Chapter 5
Chapter 5
MULTIPLE CHOICE QUESTIONS Part 5: Stereochemistry
Answers on page 24-26
Topic: Identifications and Comparisons
5. Pairs of enantiomers are:
CH3
H3C
1. Which of the following is the enantiomer of the following substance?
H
H
H
Br
A)
B)
C)
D)
E)
CH3
Br
H
CH3
CH3
CH3
Br
H
H
I
C C
C
H
HO2C
CH3
H
II
F
III
3. Hexane and 3-methylpentane are examples of:
A) enantiomers.
B) stereoisomers.
C) diastereomers.
D) constitutional isomers.
E) None of these
CH2CH3
Cl
A)
B)
C)
D)
E)
III
H
CO2H
IV
CH3
HO
Br
H
H
CH2CH3
I
II
constitutional isomers.
enantiomers.
non-superposable mirror images.
diastereomers.
not isomeric.
1
H
CH2CH2CH3
V
6. Chiral molecules are represented by:
CH3
CH2CH3
H3C
V
Cl
CH3
H 3C
C2H5
II
I
I, II, III, IV and V
I, II, III and IV
I and II
III and IV
IV alone
A)
B)
C)
D)
E)
7. The molecules shown are:
H
H
OH
H
Br
H
H
OH
Br
C2H5
H
CH3
Cl
C2H5
A)
B)
C)
D)
E)
CH2Cl
CH2Cl
H
Cl
IV
I, II and III, IV
I, II
III, IV
IV, V
None of the structures
CH3
4. I and II are:
H
OH
HO
H
Cl
I
II
III
IV
V
H3C
H
Br
OH
I
A)
B)
C)
D)
E)
CO2H
OH
II
CH2CH2CH3
A)
B)
C)
D)
E)
Cl
I
H
CO2H
H
H
H3C
CH2CH2CH3
H3C
2. Which of the following molecules is achiral?
H 3C
H
CH3
CH2CH2CH3
III
I
II
III
It does not have a non-superposable enantiomer.
Both II and III
Cl
CH2CH2CH3
H
Br
H
II
CH3
Cl
H
CH3
constitutional isomers.
enantiomers.
diastereomers.
identical.
None of these
2
Cl
H 3C
Cl
CH2Cl
H
H
C2H5
H
C 2H 5
III
IV
V
Chapter 5
Chapter 5
The
8. The molecules shown are:
12. The molecules shown are:
Cl
H3CH2C
H
H
Cl
and
Cl
CH2CH3
Cl
H
CH2CH3
A)
B)
C)
D)
E)
H
H
are
enantiomers.
diastereomers.
constitutional isomers.
two conformations of the same molecule.
not isomeric.
H
H
CH3
A)
B)
C)
D)
E)
constitutional isomers.
enantiomers.
diastereomers.
identical.
None of these
H
H
F
H
H
CH3
F
H
F
constitutional isomers.
enantiomers.
diastereomers.
identical.
None of these
A)
B)
C)
D)
E)
10. The molecules below are:
F
OH
13. The molecules shown are:
CH3
H
OH
H
CH2CH3
9. The molecules shown are:
A)
B)
C)
D)
E)
CH3
H
F
constitutional isomers.
enantiomers.
diastereomers.
identical.
None of these
14. The molecules below are:
H
CH3
H
H
CH3
H
H
F
H
H
F
F
A)
B)
C)
D)
E)
constitutional isomers.
enantiomers.
diastereomers.
identical.
stereoisomers.
CH3
A)
B)
C)
D)
E)
11. The molecules shown are:
CH3
Cl
H
CH3
A)
B)
C)
D)
E)
H
H
Cl
Cl
Cl
CH3
CH3
H
CH3
enantiomers.
diastereomers.
constitutional isomers.
two different conformations of the same molecule.
not isomeric.
3
structural isomers.
enantiomers.
diastereomers.
identical.
None of these
15. Cis-trans isomers are:
A) diastereomers.
B) enantiomers.
C) stereoisomers.
D) constitutional isomers.
E) More than one of these
Ans: E
4
Chapter 5
16. The molecules below are:
20. The molecules below are:
Cl
CH3
Cl
F
Br
CH3
I
II
A)
B)
C)
D)
E)
constitutional isomers.
enantiomers.
diastereomers.
identical.
