Question 1

Which of the following statements best describes the difference between absolute and relative configuration in stereochemistry?

Accepted Answer

Absolute configuration refers to the exact spatial arrangement of atoms in a molecule, while relative configuration compares the arrangement of atoms in two molecules without specifying the exact arrangement.

Question 2

Which of the following best explains why enantiomers are difficult to separate, while diastereomers are not?

Accepted Answer

Enantiomers have identical physical properties except for the direction in which they rotate plane-polarized light, while diastereomers have different physical properties such as melting point and boiling point.

Question 3

A racemic mixture of a chiral drug is passed through a column packed with a chiral stationary phase. What is the most likely outcome?

Accepted Answer

The two enantiomers will be separated because they interact differently with the chiral stationary phase.

Question 4

Which of the following is true about the D and L system for sugars and amino acids?

Accepted Answer

D and L are assigned based on the relative configuration to (+)-glyceraldehyde and (−)-glyceraldehyde, respectively.

Question 5

Which of the following molecules is chiral?

Accepted Answer

$$\mathrm{CHBrClF}$$

Question 6

Which of the following best describes a meso compound?

Accepted Answer

A compound with multiple stereocenters that is achiral due to an internal plane of symmetry.

Question 7

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

Accepted Answer

Reacting a racemic mixture with a pure chiral compound forms diastereomers, which can be separated due to their different physical properties.

Question 8

Which of the following is NOT a characteristic of enantiomers?

Accepted Answer

They have different melting points.

Question 9

Which of the following best describes the process of homolytic bond cleavage?

Accepted Answer

Each atom involved in the bond receives one electron, forming two radicals.

Question 10

Which arrow notation is used to indicate the movement of a single electron in a reaction mechanism?

Accepted Answer

A half-headed curved arrow (fishhook)

Question 11

Which of the following best describes a substitution reaction in organic chemistry?

Accepted Answer

One $$\sigma$$ bond is broken and another $$\sigma$$ bond is formed at the same carbon atom.

Question 12

Which of the following is a correct statement about the physical properties of diastereomers?

Accepted Answer

Diastereomers have different melting points and boiling points.

Question 13

Which of the following is true regarding the chirality of cis- and trans-1,2-dichlorocyclopentane?

Accepted Answer

Cis-1,2-dichlorocyclopentane is achiral due to an internal plane of symmetry, while trans-1,2-dichlorocyclopentane is chiral.

Question 14

Which of the following best explains why a molecule with only one asymmetric carbon is always chiral?

Accepted Answer

It cannot have an internal plane of symmetry, so its mirror image will always be non-superimposable.

Question 15

Which of the following is a correct statement about the R and S system of nomenclature?

Accepted Answer

The R and S system describes the absolute configuration of a chiral center based on the Cahn-Ingold-Prelog priority rules.

Question 16

Which of the following is a correct description of an addition reaction?

Accepted Answer

A $$\pi$$ bond is broken and two $$\sigma$$ bonds are formed.

Question 17

Which of the following best describes the process of chemical resolution of enantiomers?

Accepted Answer

Reacting a racemic mixture with a pure chiral compound to form diastereomers, which are then separated and hydrolyzed to yield pure enantiomers.

Question 18

Which of the following is NOT a requirement for a carbon atom to be considered an asymmetric (chiral) center?

Accepted Answer

It must be bonded to four identical groups.

Question 19

Which of the following best explains why thalidomide caused severe birth defects when prescribed as a racemic mixture?

Accepted Answer

One enantiomer was therapeutic, while the other was teratogenic, demonstrating that enantiomers can have drastically different biological effects.

Stereochemistry and Organic Reaction Mechanisms: Mini-Textbook Study Notes

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