OChem2Ch11

Stability of radicals (lowest to highest)
- Methyl < primary < secondary << tertiary
- 1* benzylic ~ secondary
- 2* allylic ~tertiary
Three stages of a radical reaction
- Initiation: creation of radicals
- Propagation: movement of upaired e-
- Termination: two radicals form a bond
- NOTE - propagation step is responsible for the observed reaction
- NOTE - don't forget ALL POSSIBLE termination steps
Describe why Br2 is more selective than Cl2 in a radical addition
- The rate determining step is when the radical C is created from the radical halogen
- This is an exothermic rxn for Cl2, but an endothermic rxn for Br2
- Since it is endothermic the transition state is actually closer to the products than reactants and will resemble them more (Hammond's Postulate)
What are some alternate methods of radical formation?
- Peroxide + heat -> 2 RO* (which can cause other radicals)
- NBS + heat -> succinimide* + Br* (good method for keeping Br* in solution w/o Br2 or HBr
Important things to remember when doing radical rxns
- Anti-Markovnikov (Br2/HOOH)
- Radical goes to weakest bond
- Most stable radical is formed
- No rearrangement
- Racemix mixture

Author

victimsofadown

202027

Card Set

OChem2Ch11

Description

OChem2Ch11

Updated

2013-03-14T16:34:59Z

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