes with the consumption of the starting substrate (more positive in case of oxidation or more negative in case of reduction). Therefore the product selectivity and current efficiency sometimes decrease, particularly at the late stage of electrolysis. 

The two-electron reduction of Ceo to produce Ceo can be achieved electrochemically in the presence of methyl iodide to yield the dimethyl adduct, Mc2Ceo [139]. In this context, catalytic currents are observed for the electrochemical reduction of Ceo or C70 to produce Ceo or C70 , respectively, in the presence of vicinal dibromides [140] or a,to-dihaloalkanes [141, 142]. Electrosynthesis of methano-fullerenes has been achieved by the reaction of Ceo with j o-brominated and... 

Electrosynthesis is a process used in heavy industry because, depending on the material being produced, its energetic yield is higher than that found in thermal synthesis processes. Moreover, the processes used are selective and easy to control by means of the voltage, the current and the amount of charge, which is a very accurate indicator of the advancement rate in production. The raw materials produced in the greatest quantities by electrosynthesis are aluminium, dichlorine and sodium hydroxide. 

Reduced current efficiency, which may in turn result in unwanted byproducts, non-uniform wear of electrodes and decreased space- time yield in the case of reactors for electrosynthesis. 

A similar approach was followed by Chen and coworkers in 2003 [325] in the preparahon of copper nanorods. These authors used a controlled-current electrochemical method and showed how the shape and yield of the nanorods depended on the current density applied during the electrosynthesis process. 

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