Homolysis (chemistry)

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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.[1] That is, the two electrons involved in the original bond are distributed between the two fragment species.

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Such reactions can be induced by irradiation in the UV region, diffused sunlight, or peroxide[how?], because energy must be supplied to cause bonds to cleave homolytically. High temperatures in the absence of oxygen (pyrolysis) can also induce homolytic elimination of carbon compounds.[2]

The energy involved in this process is called bond dissociation energy. Bond cleavage is also possible by a process called heterolysis.


  1. ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "homolysis (homolytic)".
  2. ^ I. Pastorova, "Cellulose Char Structure: a Combined Analytical Py-GC-MS, FTIR, and NMR Study", Carbohydrate Research, 262 (1994) 27-47.

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