University of New England

CHEM 1020

Chapter 5 Stereoisomerism

MULTIPLE CHOICE

1)Which of the following objects is chiral?

1. 1. egg
   2. pencil
   3. cross country skis
   4. paperclip
   5. shoes

2. Chiral molecules that have nonsuperimposable mirror images are called:
   1. enantiomers
   2. diastereomers
   3. meso compounds
   4. stereogenic
   5. symmetrical

3. Which of the following molecules has a mirror plane of symmetry?

1. 1. 1
   2. 2
   3. 3
   4. 4
   5. all of them

4. What is the process that separates enantiomers?
   1. separation
   2. decoupling
   3. resetting
   4. resolution
   5. selective binding

5. A 50:50 mixture of enantiomers

1. 1. is a meso form.
   2. is a pair of diastereomers.
   3. is a racemic mixture.
   4. rotates plane polarized light.
   5. is a pair of conformers.

6. The terms that best describe the isomeric relationship between staggered and eclipsed ethane are
   1. configurational, achiral, diastereomers.
   2. conformational, chiral, enantiomers.
   3. conformational, achiral, diastereomers.
   4. configurational, chiral, enantiomers.
   5. conformational, achiral, enantiomers.

7. Which of the molecules below has a stereogenic carbon atom?

1. 1. 1
   2. 2
   3. 3
   4. 2 and 3
   5. 1, 2, and 3

8. How many stereogenic centers are present in the following molecule?

1. 1. 1
   2. 2
   3. 3
   4. 4
   5. 5

9. How many stereogenic centers are present in the following molecule?

1. 1. 1
   2. 2
   3. 4
   4. 6
   5. 8

10. How many chiral stereoisomers can be drawn for CH₃CHClCHBrCH₃?
    1. 1
    2. 2
    3. 3
    4. 4
    5. 8

11. How many stereogenic carbons are in the following molecule?

1. 1. 0
   2. 1
   3. 2
   4. 3
   5. 4

12. How many stereoisomers can be obtained from the monobromination of pentane?
    1. 1
    2. 2
    3. 3
    4. 4
    5. 5

13. How many stereoisomers with the formula CH₃CHICHICH₃ are possible?
    1. 1

1. 2. 2
   3. 3
   4. 4
   5. 5

14. 
    The number of stereogenic centers in progesterone is:

progesterone (no stereochemistry shown)

1. 1. 2
   2. 3
   3. 4
   4. 5
   5. 6

15. The total number of possible stereoisomers of                                             is:

1. 1. 2
   2. 4
   3. 6
   4. 8
   5. 0

16. The total number of possible stereoisomers of 1-bromo-2-chlorocyclopentane is:
    1. 2
    2. 4
    3. 6
    4. 8
    5. 0

17. An unknown sample is tested with a polarimeter for optical activity. The results of the test required no movement of the analyzer. What samples would give this result?
    1. pure enantiomer
    2. meso compound
    3. racemic mixture

1. 4. both B and C
   5. none of these

18. An unknown sample is tested with a polarimeter for optical activity. The results of the test require movement of the analyzer. What samples would give this result?
    1. pure enantiomer
    2. meso compound
    3. racemic mixture
    4. both B and C
    5. none of these

19. Which of the following statements about enantiomers is INCORRECT?
    1. they cannot be differentiated by spectra
    2. they have the same melting and boiling points
    3. the mirror image of the R enantiomer is the S enantiomer
    4. the specific rotation of enantiomers has the same magnitude
    5. without exception, S enantiomers will rotate plane-polarized light to the left (counterclockwise)

20. The observed rotation for 100 mL of an aqueous solution containing 1 g of sucrose, placed in a 2-decimeter sample tube, is +1.33° at 25°C. What is the specific rotation of sucrose?

A) +66.5°

B) +266°

C) +41.5

D) +133°

E) 108°

21. Which of the following molecules are the same?

1. 1. 1 and 2
   2. 3 and 4
   3. 1 and 3
   4. 2 and 3
   5. 2 and 4

22. Which of the three molecules below is the enantiomer of the following molecule?

1. 1. I
   2. II
   3. III
   4. there are no enantiomers
   5. both II and III

23. Which of the three molecules below is a diastereomer of the following molecule?

1. 1. I
   2. II
   3. III
   4. there are no diastereomers
   5. both I and II

24. Which of the following are achiral conformers?
    1. staggered and eclipsed forms of ethane
    2. cis and trans-2-butene
    3. meso and (2R,3R)-2,3-dibromobutane
    4. (R) and (S)-lactic acid

25. Which of the following would constitute a pair of enantiomers?
    1. staggered and eclipsed forms of ethane
    2. cis and trans-2-butene
    3. meso- and (2R,3R)-2,3-dibromobutane
    4. (2R,3R) and (2S,3S)-tartaric acid
    5. none of these

26. The terms that best describe the relationship between (2R,3S)-2,3-butanediol and (2S,3S)-2,3- butanediol are
    1. configurational, diastereomers.
    2. conformational, enantiomers.
    3. conformational, diastereomers
    4. configurational, enantiomers.
    5. configurational, cis/trans.

27. The terms that best describe the relationship between (2R,3S)-2-bromo-3-chlorobutane and (2S,3R)-2-bromo-3-chlorobutane are
    1. configurational, achiral, diastereomers.
    2. conformational, chiral, diastereomers.
    3. configurational, chiral, enantiomers.
    4. conformational, chiral, enantiomers.
    5. configurational, chiral, diastereomers.