None of these
H
CH3
Cl
H
F
H
Cl
Br
H
Br
Cl
H3C
F
Br
H
H
Cl
Cl
F
F
A)
B)
C)
D)
E)
CH3
21. Which molecule is achiral?
CH3
CH3
Cl
CH3
Cl
17. The molecules below are:
H2N
H
H
constitutional isomers.
enantiomers.
diastereomers.
identical.
None of these
H
H
H
Br
F
A)
B)
C)
D)
E)
Chapter 5
Cl
NH2
constitutional isomers.
enantiomers.
diastereomers.
identical.
None of these
18. The molecules shown are:
H
CH3
F
F
Br
III
22. Which molecule is achiral?
A)
B)
C)
D)
E)
H
constitutional isomers.
enantiomers.
diastereomers.
identical.
None of these
Cl
CH3
F
Cl
H
A)
B)
C)
D)
E)
F
H
Br
Br
Cl
H
Cl
H
Br
Cl
Br
Br
A)
B)
C)
D)
E)
19. The molecules below are:
Br
H
Cl
I
H
H
Cl
H
II
I
II
III
More than one of the above
None of the above
III
CH3
constitutional isomers.
enantiomers.
diastereomers.
identical.
None of these
5
Br
Br
I
II
I
II
III
More than one of these
None of these
A)
B)
C)
D)
E)
Br
6
Chapter 5
Chapter 5
26. Which structure(s) represent(s) diastereomer(s) of I?
23. The molecules below are:
H
H
H
F
F
H
H
H
F
H
H
H
H
HO
HO
H
H
A)
B)
C)
D)
E)
I
F
A)
B)
C)
D)
E)
24. The structures
OH
OH
CH3
H
A)
B)
C)
D)
E)
CH3
OH
H
OH
CH3
II
I
CH3
OH
HO
OH
OH
CH3
CH3
H
H
OH
CH3
OH
CH3
OH
H
CH3
IV
V
HO
H
III
H
H
HO
II
II and III
II and IV
III and V
IV and V
Cl
H
CH3
H
H
HO
H
H
H
II
Br
H
H
HO
HO
CH3
OH
HO
HO
H
H
H
CH3
H
CH3
OH
CH3
CH3
OH
H
CH3
III
IV
V
I and II
II and III
III and IV
III and V
IV and V
H
OH
H
H
HO
F
H
Br
F
A)
B)
C)
D)
E)
25. Which pair of structures represents the same compound?
CH3
OH
H
27. The two compounds shown below are:
CH3
CH3
represent:
A) a single compound.
B) enantiomers.
C) meso forms.
D) diastereomers.
E) conformational isomers.
H
H
H
H
H
I
II
constitutional isomers.
enantiomers.
diastereomers.
identical.
None of these
CH3
CH3
OH
H
HO
OH
H
CH3
H
CH3
H
H
CH3
OH
Cl
enantiomers.
diastereomers.
constitutional isomers.
identical.
different but not isomeric.
28. The two compounds shown below are:
Br
Br
H
H
A)
B)
C)
D)
E)
Br
H
and
H
Br
are:
identical.
enantiomers.
diastereomers.
conformational isomers.
meso forms.
29. (2R,4S) –2,4–Dichloropentane and (2S,4R)-2,4-dichloropentane are:
A) enantiomers
B) diastereomers
C) identical
D) conformational isomers
E) constitutional isomers
7
8
Chapter 5
Chapter 5
30. Which of the following is a meso compound?
H
HO
H3C
CH3
H
A)
B)
C)
D)
E)
H2
C
OH
CH3
H
H3C
HO
H
I
H
H
II
CH2OH
OH
33. Which of the following is(are) meso?
OH
CH3
CH2OH
H
H
OH
CH2OH
CH2OH
CH3
III
I
II
III
IV
V
IV
V
A)
B)
C)
D)
E)
H
Br
H
Br
Br
I
A)
B)
C)
D)
E)
II
I
II
III
IV
Two of the above
F
CH3
H
H
H
Cl
CH3
CH3
Cl
H
H
Cl
Cl
H
Cl
H
Cl
CH3
CH3
CH3
I
II
III
I
II
III
Both II and III
Both I and III
Br
Cl
H
H
H
Br
Br
III
I
A)
B)
C)
D)
E)
