1. L
TOPIC 8. ADDITIONS TO ALKENES AND ALKYNES (Chapter 8 and parts of chapters 7, 10 and 11)

2. OBJECTIVES
1. Describe mechanisms for addition reactions of alkenes and alkynes
Predict the structure of the product(s) of addition reactions
Understand the mechanisms which explain the regiochemical and stereochemical outcome of addition reactions
Use combination of substitution, elimination and addition chemistry to propose synthetic routes to useful value-added compounds

3. ~MAKE FLASHCARDS AFTER EACH LECTURE~
ADDITION REACTIONS
Lecture 1
Lecture 2
Lecture 3
Lecture 4
Lecture 5
Addition of H2
- H2/Pd (alkene, alkyne)
- H2/Lindlar catalyst (alkyne → cis alkene)
- dissolving metal reduction (alkyne → trans alkene)
Addition of H-Hal
- Markovnikov
- anti-Markovnikov
Addition of H2O
- H3O+ (regiochemistry)
- Oxymercuration-demercuration (regiochemistry, stereochemistry)
- Hydroboration-oxidation (regiochemistry, stereochemistry)
- hydration of alkynes (regiochemistry)
Addition of Hal2
- Hal2 (regiochemistry, stereochemistry)
- Hal2/H2O (regiochemistry)
Generation and reaction of carbenes
Epoxidation
Nucleopihilic ring opening reactions of epoxides (H2O, ROH, HCN, RMgHal)
syn-Hydroxylation
Oxidative cleavage of alkenes and alkynes
- KMnO4
- Ozonolysis
Radical Polymerization
~MAKE FLASHCARDS AFTER EACH LECTURE~

4. HYDROGENATION OF ALKENES AND ALKYNES
Prob: ; 8.30e,g,i, 37,45
Hydrogenation of Alkenes

5. Hydrogenation of Alkynes
Complete Hydrogenation
cis-Semihydrogenation

6. Dissolving Metal Reduction

7. PRS PREVIEW OF REACTIVITY
Alkenes and Alkynes are Weakly _____ and Weakly _____________
S:8.1
PRS

8. ADDITION OF HYDROGEN HALIDES TO ALKENES AND ALKYNES
Prob: 8.27,28a,b,f,j,29b-g,35
Overview

9. Addition of H-Hal to Alkenes
Mechanism

10. Regiochemistry
Markovnikov’s Rule
In the addition of HX to an unsymmetrical alkene, the hydrogen adds to the
_____________ substituted carbon and the X groups adds to the
_____________ substituted carbon.

11. PRS The Basis of Markovnikov’s Rule: Stability of Carbocations
The more substituted carbocation is formed. Remember hyperconjugation!
Mechanistic Restatement of Markovnikov’s Rule
In the ionic addition of HX to an unsymmetrical alkene, protonation gives the more stable carbocation as an intermediate.

12. Stereochemistry of H–Hal Addition to Alkenes

13. Anti-Markovnikov Addition of H-Hal to Alkenes
Mechanistic Rationale for Anti-Markovnikov Addition

14. Addition of H-Hal to Alkynes

15. ~ MAKE FLASHCARDS ~ Hydrogenation Dissolving metal reduction
Hydrogenation over Lindlar catalyst
Markovnikov addition of H-Hal
Anti-Markovnikov addition of H-Hal
…..more next lecture

16. SYNTHESIS OF ALCOHOLS BY HYDRATION OF ALKENES
Prob: 8.27c,32, ,35(a-g),38(a,d), 39,46,48
Addition of Water to Alkenes
PRS

17. Proceeds via Markovnikov addition

18. Rearrangements During Acid Catalyzed Hydration of Alkenes
Intermediate carbocations can rearrange.

19. Oxymercuration-Demercuration of Alkenes
e.g.,
Step 1: Oxymercuration
Step 2: Demercuration

20. Mechanism

21. Hydroboration-Oxidation: Anti-Markovnikov Hydration of Alkenes
e.g.,
Step 1: Hydroboration
Step 2: Oxidation

22. Mechanism: Regiochemistry

23. Stereochemistry

24. Hydration of Alkynes (covered in 16.5B)

25. SYNTHETIC STRATEGIES
Prob:7.24
Problem: Synthesize cis-1-cyano-2-methylcyclohexane (shown below) using any hydrocarbon.

