Question 1

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

Accepted Answer

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

Question 2

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

Accepted Answer

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

Question 3

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

Accepted Answer

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

Question 4

Which of the following molecules has an S configuration?

Accepted Answer

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

Question 5

Among the following groups, what is the correct priority ordering in the R,S system?

Accepted Answer

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

Question 6

The drugs Prilosec and Nexium both contain the same active ingredient. Nexium contains a single enantiomer but Prilosec is a racemic mixture. Which of the following is probably true regarding 20 mg doses of the two different drugs?

Accepted Answer

A)  Both drugs will be equally effective. 
B)  Both drugs can be prepared using the same synthetic procedure. 
C)  Nexium will be more effective than Prilosec. 
D)  Prilosec will be more effective than Nexium. 
A)  Both drugs will be equally effective. 
B)  Both drugs can be prepared using the same synthetic procedure. 
C)  Nexium will be more effective than Prilosec. 
D)  Prilosec will be more effective than Nexium.

Question 7

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

Accepted Answer

A)  251 
B)  2 × 251 
C)  2251 
D)  10251 
A)  251 
B)  2 × 251 
C)  2251 
D)  10251

Question 8

Consider the following ball-and-stick model. Atoms other than carbon and hydrogen are indicated by the chemical symbol of the element.   If the specific rotation of this substance is +2.6°, what will be the specific rotation of the following substance?

Accepted Answer

A)  +2.6° 
B)  -2.6° 
C)  0° 
D)  +5.2° 
E)  Cannot be determined from the given data. 
A)  +2.6° 
B)  -2.6° 
C)  0° 
D)  +5.2° 
E)  Cannot be determined from the given data.

Question 9

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

Accepted Answer

A)  Only 1,1,3-trimethylcyclohexane is chiral. 
B)  Only 1,1,4-trimethylcylcohexane is chiral. 
C)  Both are chiral. 
D)  Neither is chiral. 
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 10

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

Accepted Answer

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

Question 11

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?

Accepted Answer

A)  +2° 
B)  +4° 
C)  +16° 
D)  +32° 
A)  +2° 
B)  +4° 
C)  +16° 
D)  +32°

Question 12

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

Accepted Answer

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. 
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 13

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

Accepted Answer

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

Question 14

Which of the following would represent a racemic mixture?

Accepted Answer

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

Question 15

Which of the following is a liver toxin?

Accepted Answer

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

Question 16

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

Accepted Answer

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

Question 17

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

Accepted Answer

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

Question 18

Consider the following ball-and-stick model. Atoms other than carbon and hydrogen are indicated by the chemical symbol of the element.   Which of the numbered groups is assigned the highest priority?

Accepted Answer

A)  1 
B)  2 
C)  3 
D)  4 
E)  1 and 3 are equal priority. 
A)  1 
B)  2 
C)  3 
D)  4 
E)  1 and 3 are equal priority.

Question 19

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

Accepted Answer

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

Question 20

Consider the following two ball-and-stick models. Atoms other than carbon and hydrogen are indicated by the chemical symbol of the element.     Which of the following correctly describes the compound represented by these models?

Accepted Answer

A)  chiral 
B)  stereoisomers 
C)  enantiomers. 
D)  all of these 
A)  chiral 
B)  stereoisomers 
C)  enantiomers. 
D)  all of these

Exam 15: Chirality: the Handedness of Molecules

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

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

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

Which of the following molecules has an S configuration?

Among the following groups, what is the correct priority ordering in the R,S system?

The drugs Prilosec and Nexium both contain the same active ingredient. Nexium contains a single enantiomer but Prilosec is a racemic mixture. Which of the following is probably true regarding 20 mg doses of the two different drugs?

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

Consider the following ball-and-stick model. Atoms other than carbon and hydrogen are indicated by the chemical symbol of the element. If the specific rotation of this substance is +2.6°, what will be the specific rotation of the following substance?

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

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

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

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

Which of the following would represent a racemic mixture?

Which of the following is a liver toxin?

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

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

Consider the following ball-and-stick model. Atoms other than carbon and hydrogen are indicated by the chemical symbol of the element. Which of the numbered groups is assigned the highest priority?

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

Consider the following two ball-and-stick models. Atoms other than carbon and hydrogen are indicated by the chemical symbol of the element. Which of the following correctly describes the compound represented by these models?

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