The term indicates a @[email protected] of reactions such as shown in equations (1)–(3), leading from A to B :

\[\text{A} + \text{e}^{-} \rightarrow \text{A}^{\cdot- }\]	(1)
\[\text{A}^{\cdot- } \rightarrow \text{B}^{\cdot- }\]	(2)
\[\text{B}^{\cdot- } + \text{A} \rightarrow \text{B} + \text{A}^{\cdot- }\]	(3)

An analogous @[email protected] involving radical cations (A⁺·, B⁺·) is also observed. The most notable example of electron-transfer @[email protected] is the \(\text{S}_{\text{RN}}1\) (or \(\text{T}+\text{D}_{\text{N}}+\text{A}_{\text{N}}\)) reaction of aromatic halides. The term has its origin in a suggested analogy to acid-base @[email protected], with the electron instead of the @[email protected] However, there is a difference between the two catalytic mechanisms, since the electron is not a true @[email protected], but rather behaves as the @[email protected] of a @[email protected] 'Electron-transfer induced @[email protected]' is a more appropriate term for the situation described by equations (1)–(3).