26. Problem: Female houseflies attract males with a pheromone which has been shown to be Z-9-tricosene (C23H46). Synthesize this compound starting with organic compounds containing 13 or less carbon atoms.

27. ADDITION OF BROMINE AND CHLORINE TO ALKENES AND ALKYNES
Prob: 8.30(c,d), 31,54
Overview

28. Addition of Hal2 to Alkenes
Stereochemistry
PRS
PRS

29. Mechanism

30. Formation of Halohydrins

31. Mechanism

32. Addition of Hal2 to Alkynes

33. ADDITION OF CARBENES TO ALKENES
What is a Carbene?
What is a Carbenoid?

34. Additions to Alkenes
Mechanism

35. EPOXIDES S:
Prob: 11.43,44
Synthesis
MMPP
mCPBA

36. Nucleophilic Ring-opening
Stereochemistry

37. Regiochemistry

38. Addition of Other Nucleophiles

39. OXIDATION OF ALKENES AND ALKYNES
Prob: 8.27(k,n),30(j,k),46,47
Syn-Hydroxylation of Alkenes

40. Oxidative Cleavage of Alkenes
Permanganate Oxidation

41. Ozonolysis

42. Oxidative Cleavage of Alkynes
Problem: Compound X (C10H18) gave pentanoic acid upon reaction with basic potassium permanganate followed by acidification. What is the structure of compound X?

43. RADICAL POLYMERIZATION OF ALKENES (CHAIN-GROWTH POLYMERS)
About 60 x 109 pounds of ethylene are manufactured and used each year, primarily to make polyethylene
Roll of Radical Initiator (Chain Initiation) L
S:10.10

44. Chain-Growth (Chain Propagation)
End of Growth (Chain Termination)

45. Common Chain-Growth Polymers

46. SYNTHETIC STRATEGIES Add to your chart of organic reactions
Prob: ,44
Add to your chart of organic reactions
No more reactions! For now!!!

47. DESIGNING SYNTHESES One Step Syntheses Two Step Syntheses
This is just the opposite of learning reactions - just think backwards. Although one step syntheses are relatively easy, they are harder than learning reactions.
Two Step Syntheses
This is involves considerable imagination and is quite different than “just the opposite of learning reactions”. You must be able to conceive of the intermediate. However, there is a direct link between the intermediate and both the product and the starting material. Think “retro” (retrosynthesis) - how do you synthesize the product from anything? Can you then synthesize your proposed synthetic intermediate from the starting material?

48. Three Step Syntheses
Three design of three-step organic syntheses requires a little more imagination and can be a little more difficult than two-step syntheses. You must be able to conceive of two intermediates. In this case there may not be a clear link between intermediate one and the product or intermediate two and the starting material. Again “think retro”. Can you think of ANY compounds that could be converted to the product by chemistry you know? Can you then think of one or more compounds that could be converted to these proposed intermediates by chemistry you know? Can any of these second proposed intermediates be synthesized from the starting material?

49. Problem: Solomons 8.31(b). Show how 1-butyne could be synthesized from each of the following: (b) 1-chlorobutane

50. Problem:

51. Problem:

52. Problem:

53. Problem: Propose a synthesis of 1-methyl-1,2-cyclopentanediol (with the two hydroxy groups trans to one another) from methylcyclopentane.
Prob: 11.30,35, 37,38,46

54. Problem: An insect physiologist required 4Z-hexen-2-ol for the study of insect pheromones. Propose a synthesis of 4Z-hexen-2-ol from propene.

55. TOPIC 8 ON EXAM 4 Types of Questions
- Describe addition reaction mechanisms
- Predict the products of addition reactions
The problems in the book are good examples of the types of problems on the exam.
Preparing for Exam 4:
- Work as many problems as possible.
- Work in groups.
- Do the “Learning Group Problem” at the end of the chapter.
- Work through the practice exam