Question 1

Louis Pasteur's investigation of tartaric acid salts led to the discovery of molecular chirality. Which property did he observe that distinguished the two forms of tartaric acid?

Accepted Answer

They rotated plane-polarized light in opposite directions.

Question 2

Which of the following best defines a stereocenter?

Accepted Answer

A location at which the interchange of two substituents will generate a stereoisomer.

Question 3

Consider the molecule 2-bromobutane. Which statement about its enantiomers is correct?

Accepted Answer

They have identical physical properties except for their ability to rotate plane-polarized light in opposite directions.

Question 4

A racemic mixture contains:

Accepted Answer

A 50:50 mixture of two enantiomers.

Question 5

Thalidomide is a drug with two enantiomers, one of which caused birth defects. What does this illustrate about the importance of stereochemistry in pharmaceuticals?

Accepted Answer

The biological activity of a drug can depend on its stereochemistry.

Question 6

When assigning R/S configuration to a stereocenter, which rule is used to rank the substituents?

Accepted Answer

The Cahn-Ingold-Prelog (CIP) priority rules.

Question 7

How many possible stereoisomers exist for a molecule with three stereocenters, assuming none are meso?

Accepted Answer

$$2^3 = 8$

Question 8

Which statement about meso compounds is correct?

Accepted Answer

Meso compounds are achiral despite having stereocenters.

Question 9

Which of the following pairs are diastereomers?

Accepted Answer

Two stereoisomers that are not mirror images.

Question 10

In cyclic compounds, cis/trans nomenclature is used to describe:

Accepted Answer

The relative positions of substituents on the ring.

Question 11

Which of the following molecules is chiral?

Accepted Answer

A molecule with a non-superimposable mirror image.

Question 12

Which technique is commonly used to separate enantiomers in a laboratory setting?

Accepted Answer

Chiral chromatography.

Question 13

Fischer projections are especially useful for representing:

Accepted Answer

Chiral molecules, especially sugars.

Question 14

Which of the following is true about the vertical axis in a Fischer projection?

Accepted Answer

It represents bonds going away from the viewer.

Question 15

Which of the following is an example of an 'oddball' chiral molecule?

Accepted Answer

A biphenyl with restricted rotation.

Question 16

A molecule has two stereocenters. If one stereoisomer is achiral and the other is chiral, what is the achiral stereoisomer called?

Accepted Answer

Meso compound.

Question 17

Which of the following statements about enantiomers is FALSE?

Accepted Answer

Enantiomers are superimposable mirror images.

Question 18

Which of the following is the correct relationship between the two molecules shown below? (Assume they are 1-chloro-2-methylcyclohexane with different stereochemistry at both centers.)

Accepted Answer

They are diastereomers.

Question 19

If a molecule is dextrorotatory, what does this mean?

Accepted Answer

It rotates plane-polarized light to the right.

Question 20

Which of the following is NOT a method for chiral resolution?

Accepted Answer

Fractional distillation.

Stereochemistry: Concepts, Nomenclature, and Applications

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