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Chapter 3 Quiz Solutions
Organic Chemistry I Honors (University of Alabama at Birmingham)
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CHAPTER 3—STEREOISOMERISM AND CHIRALITY
MULTIPLE CHOICE
1.
Which of the following is the definition of a pair of enantiomers?
a. A pair of structures that are superposable mirror images of one another
b. A pair of stereoisomers that are non-superposable mirror images of one another
c. A pair of stereoisomers that are not mirror images of one another
d. A pair of stereoisomers that have equal specific rotations
ANS: B
2.
Which of the following is the definition of a pair of diastereomers?
a. A pair of structures that are superposable mirror images of one another
b. A pair of stereoisomers that are non-superposable mirror images of one another
c. A pair of stereoisomers that are not mirror images of one another
d. A pair of stereoisomers that have equal specific rotations
ANS: C
3.
Which of the following is the definition of chirality?
a. The non-superposability of an object on its mirror image
b. The superposability of an object on its mirror image
c. A molecule that has a carbon atom with four different substituents
d. A molecule with a mirror image
ANS: A
4.
Which of the following is the definition of a meso compound?
a. A molecule with stereocenter centers which is chiral
b. A molecule with stereocenter centers which is not chiral
c. A diastereomer with no stereocenter centers
d. A chiral compound with more than one stereocenter center
ANS: B
5.
Which of the following statements is not true regarding pairs of enantiomers?
a. They have identical melting points
b. They have identical boiling points.
c. They rotate plane polarized light in opposite directions
d. They react at identical rates with chiral reagents
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ANS: D
6.
Which of the following statements is true?
a. All mirror images are enantiomers
b. All molecules that have stereocenter centers are chiral
c. Isomers that are not superposable on their mirror images are enantiomers
d. Superposable structural isomers are enantiomers
ANS: C
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7.
Which of the following structures is different from the other three?
!
a. 1
b. 2
c. 3
d. 4
ANS: D
8.
Which of the following structures is different from the other three?
!
a. 1
b. 2
c. 3
d. 4
ANS: C
9.
Which of the following compounds is/are chiral?
!
a. only 1
b. only 1 and 2
c. only 2 and 3
d. 1, 2 and 3
ANS: A
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10.
Which of the following compounds is/are chiral?
!
a. only 1
b. only 1 and 2
c. only 2 and 3
d. 1, 2 and 3
ANS: A
11.
Which of the following have the S configuration?
!
a. only 1
b. only 2
c. only 1 and 2
d. 1, 2 and 3
ANS: C
12.
Which of the following have the R configuration?
!
a. only 1
b. only 2
c. only 1 and 2
d. 1, 2 and 3
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ANS: D
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13.
What is the configuration of the two chiral centers in the following molecule?
!
a. 3R,5R
b. 3R,5S
c. 3S,5R
d. 3S,5S
ANS: B
14.
What is the configuration of the two chiral centers in the following molecule?
!
a. 3R,5R
b. 3R,5S
c. 3S,5R
d. 3S,5S
ANS: C
15.
Which of the following Newman projections represents (2R,3R)-dibromobutane?
!
a. 1
b. 2
c. 3
d. 4
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ANS: A
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16.
Which of the following Newman projections represents meso-2,3-dibromobutane?
!
a. 1
b. 2
c. 3
d. 4
ANS: C
17.
Which of the following structures represent the same stereoisomer?
!
a. only 1 and 2
b. only 1 and 3
c. only 2 and 3
d. 1, 2 and 3
ANS: C
18.
Which of the following structures represent the same stereoisomer?
!
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a. only 1 and 2
b. only 1 and 3
c. only 2 and 3
d. 1, 2 and 3
ANS: C
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19.
Which of the following structures represent the same stereoisomer?
!
a. only 1 and 2
b. only 1 and 3
c. only 2 and 3
d. 1, 2 and 3
ANS: A
20.
Which of the following compounds is a meso compound?
a. (2R,3R)-dibromobutane
b. (2R,3S)-dibromobutane
c. (2R,3S)-3-bromo-2-butanol
d. (2R,3R)-3-bromo-2-butanol
ANS: B
21.
