Question 1

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

Accepted Answer

Absolute configuration describes the exact 3D arrangement of atoms in a molecule, while relative configuration is the experimentally determined relationship between the configurations of two molecules.

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 their interaction with plane-polarized light and chiral environments, while diastereomers have different physical properties such as melting point and boiling point.

Question 3

A racemic mixture of a chiral drug is synthesized in the lab. Which method would be most effective for separating the enantiomers?

Accepted Answer

Chromatography using a 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 by comparing the configuration of a compound to that of (+)- or (−)-glyceraldehyde.

Question 5

Which of the following best describes a meso compound?

Accepted Answer

A compound that is achiral despite having chiral centers due to an internal plane of symmetry.

Question 6

Which of the following statements about the physical properties of enantiomers and diastereomers is correct?

Accepted Answer

Diastereomers have different physical properties, while enantiomers have identical physical properties except for their interaction with plane-polarized light.

Question 7

Which of the following molecules is chiral?

Accepted Answer

$$\mathrm{CHBrClF}$$

Question 8

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

Accepted Answer

The bond breaks so that each atom gets one electron, forming radicals.

Question 9

In the halogenation of methane, what is the role of light ($$h
u) or $$heat ($$\Delta$$)?

Accepted Answer

To initiate the chain reaction by causing homolytic cleavage of the $$\mathrm{Cl-Cl}$$ bond.

Question 10

Which of the following is a correct representation of a general substitution reaction?

Accepted Answer

$$\mathrm{C-Z + Y \rightarrow C-Y + Z}$$

Question 11

A molecule has two asymmetric carbons and an internal plane of symmetry. Which of the following is true?

Accepted Answer

The molecule is achiral and optically inactive.

Question 12

Which of the following best describes the difference between a chiral and an achiral molecule?

Accepted Answer

A chiral molecule is not superimposable on its mirror image, while an achiral molecule is superimposable on its mirror image.

Question 13

Which of the following is NOT a correct statement about stereocenters?

Accepted Answer

All tetrahedral carbons are stereocenters.

Question 14

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

Accepted Answer

Reacting a racemic mixture with a chiral compound to form diastereomers, which can then be separated.

Question 15

Which of the following is true about the physical properties of a racemic mixture compared to its pure enantiomers?

Accepted Answer

The racemic mixture has different physical properties (such as melting point and solubility) compared to the pure enantiomers.

Question 16

Which of the following is a correct representation of a general elimination reaction?

Accepted Answer

$$\mathrm{C-C(X)(Y) + reagent \rightarrow C=C + X-Y}$$

Question 17

Which of the following is a correct representation of a general addition reaction?

Accepted Answer

$$\mathrm{C=C + X-Y \rightarrow C-C(X)(Y)}$$

Question 18

Which of the following arrows is used to show the movement of a single electron in a reaction mechanism?

Accepted Answer

Half-headed curved arrow (fishhook)

Question 19

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

Accepted Answer

One enantiomer is a sedative, while the other causes severe birth defects.

Stereochemistry and Organic Reaction Mechanisms: Mini-Textbook Study Notes

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