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Reactions Involving Free Radicals

Reactions Involving Free Radicals. Free radical reactions involve one electron species, frequently generated by homolysis (shown below). Radical reactions can be divided into three steps: 1) Initiation 2) Propagation 3) Termination. Weaker bonds are more readily cleaved by homolysis.

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Reactions Involving Free Radicals

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  1. Reactions Involving Free Radicals

  2. Free radical reactions involve one electron species, frequently generated by homolysis (shown below)

  3. Radical reactions can be divided into three steps: 1) Initiation 2) Propagation 3) Termination

  4. Weaker bonds are more readily cleaved by homolysis

  5. Some bonds can be cleaved by heating

  6. Radical Initiators AIBN Link Benzoyl Peroxide

  7. Radical Bromination

  8. Link

  9. Allylic (and benzylic) bromination with NBS (N-Bromosuccinimide)

  10. NBS is regarded as a source of trace amounts of Br2 via the mechanism shown below.

  11. Reductions utilizing tributyltin hydride as a hydrogen atom donor The Sn-H bond is relatively weak (82 kcal/mole), relative to the C-H bond (99 kcal/mole) By contrast, tin forms stronger bonds to bromine, iodine, and sulfur than does carbon. C-S 65 kcal C-Br68 kcal C-I 51 kcal Sn-S 111 kcal Sn-Br 132 Kcal Sn-I 56 kcal

  12. The Barton-McCombieDeoxygenation

  13. Mechanism

  14. Radical Reaction with Allyltributylstannane

  15. The Barton Decarboxylation

  16. Free Radical Polymerization Link

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