Deck 14: Chirality: the Handedness of Molecules

Question 1

Which of the following molecules is chiral?

A) 2-methyl-2-propanol
B) 2-butene
C) 2-bromopropane
D) 2-chlorobutane

Answer 1

D

Question 2

Identify a molecule that is achiral.

A) 2-chlorobutane
B) 1,2-dichloropropane
C) 3-bromopentane
D) 3-bromo-1-butene

Answer 2

C

Question 3

Which of the following three isomeric alcohols is chiral: 2,2-dimethyl-1-butanol, 2-methyl-2-pentanol, and 2-methyl-3-pentanol?

A) Only 2,2-dimethyl-1-butanol is chiral.
B) Only 2-methyl-3-pentanol is chiral.
C) Both 2,2-dimethyl-1-butanol and 2-methyl-3-pentanol are chiral.
D) Both 2-methyl-2-pentanol and 2-methyl-3-pentanol are chiral.

Answer 3

B

Question 4

Given the compounds cis-1,4-dimethylcyclohexane and trans-1,4-dimethylcyclohexane, which of the following statements is/are true? (i) these two compounds are related to each other as stereoisomers;
(ii) cis-1,4-dimethylcyclohexane is chiral;
(iii) trans-1,4-dimethylcyclohexane is chiral.

A) Only (i) is true.
B) Only (i) and (ii) are true.
C) Only (ii) and (iii) are true.
D) Only (i) and (iii) are true.

Question 5

Identify a class of isomers that has the same connectivity of atoms without any stereocenters.

A) enantiomers
B) diastereomers
C) constitutional isomers
D) cis-trans isomers

Question 6

Why is 4-ethyl-1,1-dimethylcyclohexane achiral?

A) because it has nonsuperimposable mirror images
B) because it has more than one stereocenter
C) because all ring carbon atoms are bonded to two identical groups
D) because all ring carbon atoms are bonded to four different groups

Question 7

Given the compounds 2,3-dimethylpentane and 3-methylhexane, which of the following is true?

A) Only 2,3-dimethylpentane is chiral.
B) Only 3-methylhexane is chiral.
C) Both are chiral.
D) Neither is chiral.

Question 8

Which of the following three isomeric alcohols, 2-pentanol, 2-methyl-2-butanol, and 3-methyl-2-butanol, is/are chiral?

A) only 2-pentanol
B) only 2-methyl-2-butanol
C) both 2-pentanol and 2-methyl-2-butanol
D) both 2-pentanol and 3-methyl-2-butanol

Question 9

How many stereocenters are present in the following compound?

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

Question 10

Which statement is true regarding the optical activity of a pair of enantiomers?

A) Each of its members rotates the plane of polarized light by unequal degrees in opposite directions.
B) Each of its members rotates the plane of polarized light by unequal degrees in the same direction.
C) Each of its members rotates the plane of polarized light by equal degrees in opposite directions.
D) Each of its members rotates the plane of polarized light by equal degrees in the same direction.

Question 11

Which of the following would represent a racemic mixture?

A) a 1:1 mixture of 1-butanol and 2-butanol
B)
C)
D) all of these

Question 12

Which of the given structures represents the enantiomer of the following compound?

A) only
B) only
C) both and

D) none of these

Question 13

Which statement is true of a carbon atom that is a stereocenter?

A) It is bonded to two identical groups and two different groups by single bonds.
B) It has a double bond and two single bonds.
C) It is bonded to four different groups by single bonds.
D) It is bonded to two pairs of groups, with the groups of each pair being identical.

Question 14

Given the compounds 3-methyl-1-pentene and trans-3-methyl-2-pentene, which of the following statements is true?

A) Only 3-methyl-1-pentene is chiral.
B) Only trans-3-methyl-2-pentene is chiral.
C) Both are chiral.
D) Neither is chiral.

