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- 2. Figure 5.3 A comparison of consitutional isomers and stereoisomers
- 3. Are the following pairs of compounds consitutional isomers or stereoisomers? a) b) c) constitutional constitutional stereoisomer
- 4. Although everything has a mirror image, mirror images may or may not be superimposable. Some molecules
- 5. Other molecules are like socks. Two socks from a pair are mirror images that are superimposable.
- 6. We can now consider several molecules to determine whether or not they are chiral.
- 7. The molecule labeled A and its mirror image labeled B are not superimposable. No matter how
- 8. In general, a molecule with no stereogenic centers will not be chiral. There are exceptions to
- 10. Summary of the Basic Principles of Chirality: Everything has a mirror image. The fundamental question is
- 11. Clasiffy each of the following pairs as chiral or achiral. a) b) c) achiral chiral chiral
- 12. To locate a stereogenic center, examine each tetrahedral carbon atom in a molecule, and look at
- 13. Larger organic molecules can have two, three or even hundreds of stereogenic centers.
- 14. Label the stereogenic centers in each molecule and decide if it is chiral. a) CH3CH2CH(Cl)CH2CH3 achiral
- 15. How many stereogenic centers does each molecule have? a) b)
- 16. c) Only carbons attached to four different groups.
- 17. To draw both enantiomers of a chiral compound such as 2-butanol, use the typical convention for
- 18. Figure 5.5 Three-dimensional representations for pairs of enantiomers
- 19. Locate each stereogenic center and draw both enantiomers. a) CH3CH(Cl)CH2CH3 b)CH3CH2CH2CH(NH2)COOH
- 20. Stereogenic centers may also occur at carbon atoms that are part of a ring. To find
- 21. In 3-methylcyclohexene, the CH3 and H substituents that are above and below the plane of the
- 22. Locate the stereogenic center in the following: a) No stereogenic centers. b)
- 23. Since enantiomers are two different compounds, they need to be distinguished by name. This is done
- 24. If two atoms on a stereogenic center are the same, assign priority based on the atomic
- 25. If two isotopes are bonded to the stereogenic center, assign priorities in order of decreasing mass
- 26. To assign a priority to an atom that is part of a multiple bond, treat a
- 27. Figure 5.6 Examples of assigning priorities to stereogenic centers
- 29. Labeling Stereogenic Centers with R or S
- 31. Figure 5.7 Examples: Orienting the lowest priority group in back
- 32. Which group in each pair has the highest priority? a) -CH3 or -CH2CH3 b) -I or
- 33. Rank in order of decreasing priority: a) -COOH -H -NH2 -OH b) 3 2 1 4
- 34. Label each compound as R or S. a) S b) R
- 35. For a molecule with n stereogenic centers, the maximum number of stereoisomers is 2n. Let us
- 36. If you have drawn the compound and the mirror image in the described manner, you have
- 37. Switching the positions of H and Br (or any two groups) on one stereogenic center of
- 38. Figure 5.8 Summary: The four stereoisomers of 2,3- dibromopentane
- 39. Label the stereogenic centers and draw all stereoisomers. a) CH3CH2CH(Cl)CH(OH)CH2CH3
- 40. Let us now consider the stereoisomers of 2,3-dibromobutane. Since this molecule has two stereogenic centers, the
- 41. To find the other two stereoisomers if they exist, switch the position of two groups on
- 42. Compound C contains a plane of symmetry, and is achiral. Meso compounds generally contain a plane
- 43. Figure 5.9 Summary: The three stereoisomers 2,3- dibromobutane
- 44. Draw the enantiomer and one diastereomer for the following compound.
- 45. Superimposable mirror images, same compound Meso compound due to presence of plane of symmetry.
- 46. When a compound has more than one stereogenic center, R and S configurations must be assigned
- 47. Consider 1,3-dibromocyclopentane. Since it has two stereogenic centers, it has a maximum of four stereoisomers. Disubstituted
- 48. To find the other two stereoisomers if they exist, draw the mirror images of each compound
- 49. The trans isomer is not superimposable on its mirror image, labeled C, making B and C
- 50. Figure 5.10 Summary—Types of isomers
- 51. Figure 5.11 Determining the relationship between two nonidentical molecules
- 52. Without looking at the structures, label each pair as either enantiomers or diastereomers. a) (2R,3S)-2,3-hexanediol or
- 53. Which of the following are meso compounds? a) b) Not meso, no plane of symmetry meso
- 54. Draw all possible stereoisomers, then pair up enantiomers and diastereomers A and B are enatiomers, and
- 55. Stae how each pair are related: eantiomers, diastereomers, constitutional isomers or identical. a) Same formula Same
- 56. The chemical and physical properties of two enantiomers are identical except in their interaction with chiral
- 57. With achiral compounds, the light that exits the sample tube remains unchanged. A compound that does
- 58. With chiral compounds, the plane of the polarized light is rotated through an angle α. The
- 59. The rotation of polarized light can be clockwise or anticlockwise. If the rotation is clockwise (to
- 60. An equal amount of two enantiomers is called a racemic mixture or a racemate. A racemic
- 61. Specific rotation is a standardized physical constant for the amount that a chiral compound rotates plane-polarized
- 62. Enantiomeric excess (optical purity) is a measurement of how much one enantiomer is present in excess
- 63. Since enantiomers have identical physical properties, they cannot be separated by common physical techniques like distillation.
- 64. A compound was isolated in the lab and the observed roation was +10 when measured in
- 65. What is the ee of the following racemic mixture? 95% A and 5% B ee =
- 66. A pure compound has a specific rotation of +24, a solution of this compound has a
- 67. Two enantiomers have exactly the same chemical properties except for their reaction with chiral non-racemic reagents.
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