Chapter 9

1. Chapter 9 Stereochemistry Chapter 9 - Stereochemistry

2. Chapter 9 • Enantiomers • Diastereomers • Reactions involving enantiomers. Chapter 9 - Stereochemistry

3. Types of Isomers Chapter 9 - Stereochemistry

4. Molecular Model Chapter 9 - Stereochemistry

5. molecule mirror mirror image Chapter 9 - Stereochemistry

6. mirror mirror image molecule Molecule is chiral if molecule and its mirror image are NOT superimposable. Whether molecule and its mirror image are superimposable or not superimposable depends on the attached groups. Chapter 9 - Stereochemistry

7. mirror mirror image molecule When the groups are different, the molecule and its mirror image are NOT superimposable. The molecule is said to be chiral. Chapter 9 - Stereochemistry

8. mirror Molecule 2 Molecule 1 When two molecules are mirror images and NOT superimposable, they are called enantiomers. Chapter 9 - Stereochemistry

9. molecule The above molecule has a plane of symmetry. When a plane of symmetry exist, the molecule is achiral. Chapter 9 - Stereochemistry

10. molecule When four groups are different, a plane of symmetry does not exist and therefore the molecule is chiral. Chapter 9 - Stereochemistry

11. * molecule Chiral center is indicated by an *. Chapter 9 - Stereochemistry

12. Cl Methylene chloride C Cl H H A plane (formed by Cl - Cl - C) of symmetry exist. The molecule and its mirror image are superimposable. Methylene chloride is achiral. Chapter 9 - Stereochemistry

13. F Cl C I H No plane of symmetry exist. The molecule and its mirror image are not superimposable. The molecule is chiral. “C” is the asymmetric carbon. Chapter 9 - Stereochemistry

14. achiral & chiral achiral achiral chiral chiral * * A B Are A and B different? Chapter 9 - Stereochemistry

15. 180o * * * * mirror A B A and B are enantiomers (because they are mirror images but not superimposable). Chapter 9 - Stereochemistry

16. * * Lactic acid Lactic acid A new naming system is needed. Chapter 9 - Stereochemistry

17. * Polarimetry Lactic acid is chiral or optically active. Lactic acid is d or +. Dextrorotatory d(+) and levorotatory l(-) Chapter 9 - Stereochemistry

18. * * From polarimetry results ... (l or -) - Lactic acid (d or +) - Lactic acid Chapter 9 - Stereochemistry

19. Coniine Toluene Phenobarbital Camphor Place * at all chirality centers. Indicate whether the compound is optically active. If it is, assign d or l. Menthol Chapter 9 - Stereochemistry

20. Answer Key * * * * Menthol Coniine Toluene (inactive) (active) (active) * * Phenobarbital Camphor (inactive) (active) d or l can only be assigned after doing the experiment. Chapter 9 - Stereochemistry

21. 4 1 8 1 6 2 6 3 8 Assignment based on atomic number (Same rule as E,Z) Cahn-Ingold-Prelog R, S Assignment 1 4 2 3 S Chapter 9 - Stereochemistry

22. R, S Assignment Clockwise - R Anti-clockwise - S Chapter 9 - Stereochemistry

23. R, S & d, l R, S - from molecular geometry (absolute configuration). d(+), l(-) - from experiment (polarimetry). R, S, and d, l - no relationship (see Fig 9.8, p 317). Chapter 9 - Stereochemistry

24. Assign R or S to the chirality center ... Chapter 9 - Stereochemistry

25. Answer Key R S S Chapter 9 - Stereochemistry

26. Draw a tetrahedral representation of (S)-2-pentanol Chapter 9 - Stereochemistry

27. Answer Key Chapter 9 - Stereochemistry

28. Chapter 9 • Enantiomers • Diastereomers • Reactions involving enantiomers. Chapter 9 - Stereochemistry

29. Types of Isomers Chapter 9 - Stereochemistry

30. mirror symmetry plane Diastereomers - cis & trans Not mirror images of each other. Enantiomers Achiral Chapter 9 - Stereochemistry

31. Types of Isomers Chapter 9 - Stereochemistry

32. 3 1 2 4 * 1 * 4 2 3 Diastereomers - configurational(two or more chiral carbons) 1 S * 2 R 3 * 4 Chapter 9 - Stereochemistry

33. Diastereomers - configurational(two or more chiral carbons) 1 2R 2S * 2 3S 3R 3 * 4 Chapter 9 - Stereochemistry

34. R,S Permutations 2R 2S 3R 3S 2R 2R,3R 2R,3S 2n rule 2S 2S,3R 2S,3S 3R 3S Red - Red - enantiomers Green - Green - enantiomers Red - Green - diastereomers Chapter 9 - Stereochemistry

35. 2S,3R 2R,3S 2S,3S 2R,3R enantiomers enantiomers diastereomers Chapter 9 - Stereochemistry

36. * * * * meso 2n rulefails 2n ruleworks Chapter 9 - Stereochemistry

37. meso diastereomers enantiomers 2-bromo-3-chlorobutane 2n = 4 * * (2S,3S) (2R,3S) (2S,3R) (2R,3R) 2-bromo-3-chlorobutane has only 3 stereoisomers, not 4! The meso is achiral. Chapter 9 - Stereochemistry

38. Types of Isomers Chapter 9 - Stereochemistry

39. Assign R, S to each chiral centers. Which are enantiomers, and which are diastereomers? Chapter 9 - Stereochemistry

40. Answer Key 4 3 R S R S 2 R R S S 1 (2R,3R) (2R,3S) (2S,3R) (2S,3S) (2R,3S) and (2S,3R) are mirror images, therefore they are enantiomers. (2R,3R) and (2S,3S) are mirror images, therefore they are enantiomers. (2R,3S) and (2S,3R) are diastereomers with (2R,3R) and (2S,3S). Chapter 9 - Stereochemistry

41. Which of the following structures represent meso compounds? Chapter 9 - Stereochemistry

42. Answer Key meso meso Chapter 9 - Stereochemistry

43. Fischer Projection A A B = D B D C C Chapter 9 - Stereochemistry

44. D Allowed Fischer Rotations C D B A 180o A B D B Holding D (A, B, or C) C C A Chapter 9 - Stereochemistry

45. Fischer Projection determine if two structures represent the same or different enantiomers. Chapter 9 - Stereochemistry

46. Which of the following Fischer projections represent the same enantiomer? A B C D Chapter 9 - Stereochemistry

47. Answer Key A = B C = D enantiomeric Chapter 9 - Stereochemistry

48. Assign R or S to the following molecules. Chapter 9 - Stereochemistry

49. Answer Key S R S Chapter 9 - Stereochemistry

50. R, S, +, - R (-) Lactic acid S (-) Glyceraldehyde Chapter 9 - Stereochemistry