How many stereoisomers of 2,3-dimethylbutane, (CH3)2CHCH(CH3)2, exist?
a. 1
b. 2
c. 3
d. 4
ANS: A
22.
How many stereoisomers of 3-chloro-2-methylbutane, (CH3)2CHCHClCH3, exist?
a. 1
b. 2
c. 3
d. 4
ANS: B
23.
How many stereoisomers of 3-bromo-2-butanol, CH3CH(OH)CHBrCH3, exist?
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a. 1
b. 2
c. 3
d. 4
ANS: D
24.
How many stereoisomers of 2,3-butanediol, CH3CH(OH)CH(OH)CH3, exist?
a. 1
b. 2
c. 3
d. 4
ANS: C
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25.
How many stereoisomers of 2,4-dimethylpentane, (CH3)2CHCH2CH(CH3)2, exist?
a. 1
b. 2
c. 3
d. 4
ANS: A
26.
How many stereoisomers of 4-chloro-2-methylpentane (CH3)2CHCH2CHClCH3,
exist?
a. 1
b. 2
c. 3
d. 4
ANS: B
27.
How many stereoisomers of 4-bromo-2-pentanol, CH3CH(OH)CH2CHBrCH3, exist?
a. 1
b. 2
c. 3
d. 4
ANS: D
28.
How many stereoisomers of 2,4-pentanediol, CH3CH(OH)CH2CH(OH)CH3, exist?
a. 1
b. 2
c. 3
d. 4
ANS: C
29.
How many isomers (constitutional and stereoisomers) exist for dimethylcyclobutane?
a. 3
b. 4
c. 5
d. 6
ANS: D
30.
How many isomers (constitutional and stereoisomers) exist for dimethylcyclohexane?
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a. 3
b. 5
c. 6
d. 9
ANS: D
31.
How many isomers (constitutional and stereoisomers) exist for dimethylcyclopentane?
a. 3
b. 5
c. 7
d. 9
ANS: C
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32.
How many isomers (constitutional and stereoisomers) exist for dimethylpentane?
a. 2
b. 3
c. 4
d. 5
ANS: C
33.
Which of the following statements regarding optical rotation is not true?
a. All (+) enantiomers are dextrorotatory.
b. All R enantiomers are dextrorotatory.
c. All (−) enantiomers rotate plane-polarized light in a counterclockwise direction.
d. All (+) and (−) enantiomers rotate plane-polarized light in opposite directions.
ANS: B
34.
How much of the R enantiomer is present in 10 g of a mixture which has an
enantiomeric excess of 20% of the S isomer?
a. 1 g
b. 2 g
c. 4 g
d. 6 g
ANS: C
35.
How much of the R enantiomer is present in 10 g of a mixture which has an
enantiomeric excess of 60% of the R isomer?
a. 2 g
b. 4 g
c. 6 g
d. 8 g
ANS: D
36.
A solution containing 0.2 g/mL of a pure R enantiomer in a 1 dm polarimeter rotates
plane polarized light by +3°. What is the specific rotation of the R isomer?
a. +0.6°
b. +15°
c. +67°
d. +150°
ANS: B
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38.
A solution containing 0.2 g/mL of a pure R enantiomer in a 1 dm polarimeter rotates
plane polarized light by +2.8°. What is the rotation of a solution containing 0.4 g/mL of the R isomer
in the same polarimeter?
a. +0.7°
b. +1.4°
c. +2.8°
d. +5.6°
ANS: D
40.
A pure sample of the R enantiomer of a compound has a specific rotation, [α], of
+20°. A solution containing 0.2 g/mL of a mixture of enantiomers rotates plane polarized light by −2°
in a 1 dm polarimeter. What is the enantiomeric excess (%ee) of the mixture?
a. 25% R
b. 40% S
c. 50% S
d. 70% R
ANS: C
42.
Which of the following structures has a center of symmetry?
!
a. 1
b. 2
c. 3
d. 4
ANS: C
43.
Which of the following structures has a center of symmetry (i.e., center of inversion)?
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!
a. 1
b. 2
c. 3
d. 4
ANS: C
44.
Which of the following structures have a plane of symmetry?
