Deck 5: Stereochemistry: Chiral Molecules

Question 1

Which of the following is the enantiomer of the following substance?

A) I
B) II
C) III
D) It does not have a non-superposable enantiomer.
E) Both II and III

Answer 1

It does not have a non-superposable enantiomer.

Question 2

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

Answer 2

C₇H₁₆

Question 3

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

Answer 3

trans-1,4- Dimethylcycloheptane

Question 4

Which molecule is achiral?

A) I
B) II
C) III
D) More than one of the above
E) None of the above

Question 5

Which structure represents (S)-2-bromobutane?

A) I
B) II
C) III
D) More than one of the above
E) None of the above

Question 6

How many stereogenic centers are there in Lovastatin ( Mevacor® : a cholesterol-lowering drug)?

A) 4
B) 5
C) 6
D) 7
E) 8

Question 7

Which of the following represent (R)-2-butanol?

A) III and V
B) I,III,IV and V
C) I,IV and V
D) I and III
E) I,II,IV and V

Question 8

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.

Question 9

Which structure represents (R)-1-chloro-1-fluoroethane?

A) I
B) II
C) III
D) More than one of the above
E) None of the above

Question 10

Which structure represents (S)-1-chloro-1-fluoroethane?

A) I
B) II
C) III
D) More than one of the above
E) None of the above

Question 11

Pairs of enantiomers are:

A) I,II and III,IV
B) I,II
C) III,IV
D) IV,V
E) None of the structures

Question 12

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

Question 13

Chiral molecules are represented by:

A) I,II,III,IV and V
B) I,II,III and IV
C) I and II
D) III and IV
E) IV alone

Question 14

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.

Question 15

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.

Question 16

Cis-trans isomers are:

A) diastereomers.
B) enantiomers.
C) stereoisomers.
D) constitutional isomers.
E) More than one of these

Question 17

(R)-2-Chlorobutane is represented by:

A) I
B) II
C) III
D) IV
E) V

Question 18

Which of the following is true about any (R)-enantiomer?

A) It is dextrorotatory.
B) It is levorotatory.
C) It is an equal mixture of + and -.
D) It is the mirror image of the (S)-enantiomer.
E) (R)indicates a racemic mixture.

Question 19

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.

Question 20

Which molecule is achiral?

A) I
B) II
C) III
D) More than one of these
E) None of these

Question 21

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

Question 22

Which of the following is(are)meso compound(s)?

A) I
B) II
C) III
D) Both II and III
E) Both I and III

Question 23

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.

Question 24

What is the percent composition of a mixture of (S)-(+)-2-butanol,[ $\alpha$ ]

= +13.52º,and (R)-(-)-2-butanol,[ $\alpha$ ]


= -13.52º,with a specific rotation [ $\alpha$ ]
= +6.76º?

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)

Question 25

The reaction of with H₂/Ni forms:

A) 2-methylheptane
B) (R)-2-methyl-5-heptanol
C) (S)-6-methyl-3-heptanol
D) (R and S)-6-methyl-3-heptanol
E) Achiral 6,6-dimethyl-3-hexanol

Question 26

Which of the following is a meso compound?

A) I
B) II
C) III
D) IV
E) V

Question 27

What can be said with certainty if a compound has [ $\alpha$ ] = -9.25 ?

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%.

Question 28

How many chiral stereoisomers can be drawn for CH₃CHFCHFCH(CH₃)₂?

A) 1
B) 2
C) 3
D) 4
E) 8

Question 29

Which of the following is(are)meso?

A) I
B) II
C) III
D) IV
E) Two of the above

Question 30

How many discrete dimethylcyclopropanes are there?

A) 2
B) 3
C) 4
D) 5
E) 6

Question 31

The structures represent:

A) a single compound.
B) enantiomers.
C) meso forms.
D) diastereomers.
E) conformational isomers.

Question 32

The compounds whose molecules are shown below would have:

A) the same melting point.
B) different melting points.
C) equal but opposite optical rotations.
D) More than one of the above
E) None of the above

Question 33

CH₃CHBrCH₂CHClCH₃ is the generalized representation of what number of stereoisomers?

A) 3
B) 4
C) 5
D) 6
E) 7

Question 34

Which molecule is a meso compound?

A) I
B) II
C) III
D) More than one of the above
E) None of the above

Question 35

I and II are:

A) constitutional isomers.
B) enantiomers.
C) identical.
D) diastereomers.
E) not isomeric.

Question 36

For the generalized structure BrCH₂CHClCH₂CHClCH₂Br there exists what number of stereoisomers?

A) 2
B) 3
C) 4
D) 6
E) 8

Question 37

An alkane which can exhibit optical activity is:

A) Neopentane
B) Isopentane
C) 3-Methylpentane
D) 3-Methylhexane
E) 2,3-Dimethylbutane

Question 38

I and II are:

A) constitutional isomers.
B) enantiomers.
C) identical.
D) diastereomers.
E) not isomeric.

Question 39

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.

