Chapter 5
Chapter 5
MULTIPLE CHOICE CHOICE QUESTIONS Part 5: Stereochemistr y Answers on page 24-26
5. Pairs of enantiomers enantiomers are: CH3
Topic: Identifications and Comparisons H3C
1. Which of the following is the enantiomer of the following substance? substance? H
H H Br
CH3
Br H
CH3
CH3
Br H
H
I
A) B) C) D) E)
CH3
C
C
C
H
HO2C CH3
H
II
F
III
I II III IV V
3. Hexane and 3-methylpentane 3-methylpentane are examples of: A) enantiomers. B) stereoisomers. C) diastereomers. D) constitutional constitutional isomers. E) None of these
CH2CH3
A) B) C) D) E)
Cl
H CO2H
IV
CH3 HO
Br
H
H
CH2CH3
I
II
V
CH3 H3C
V
A) B) C) D) E)
Cl
CH3
C2H5
C2H5
I
II
H3C
III
7. The molecules shown shown are: H
H OH
H
H
Br
Br
Cl C2H5
I, II, III, IV and V I, II, III and IV I and II III and IV IV alone
H
C2H5
H
CH3 Cl
OH H CH3
constitutional constitutional isomers. enantiomers. diastereomers. identical. None of these
constitutional constitutional isomers. enantiomers. non-superposable mirror images. diastereomers. not isomeric.
1
H CH2CH2CH3
6. Chiral molecules are are represented by:
CH2CH3
A) B) C) D) E)
CH2Cl H
CH2Cl H
Cl
I, II and III, IV I, II III, IV IV, V None of the structures
CH3
4. I and II are: are: H3C
OH
HO
H Cl
OH
I
A) B) C) D) E)
H
Br
III
IV
CO2H
OH
II
CH2CH2 CH3
A) B) C) D) E)
Cl
I
H
CO2H H
H3C
CH2CH2CH3
H3C
2. Which of the following molecules is achiral? H
H
CH3 CH2CH2CH3
III
I II III It does does not not have have a non-superposable non-superposable enantiomer. Both II and III
H3C
Cl
CH2CH2CH3
H Br
H
II
CH3
Cl
2
H3C
Cl H
IV
CH2Cl H
H C2H5
V
Chapter 5
Chapter 5
The
8. The molecules shown are:
12. The molecules shown are:
Cl H3CH2C
H
H
Cl
Cl
and
are
H
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
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
CH2CH3
Cl
CH2CH3
A) B) C) D) E)
H
H
H
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)
CH3
structural isomers. enantiomers. diastereomers. identical. None of these
H H
Cl
Cl
Cl
CH3 H CH3
enantiomers. diastereomers. constitutional isomers. two different conformations of the same molecule. not isomeric.
3
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
NH2
constitutional isomers. enantiomers. diastereomers. identical. None of these
CH3
F
F
Br
I
II
A) B) C) D) E)
18. The molecules shown are: H
Cl
Br Br Br
III
I II III More than one of these None of these
22. Which molecule is achiral?
A) B) C) D) E)
H
constitutional isomers. enantiomers. diastereomers. identical. None of these
Cl H
A) B) C) D) E)
F
Cl
H
Cl
H
Br
Cl
Br
Br
I
A) B) C) D) E)
Cl
CH3 F
H
Br
Br
Cl
19. The molecules below are:
Br
H
Cl
H
H
II
III
I II III More than one of the above None of the above
CH3
constitutional isomers. enantiomers. diastereomers. identical. None of these
5
H
6
Chapter 5
Chapter 5
26. Which structure(s) represent(s) diastereomer(s) of I? 23. The molecules below are: H
CH3
H F
H H
F
H
H
H
H
H
F
H
H
I
II
A) B) C) D) E)
constitutional isomers. enantiomers. diastereomers. identical. None of these
H
HO
H
H
CH3
OH
HO
H
H
H
H
OH
HO
H
H
OH
H
OH
H
OH
OH OH
HO
H
CH3
CH3
CH3
CH3
CH3
I
II
III
IV
V
II II and III II and IV III and V IV and V
Br
H
H
Cl
CH3
H
CH3
CH3
H
OH
H
H
OH
HO
H
OH
H
CH3
I
OH
Br
A) B) C) D) E)
25. Which pair of structures represents the same compound? CH3 H
CH3
CH3
OH
HO
H
H
OH
H
H
OH
H
HO
H
HO
OH
HO
H
H
OH
HO
CH3
CH3
CH3
II
III
IV
V
I and II II and III III and IV III and V IV and V
Cl
enantiomers. diastereomers. constitutional isomers. identical. different but not isomeric.
28. The two compounds shown below are: Br Br
H H
H
CH3
F H
F
H
represent: A) a single compound. B) enantiomers. C) meso forms. D) diastereomers. E) conformational isomers.
A) B) C) D) E)
HO
CH3
H
27. The two compounds shown below are: CH3
CH3 CH3
H
CH3
OH
H
HO
A) B) C) D) E)
24. The structures
CH3
OH
H
H
F
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
OH H2 C
H
CH3
HO
HO
I
CH2OH
CH2OH H
OH
H
H
OH
CH2OH
CH2OH
CH3
III
IV
V
A) B) C) D) E)
I II III IV V
A) B) C) D) E)
A) B) C) D) E)
Br
Br
Br
H
H
Cl
H
Cl
H
Cl
CH3
CH3
CH3
I
II
III
I II III Both II and III Both I and III
H
H
CH3
H
H H Cl
CH3
Cl
Cl
I
A) B) C) D) E)
CH3 CH3
II
III
I II III More than one of these None of these
35. Which molecule has a plane of symmetry? H
CH2CH3
CH3
H
H
H HO
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)
CH3
HO
II
H
IV
H
F
Br
H
H
III
I II III IV Two of the above
H
Cl
H
II
Cl
CH3 CH3
H
Topic: Meso compounds 34. Which molecule has a plane of symmetry?
