The term indicates a sequence of reactions such as shown in equations (1)-(3), leading from A to B:
A + e- A. - (1)
A. - B. - (2)
B. - + A B + A. - (3)
An analogous sequence involving radical cations (A.+, B.+) is also observed.
The most notable example of electron-transfer catalysis is the SRN1 (or T+DN+AN) reaction of aromatic halides.
The term has its origin in a suggested analogy to acid-base catalysis, with the electron instead of the proton. However, there is a difference between the two catalytic mechanisms, since the electron is not a true catalyst, but rather behaves as the initiator of a chain reaction. "Electron-transfer induced chain reaction" is a more appropriate term for the situation described by equations (1)-(3). EBERSON (1987).
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