28. Which of the following statements about the pair of molecules shown below is not true?

1. 1. They have the same boiling point.
   2. One rotates plane polarized light in the opposite direction from the other.
   3. They have the same density.
   4. One rotates plane polarized light a different number of degrees than the other.
   5. They are mirror images of each other.

29. According to the R-S convention, which priority is correct for the following sets of groups?
    1. NH₂ > Cl > CH₃ > H
    2. Cl > NH₂ > CH₃ > H
    3. Cl > CH₃ > NH₂ > H
    4. H > Cl > CH₃ > NH₂
    5. CH₃ > NH₂ > Cl > H

30. (R)-2-chlorobutane is correctly represented by which of the following:

1. 1. I
   2. II
   3. III
   4. IV
   5. V

31. Which of the following groups has the highest priority for assigning R-S absolute configuration?
    1. CH₂=CH–
    2. (CH₃)₂CH–
    3. (CH₃)₃C–
    4. CH₃CH₂–
    5. CH₃–

32. 
    The correct IUPAC name for the following molecule is:

1. 1. (E)-2-bromo-3-chloro-5-methyl-2-hexene
   2. (E)-2-bromo-3-chloro-5-methyl-3-hexene
   3. (Z)-2-bromo-3-chloro-5-methyl-3-hexene
   4. (Z)-2-bromo-3-chloro-5-methyl-2-hexene
   5. (E)-5-bromo-4-chloro-2-methyl-4-hexene

33. 
    Which of the following structures is (E)-2,3-dichloro-2-pentene?

1. 1. 1
   2. 2
   3. 3
   4. 4
   5. 5

34. 
    Of the following structures, how many are classified “E”?

1. 1. 1
   2. 2
   3. 3
   4. 4
   5. 5

35. 
    Of the following structures, how many are classified “Z”?

1. 1. 1
   2. 2
   3. 3
   4. 4
   5. 5

36. Which of the following structures depicts (R)-3-ethyl-2,3-dimethylhexane?
    1. 
       D)
    2. E)

C)

37. The priority order for R/S nomenclature is
    1. —CH=CH₂ > —OH > —CH₃ > —CH₂CH₃
    2. —OH > —CH₂CH₃ > —CH=CH₂ > —CH₃
    3. —OH > —CH=CH₂ > —CH₂CH₃ > —CH₃
    4. —CH₃ > —CH₂CH₃ > —CH=CH₂ > —OH
    5. —CH₂CH₃ > —CH₃ > —CH=CH₂ > —OH

38. Which name describes the following structure?

1. 1. (R)-3-methyl-1-penten-3-ol

1. 2. (S)-3-methyl-1-penten-3-ol
   3. (R)-3-ethyl-1-buten-3-ol
   4. (R)-3-methyl-1-pentyn-3-ol
   5. (S)-3-ethyl-1-buten-3-ol

39. Which name describes the following structure?

1. 1. (R)-4-methyl-1-hexen-4-ol
   2. (S)-4-ethyl-1-penten-4-ol
   3. (R)-4-ethyl-1-penten-3-ol
   4. (S)-4-methyl-1-hexen-4-ol
   5. (S)-4-methyl-1-hexyn-4-ol

40. 
    What is correct name for the following structure?

1. 1. (R,S)-2,3-dichlorobutane
   2. (2R,3S)-2,3-dichlorobutane
   3. (2S,3S)-2,3-dichlorobutane
   4. (2R,3R)-2,3-dichlorobutane
   5. none of these

41. What is the absolute configuration around C-2 and C-3?

1. 1. R, R
   2. S, S
   3. R, S

1. 4. S, R
   5. E, Z

42. 
    The absolute configuration around the stereogenic center of the molecule below is:

1. 1. R
   2. S
   3. E
   4. Z
   5. trans

43. The Fischer projection formula for (S)-lactic acid (2-hydroxypropanoic acid) is
    1. D)

1. 2. E)

C)

44. The Fischer projection that represents the same molecule as                                    is:

1. 1. D)

1. 2. 
      E)

C)

45. represents

1. 1. (2R,3R)-2,3-butanediol.
   2. (2S,3S)-2,3-butanediol.
   3. the most stable conformer of (2R,3R)-2,3-butanediol.
   4. the least stable conformer of (2R,3R)-2,3-butanediol.
   5. meso-2,3-butanediol.

46. Which one of the following structures represents a meso compound?
    1. 
       D)
    2. E)

47. When (R)-3-bromo-2-methyl-1-butene is reacted with HBr, two stereoisomers are formed. What is the relationship of these stereoisomers?
    1. enantiomers
    2. meso compounds
    3. diastereomers
    4. E
    5. Z

48. Treating 1-butene with HBr produces a product with one stereogenic carbon. What is the name of the product?
    1. 2-bromo-1-butene
    2. 1-bromobutane
    3. (R)-2-bromobutane
    4. (S)-2-bromobutane
    5. both C and D in equal amounts

49. When (S)-3-bromo-1-butene is treated with HBr, two stereoisomeric products form. What is the relationship of these two products?
    1. enantiomers
    2. diastereomers
    3. meso compounds
    4. racemic mixture
    5. cis/trans

50. How many stereogenic carbons are produced from the following sequence of reactions?