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Thermodynamic insight into formation of detected products

In this study, research on transition metal catalyzed electrochemical functionalization reactions of carbon-hydrogen and carbon-carbon double bonds is summarized. Electrochemical functionalization methods are examined because these reactions can potentially replace conventional redox reagents by electrodes. By changing the redox reagent to electrons, less organic byproducts are formed and this results in an easier separation and less waste, making the reaction more sustainable. The atom economy will be improved as well as the redox economy since the synthesis of the redox reagents is no longer required, which reduces the amount of oxidation and reduction steps. Also the required amount of energy can be reduced as the applied voltage can be tuned, resulting in mild(er) reaction conditions. However, in an electrochemical cell electrolyte is required and the other electrode may give an unwanted byproduct, therefore product separation is still needed. This study shows that methods are present in which C-H halogenation, C-H phosphorylation, conversion of C-H into C-O bonds, C-H olefination, C-H fluoroalkylation, diazidation of alkenes and fluoroalkylation of alkenes can be performed electrochemically. These methods give the desired products in comparable or higher yields than non-electrochemical ones, but without the presence of additional oxidants. In general, expanding the substrate scope expansion is desirable for these methods to obtain a method that tolerates (more) substrates. In C-H bond functionalization reactions, substrates with a nitrogen based directing group are used to facilitate the C-H activation, but this limits the substrate scope to these compounds. Therefore, it would be promising to examine the possibility of using substrates without a directing group, to obtain an even broader implementation of the method. In addition, further research is desirable to understand the mechanisms of the reactions and to examine the reactions at the other electrode because the byproduct might be useful such as hydrogen gas. It can be concluded that these electrochemical methods are promising additions to functionalization reactions in general and that they show advantages in making the reactions more sustainable.