H
H
CH3
H
CH3
CH3
II
I
II
III
More than one of these
None of these
III
35. Which molecule has a plane of symmetry?
H
32. Which of the following molecules is achiral?
A) (2R,3R)-2,3-Dichloropentane
B) (2R,3S)-2,3-Dichloropentane
C) (2S,4S)-2,4-Dichloropentane
D) (2S,4R)-2,4-Dichloropentane
E) Two of these
9
CH3
I
A)
B)
C)
D)
E)
CH2CH3
CH3
HO
H
HO
CH3
II
H
IV
H
Cl
Br
H
H
Topic: Meso compounds
34. Which molecule has a plane of symmetry?
31. Which of the following is(are) meso compound(s)?
Cl
Br
H
H
F
F
III
I
II
III
More than one of these
None of these
10
Chapter 5
Chapter 5
36. Which compound does NOT possess a plane of symmetry?
H
H
Cl
F
F
H
H
CH3
H
39. Which of the following substances is achiral ?
Br
Br
H
Br
CH3
Cl
H
A)
B)
C)
D)
E)
I
Br
II
IV
III
I, II and V
I, III and IV
II, III and IV
III and IV
V
H3C
H
Br
H3C
H
Br
H
H
OH
H3C
CH3
F
H
F
CH3
OH
CH3
I
II
III
A)
B)
C)
D)
E)
CH3
F
V
F
H
H
Br
II
CH3
Br
H
HO
III
IV
I
II
III
IV
More than one of these
40. Which statement is not true for a meso compound?
A) The specific rotation is 0º.
B) There are one or more planes of symmetry.
C) A single molecule is identical to its mirror image.
D) More than one stereogenic center must be present.
E) The stereochemical labels, (R) and (S), must be identical for each stereogenic
center.
37. Which molecule is a meso compound?
H
H
I
A)
B)
C)
D)
E)
CH3
H
41. Which is a meso compound?
A) (2R,3R)-2,3-Dibromobutane
B) (2R,3S)-2,3-Dibromopentane
C) (2R,4R)-2,4-Dibromopentane
D) (2R,4S)-2,4-Dibromopentane
E) (2R,4S)-2,4-Dibromohexane
I
II
III
More than one of the above
None of the above
38. Which molecule is a meso compound?
H
H
H
F
H
H
H
CH3
F
CH3
OH
F
F
H
H
F
H
CH3
F
CH3
I
A)
B)
C)
D)
E)
II
III
IV
I and II
IV and V
II and III
I, II and III
None of the above
V
Topic: Specific names
42. (R)-2-Chlorobutane is represented by:
A)
B)
C)
D)
E)
11
CH3
CH3
H3C
Cl
Cl
CH3
H
H3C
CH2Cl
CH2CH3
Cl
H3C
Cl
H
H
CH2CH3
CH2CH3
CH2CH3
H
CH2CH3
I
II
III
IV
V
I
II
III
IV
V
12
Chapter 5
Chapter 5
43. Which of the following represent (R)-2-butanol?
H3C
H
OH
CH3
HO
H
CH2CH3
CH2CH3
CH3
I
II
III
IV
V
CH3
F
F
Cl
H
H
H
Cl
CH3
F
I
II
III
CH3
H
Cl
Cl
F
CH3
II
I
II
III
More than one of the above
None of the above
III
46. Which structure represents (S)-2-bromobutane?
Br
CH2CH3
A)
B)
C)
D)
E)
I
Br
H
48. The Cahn-Ingold-Prelog stereochemical designations used for the following substance
are:
H
Cl
Cl
Cl
2R,4S
2S,4R
2R,4R
2S,4S
The “R,S” terminology doesn't apply in this case.
49. Which of these is not a correct Fischer projection formula of the (S) form of
3-bromo-1,1-dichloro-2-propanol ?
