Bond cleavage

[3] In homolytic cleavage, or homolysis, the two electrons in a cleaved covalent bond are divided equally between the products.

[2] In heterolytic cleavage, or heterolysis, the bond breaks in such a fashion that the originally-shared pair of electrons remain with one of the fragments.

[2] Heterolysis occurs naturally in reactions that involve electron donor ligands and transition metals which have empty orbitals.

For example, an epoxide ring can be opened by heterolytic cleavage of one of the polar carbon–oxygen bonds to give a single acyclic structure.

Enzymes which catalyse bond cleavage are known as lyases, unless they operate by hydrolysis or oxidoreduction, in which case they are known as hydrolases and oxidoreductases respectively.