Alpha cleavage
Alpha-cleavage in organic chemistry refers to the act of breaking the carbon-carbon bond adjacent to the carbon bearing a specified functional group.Mass spectrometry
Generally this topic is discussed when covering tandem mass spectrometry fragmentation and occurs generally by the same mechanisms.
For example, of a mechanism of alpha-cleavage, an electron is knocked off an atom lone pair electrons, 2) pi bond electrons, 3) sigma bond electrons.
One of the lone pair electrons moves down to form a pi bond with an electron from an adjacent bond. The other electron from the bond moves to an adjacent atom creating a radical. This creates a double bond adjacent to the lone pair atom and breaks/cleaves the bond from which the two electrons were removed.
In molecules containing carbonyl groups, alpha-cleavage often competes with McLafferty rearrangement.Photochemistry
In photochemistry, it is the homolytic cleavage of a bond adjacent to a specified group.
