Discrete Practice Questions

  1. Which of the following does NOT show optical activity?

    1. (R)-2-butanol
    2. (S)-2-butanol
    3. A solution containing 1 M (R)-2-butanol and 2 M (S)-2-butanol
    4. A solution containing 2 M (R)-2-butanol and 2 M (S)-2-butanol

  2. How many stereoisomers exist for the following aldehyde?

    5-carbon chain with a carbonyl on the end and OH bonded to the remaining 4 carbons
    1. 2
    2. 8
    3. 9
    4. 16

  3. Which of the following compounds is optically inactive?

    1. 4-carbon Fischer diagram with Cl pointing to the right on C-2 and Cl pointing to the left on C-3
    2. 4-carbon Fischer diagram with Cl pointing to the left on C-2 and Cl pointing to the right on C-3
    3. 4-carbon Fischer diagram with Cl pointing to the right on C-2 and C-3
    4. 4-carbon Fischer diagram with Cl pointing to the right on C-2 only

  4. Cholesterol, shown below, contains how many chiral centers?

    The structure of a cholesterol molecule C27H46O
    1. 5
    2. 7
    3. 8
    4. 9

  5. Which isomer of the following compound is the most stable?

    1. trans-1,2-dimethylcyclohexane in chair conformation with methyl groups in axial position
    2. trans-1,2-dimethylcyclohexane in chair conformation with methyl groups in equatorial position
    3. trans-1,3-dimethylcyclohexane in boat conformation
    4. They are all equally stable.

  6. The following reaction results in:

    Central carbon bonded to OH and H with a wedge, CH3 with a dash, and CH2CH3 reacts with CH3COCl to yield HCl and a central carbon bonded to COOCH3 and H with a wedge, CH3 with a dash, and CH2CH3
    1. retention of relative configuration and a change in the absolute configuration.
    2. a change in the relative and absolute configurations.
    3. retention of the relative and absolute configurations.
    4. retention of the absolute configuration and a change in the relative configuration.

  7. The following molecules are considered to be:

    left: 6-membered carbon ring bonded to CH3 with a wedge and the adjacent carbon bonded to another CH3 with a dash. Right: The mirror image of the molecule on the left
    1. enantiomers.
    2. diastereomers.
    3. meso compounds.
    4. structural isomers.

  8. (+)-Glyceraldehyde and (–)-glyceraldehyde refer to the (R) and (S) forms of 2,3-dihydroxypropanal, respectively. These molecules are considered:

    1. enantiomers.
    2. diastereomers.
    3. meso compounds.
    4. structural isomers.

  9. Consider (E)-2-butene and (Z)-2-butene. This is a pair of what type(s) of isomers?

    1. Cis–trans isomers
    2. Diastereomers
    3. Enantiomers
    1. I only
    2. II only
    3. I and II only
    4. I and III only

  10. 3-methylpentane and hexane are related in that they are:

    1. enantiomers.
    2. diastereomers.
    3. constitutional isomers.
    4. conformational isomers.

  11. (R)-2-chloro-(S)-3-bromobutane and (S)-2-chloro-(S)-3-bromobutane are:

    1. enantiomers.
    2. diastereomers.
    3. meso compounds.
    4. the same molecule.

  12. A scientist takes a 0.5  solution of an unknown pure dextrorotatory organic molecule and places it in a test tube with a diameter of 1 cm. He observes that a plane of polarized light is rotated 12° under these conditions. What is the specific rotation of this molecule?

    1. –240°
    2. –24°
    3. +24°
    4. +240°

  13. Omeprazole is a proton pump inhibitor commonly used in gastroesophageal reflux disease. When omeprazole, a racemic mixture, went off-patent, pharmaceutical companies began to manufacture esomeprazole, the (S)-enantiomer of omeprazole, by itself. Given 1 M solutions of omeprazole and esomeprazole, which solution(s) would likely exhibit optical activity?

    1. Omeprazole only
    2. Esomeprazole only
    3. Both omeprazole and esomeprazole
    4. Neither omeprazole nor esomeprazole

  14. (2R,3S)-2,3-dihydroxybutanedioic acid and (2S,3R)-2,3-dihydroxybutanedioic acid are:

    1. meso compounds.
    2. the same molecule.
    3. enantiomers.
    1. I only
    2. III only
    3. I and II only
    4. I and III only

  15. If the methyl groups of butane are 120° apart, as seen in a Newman projection, this molecule is in its:

    1. highest-energy gauche form.
    2. lowest-energy staggered form.
    3. middle-energy eclipsed form.
    4. highest-energy eclipsed form.