What is "homolysis"

n. 1 (context chemistry English) The decomposition of a substance without reacting with other substances 2 The lysis of blood cells by homolysin

In chemistry, homolysis (from Greek ὅμοιος, homoios, "equal," and λύσις, lusis, "loosening") or homolytic fission is chemical bond dissociation of a molecule by a process where each of the fragments retains one of the originally bonded electrons. During homolytic fission of a neutral molecule with an even number of electrons, two free radicals will be generated. That is, the two electrons involved in the original bond are distributed between the two fragment species. The energy involved in this process is called bond dissociation energy. Bond cleavage is also possible by a process called heterolysis.

Because the relatively high energy required to break bonds in this manner, homolysis only occurs under certain circumstances:

• Ultraviolet radiation (e.g. sunlight causing sunburns)
• Heat
  • Certain intramolecular bonds, such as the O–O bond of a peroxide, are weak enough to spontaneously homolytically dissociate with a small amount of heat.
  • High temperatures in the absence of oxygen ( pyrolysis) can induce homolytic elimination of carbon compounds.

The term homolysis generally means breakdown (lysis) to equal pieces (homo = same). There are separate meanings for the word in chemistry and biology:

• Homolysis (biology), the fact that the dividing cell gives two equal-size daughter cells
• Homolysis (chemistry), a chemical bond dissociation of a neutral molecule generating two free radicals

In biology, homolysis means that dividing cell gives two equal-size daughter cells.