Kharasch addition

Last updated
chemical reactions for the Kharasch addition reaction of chloroform to a terminal alkene. KharaschAddnCHCl3.svg
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. [1] The reaction is used to append trichloromethyl or dichloromethyl groups to terminal alkenes. The method has attracted considerable interest, [2] but it is of limited value because of narrow substrate scope and demanding conditions. [3]

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. [4] This addition is a step in a protocol known as atom transfer radical polymerization. [5]

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: [6]

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

History

The reaction was discovered by Morris S. Kharasch in the 1940s. [7] [8] [9]

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. Bibcode:1945JAChS..67.1626K. 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. Bibcode:1995JAChS.117.5614W. 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. Bibcode:1947JAChS..69.1100K. 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.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.