H
H
Br
Br
I
31. Which of the following is(are) meso compound(s)? Cl
H
Br
H
II
CH3 H
Br
CH3
H3C
H
H3C
33. Which of the following is(are) meso? OH
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
F
F
Cl
H
H
CH3
H
39. Which of the following substances is achiral ? CH3
Br
Br
H
Br
Cl
H
H
I
Br
II
A) B) C) D) E)
IV
A) B) C) D) E)
H
Br
H3C
H
Br
H
H OH
H3C
CH3
F
H
F
CH3
OH
CH3
I
II
III
A) B) C) D) E)
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? CH3
F
V
I, II and V I, III and IV II, III and IV III and IV V
H
F
CH3
I
H3C
III
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
OH
H
H
F
F
F
H
H
H
H
H
F
H
CH3
F
CH3
F
CH3 CH3
Topic: Specific names
42. (R)-2-Chlorobutane is represented by:
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
H3C
A) B) C) D) E)
11
Cl
H
CH3
CH3
I
Cl
CH3
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
CH2CH3
CH3
HO
OH
CH3
HO
H
H
OH
CH2CH3
CH2CH3
CH2CH3
CH2CH3
CH3
I
II
III
IV
V
A) B) C) D) E)
44. Which structure represents (S)-1-chloro-1-fluoroethane? CH3
F
Cl
H
H
H
Cl
Cl
H
CH3
Cl
H CH3
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
48. The Cahn-Ingold-Prelog stereochemical designations used for the following substance are: H
Cl
Cl Cl
CH3
CH3
F
I
II
III
A) B) C) D) E)
H
A) B) C) D) E)
III and V I, III, IV and V I, IV and V I and III I, II, IV and V
F
CH2CH3
47.
H
CH3
H
H Cl
I II III More than one of the above None of the above
A) B) C) D) E)
Cl
2R,4S 2S,4R 2R,4R 2S,4S The “R,S” terminology doesn't apply in this case.
45. Which structure represents (R)-1-chloro-1-fluoroethane? CH3
F
F Cl
H
H
H
Cl
Cl
CH3
F
I
II
III
H
I II III More than one of the above None of the above
46. Which structure represents (S)-2-bromobutane?
A) B) C) D) E)
Br
Br
H
HO
H
Cl2HC
OH CH2Br
H3C
CH2CH3
CH2CH3
I
II
III
OH BrH2C
CHCl2
OH
CH2Br
H
I
II
III
IV
V
I II III IV V
I II III More than one of the above None of the above
13
CHCl2
CHCl2
Br
CH2CH3
H
CH2Br
H
CH3
CH3 H
A) B) C) D) E)
OH
H
CH2Br
CHCl2
CH3
A) B) C) D) E)
49. Which of these is not a correct Fischer projection formula of the (S) form of 3-bromo-1,1-dichloro-2-propanol ?
14
Chapter 5
Chapter 5
54. The compounds whose molecules are shown below would have:
Topic: Optical activity
H
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 D D A) B) C) D) E)
75%(R) 25%(S) 25%(R) 75%(S) 50%(R) 50%(S) 67%(R) 33%(S) 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
= +6.76º?
H
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
OH
CH3 Br
F
CH2CH3 H
CH3
I
II
A) B) C) D) E)
A) B) C) D) E)
F
CH2CH3
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
CH3
Br Br
52. The compounds whose molecules are shown below would have: CH3
OH
55. The compounds whose structures are shown below would have:
CH3
H
H
Br CH3
the same melting point. different melting points. equal but opposite optical rotations. More than one of these None of these
(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 [
the same melting point. different melting points. equal but opposite optical rotations. More than one of the above None of the above
15
A) B) C) D) E)
] 25 = -9.25º ? D
!
The compound has the (S) configuration. The compound has the (R) configuration. The compound is not a meso form. The compound possesses only one stereogenic center. 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) PBr 3 (R) OH Br O
B) Br
(R)
Br OH
OH
O
HA
O Br
C) (R) D) E)
OH
OH
H2O
OH
All of the above Answers A) and B) only
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. CH3CHBrCH 2CHClCH3 is the generalized representation of what number of stereoisomers? A) 3 B) 4 C) 5 D) 6 E) 7 75. For the generalized structure BrCH 2CHClCH 2CHClCH 2Br 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
OH
H
I
II
III
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
CH3 H
OH
H3C
H OH
IV
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 H3C
two B
H
H OH
88:
89:
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
H
H
OH
H
H
Br
H
H CH2Br
C2H5
(3R)-6-Bromo-1-hexen-3-ol.
CH3
92: (1S)-1-ethyl-1,3,3-trimethylcyclopentane 93: (1R,3S)-1-methylcyclopentane-1,3-diol CH3
94: Br
CH3
CH3
CH3
H
H
Br
H
Br
H
H
H
H
H
H
H
H
Br
H
H
Br
Br
H
H
Br
H
H
H
H
H
H
H
CH3
CH3
CH3
2R,4S
2S,4R
2S,4S
Br
H
H CH3
2R,4R
2,4-dibromohexane
95:
1-bromo-3-isopropylcyclohexane H
H
H
H
Br
1S, 3R
H
Br
H
H
1R, 3S
Br
1S, 3S
25
Br
H
1R, 3R
H CH3
90:
CH3
H
H
CH3
2,4-dimethyl-3-hexanol
91:
H
H3C
CH3
97:
Br
H
HO
CH3
Br
Br
CH3 H3C
26
