Single potential step electrogenerated

The simplest and most useful case that one can study by single potential step chronoamperometry is that in which " /2> 0/i (z.e. AEor = E2 - E 5 180 mV). This means that the primarily electrogenerated species Red converts to a new species Ox, which is more easily reducible than the initial species Ox. As seen in Section 1.4.3, in cyclic voltammetry such a system exhibits a single reversible process in the forward scan. 

Fig. 1 [1]. The first step involves transfer of a single electrcai to form a free radical. A second electron transfer can take place to convert the radical to a carbanion. In aU but a few cases, the reduction potential of the radical (E2) is positive of that of the starting hahde (Ei) so that the reduction to aU intents and purposes is an overall two-electron process. In a few exceptional cases such as benzylic and tertiary butyl bromides and iodides, E2 is negative of El, the process occurs in two discrete steps. It is not generally possible to trap the intermediate radical because of its short lifetime. However, electrogenerated carbanions are readily trapped by added electrophiles. In fact, since electrogeneration is carried out under neutral conditions, it can be used to prepare carbanions from base-sensitive substrates that would not survive other procedures for producing carbanions. Representative examples of use of electrogenerated carbanions are shown in Fig. 8.

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