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Influence of Electrosorption on Kinetics and Selectivity of Electroorganic Synthetic Reactions
Author(s) -
Köster K.,
Riemenschneider P.,
Wendt H.
Publication year - 1979
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.197900018
Subject(s) - chemistry , anode , inorganic chemistry , electrolyte , supporting electrolyte , adsorption , selectivity , photochemistry , acetonitrile , electrochemistry , electrode , organic chemistry , catalysis
Necessary conditions for the use of the influence of electrosorption on electrode kinetics, consecutive chemical kinetics and selectivity of electroorganic synthetic reactions are discussed. The role of electrosorption for the performance of four selected examples of electroorganic reactions is demonstrated. Three of these reactions are anodic and the fourth is cathodic. In the two cases of anodic formation of disaryliodonium cations and anodic oxidation of olefins, it is shown that the adsorptive character of the anode material is decisive for the success of the respective synthesis. For the first reaction, high current yields with only little loss of the precious iodoarene by formation of polymers, as well as avoidance of self coupling can only be obtained at Pt‐anodes in acetonitrile. Anodic dimer formation by olefin oxidation only gives high yields at graphitic carbon anodes in methanol. Here semiquantitative data for electrosorption of olefins and supporting electrolyte anions have been obtained by electrode‐kinetic measurements. They explain the influence of the supporting electrolyte anion on the dimer yield by the different spacial demands of the adsorbed anions of the supporting electrolyte. Due to very poor adsorption of radicals at Pt‐anodes and strong radical adsorption at carbon‐anodes, the anodic radical addition to olefins yields quite different product mixtures at these two anode materials. The optical inductive effect of electrosorbed strychninium cations on the cathodic reduction of acetylpyridine are shown to be caused by the enormous concentration enhancement of the alkaloid due to adsorption at the interphase. This is the precondition for complex formation between the negatively charged carbonation formed by disproportionation of the 1‐e reduction product and the positively charged inductor cation. The preference of one of the two possible steroisomers is obtained only by this complex formation.