Question 15

Given the compounds 2-methyl-1-pentene and 3-methyl-1-pentene, which of the following statements is true?

A) Only 2-methyl-1-pentene is chiral.
B) Only 3-methyl-1-pentene is chiral.
C) Both are chiral.
D) Neither is chiral.

Question 16

Given the compounds 2,3-dimethylpentane and 2,4-dimethylpentane, which of the following is true?

A) Only 2,3-dimethylpentane is chiral.
B) Only 2,4-dimethylpentane is chiral.
C) Both are chiral.
D) Neither is chiral.

Question 17

There are four alcohols with the molecular formula C₄H₉OH. How many of these are chiral?

A) 0
B) 1
C) 2
D) 3

Question 18

Given the compounds 1,1,3-trimethylcyclohexane and 1,1,4-trimethylcyclohexane, which of the following statements is true?

A) Only 1,1,3-trimethylcyclohexane is chiral.
B) Only 1,1,4-trimethylcylcohexane is chiral.
C) Both are chiral.
D) Neither is chiral.

Question 19

Which of the three isomeric alcohols, 2-butanol, 2-methyl-1-propanol, and 2-methyl-2-propanol, is/are chiral?

A) only 2-butanol
B) only 2-methyl-1-propanol
C) both 2-butanol and 2-methyl-1-propanol
D) both 2-methyl-1-propanol and 2-methyl-2-propanol

Question 20

Identify a class of isomers that has different connectivity of atoms.

A) stereoisomers
B) enantiomers
C) cis-trans isomers
D) constitutional isomers

Question 21

What are the R/S configurations at the stereocenters of the following compounds?

A) (i) = R; (ii) = R
B) (i) = R; (ii) = S
C) (i) = S; (ii) = R
D) (i) = S; (ii) = S

Question 22

Which of the following molecules has an R configuration?

A) ​

B) ​

C) both and

D) none of these

Question 23

Based on the R,S system, which statement is true of the active enantiomer of ibuprofen?

A) The order of priority assigned to groups bonded to the stereocenter is as follows: -C₆H₅ > -COOH > -H > -CH₃.
B) Based on priority, the reading of the groups bonded to the stereocenter proceeds in a counterclockwise direction.
C) The -H bonded to the stereocenter points toward an observer.
D) The -CH₃ bonded to the stereocenter points away from an observer.

Question 24

Which of the following compounds can exist as a pair of enantiomers?

A) (i) and (ii) only
B) (ii) and (iii) only
C) and (iii) only
D) (i) only

Question 25

In the R,S system, which of the following groups has the highest priority?

A) alkyl
B) amino
C) hydroxyl
D) thiol

Question 26

What are the R/S configurations at the stereocenters of the following compounds?

A) (i) R; (ii) R
B) (i) R; (ii) S
C) (i) S; (ii) R
D) (i) S; (ii) S

Question 27

Which of the following is the correct order of priorities in the R,S system?

A) tert-butyl > butyl > isopropyl > propyl
B) tert-butyl > isopropyl > butyl > propyl
C) isopropyl > tert-butyl > propyl > butyl
D) propyl > butyl >isopropyl > tert-butyl

Question 28

Identify the type of isomerism shown by 1,2-dimethyl-cyclohexane.

A) constitutional isomerism
B) enantiomerism
C) cis-trans isomerism
D) diastereomerism

Question 29

Which of the following is the correct order of priorities in the R,S system?

A) aldehyde > carboxyl > ketone > primary alcohol
B) carboxyl > ketone > aldehyde > primary alcohol
C) primary alcohol > aldehyde > ketone > carboxyl
D) primary alcohol > ketone > carboxyl > aldehyde

Question 30

Which of the following molecules has an R configuration?

A) ​

B) ​

C) both and

D) none of these

Question 31

Among the following groups, which is the correct order of priorities in the R,S system?

