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

3. YSU

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

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

7. 6.3 Stereochemistry of Alkene Hydrogenation
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Figure 6.2

8. 6.4 Electrophilic Addition of Hydrogen Halides to Alkenes
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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
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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
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Figure 6.4

12. Figure 6.5

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

15. 6.8 Free Radical Addition of H-Br to Alkenes
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Peroxides = HOOH, ROOR (R = organic)

16. 6.8 Free Radical Addition of H-Br to Alkenes
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Mechanism 6.3

17. 6.9 Electrophilic Addition of Sulfuric Acid
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6.10 Acid-catalyzed hydration of alkenes
Note the Markovnikoff regioselectivity

18. Mechanism 6.5

19. 6.10 Acid-catalyzed hydration of alkenes
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Table 6.2

20. 6.11 Thermodynamics of addition-elimination
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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

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

22. 6.12 Hydroboration – Avoiding Steric Interactions
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23. 6.13 Stereochemistry of Hydroboration
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Addition of BH3 is a concerted syn addition
Oxidation step retains the stereochemistry from first step

24. 6.14 Mechanism of Hydroboration/Oxidation
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Mechanism 6.6

25. 6.14 Mechanism of Hydroboration/Oxidation
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Larger BR2 group adds to less substituted end of the alkene

26. 6.14 Mechanism of Hydroboration/Oxidation
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The oxidation features a concerted alkyl migration so the syn stereochemistry is retained from the R2BH addition in the first step.

27. 6.15-6.17 Addition of Halogens - Anti addition via cations
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No syn addition product formed
Stepwise mechanism???:

28. 6.18 Addition of “X-OH” - Halohydrin Formation
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Regioselectivity:

29. 6.19 Epoxides from Alkenes YSU Via bromohydrins:
By direct epoxidation:

30. 6.19 Epoxides – essential synthetic intermediates
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31. 6.20 Ozonolysis of Alkenes - cleavage of the double bond
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32. 6.21 Introduction to Organic Chemical Synthesis
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Chapters 2-6

33. 6.22 Reactions of Alkenes with Alkenes - Polymerization
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34. 6.22 Radical Polymerization
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Mechanism 6.12