The term indicates a sequence of reactions such as shown in equations (1)–(3), leading from A to B :

	(1)
	(2)
	(3)

An analogous sequence involving radical cations (A^+., B^+.) is also observed. The most notable example of electron-transfer catalysis is the (or ) 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).