H
A)
B)
C)
D)
E)
CHCl2
OH
CH2Br
I
HO
CH2Br
H
CHCl2
II
H
Cl2HC
CH2Br
OH
H3C
CH2CH3
II
I
II
III
More than one of the above
None of the above
Br
CH2CH3
III
13
H
OH
CHCl2
CH2Br
IV
III
I
II
III
IV
V
H
CH3
CH3
H
is properly named:
(3R,4S,5R)- 3,5-Dichloro-4-methylhexane
(2S,3S,4S)- 2,4-Dichloro-3-methylhexane
(2S,3R,4R)- 2,4-Dichloro-3-methylhexane
(2S,3R,4S)-2,4-Dichloro-3-methylhexane
(2S,3S,4R)- 2,4-Dichloro-3-methylhexane
A)
B)
C)
D)
E)
F
H
CH3
H
CH3
H
45. Which structure represents (R)-1-chloro-1-fluoroethane?
H
CH3
Cl
Cl
I
II
III
More than one of the above
None of the above
F
Cl
H
Cl
CH3
Cl
H
A)
B)
C)
D)
E)
44. Which structure represents (S)-1-chloro-1-fluoroethane?
I
OH
CH2CH3
III and V
I, III, IV and V
I, IV and V
I and III
I, II, IV and V
A)
B)
C)
D)
E)
H
CH2CH3
A)
B)
C)
D)
E)
A)
B)
C)
D)
E)
CH2CH3
CH3
HO
OH
CH2CH3
47.
H
CH3
H
14
BrH2C
OH
CHCl2
H
V
Chapter 5
Topic: Optical activity
Chapter 5
54. The compounds whose molecules are shown below would have:
50. What is the percent composition of a mixture of (S)-(+)-2-butanol,[!] 25
= +13.52º,
D
and (R)-(-)-2-butanol,[!] 25
= -13.52º, with a specific rotation [!] 25
= +6.76º?
D
D
A) 75%(R) 25%(S)
B) 25%(R) 75%(S)
C) 50%(R) 50%(S)
D) 67%(R) 33%(S)
E) 33%(R) 67%(S)
51. Which one of the following can exist in optically active forms?
A) cis-1,3-Dichlorocyclohexane
B) trans-1,3-Dichlorocyclohexane
C) cis-1,4-Dichlorocyclohexane
D) trans-1,4-Dichlorocyclohexane
E) cis-1,2-Dichlorocyclohexane
H
OH
OH
A)
B)
C)
D)
E)
the same melting point.
different melting points.
equal but opposite optical rotations.
More than one of these
None of these
CH2CH3
H
F
H
F
CH2CH3
CH3
I
II
A)
B)
C)
D)
E)
the same melting point.
different melting points.
equal but opposite optical rotations.
More than one of the above
None of the above
53. The compounds whose molecules are shown below would have:
CH3
H
F
H
CH3
F
A)
B)
C)
D)
E)
CH3
F
H
H3C
F
H
the same melting point.
different melting points.
equal but opposite optical rotations.
More than one of the above
None of the above
15
H
OH
OH
55. The compounds whose structures are shown below would have:
CH3
Br
CH3
CH3
Br
A)
B)
C)
D)
E)
the same melting point.
different melting points.
equal but opposite optical rotations.
More than one of these
None of these
52. The compounds whose molecules are shown below would have:
CH3
H
H
Br
Br
CH3
(Ej .56. 57)
58. Which of these is a comparatively insignificant factor affecting the magnitude of
specific optical rotation?
A) Concentration of the substance of interest
B) Purity of the sample
C) Temperature of the measurement
D) Length of the sample tube
E) All of the above are equally significant.
59. What can be said with certainty if a compound has [!] 25
= -9.25º ?
D
A) The compound has the (S) configuration.
B) The compound has the (R) configuration.
C) The compound is not a meso form.
D) The compound possesses only one stereogenic center.
E) The compound has an optical purity of less than 100%.
16
Chapter 5
Chapter 5
60. An alkane which can exhibit optical activity is:
A) Neopentane
B) Isopentane
C) 3–Methylpentane
D) 3–Methylhexane
E) 2,3–Dimethylbutane
67. Enantiomers are:
A) molecules that have a mirror image.
B) molecules that have at least one stereogenic center.
C) non-superposable molecules.
D) non-superposable constitutional isomers.
