Cleavage Reactions

A second kind of mechanism is seen in cleavage reactions, in which a covalent bond is broken. This can occur in two ways, depending on how the electrons move
In the first type of cleavage, both electrons in the bond remain together. For example, in the cleavage of a C-H bond, a proton and carbanion are produced, with the 2 electrons remaining on the carbon:

R₃-C-H → R₃-C:^- + H⁺

The alternative is for the electrons to go with the hydrogen, giving a hydride ion and a carbocation:

R₃-C-H → R₃-C⁺ + H^-

In the second type of cleavage, which is less common, the paired electrons are split, producing unstable free radicals:

R₁O-OR₂ → R₁O· + ·OR₂