Question 40

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) +50
B) +25
C) +15
D) +7.5
E) +4.0

Question 41

The molecules below are:

A) constitutional isomers.
B) enantiomers.
C) diastereomers.
D) identical.
E) stereoisomers.

Question 42

The molecules below are:

A) constitutional isomers.
B) enantiomers.
C) diastereomers.
D) identical.
E) None of these

Question 43

The molecules below are:

A) structural isomers.
B) enantiomers.
C) diastereomers.
D) identical.
E) None of these

Question 44

The molecules below are:

A) enantiomers.
B) diastereomers.
C) constitutional isomers.
D) two different conformations of the same molecule.
E) not isomeric.

Question 45

I and II are:

A) constitutional isomers.
B) enantiomers.
C) identical.
D) diastereomers.
E) not isomeric.

Question 46

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.

Question 47

I and II are:

A) constitutional isomers.
B) enantiomers.
C) identical.
D) diastereomers.
E) not isomeric.

Question 48

I and II are:

A) constitutional isomers.
B) enantiomers.
C) identical.
D) diastereomers.
E) not isomeric.

Question 49

The molecules below are:

A) constitutional isomers.
B) enantiomers.
C) diastereomers.
D) identical.
E) None of these

Question 50

The molecules shown are:

A) constitutional isomers.
B) enantiomers.
C) diastereomers.
D) identical.
E) None of these

Question 51

I and II are:

A) constitutional isomers.
B) enantiomers.
C) identical.
D) diastereomers.
E) not isomeric.

Question 52

The molecules below are:

A) constitutional isomers.
B) enantiomers.
C) diastereomers.
D) identical.
E) None of these

Question 53

The molecules below are:

A) constitutional isomers.
B) enantiomers.
C) diastereomers.
D) identical.
E) None of these

Question 54

I and II are:

A) constitutional isomers.
B) enantiomers.
C) identical.
D) diastereomers.
E) not isomeric.

Question 55

The two compounds shown below are: are:

A) identical.
B) enantiomers.
C) diastereomers.
D) conformational isomers.
E) meso forms.

Question 56

I and II are:

A) constitutional isomers.
B) enantiomers.
C) identical.
D) diastereomers.
E) not isomeric.

Question 57

Hexane and 3-methylpentane are examples of:

A) enantiomers.
B) stereoisomers.
C) diastereomers.
D) constitutional isomers.
E) None of these

Question 58

The molecules below are:

A) constitutional isomers.
B) enantiomers.
C) diastereomers.
D) identical.
E) None of these

Question 59

The molecules below are:

A) constitutional isomers.
B) enantiomers.
C) diastereomers.
D) identical.
E) None of these

Question 60

The molecules below are:

A) constitutional isomers.
B) enantiomers.
C) diastereomers.
D) identical.
E) None of these

Question 61

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

Question 62

The compounds whose molecules are shown below would have:

A) the same melting point.
B) different melting points.
C) equal but opposite optical rotations.
D) More than one of the above
E) None of the above

Question 63

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"

Question 64

The molecules shown are:

A) constitutional isomers.
B) enantiomers.
C) diastereomers.
D) identical.
E) None of these

Question 65

I and II are:

A) constitutional isomers.
B) enantiomers.
C) identical.
D) diastereomers.
E) not isomeric.

Question 66

Which compound does NOT possess a plane of symmetry?

A) I,II and V
B) I,III and IV
C) II,III and IV
D) III and IV
E) V

Question 67

I and II are:

A) constitutional isomers.
B) enantiomers.
C) identical.
D) diastereomers.
E) not isomeric.

Question 68

I and II are:

A) constitutional isomers.
B) enantiomers.
C) identical.
D) diastereomers.
E) not isomeric.

Question 69

Which molecule has a plane of symmetry?

A) I
B) II
C) III
D) More than one of these
E) None of these

Question 70

Which compound above (I-IV)is (2R,3R)-2,3-butanediol?

A) I
B) II
C) III
D) IV
E) None of these

Question 71

Which of the following substances is achiral ?

A) I
B) II
C) III
D) IV
E) More than one of these

Question 72

The The molecules shown are:

A) enantiomers.
B) diastereomers.
C) constitutional isomers.
D) two conformations of the same molecule.
E) not isomeric.

Question 73

Which molecule has a plane of symmetry?

A) I
B) II
C) III
D) More than one of these
E) None of these

Question 74

I and II are:

A) constitutional isomers.
B) enantiomers.
C) identical.
D) diastereomers.
E) not isomeric.

Question 75

I and II are:

A) constitutional isomers.
B) enantiomers.
C) identical.
D) diastereomers.
E) not isomeric.

Question 76

Which compound above (I-IV)is a meso compound?

A) I
B) II
C) III
D) IV
E) None of these

Question 77

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

Question 78

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

Question 79

Which molecule is a meso compound?

A) I and II
B) IV and V
C) II and III
D) I,II and III
E) None of the above

Question 80

The molecules shown are:

A) constitutional isomers.
B) enantiomers.
C) diastereomers.
D) identical.
E) None of these