E) non-superposable molecules that are mirror images of each other.
61. In the absence of specific data, it can only be said that (R)–2–bromopentane is:
A) dextrorotatory (+).
B) levorotatory (–).
C) optically inactive.
D) achiral.
E) analogous in absolute configuration to (R)–2–chloropentane.
68. Which of the following is NOT true of enantiomers? They have the same:
A) boiling point.
B) melting point.
C) specific rotation.
D) density.
E) chemical reactivity toward achiral reagents.
62. If a solution of a compound (30.0 g/100 mL of solution) has a measured rotation of +15º
in a 2 dm tube, the specific rotation is:
A) +50º
B) +25º
C) +15º
D) +7.5º
E) +4.0º
69. Which statement is true of 1,3-dimethylcyclobutane?
A) Only one form of the compound is possible.
B) Two diastereomeric forms are possible.
C) Two sets of enantiomers are possible.
D) Two enantiomeric forms and one meso compound are possible.
E) None of the previous statements is true.
63. Which compound would show optical activity?
A) cis 1,4- Dimethylcyclohexane
B) trans 1,4- Dimethylcyclohexane
C) cis 1,4- Dimethylcycloheptane
D) trans 1,4- Dimethylcycloheptane
E) More than one of these
64. Of the compounds which correspond to the general name "dichlorocyclobutane", how
many are optically active?
A) 0
B) 1
C) 2
D) 3
E) 4
Topic: General definitions
(Ej .65)
66. Which of the following is true of any (S)-enantiomer?
A) It rotates plane-polarized light to the right.
B) It rotates plane-polarized light to the left.
C) It is a racemic form.
D) It is the mirror image of the corresponding (R)-enantiomer.
E) It has the highest priority group on the left.
17
70. In which of the following reactions is the absolute configuration of the product likely to
be the same as that of the reactant?
Br
Br
A)
PBr3
(R)
OH
Br
O
B)
Br
(R)
OH
Br
OH
O
HA
O
C)
D)
E)
Br
OH
H2O
OH
(R)
All of the above
Answers A) and B) only
OH
Topic: Reaction stereochemistry
(Ej 71, 72)
73.
O
The reaction of
with H2/Ni forms:
A) 2-methylheptane.
B) (R)-2-methyl-5-heptanol
C) (S)-6-methyl-3-heptanol
D) (R,S)-6-methyl-3-heptanol
E) Achiral 6,6-dimethyl-3-hexanol
18
Chapter 5
74. CH3CHBrCH2CHClCH3 is the generalized representation of what number of
stereoisomers?
A) 3
B) 4
C) 5
D) 6
E) 7
75. For the generalized structure BrCH2CHClCH2CHClCH2Br there exists what number of
stereoisomers?
A) 2
B) 3
C) 4
D) 6
E) 8
76. How many discrete dimethylcyclopropanes are there?
A) 2
B) 3
C) 4
D) 5
E) 6
77. What is the molecular formula for the alkane of smallest molecular weight which
possesses a stereogenic center?
A) C4H10
B) C5H12
C) C6H14
D) C7H16
E) C8H18
78. How many chiral stereoisomers can be drawn for CH3CHFCHFCH(CH3)2?
A) 1
B) 2
C) 3
D) 4
E) 8
79. How many different compounds are there which correspond to the general name "3-(1methylbutyl)cyclobutanol”?
A) 2
B) 4
C) 6
D) 8
E) None of the above
19
Chapter 5
80. How many stereogenic centers are there in Lovastatin ( Mevacor® : a cholesterollowering drug) ?
HO
O
O
O
A)
B)
C)
D)
E)
(Lovastatin)
4
5
6
7
8
81. What is the total number of compounds, stereoisomers included, designated by the
general name "dichlorocyclopentane"?
A) 4
B) 5
C) 7
D) 8
E) 9
Use the following to answer questions 82-85:
Consider the following compounds:
CH2OH
H
OH
H
H
H
CH3
HO
CH3
HO
H
H
CH3
HO
CH3
CH3
H
OH
H3C
H
CH3
OH
H
OH
I
II
III
IV
82. Which of the compounds above (I-IV) represent enantiomers?
A) I and II
B) II and III
C) III and IV
D) II and IV
E) III and IV
20
Chapter 5
83. Which compound above (I-IV) is a meso compound?
A) I
B) II
C) III
D) IV
E) None of these
Chapter 5
SHORT ANSWER QUESTIONS Answers on p. 25-26
86. The molecule of aspartame ( Nutrasweet® ), depicted below, has ___________ ( how
many? ) stereogenic centers.
