1. WWU -- Chemistry Reactions of  Hydrogens: Condensation Reactions Chapter 21 These images should be printed in color, if possible, otherwise the images are very faint! It would be better to look at them on a computer monitor.

2. WWU -- Chemistry Assignments for Chapter 21 and 22 Chapter 20, hardly any, attend class! Skip these sections from Chap. 21 21.4, 21.6, 21.8, 21.11, 21.17 and 21.21 Skip these sections from Chap. 22 22.3, 22.4, 22.13 through 22.15 Keep 22.16 and 22.17!!!

3. WWU -- Chemistry Problems for Chapter 21 In-Text Problems: –2, 3, 4, 8, 13, 14, 18, 19, 26, 29, 30, 32, 34, 35, 36, 37, 40, 46 and 50 End-of-Chapter Problems: –2, 4, 5, 9, 13, 16, 17 and 21

4. WWU -- Chemistry Sect. 21.1: Keto-Enol Tautomerism

5. WWU -- Chemistry Keto-Enol Tautomerism in 1,3- Dicarbonyl Compounds

6. WWU -- Chemistry Keto-Enol Tautomerism in 1,3- Dicarbonyl Compounds The equilibrium lies substantially to the right with 1,3-dicarbonyl compounds. In simple ketones, such a hydrogen-bonded structure cannot form, and the percentage of enol found in an equilibrium mixture is very small (equilibrium lies to left).

7. WWU -- Chemistry Some Representative Enol Percents

8. WWU -- Chemistry Sect. 21.2 Acidity of  - Hydrogens The acidity of a hydrogen attached to the  -carbon of a carbonyl compound is much higher than the acidity of a typical C-H hydrogen. pK a values range from about 19 to 20 (compared with 48 to 50) for alkanes.

9. WWU -- Chemistry Acidity of  -Hydrogens: The Reason

10. WWU -- Chemistry Acidity of  -Hydrogens Resonance stabilization of the enolate ion shifts the equilibrium to the right, thereby making the C-H bond more acidic. Once formed, the enolate ion is capable of reacting as a nucleophile. The  - carbon of the enolate ion bears substantial negative charge.

11. WWU -- Chemistry Sect. 21.3 Halogenation of Ketones

12. WWU -- Chemistry Mechanism

13. Example

14. But... The halogenation is difficult to stop at the mono-substitution stage. Often, poly-halogenated products are formed in this reaction.

15. WWU -- Chemistry With an excess of bromine:

16. WWU -- Chemistry In base, bromoform is formed

17. WWU -- Chemistry Section 21.5: Iodoform reaction

18. WWU -- Chemistry Sect. 21.7: Alkylation Reactions

19. WWU -- Chemistry Example

20. Sect. 21.9: Alkylation of Active Methylene Compounds

21. WWU -- Chemistry Sect: 21.10: Hydrolysis and decarboxylation

22. WWU -- Chemistry Mechanism of decarboxylation

23. WWU -- Chemistry Alkylation of ethyl acetoacetate

24. WWU -- Chemistry Sect. 21.10: Decarboxylation

25. WWU -- Chemistry Sect. 21.12: The Aldol Condensation

26. WWU -- Chemistry Aldol Condensation -- Mechanism

27. WWU -- Chemistry An example

28. WWU -- Chemistry One More:

29. WWU -- Chemistry Synthesis Problem

30. WWU -- Chemistry Sect. 21.13: Dehydration of Aldol products Aldol products easily dehydrate in acid and sometimes in base.

31. WWU -- Chemistry Dehydration of Aldol Products

32. WWU -- Chemistry Dehydration of Aldol Products Note here that iodine is a sufficiently strong Lewis acid to bring about dehydration.

33. WWU -- Chemistry Also:

34. Synthesis of:

35. WWU -- Chemistry Synthesis of a Compound used in Perfumery

36. WWU -- Chemistry Preparation via Aldol Condensation and reduction

37. WWU -- Chemistry Preparation via Aldol Condensation and reduction!

38. WWU -- Chemistry Synthesis of an Insect Repellent

39. WWU -- Chemistry Sect. 21.14: Crossed Aldol Condensations Reaction of two different aldehydes: One with an " -hydrogen (donor) Other with no " -hydrogen (acceptor)

40. WWU -- Chemistry Crossed Aldol Condensations acceptor donor

41. WWU -- Chemistry Chalcone formation: part 1

42. WWU -- Chemistry Chalcone Formation: part 2 (formed from an aldol condensation)

43. WWU -- Chemistry Do the synthesis of:

44. WWU -- Chemistry Sect. 21.15: The Claisen Ester Condensation

45. WWU -- Chemistry Claisen Ester Condensation -- Mechanism (Part One)

46. WWU -- Chemistry Claisen Ester Condensation -- Mechanism (Part Two)

47. WWU -- Chemistry Example

48. Another Example

49. WWU -- Chemistry Example of a Ring Formation This reaction is known as the Dieckmann cyclization.

50. WWU -- Chemistry Sect. 21.16: Crossed Claisen Condensation In the crossed Claisen condensation, we choose one of the esters to be the acceptor. The acceptor does not have  -hydrogens. The other ester, the donor, does have  - hydrogens. It can react with base to form a nucleophilic enolate ion. With such an experimental design, the crossed Claisen condensation can be used successfully.

51. WWU -- Chemistry Crossed Claisen Condensation -- An Example

52. WWU -- Chemistry Synthesize this:

53. WWU -- Chemistry Sect. 21.18: 1,2 vs. 1,4-addition

54. WWU -- Chemistry Sect. 21.19: Conjugate addition: Michael reaction

55. WWU -- Chemistry Sect. 21.20: copper catalyzed conjugate addition reactions