Deck 15: Chirality: the Handedness of Molecules

Question 1

Which of the following three isomeric alcohols, 2-pentanol, 2-methyl-2-butanol, and 3-methyl-2-butanol, 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

Answer 1

D

Question 2

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.

Answer 2

B

Question 3

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.

Answer 3

A

Question 4

Given the compounds 1,1-diethyl-4-methylcyclohexane, and 4-ethyl-1,1-dimethylcyclohexane, which of the following statements is true?

A) Only 1,1-diethyl-4-methylcyclohexane is chiral.
B) Only 4-ethyl-1,1-dimethylcyclohexane is chiral.
C) Both are chiral.
D) Neither is chiral.

Question 5

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 6

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

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

Question 7

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 the above

Question 8

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

A) only
B) only
C) both a and b
D) neither b nor b

Question 9

There are six alcohols with the molecular formula C₅H₁₁OH. How many of these are chiral?

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

Question 10

Which of the three isomeric alcohols, 2-butanol, 2-methyl-1-propanol, and 2-methyl-2-propanol, 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 11

Which of the following is true of a molecule which contains one stereocenter?

A) It will never be chiral.
B) It will sometimes be chiral.
C) It will always be chiral.
D) There is no relationship between chirality and the presence of a stereocenter.

Question 12

What is the fewest number of carbon atoms present in a chiral noncyclic alkane?

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

Question 13

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

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

Question 14

Which of the following statements is true?

A) Biologically important organic molecules never exhibit enantiomerism.
B) Very few biologically important organic molecules exhibit enantiomerism.
C) The vast majority of biologically important organic molecules exhibit enantiomerism.
D) All biologically important organic molecules exhibit enantiomerism.

Question 15

How many stereocenters are present in the following compound?

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

Question 16

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 17

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 18

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 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 19

If a carbon atom is a stereocenter, which of the following statements must be true about that carbon?

A) It has four single bonds.
B) It has a double bond and two single bonds.
C) It has two double bonds.
D) Any of these bonding arrangements can be associated with a stereocenter.

Question 20

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

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

Question 21

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 22

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 23

Which of the following molecules has an R configuration?

A)
B)
C) both a and b
D) neither a nor b

Question 24

Among the following groups, what is the correct priority ordering 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 25

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

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

Question 26

Which of the following molecules has an R configuration?

A)
B)
C) both a and b
D) neither a nor b

Question 27

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

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

Question 28

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 29

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

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

Question 30

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

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

Question 31

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

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

Question 32

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

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

Question 33

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

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

Question 34

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

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

Question 35

Which of the following molecules has an R configuration?

A)
B)
C) both a and b
D) neither a nor b

Question 36

Which of the following molecules has an S configuration?

A)
B)
C) both a and b
D) neither a nor b

Question 37

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 38

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

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

Question 39

Which of the following molecules has an R configuration?

A)
B)
C) both a and b
D) neither a nor b

Question 40

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 41

How many stereocenters are present in the following carbohydrate?

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

Question 42

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 43

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

A)
B)
C)
D) they all have an (S)-stereocenter

Question 44

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

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

Question 45

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

A)
B)
C) both a and b
D) neither a nor b

Question 46

How many stereoisomers are possible for the following compound?

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

Question 47

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

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

Question 48

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) none of them

Question 49

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 50

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

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

Question 51

Illustrated here are the four stereoisomers of an amino acid which 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 52

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

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

Question 53

How many stereocenters are present in the following triglyceride?

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

Question 54

How many chiral stereoisomers are possible for 2-chlorocyclopentanol?

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

Question 55

How many stereoisomers are possible for the following triglyceride? (Hint: include all types of stereoisomers!)

A) 2
B) 8
C) 32
D) 64

Question 56

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

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

Question 57

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

A)
B)
C) both a and b
D) neither a nor b

Question 58

The sugar in deoxyribonucleic acid, DNA, is called 2-deoxy-D-ribose. It is found as a single stereoisomer. How many enantiomers of 2-deoxy-D-ribose exist?

A) 0
B) 1
C) 2
D) 4

Question 59

How many stereoisomers exist for the following compound? ?

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

Question 60

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

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

Question 61

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 62

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 63

If the specific rotation of the (R)-enantiomer of a compound is -4.8^o, what will the specific rotation be for the (S)-enantiomer of the compound?

A) +4.8°
B) -4.8°
C) 0°
D) There is no way to tell.

Question 64

Which of the following is true of the ibuprofen-containing drugs Advil and Motrin?

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

Question 65

Which of the following is true of chiral drugs that are administered as single enantiomers?

A) They all have the R configuration.
B) They all have the S configuration.
C) Their enantiomers are always highly toxic.
D) None of the above is correct.

Question 66

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 67

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 68

Which of the following is essentially biologically inactive?

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

Question 69

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 70

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 polarizer and analyzer are parallel to each other.
B) The maximum transmission of light occurs when the polarizer and analyzer are perpendicular to each other.
C) The maximum transmission of light occurs when 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 transmission.

Question 71

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 which 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 72

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 73

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 74

How are the following two carbohydrates related to each other?

A) enantiomers
B) diastereomers
C) constitutional isomers
D) They are not related to each other.

Question 75

Which of the following correctly describes the relationship between the R,S system and the +/− system associated with optically active compounds?

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

Question 76

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 77

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 78

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 79

If the specific rotation of the (R)-enantiomer of a compound is -4.8^o, what will the specific rotation be for a racemic mixture of the compound?

A) +4.8^o
B) -4.8^o
C) 0⁰
D) There is no way to tell.

Question 80

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