O
O
HO
84. Which compound above (I-IV) is (2R,3R)-2,3-butanediol?
A) I
B) II
C) III
D) IV
E) None of these
85. Which compounds above (I-IV) form a set of stereoisomers?
A) I, II and III
B) II, III and IV
C) II and III
D) I, III and IV
E) I, II, III and IV
HN
O
O
H2N
Aspartame
87. True or false: A sample consisting of the pure R enantiomer of a compound will always
rotate plane-polarized light in a clockwise direction.
A) True
B) False
88. Draw a dash-wedge structure for (3R)-3-methyl-5-hexen-3-ol
89. Draw a dash-wedge structure for (1R)-1-bromo-1,3,3-trimethylcyclohexane
90. Draw a dash-wedge structure for (1R,3R)-1,3-dibromo-1,3-dimethylcyclohexane
91. Draw a dash-wedge structure for (1S,3R)-1-ethyl-1,3-dimethylcyclopentane
92. What is the complete IUPAC name of the following substance? (Remember to give
stereochemical details, as relevant.)
H
C2H5
H3C
21
CH3
22
Chapter 5
93. What is the complete IUPAC name of the following substance? (Remember to give
stereochemical details, as relevant.)
H
OH
H3C
OH
94. Draw Fischer projection formulas for all stereoisomers of 2,4-dibromohexane, giving
stereochemical details for each structure.
95. Draw dash-wedge structures for all stereoisomers of 1-bromo-3-isopropylcyclohexane,
giving stereochemical details for each structure.
Topic: Fischer projections
96. Draw Fischer projection formulas for all stereoisomers of 2,4-dimethyl-3-hexanol,
giving stereochemical details for each structure.
97. Draw a Fischer projection formula of (3R)-6-Bromo-1-hexen-3-ol.
23
Chapter 5
Svar Part 5: Stereochemistry
Fråga
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
Svar
D
B
D
A
C
D
B
B
B
A
A
B
E
C
E
D
C
A
D
B
A
C
A
A
D
B
A
B
C
A
E
D
E
D
D
D
D
E
E
E
D
C
C
Rätt/Fel
Fråga
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
Svar
D
B
A
D
C
D
B
B
D
B
B
D
C
C
C
C
D
E
B
D
C
D
D
E
C
B
E
D
D
D
B
B
C
D
D
B
E
C
B
D
C
B
24
Rätt/Fel
Chapter 5
Chapter 5
96:
Answer 86 – 97
86:
87:
CH3
two
B
H3C
H
OH
88:
89:
CH3
H
OH
CH3
CH3
H3C
H
H3C
H
HO
H
H
OH
H3C
H
H
CH3
H
CH3
H
H
H
H
H
H
3S,4S
3R,4R
3S,4R
3R,4S
H2C
*
OH
H
92:
93:
Br
H
H
OH
H
H
H
H
CH2Br
C2H5
(3R)-6-Bromo-1-hexen-3-ol.
CH3
(1S)-1-ethyl-1,3,3-trimethylcyclopentane
(1R,3S)-1-methylcyclopentane-1,3-diol
CH3
94:
Br
CH3
CH3
H
Br
H
Br
H
H
H
H
H
H
Br
H
H
Br
Br
H
H
Br
H
H
H
H
H
H
H
H
H
CH3
CH3
2R,4S
95:
CH3
H
Br
H
H
CH3
CH3
2S,4R
2S,4S
2,4-dibromohexane
2R,4R
1-bromo-3-isopropylcyclohexane
H
H
H
H
Br
1S, 3R
H
Br
H
H
1R, 3S
Br
1S, 3S
25
Br
H
CH3
90:
CH3
H
H
CH3
2,4-dimethyl-3-hexanol
91:
H
H3C
CH3
97:
Br
H
HO
CH3
Br
Br
H3C
H
1R, 3R
26