Methods for Organic Electrosynthesis - Fundamentals and Applications of Organic Electrochemistry - page 84

Figure 4.13 Anodic shift of reduction potential
owing to protonation
Furthermore, the reduction potentials of
ketones often shift to positive in the presence of
Lewis acids. This is due to the coordination of
the Lewis acid to the oxygen atom of the
carbonyl group resulting in a decrease in the
electron density of the carbonyl group or
coordination of the Lewis acid to the anion
radical intermediate generated by one-electron
reduction of the carbonyl group resulting in
stabilization of the intermediate, as shown in
Figure 4.14 .