Electrosynthesis Elimination

Preparative electrochemistry in both its modes -preventive (electrosynthesis) and curative (elimination, recovery, and recycling of wastes) is finally catching up. 

Another group of applications consists of electrosynthesis of substances that can be otherwise synthesized only with difficulty. The chemical reduction of p-aminoketones is complicated by the elimination of these compounds. A polarographic two-electron wave in acidic solution, corresponding to the reduction of carbonyl grouping to p-aminoalcohol... 

It is very difficult (but, we believe, not impossible) to carry out direct one-step electrosynthesis of metal-free Pc starting from urea and PA. The Pc could be synthesized from PN or 1,3-D in a one-step process, according to the reported [9,10] results. Using urea and PA, the synthesis of Pc must include three steps (a) interaction between PA, urea, and NH4NO3 [30], forming 1,3-D HN03 (b) elimination of N03 by NaOH, forming 1,3-D [37] (c) (electro)synthesis of Pc from 1,3-D. 

The polymerization of benzene in chloroaluminate salts has attracted attention from a number of authors. The electrosynthesis of this polymer is highly desirable but challenging, with one of the primary considerations being the strict elimination of water from the reaction medium, which is most commonly effected using difficult systems such as liquid sulfur dioxide, concentrated sulfuric acid or HF. The polymerization of benzene and biphenyl in organic solvents yields only low conductivity films with low degrees of polymerization. 

Since boron-doped diamond electrodes are commercially available, most of these suppliers offer a wide variety of electrolysis cells. Modular electrochemical cells equipped with BDD electrodes have been reported in detail [122]. However, most of these cells were designed for waste water treatment and were not suitable for electrosynthesis in organic media. Electrolysis cells for synthetic purposes designed for a small volume made of organic-compatible materials are required. Additionally, any contact of the support with the organic electrolyte has to be strictly eliminated in order to avoid the corrosion. Most BDD electrodes are on a silicon support which causes eventual loss of the BDD electrode by the brittle nature of crystalline silicon. Consequently, the material used for sealing has to be inert but soft enough to avoid friction of the silicon support. The available BDD... 

Electrolytic decarboxylative coupling of sodium salts of carboxylic acids takes place during their electrolysis. Carbon dioxide is eliminated, and the free radicals thus generated couple to form hydrocarbons or their derivatives. The reaction is referred to as the Kolbe electrosynthesis and is exemplified by the synthesis of 1,8-difluorooctane from 5-fluorovaleric acid (equation 469) [574]. Yields of homologous halogenated acids range from 31% to 82% [574]. 

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 ... 

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