Question 1

Which of the following statements best describes an enantiomer?

Accepted Answer

A stereoisomer that is nonsuperimposable on its mirror image.

Question 2

Which property distinguishes enantiomers from each other?

Accepted Answer

Ability to rotate plane-polarized light

Question 3

According to the Cahn-Ingold-Prelog rules, which group has the highest priority when attached to a stereogenic center?

Accepted Answer

Bromine

Question 4

A molecule has four different substituents: -H, -OH, -CH3, and -COOH. Which of the following is true about its stereochemistry?

Accepted Answer

It can exist as a pair of enantiomers.

Question 5

If the lowest priority group is pointing away from you and the order of decreasing priority (1→2→3) follows a clockwise rotation, what is the absolute configuration?

Accepted Answer

R (rectus)

Question 6

Which of the following best describes a racemic mixture?

Accepted Answer

A mixture containing equal amounts of two enantiomers.

Question 7

Which term describes the less active enantiomer of a chiral drug?

Accepted Answer

Distomer

Question 8

The eudismic ratio (ER) is defined as:

Accepted Answer

The ratio of the activity of the eutomer to the distomer.

Question 9

Which of the following is a consequence of the distomer in a racemic drug mixture?

Accepted Answer

It may be inactive or display no undesirable effects.

Question 10

Quinine and quinidine are classical examples of:

Accepted Answer

Enantiomers with independent therapeutic benefits.

Question 11

Which of the following statements about thalidomide is correct?

Accepted Answer

The (S) enantiomer is teratogenic, while the (R) enantiomer is sedative.

Question 12

Ibuprofen is supplied as a racemic mixture. Why does the racemate provide more than 50% of the expected analgesic activity?

Accepted Answer

The inactive (R)-(-)-isomer is metabolically converted to the active (S)-(+)-isomer.

Question 13

Which intermediate is formed during the acid-catalyzed racemization of ibuprofen?

Accepted Answer

Enediol

Question 14

Which of the following is NOT a type of stereoisomerism?

Accepted Answer

Structural isomerism

Question 15

A molecule with two chiral centers can be a meso compound if:

Accepted Answer

It has a plane of symmetry and is optically inactive.

Question 16

Which step is NOT part of the Cahn-Ingold-Prelog system for assigning R/S configuration?

Accepted Answer

Assigning priorities based on boiling point.

Question 17

Which of the following best explains the three-point receptor theory for chiral drugs?

Accepted Answer

Only one enantiomer has the optimal spatial arrangement to interact with the receptor.

Question 18

Which of the following is the correct order of priority for the following atoms attached to a stereocenter: F, Cl, Br, I?

Accepted Answer

$$	ext{I} \u003e 	ext{Br} \u003e 	ext{Cl} \u003e 	ext{F}$$

Question 19

Which of the following is true about the physical properties of enantiomers?

Accepted Answer

They have identical physical properties except for optical rotation.

Question 20

A chiral drug is administered as a racemic mixture. Which scenario would justify this practice?

Accepted Answer

The distomer is inactive and displays no undesirable effects.

Stereochemistry II: Chirality, Enantiomers, and Biological Activity

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