Modifications of the Substrate before Electron Transfer

Chemical Modifications of the Substrate Before Electron Transfer 

The following modifications of the substrate, apart from purely chemical transformations, have been observed  

Of these, acid-base reactions are by far the most important and best studied cases, since cathodic processes in water-containing media are often strongly dependent on the pH. In superacidic media interesting consequences of protonation appear at the anode, too. 

Charge transfer (CT) complexes are kept together by rather weak forces, and it is not to be expected that such forces should influence their electrochemical behaviour significantly. Thus, the CT complex between tetracyanoethylene and hexamethylbenzene has its halfwave potential for reduction shifted 0-039 V towards a more negative potential as compared to tetracyanoethylene itself (Peover, 1967) as is predictable from theoretical considerations of the formation of the CT complexes. 

Cation (anion) radicals of aromatic hydrocarbons should in principle be strong 7r-acceptors (ir-donors) and it is interesting to speculate that CT complexes between substrate and radical ion might play a role in coupling reactions, such as the biaryl coupling mechanism shown in eqn (57). A CT complex of the [ArH—ArH] + type would certainly be more difficult to oxidize than ArH. Thus ArH might be protected from oxidation, and coupling within the complex would take place instead. 

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Solvent and Supporting Electrolytes. Chemical Modifications of the Substrate before Electron Transfer Some Case Studies. ... 

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