A) (ii) > (i) > (iii) > (iv)
B) (iii) > (iv) > (ii) > (i)
C) (i) > (iii) > (ii) > (iv)
D) (iv) > (iii) > (i) > (ii)

Question 32

Among the following groups, what is the correct order of priorities in the R,S system?

A) (i) > (ii) > (iii) > (iv)
B) (ii) > (i) > (iv) > (iii)
C) (iv) > (ii) > (i) > (iii)
D) (ii) > (iv) > (i) > (iii)

Question 33

Which of the following is true of 2-butanol?

A) 2-butanol is superposable on its mirror image.
B) 2-butanol and its mirror image form a pair of constitutional isomers.
C) 2-butanol and its mirror image form diastereomers.
D) 2-butanol is nonsuperposable on its mirror image.

Question 34

Which of the following molecules has an S configuration?

A) ​

B) ​

C) both and

D) none of these

Question 35

Which of the following molecules has an R configuration?

A) ​

B) ​

C) both and

D) none of these

Question 36

Which of the following carbons is a stereocenter?

A) a carbon that is bonded to two hydrogen atoms and two chlorine atoms
B) a carbonyl carbon that is bonded to a hydroxyl group and a methyl group
C) a carbon that is bonded to a hydrogen atom, a chlorine atom, a bromine atom, and an iodine atom
D) a carbonyl carbon that is bonded to a methyl group and an ethyl group

Question 37

Identify a true statement about the R,S system for specifying the configuration of a stereocenter.

A) Priorities are assigned to groups based on atomic numbers; the group with the highest atomic number is assigned the highest priority.
B) Priorities are assigned to groups based on orientation in space; a group directed toward a viewer is assigned the highest priority.
C) Priorities are assigned to groups based on atomic number; the group with the lowest atomic number is given the highest priority.
D) Priorities are assigned to groups based on orientation in space; a group directed away from a viewer is assigned the highest priority.

Question 38

Which of the following is the correct order of priorities in the R,S system?

A) alkyl > amino > hydroxyl > thiol
B) alkyl > hydroxyl > amino > thiol
C) thiol > amino > hydroxyl > alkyl
D) thiol > hydroxyl > amino > alkyl

Question 39

Which of the following is the correct order of priorities in the R,S system?

A) butyl < ethyl < methyl < propyl
B) propyl < methyl < ethyl < butyl
C) butyl < propyl < ethyl < methyl
D) methyl < ethyl < propyl < butyl

Question 40

Which of the following molecules has an R configuration?

A) ​

B) ​

C) both and

D) none of these

Question 41

How many stereoisomers are possible for 3-ethyl-4-methyl-2-hexanol?

A) 2
B) 4
C) 8
D) 16

Question 42

Illustrated here are the four stereoisomers of an amino acid that has two stereocenters. Which structure(s) is/are the diastereomer(s) of structure A?

A) B only
B) C only
C) D only
D) B and D only

Question 43

Which of the following molecules does not have an S configuration at a stereocenter?

A) ​

B) ​

C) ​

D) All these molecules have an (S)-stereocenter.

Question 44

Given the three molecules 1-methylcyclohexanol, trans-2-methylcyclohexanol, and trans-4-methylcyclohexanol, which of the following statements is true?

A) All three molecules are chiral.
B) Only 1-methylcyclohexanol and trans-2-methylcyclohexanol are chiral.
C) Only trans-2-methylcyclohexanol is chiral.
D) Only trans-2-methylcyclohexanol and trans-4-methylcyclohexanol are chiral.

Question 45

How many chiral stereoisomers are possible for 2-chlorocyclopentanol?

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

Question 46

Progesterone, which is present in humans as a single stereoisomer, has six stereocenters. Human progesterone is one of how many possible stereoisomers for this structure?

A) 6
B) 32
C) 64
D) 128

Question 47

Illustrated here are the four stereoisomers of an amino acid that has two stereocenters. Which structure(s) is/are the enantiomer(s) of structure A?

