Question 1

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

Accepted Answer

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

Question 2

Which of the following molecules has an S configuration?

Accepted Answer

A)  ​
  
B)  ​
  
C)  both   and
  
D)  none of these 
A)  ​
  
B)  ​
  
C)  both   and
  
D)  none of these

Question 3

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

Accepted Answer

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. 
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 4

How are the following two carbohydrates related to each other?

Accepted Answer

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

Question 5

Which of the following molecules is chiral?

Accepted Answer

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

Question 6

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?

Accepted Answer

A)  +4.8° 
B)  −4.8° 
C)  0° 
D)  +9.6 o 
A)  +4.8° 
B)  −4.8° 
C)  0° 
D)  +9.6 o

Question 7

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

Accepted Answer

A)  ​
  
B)  ​
  
C)  both   and
  
D)  none of these 
A)  ​
  
B)  ​
  
C)  both   and
  
D)  none of these

Question 8

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

Accepted Answer

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. 
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 9

Which of the following molecules has an R configuration?

Accepted Answer

A)  ​
  
B)  ​
  
C)  both   and
  
D)  none of these 
A)  ​
  
B)  ​
  
C)  both   and
  
D)  none of these

Question 10

Consider the following two ball-and-stick models. Elements other than hydrogen and carbon are labeled.   If a solution contains 0.0500 mol of each substance, which of the following describes the solution?

Accepted Answer

A)  dextrorotatory 
B)  levorotatory 
C)  racemic 
D)  none of these 
A)  dextrorotatory 
B)  levorotatory 
C)  racemic 
D)  none of these

Question 11

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

Accepted Answer

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

Question 12

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?

Accepted Answer

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

Question 13

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

Accepted Answer

A)    only 
B)    only 
C)  both   and
  
D)  none of these 
A)    only 
B)    only 
C)  both   and
  
D)  none of these

Question 14

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

Accepted Answer

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. 
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 15

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?

Accepted Answer

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

Question 16

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 17

Identify a molecule that is achiral.

Accepted Answer

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

Question 18

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

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 19

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

Accepted Answer

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. 
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.

Question 20

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

Accepted Answer

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

Exam 14: Chirality: the Handedness of Molecules

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

Which of the following molecules has an S configuration?

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

How are the following two carbohydrates related to each other?

Which of the following molecules is chiral?

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?

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

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

Which of the following molecules has an R configuration?

Consider the following two ball-and-stick models. Elements other than hydrogen and carbon are labeled. If a solution contains 0.0500 mol of each substance, which of the following describes the solution?

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

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?

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

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

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

Identify a molecule that is achiral.

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

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

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

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