!
a. only 1 and 2
b. only 2 and 4
c. only 3 and 4
d. 1, 2, 3 and 4
ANS: C
45.
Which of the following structures does not have a plane of symmetry?
!
a. only 2
b. only 1 and 2
c. only 3 and 4
d. only 1, 2 and 4
ANS: A
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46.
How many stereogenic centers are there in the following molecule (the naturally
occurring stereoisomer is the male hormone testosterone)?
!
a. Three
b. Four
c. Six
d. Seven
ANS: C
47.
How many stereogenic centers are there in the following molecule (the naturally
occurring stereoisomer is camphor, a pungent moth repellent)?
!
a. Two
b. Three
c. Four
d. Five
ANS: A
49.
Which of the following structures is chiral?
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!
a. 1
b. 2
c. 3
d. 4
ANS: C
50.
Which of the following substituents has the highest priority according to the CahnIngold-Prelog system used in assigning R and S configurations?
a. −COOH
b. −CHO
c. −CH2OH
d. −CH3
ANS: A
51.
Which of the following substituents has the highest priority according to the CahnIngold-Prelog system used in assigning R and S configurations?
a. −NH2
b. −NHCH3
c. −CH2NH2
d. −CH2NHCH3
ANS: B
52.
What is the correct order of the Cahn-Ingold-Prelog ranking of the following
substituents as used in assigning R and S configurations of chiral centers? (higher ranking > lower
ranking)
1.
−C≡CH
2.
−CH2NH2
3.
−NHCH3
4.
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a. 3 > 4 > 2 > 1
b. 4 > 3 > 1 > 2
c. 3 > 4 > 2 > 1
d. 4 > 3 > 2 > 1
ANS: C
53.
What is the correct order of the Cahn-Ingold-Prelog ranking of the following
substituents as used in assigning R and S configurations of chiral centers? (higher ranking > lower
ranking)
1.
−CH2OH
2.
−CHO
3.
−OCH3
4.
−OCOCH3
a. 3 > 4 > 1 > 2
b. 4 > 3 > 1 > 2
c. 3 > 4 > 2 > 1
d. 4 > 3 > 2 > 1
ANS: D
54.
What is the relationship between the following pair of structures?
!
a. They are enantiomers
b. They are diastereomers
c. The are constitutional isomers
d. They are identical
ANS: D
55.
What is the relationship between the following pair of structures?
!
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a. They are enantiomers
b. They are diastereomers
c. The are constitutional isomers
d. They are identical
ANS: B
56.
What is the relationship between the following pair of structures?
!
a. They are enantiomers
b. They are diastereomers
c. The are constitutional isomers
d. They are identical
ANS: A
PROBLEM
1.
Complete the following diagram so that it represents (S)-2-butanol.
2.
Complete the following diagram so that it represents (S)-2-butanol.
!
ANS:
!
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!
ANS:
!
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3.
Complete the following diagram so that it represents (R)-2-bromobutane.
4.
Complete the following diagram so that it represents (R)-2-bromobutane.
!
ANS:
!
!
ANS:
!
9.
Complete the following zig-zag structure so that it represents (2R,3S)-3chlorobutan-2-ol.
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!
ANS:
!
10.
Complete the following zig-zag structure so that it represents (2R,3R)-3chlorobutan-2-ol.
!
ANS:
!
11.
Complete the following zig-zag structure so that it represents (2R,3S)-2,3-butanediol.
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!
ANS:
!
12.
Complete the following zig-zag structure so that it represents (2S,3R)-2,3dibromobutane.
!
ANS:
!
13.
Complete the following Newman projection so that it represents (2R,3R)-2,3dibromobutane.
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!
ANS:
!
14.
Complete the following Newman projection so that it represents (2R,3S)-2,3dibromobutane.
!
ANS:
!
15.
butanediol.
Complete the following Newman projection so that it represents (2S,3S)-2,3-
!
ANS:
!
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16.
butanediol.
Complete the following Newman projection so that it represents (2R,3S)-2,3-
!
ANS:
!
19.
The specific rotation of the S-enantiomer of a compound is -120º. What is the
enantiomeric excess of a sample of the compound that has a measured specific rotation of -30º.
ANS:
ee = 25% of the S-enantiomer
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