A) B only
B) C only
C) D only
D) C and D only

Question 48

How many stereoisomers are possible for the following compound?

A) 2
B) 4
C) 8
D) 16

Question 49

How many stereocenters are present in 3-methyl-2-pentanol?

A) 1
B) 2
C) 3
D) 5

Question 50

Which of the following classes of isomers has a pair of stereoisomers that are nonsuperposable mirror images?

A) diastereomers
B) enantiomers
C) cis-trans isomers
D) constitutional isomers

Question 51

How many stereocenters are present in the following triglyceride?

A) 0
B) 1
C) 4
D) 6

Question 52

How many chiral stereoisomers are possible for the following triglyceride?

A) 2
B) 4
C) 8
D) 32

Question 53

How many stereoisomers are possible for the following triglyceride? (Include all types of stereoisomerism!)

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

Question 54

What is the maximum number of stereoisomers possible for a molecule that has three stereocenters (assuming no other structural features that lead to stereoisomerism exist)?

A) 2
B) 4
C) 8
D) 16

Question 55

Which of the following pairs of stereoisomers are related as enantiomers?

A) A and B; C and D
B) A and C; B and D
C) A and D; B and C
D) C and D; B and C

Question 56

Which of the following represents the enantiomer of the following compound?

A) ​

B) ​

C) both and

D) none of these

Question 57

How many stereoisomers exist for the following compound?

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

Question 58

How many stereocenters are present in the following carbohydrate?

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

Question 59

How many stereocenters are present in 2,4-dichloro-3-hexanol?

A) 1
B) 2
C) 3
D) 5

Question 60

Which of the following represents the enantiomer of the following compound?

A) ​

B) ​

C) both and

D) none of these

Question 61

The actual rotation of a sample measured in a 10 cm cell can be directly reported as the specific rotation if the concentration of the sample is which of the following?

A) 1 M
B) 1 mg/L
C) 1 g/mL
D) 1 g/L

Question 62

Which of the following correctly describes the relationship between the R,S system and the actual rotation associated with optically active compounds?

A) All R enantiomers are dextrorotatory.
B) All S enantiomers are dextrorotatory.
C) No S enantiomers are dextrorotatory, but some R enantiomers are levorotatory.
D) There is no general relationship between the R,S designation and the actual direction of rotation of plane-polarized light.

Question 63

Which of the following statements is true of a hypothetical enzyme that catalyzes glyceraldehyde?

A) It has two binding sites: one specific for -OH and the second specific for -CHO.
B) It has two binding sites: one specific for -COOH and the second specific for -CHO.
C) It has three binding sites: one specific for -H, the second specific for -COOH, and the third specific for -CHO.
D) It has three binding sites: one specific for -H, the second specific for -OH, and the third specific for -CHO.

Question 64

Which of the following is true of 2-butanol and 2-propanol?

A) Both 2-butanol and 2-propanol have two stereocenters.
B) Both 2-butanol and 2-propanol have one stereocenter.
C) There are two stereocenters in 2-butanol and one stereocenter in 2-propanol.
D) There is one stereocenter in 2-butanol and no stereocenter in 2-propanol.

Question 65

Which of the following statements is true of dextrorotatory compounds?

A) They all rotate plane-polarized light in a clockwise direction.
B) They all rotate plane-polarized light in a counterclockwise direction.
C) They all rotate unpolarized light in a clockwise direction.
D) They all rotate unpolarized light in a counterclockwise direction.

Question 66

Which of the following is true of the drugs Motrin (ibuprofen) and Captopril?

A) They are both sold as racemic mixtures.
B) For both only a single enantiomer is manufactured and sold.
C) Motrin is sold as a racemic mixture, but Captopril is sold as a single enantiomer.
D) Captopril is sold as a racemic mixture, but Motrin is sold as a single enantiomer.

