Deck 3: Stereoisomerism and Chirality

Question 1

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

Answer 1

Isomers that are not superposable on their mirror images are enantiomers

Question 2

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

Answer 2

only 1

Question 3

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

Answer 3

only 1 and 2

Question 4

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

Question 5

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

Question 6

Which of the following Newman projections represents (2R,3R)-dibromobutane?

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

Question 7

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

Question 8

Which of the following structures is different from the other three?

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

Question 9

Which of the following structures is different from the other three?

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

Question 10

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

Question 11

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

Question 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

Question 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

Question 14

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

Question 15

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

Question 16

Which of the following Newman projections represents meso-2,3-dibromobutane?

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

Question 17

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

Question 18

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

Question 19

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

Question 20

Which of the following have the S configuration?

A) only 1
B) only 2
C) only 1 and 2
D) 1, 2 and 3

Question 21

How many stereoisomers of 2,4-pentanediol, CH₃CH(OH)CH₂CH(OH)CH₃, exist?

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

Question 22

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.

Question 23

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

Question 24

How many stereoisomers of 4-bromo-2-pentanol, CH₃CH(OH)CH₂CHBrCH₃, exist?

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

Question 25

How many stereoisomers of 2,3-dimethylbutane, (CH₃)₂CHCH(CH₃)₂, exist?

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

Question 26

How many isomers (constitutional and stereoisomers) exist for dimethylcyclohexane?

A) 3
B) 5
C) 6
D) 9

Question 27

How many stereoisomers of 3-bromo-2-butanol, CH₃CH(OH)CHBrCH₃, exist?

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

Question 28

How many isomers (constitutional and stereoisomers) exist for dimethylcyclopentane?

A) 3
B) 5
C) 7
D) 9

Question 29

How many isomers (constitutional and stereoisomers) exist for dimethylcyclobutane?

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

Question 30

A pure sample of the R enantiomer of a compound has a specific rotation, [a], of +20 $\degree$ . A solution containing 0.2 g/mL of a mixture of enantiomers rotates plane polarized light by -2 $\degree$ 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

Question 31

A solution containing 0.2 g/mL of a pure R enantiomer in a 1 dm polarimeter rotates plane polarized light by +2.8 $\degree$ . What is the rotation of a solution containing 0.4 g/mL of the R isomer in the same polarimeter?

A) +0.7 $\degree$
B) +1.4 $\degree$
C) +2.8 $\degree$
D) +5.6 $\degree$

Question 32

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

Question 33

A solution of 0.1 g/mL of a pure R enantiomer in a 1 dm polarimeter rotates plane polarized light by +4.8 $\degree$ . What is the rotation observed on this solution in a 2 dm polarimeter?

A) +2.4 $\degree$
B) +4.8 $\degree$
C) +9.6 $\degree$
D) +19.2 $\degree$

Question 34

How many stereoisomers of 4-chloro-2-methylpentane (CH₃)₂CHCH₂CHClCH₃, exist?

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

Question 35

How many stereoisomers of 2,3-butanediol, CH₃CH(OH)CH(OH)CH₃, exist?

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

Question 36

How many stereoisomers of 2,4-dimethylpentane, (CH₃)₂CHCH₂CH(CH₃)₂, exist?

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

Question 37

How many stereoisomers of 3-chloro-2-methylbutane, (CH₃)₂CHCHClCH₃, exist?

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

Question 38

A solution containing 0.04 g/mL of a pure S enantiomer in a 1 dm polarimeter rotates plane polarized light by +2 $\degree$ . What is the specific rotation of the R isomer?

A) -50 $\degree$
B) -20 $\degree$
C) +10 $\degree$
D) +50 $\degree$

Question 39

How many isomers (constitutional and stereoisomers) exist for dimethylpentane?

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

Question 40

A solution containing 0.2 g/mL of a pure R enantiomer in a 1 dm polarimeter rotates plane polarized light by +3 $\degree$ . What is the specific rotation of the R isomer?

A) +0.6 $\degree$
B) +15 $\degree$
C) +67 $\degree$
D) +150 $\degree$

Question 41

Complete the following diagram so that it represents (S)-2-butanol.

