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Kharasch addition

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chemical reactions for the Kharasch addition reaction of chloroform to a terminal alkene.

The Kharasch addition is an organic reaction and a metal-catalysed free radical addition of CXCl3 compounds (X = Cl, Br, H) to alkenes. The reaction is used to append trichloromethyl or dichloromethyl groups to terminal alkenes. The method has attracted considerable interest, but it is of limited value because of narrow substrate scope and demanding conditions.

The reaction mechanism involves free radicals of the general formula CXCl2 (X = Cl, H). For the precursors carbon tetrachloride and chloroform, the requisite radicals can arise by abstraction of a halogen atom by a electropositive metal. The addition proceeds in an anti-Markovnikov fashion. Early work linked the addition to olefin polymerization. This addition is a step in a protocol known as atom transfer radical polymerization.

An example of Kharasch addition is the synthesis of 1,1,3-trichloro-n-nonane from 1-octene and chloroform using an iron-based catalyst:

CH3(CH2)5CH=CH2 + HCCl3 → CH3(CH2)5CH(Cl)−CH2CHCl2

History

The reaction was discovered by Morris S. Kharasch in the 1940s.

References

  1. Name reactions: a collection of detailed reaction mechanisms, Jie Jack Li Springer; 2nd edition (September 17, 2003) 3540402039
  2. Minisci, Francesco (1975). "Free-radical additions to olefins in the presence of redox systems". Accounts of Chemical Research. 8 (5): 165–171. doi:10.1021/ar50089a004.
  3. Foo, Klement. "The Kharasch Reaction" (PDF).
  4. Kharasch, M. S.; Urry, W. H.; Jensen, E. V. (1945). "Addition of Derivatives of Chlorinated Acetic Acids to Olefins". Journal of the American Chemical Society. 67 (9): 1626. doi:10.1021/ja01225a517.
  5. Wang, J.S.; Matyjaszewski, K. (1995). "Controlled/"Living" Radical Polymerization. Atom Transfer Radical Polymerization in the Presence of Transition-Metal Complexes". Journal of the American Chemical Society. 117 (20): 5614. doi:10.1021/ja00125a035.
  6. D. Vofsi, M. Asscher (1965). "1,1,3-Trichlorononane". Organic Syntheses. 45: 104. doi:10.15227/orgsyn.045.0104.
  7. Kharasch, M.; Jensen, E.; Urry, W. (1945). "Addition of Carbon Tetrachloride and Chloroform to Olefins". Science. 102 (2640): 128. Bibcode:1945Sci...102..128K. doi:10.1126/science.102.2640.128. PMID 17777366.
  8. Kharasch, M. S.; Jensen, E. V.; Urry, W. H. (1947). "Reactions of Atoms and Free Radicals in Solution. X. The Addition of Polyhalomethanes to Olefins". Journal of the American Chemical Society. 69 (5): 1100–1105. doi:10.1021/ja01197a035.
  9. Kharasch, M. S.; Kuderna, B. M.; Urry, W. (1948). "Reactions of atoms and free radicals in solution; the additions of bromodichloromethane and dibromodichloromethane to olefins; the preparation of 2-alkenals". Journal of Organic Chemistry. 13 (6): 895–902. doi:10.1021/jo01164a020. PMID 18106035.
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