Question 67

When the sample chamber of a polarimeter is empty, which of the following statements is true?

A) The maximum transmission of light occurs when the axes of the polarizer and analyzer are parallel to each other.
B) The maximum transmission of light occurs when the axes of the polarizer and analyzer are perpendicular to each other.
C) The maximum transmission of light occurs when the axes of the polarizer and analyzer are at an angle of 120° to each other.
D) Since the instrument is empty, the positions of the polarizer and analyzer have no effect on the amount of light transmission.

Question 68

If the specific rotation of the (R)-enantiomer of a compound is −4.8°, what is the specific rotation for the racemic mixture of the compound?

A) +4.8°
B) −4.8°
C) 0°
D) +9.6°

Question 69

In which of the following are both compounds effective pain relievers?

A) (R)-ibuprofen and (R)-naproxen
B) (S)-ibuprofen and (S)-naproxen
C) (R)-ibuprofen and (S)-naproxen
D) (S)-ibuprofen and (R)-naproxen

Question 70

Chymotrypsin has 251 stereocenters. What is the maximum number of stereoisomers possible for a molecule with this number of stereocenters?

A) 251
B) 2 × 251
C) 2²⁵¹
D) 10²⁵¹

Question 71

In its pyranose form, naturally occurring D-glucose has five stereocenters. How many possible stereoisomers exist for this structure?

A) 5
B) 10
C) 25
D) 32

Question 72

In order to distinguish the R and S forms of a chiral molecule with a single stereocenter, an enzyme must have binding sites for how many of the groups on the stereocenter of the molecule?

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

Question 73

Which of the following correctly describes the relationship between the dextrorotatory/levorotatory system and the +/− system associated with optically active compounds?

A) All dextrorotatory compounds are (+).
B) All levorotatory compounds are (+)
C) No levorotatory compounds are (+), but some dextrorotatory compounds are (−).
D) There is no general relationship between the dextrorotatory/levorotatory designations and the +/− designations.

Question 74

If the specific rotation of the (R)-enantiomer of a compound is −4.8°, what is the specific rotation for the (S)-enantiomer of the compound?

A) +4.8°
B) −4.8°
C) 0°
D) +9.6 ^o

Question 75

How are the following two carbohydrates related to each other?

A) enantiomers
B) diastereomers
C) constitutional isomers
D) functional isomers

Question 76

Lactic acid, shown below, is produced by muscle exercise and can also be found in sour milk. Which of the following statements is true?

A) The racemic lactic acid produced by muscle exercise is identical to that found in sour milk.
B) The (−)-enantiomer is produced by muscle exercise and is also found in sour milk.
C) The (+)-enantiomer is produced by muscle exercise and is also found in sour milk.
D) Lactic acid produced by muscle exercise is the (+)-enantiomer, but that found in sour milk is the (−)-enantiomer.

Question 77

Which of the following statements is true of levorotatory compounds?

A) They all rotate plane-polarized light in a clockwise direction.
B) They all rotate plane-polarized light in a counterclockwise direction.
C) They all rotate unpolarized light in a clockwise direction.
D) They all rotate unpolarized light in a counterclockwise direction.

Question 78

Which of the following is true of diastereomers?

A) They possess different connectivity of atoms.
B) They are stereoisomers without stereocenters.
C) They are stereoisomers that are not mirror images.
D) They are stereoisomers whose mirror images are superposable.

Question 79

The specific rotation of a compound is defined as the observed rotation of the compound when its concentration is 1 g/mL in a sample tube that is 10 cm long. If a certain compound is observed to have a specific rotation of +8.0°, what rotation will be observed if the sample concentration is 0.25 g/mL and the sample tube is 20 cm long?

A) +2°
B) +4°
C) +16°
D) +32°

Question 80

Which of the following is essentially biologically inactive?

A) (R)-ibuprofen
B) (S)-ibuprofen
C) (R)-naproxen
D) (S)-naproxen