https://doi.org/10.1351/goldbook.A00004
- The fission of a bond originating at an atom which is adjacent to one assumed to bear the charge; the definition of $\ce{\upbeta\!\mbox{-}}$, $\ce{\upgamma\!\mbox{-}}$ cleavage then follows automatically. The process: would thus be described as $\ce{\upalpha\!\mbox{-}fission}$ of a ketone with expulsion of a radical $\ce{R^{1.}}$ The carbon atoms of the radical $\ce{R^{1.}}$ are called the $\ce{\upalpha\!\mbox{-}}$, $\ce{\upbeta\!\mbox{-}}$, $\ce{\upgamma\!\mbox{-}carbons}$, starting with the atom nearest the functional group.
- Homolytic cleavage of a bond connecting an atom or group to an excited chromophore. Often applied to a bond connected to a carbonyl group, in which case it is called a Norrish Type I photoreaction.Note: This reaction should be distinguished from an alpha-(α-)elimination.