Question 1

Which of the following statements best distinguishes constitutional isomers from stereoisomers?

Accepted Answer

Constitutional isomers have the same molecular formula but different order of connectivity of atoms, while stereoisomers have the same molecular formula and connectivity but different spatial arrangement of atoms.

Question 2

A compound has two chiral centers. What is the maximum number of possible stereoisomers for this compound?

Accepted Answer

$$4$$

Question 3

Which of the following compounds is expected to be optically active?

Accepted Answer

A pure sample of (R)-2-butanol

Question 4

Which of the following best describes a meso compound?

Accepted Answer

A compound with two or more chiral centers that is achiral due to a plane of symmetry

Question 5

Which of the following statements about enantiomers is correct?

Accepted Answer

Enantiomers have identical physical properties except for their interaction with plane-polarized light and other chiral compounds.

Question 6

A sample of 2-bromobutane has a specific rotation of $$-4.6^\circ. $$The pure (S)-enantiomer has a specific rotation of $$-23.0^\circ. $$What is the enantiomeric excess (% ee) of the sample?

Accepted Answer

$$80\%$$

Question 7

Which of the following is true regarding the relationship between (R)/(S) configuration and (+)/(−) optical rotation?

Accepted Answer

There is no general correlation between (R)/(S) configuration and the direction of optical rotation.

Question 8

Which of the following best describes a diastereomer?

Accepted Answer

A stereoisomer that is not a mirror image of another molecule

Question 9

Which of the following methods is commonly used to separate enantiomers in a racemic mixture?

Accepted Answer

Affinity chromatography using a chiral adsorbent

Question 10

When assigning E/Z configuration to an alkene, what is the first step according to the Cahn-Ingold-Prelog rules?

Accepted Answer

Assign priorities to the groups attached to each carbon of the double bond based on atomic number

Question 11

Which of the following statements about Fischer projections is correct?

Accepted Answer

Horizontal lines represent bonds coming out of the plane of the page.

Question 12

Which of the following compounds is most likely to be a meso compound?

Accepted Answer

cis-1,2-dibromocyclohexane

Question 13

Which of the following is an example of a molecule that can be chiral without having a chiral center?

Accepted Answer

An allene with different substituents on each end

Question 14

Which of the following statements about the separation of enantiomers is correct?

Accepted Answer

Enantiomers can be separated by converting them into diastereomers using a chiral resolving agent.

Question 15

A compound has three chiral centers. What is the maximum number of stereoisomers possible for this compound?

Accepted Answer

$$8$$

Question 16

Which of the following is NOT a requirement for a molecule to be chiral?

Accepted Answer

The molecule must have at least one chiral center.

Question 17

Which of the following best describes the relationship between cis- and trans-2-butene?

Accepted Answer

They are diastereomers.

Question 18

Which of the following is true about the optical rotation of a racemic mixture?

Accepted Answer

It is zero because the rotations of the enantiomers cancel each other.

Question 19

Which of the following is the correct sequence for assigning R/S configuration to a chiral center using the Cahn-Ingold-Prelog rules?

Accepted Answer

Assign priorities, arrange lowest priority group away from you, determine direction of 1→2→3.

Question 20

Which of the following is a correct statement about atropisomers?

Accepted Answer

They are stereoisomers that cannot interconvert due to restricted rotation around a sigma bond.

Stereochemistry: Isomerism, Chirality, and Optical Activity

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