1. Chapter 5. Alkenes and Alkynes II: Reactions

2. Elimination Reactions

3. Addition Reactions

4. Addition of Halogens

5. Examples

6. Mechanism

8. Halohydrin Formation

9. Mechanism

11. Orientation of the OH toward the more stable cabocation (follows Markovnikov addition)

12. Hydrogenation Addition of Hydrogen

13. Addition of H-H across C=C Reduction in general is addition of H 2 or its equivalent Requires Pt, Pd, or Ni as powders on carbon and H 2 Hydrogen is first adsorbed on catalyst Reaction is heterogeneous Reduction of Alkenes

15. Mechanism

16. Addition of Water to Alkenes Acid-Catalyzed Hydration Oxymercuration-Demercuration Hydroboration-Oxydation

17. Acid-Catalyzed Hydration

19. Mechanism

21. Markovnikov Addition

23. Oxymercuration-Demercuration Use mercuric acetate in THF followed by sodium borohydride Markovnikov orientation via mercurinium ion

24. Mechanism

25. Hydroboration-Oxidation Herbert Brown invented hydroboration (received the 1979 Nobel Chemistry Prize.) Borane (BH3) is electron deficient is a Lewis acid Borane adds to an alkene to give an organoborane

26. Hydroboration-Oxidation

27. BH 3 Is a Lewis Acid Six electrons in outer shell Coordinates to oxygen electron pairs in ethers

28. Addition of H-BH 2 (from BH 3 -THF complex) to three alkenes gives a trialkylborane Oxidation with alkaline hydrogen peroxide in water produces the alcohol derived from the alkene Hydroboration-Oxidation Forms an Alcohol from an Alkene

29. Orientation in Hydration via Hydroboration Regiochemistry is opposite to Markovnikov orientation (Anti-Markovnikov) –OH is added to carbon with most H’s H and OH add with syn stereochemistry, to the same face of the alkene (opposite of anti addition)

30. Anti-Markovnikov Addition

31. Syn Addition

32. Mechanism of Hydroboration Borane is a Lewis acid Alkene is Lewis base Transition state involves anionic development on B The components of BH 3 are across C=C