Question 42

Which of the following substituents has the highest priority according to the Cahn-Ingold-Prelog system used in assigning R and S configurations?

A) -COOH
B) -CHO
C) -CH₂OH
D) -CH₃

Question 43

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

Question 44

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

Question 45

Which of the following structures has a center of symmetry?

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

Question 46

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

Question 47

Which of the following is the best definition of a pair of atropisomers?

A) A pair of enantiomers which do not interconvert.
B) A pair of enantiomers which lack chiral centers.
C) A pair of enantiomeric structures which lack chiral centers and interconvert by rotation around carbon-carbon single bonds.
D) A pair of enantiomers which lack chiral centers and do not interconvert because of hindered rotation around carbon-carbon single bonds.

Question 48

Complete the following diagram so that it represents (R)-2-bromobutane.

Question 49

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

Question 50

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

Question 51

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

Question 52

Complete the following diagram so that it represents (R)-2-bromobutane.

Question 53

Complete the following diagram so that it represents (S)-2-butanol.

Question 54

Which of the following substituents has the highest priority according to the Cahn-Ingold-Prelog system used in assigning R and S configurations?

A) -NH₂
B) -NHCH₃
C) -CH₂NH₂
D) -CH₂NHCH₃

Question 55

A pure sample of the R enantiomer of a compound has a specific rotation, [a], of -15 $\degree$ . A solution containing 0.6 g/mL of a mixture of enantiomers rotates plane polarized light by -3 $\degree$ in a 1 dm polarimeter. What is the enantiomeric excess (%ee) of the mixture?

A) 33% R
B) 33% S
C) 50% R
D) 75% R

Question 56

Which of the following structures has a center of symmetry (i.e., center of inversion)?

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

Question 57

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)

A) 3 > 4 > 1 > 2
B) 4 > 3 > 1 > 2
C) 3 > 4 > 2 > 1
D) 4 > 3 > 2 > 1

Question 58

Which of the following structures is chiral?

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

Question 59

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)

A) 3 > 4 > 2 > 1
B) 4 > 3 > 1 > 2
C) 3 > 4 > 2 > 1.
D) 4 > 3 > 2 > 1

Question 60

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

Question 61

Complete the following zig-zag structure so that it represents (2S,3R)-2,3-dibromobutane.

Question 62

Complete the following zig-zag structure so that it represents (2R,3R)-3-chlorobutan-2-ol.

Question 63

Complete the following Newman projection so that it represents (2S,3S)-2,3-butanediol.

Question 64

Complete the following Newman projection so that it represents (2R,3S)-2,3-butanediol.

Question 65

Complete the following Fischer diagram so that it represents (2R,3R)-butane-2,3-diol.

Question 66

The specific rotation of the S-enantiomer of a compound is -120 $\degree$ . A student determines that a sample of the compound has a specific rotation of +60 $\degree$ . What mass of the S-enantiomer is present in 10 g of the sample

Question 67

Complete the following Fischer diagram so that it represents (2R,3S)-butane-2,3-diol.

Question 68

The specific rotation of the S-enantiomer of a compound is -120 $\degree$ . What is the enantiomeric excess of a sample of the compound that has a measured specific rotation of -30 $\degree$ .

Question 69

Complete the following Newman projection so that it represents (2R,3R)-2,3-dibromobutane.

Question 70

Complete the following zig-zag structure so that it represents (2R,3S)-2,3-butanediol.

Question 71

What mass of (S)-(-)-mandelic acid is present in a 10 g sample which has an enantiomeric excess of 30% of the S-enantiomer?

Question 72

Complete the following zig-zag structure so that it represents (2R,3S)-3-chlorobutan-2-ol.

Question 73

Complete the following Fischer diagram so that it represents (2R,3R)-3-bromobutan-2-ol.

Question 74

Complete the following Newman projection so that it represents (2R,3S)-2,3-dibromobutane.

Question 75

Complete the following Fischer diagram so that it represents (2R,3S)-3-bromobutan-2-ol.