Fundamental Principles of Organic Electrochemistry: Fundamental Aspects of Electrochemistry Dealing with Organic Molecules - Fundamentals and Applications of Organic Electrochemistry - page 25

2.8.2 Clarification of the Reaction
Mechanism
In general, organic electrode reactions include
several varieties of coupled chemical reactions,
and hence their mechanism is usually complex
compared to that for inorganic electrode
reactions. When we undertake a new organic
electrode reaction it is therefore desirable to
conduct CV measurements in advance in order
to understand the mechanism.
A CV experiment conducted by Michielli and
Elving is a good example for clarifying the
complex reaction mechanism [12]. They
employed wave clipping and addition of a
proton donor (phenol) to obtain information
about intermediates in the electrochemical
reduction of benzophenone ( 1 ). As shown in
Figure 2.8a , CV for the reduction gives two
successive cathodic peaks I c and II c at −1.8 and
−2.0 V (relative to the Ag/AgNO 3 reference
electrode), and a single anodic peak I a , as the
potential is scanned from 0 to −2.3 V and back
to −1.0 V. Wave clipping, that is, reversal of the
scan direction at a potential (−1.9 V) between
peaks I c and II c , causes peak Ia to remain, as
shown in Figure 2.8b . This proves very nicely
that peak I a is associated with oxidation of the
species formed in the first reduction step (I c )
and reduction at peak I c therefore forms a
species that is long lived on the CV time scale.
On the other hand, peak II c must produce a