Heterolysis (chemistry)

In chemistry, heterolysis or heterolytic fission (from Greek ἕτερος (heteros) 'different' and λύσις (lusis) 'loosening') is the process of cleaving/breaking a covalent bond where one previously bonded species takes both original bonding electrons from the other species.^[1] During heterolytic bond cleavage of a neutral molecule, a cation and an anion will be generated. Most commonly the more electronegative atom keeps the pair of electrons becoming anionic while the more electropositive atom becomes cationic.

Heterolytic fission almost always happens to single bonds; the process usually produces two fragment species.

The energy required to break the bond is called the heterolytic bond dissociation energy, which is similar (but not equivalent) to homolytic bond dissociation energy commonly used to represent the energy value of a bond.

One example of the differences in the energies is the energy required to break a H−H bond

${\displaystyle {\ce {H2 -> 2H.}}}$		ΔH = 104 kcal/mol
${\displaystyle {\ce {H2 -> H+ + H-}}}$		ΔH = 66 kcal/mol (in water)[2]