1. 6.19 Epoxides – essential synthetic intermediates
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2. Ch. 6 – Reactions of Alkenes: Addition Reactions
6.1 Hydrogenation of Alkenes
Needs a precious metal catalyst such as Pt or Pd
Not covering Mechanism 6.1

4. 6.2 Heats of hydrogenation of isomeric C4H8 alkenes
Figure 6.1

5. Table 6.1

6. 6.3 Stereochemistry of Alkene Hydrogenation
H atoms have added to the same face of the alkene - syn addition

7. 6.3 Stereochemistry of Alkene Hydrogenation
Figure 6.2

8. 6.4 Electrophilic Addition of Hydrogen Halides to Alkenes
Stronger acids react faster : H-I > H-Br > H-Cl >> H-F
Electrophilic Addition mechanism

9. Mechanism 6.2 a

10. 6.5 Regioselectivity in Electrophilic Addition
Markovnikov’s Rule
Since the reaction involves formation of cations, the major product arises from the most stable intermediate carbocation

11. 6.6 Mechanistic Basis for Markovnikov's rule
Figure 6.4

12. Figure 6.5

13. Examples of H-X Addition

14. 6.7 Cation Rearrangements in H-X Addition to Alkenes
2o cation undergoes intramolecular rearrangement to more stable 3o cation

15. 6.8 Free Radical Addition of H-Br to Alkenes
Mechanism 6.3

16. 6.9 Electrophilic Addition of Sulfuric Acid
6.10 Acid-catalyzed hydration of alkenes
Note the Markovnikoff regioselectivity

17. Mechanism 6.5

18. 6.10 Acid-catalyzed hydration of alkenes
Table 6.2

19. 6.11 Thermodynamics of addition-elimination
How do you get one product over the other?
In dehydration (elimination) – remove alkene
In hydration (addition) – use excess water
Both are using Le Châtelier’s principle

20. Reaction is regioselective and stereoselective
6.12 Hydroboration - Oxidation of Alkenes
1. Addition
2. Oxidation
Reaction is regioselective and stereoselective

21. 6.12 Hydroboration – Avoiding Steric Interactions

22. 6.13 Stereochemistry of Hydroboration
Addition of BH3 is a concerted syn addition
Oxidation step retains the stereochemistry from first step

23. 6.14 Mechanism of Hydroboration/Oxidation

24. 6.14 Mechanism of Hydroboration/Oxidation
Larger BR2 group adds to less substituted end of the alkene

25. 6.14 Mechanism of Hydroboration/Oxidation
The oxidation features a concerted alkyl migration so the syn stereochemistry is retained from the R2BH addition in the first step.

26. 6.15-6.17 Addition of Halogens - Anti addition via cations
No syn addition product formed
Stepwise mechanism???:

27. 6.18 Addition of “X-OH” - Halohydrin Formation
Regioselectivity:

28. 6.19 Epoxides from Alkenes
Via bromohydrins:
By direct epoxidation:

29. 6.19 Epoxides – essential synthetic intermediates
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30. 6.20 Ozonolysis of Alkenes - cleavage of the double bond

31. 6.21 Introduction to Organic Chemical Synthesis
Chapters 2-6

32. 6.22 Reactions of Alkenes with Alkenes - Polymerization

33. 6.22 Radical Polymerization
Mechanism 6.12