Deck 3: Stereoisomerism and Chirality

Question 1

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

Answer 1

3R,5S

Question 2

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

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

Answer 2

4

Question 3

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

Answer 3

They react at identical rates with chiral reagents

Question 4

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 5

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 6

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

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

Question 7

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 8

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 9

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 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

Question 11

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 12

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 13

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

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

Question 14

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 15

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 16

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

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

Question 17

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 18

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 19

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

Question 20

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 21

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

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

Question 22

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

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

Question 23

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 24

A pure sample of the R enantiomer of a compound has a specific rotation, [ $\alpha$ ], of +20 ^$\circ$ . A solution containing 0.2 g/mL of a mixture of enantiomers rotates plane polarized light by -2 ^$\circ$ 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 25

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

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

Question 26

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

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

Question 27

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

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

Question 28

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 29

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

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

Question 30

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

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

Question 31

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

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

Question 32

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

A)"-50 ^$\circ$ "
B)"-20 ^$\circ$ "
C)"+10 ^$\circ$ "
D)"+50 ^$\circ$ "

Question 33

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

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

Question 34

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

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

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 isomers (constitutional and stereoisomers) exist for dimethylpentane?

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

Question 37

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

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

Question 38

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

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

Question 39

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 40

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

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

Question 41

The specific rotation of enantiomers have the same magnitude.

Question 42

Which of the following structures has a center of symmetry?

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

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

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

Question 45

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 46

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)-CN

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

Question 47

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

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

Question 48

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 49

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 50

The terms that best describe the relationship between (2R,3S)-2,3-butanediol and (2S,3S)-2,3-butanediol are configurational and diastereomers.

Question 51

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 52

How many chiral 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 53

An unknown sample is tested with a polarimeter for optical activity. The results of the test required no movement of the analyzer. This sample could be either a meso compound or a racemic mixture.

Question 54

Which of the following structures is chiral?

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

Question 55

A pure sample of the R enantiomer of a compound has a specific rotation, [\9\alpha\)], of -5 ^$\circ$ . A solution containing 0.6 g/mL of a mixture of enantiomers rotates plane polarized light by -3 ^$\circ$ 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 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 57

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 58

How many chiral 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 59

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 60

Of the compounds listed below, only 2 has a chiral centers.

Question 61

In muscle tissue only (+)-lactic acid is found but in sour milk both (+)-lactic acid and (-)-lactic acid are present. This difference might be explained by the fact that the production of lactic acid in muscle tissue is catalyzed by biological catalysts or enzymes.

Question 62

A natural product having [ $\alpha$ ]_D = +40.3 ^$\circ$ has been isolated and purified. This indicates that the natural product is dextrorotatory.

Question 63

The process that separates enantiomers is called ______________.

Question 64

For the compound shown below the number of chiral stereoisomers that can be drawn is_____.
CH₃CHClCHBrCH₃

Question 65

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

Question 66

The absolute configurations around C-2 and C-3 in the following Fischer projection are, respectively, ____. (Enter the two configurations separated by a comma.)

Question 67

Of the following molecules, both 1 and 2 have a mirror plane of symmetry.

Question 68

The following structures depicts (__)-3-ethyl-2,3-dimethylhexane.

Question 69

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

Question 70

A natural product having [ $\alpha$ ]_D = +40.3 ^$\circ$ has been isolated and purified. Either of the following substances could be this natural product.

Question 71

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

Question 72

A work glove is chiral but disposable surgical gloves are not.

Question 73

The number of chiral centers in progesterone (shown below) is ______.

Question 74

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

Question 75

______________ are stereoisomers that are not mirror images.

Question 76

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

Question 77

A mixture containing 0.50 mmol of each enantiomer is called a ___________mixture.

Question 78

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

Question 79

The following two compounds represent a pair of enantiomers.

Question 80

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