Q: Which of the following is the correct formula for the specific rotation of a chiral compound?

$$[\alpha] = \frac{\alpha_{obs}}{l \times c}$$

Question 1

Which of the following statements best describes a chiral carbon?

Accepted Answer

A carbon atom bonded to four different groups.

Question 2

Which property distinguishes enantiomers from each other?

Accepted Answer

They rotate plane-polarized light in opposite directions.

Question 3

Given the Fischer projection of D-glyceraldehyde, which group is assigned the highest priority according to the Cahn-Ingold-Prelog (R,S) system?

Accepted Answer

The CHO group

Question 4

Which of the following molecules is optically inactive despite having chiral centers?

Accepted Answer

meso-tartaric acid

Question 5

What is the correct relationship between the D/L system and the R/S system for chiral molecules?

Accepted Answer

D/L system is based on the relationship to glyceraldehyde, while R/S is based on atomic priorities.

Question 6

A molecule has the following groups attached to a chiral carbon: Br, OH, CH3, and H. Assign priorities and determine the configuration if the lowest priority group (H) is pointing away from you and the sequence from highest to lowest priority goes clockwise.

Accepted Answer

R configuration

Question 7

Which of the following best describes the Fischer projection?

Accepted Answer

A two-dimensional representation where horizontal bonds project toward the viewer and vertical bonds project away.

Question 8

In the Cahn-Ingold-Prelog system, which atom is assigned the highest priority when attached to a chiral center?

Accepted Answer

The atom with the highest atomic number.

Question 9

If a molecule’s lowest priority group is not pointing away from you, what is the recommended method to assign R/S configuration?

Accepted Answer

Swap the lowest priority group with the group that is pointing away, assign R/S, and then reverse the result.

Question 10

Which of the following is true about enantiomers?

Accepted Answer

They have identical physical properties except for the direction in which they rotate plane-polarized light.

Question 11

Which of the following is the correct formula for the specific rotation of a chiral compound?

Accepted Answer

$$[\alpha] = \frac{\alpha_{obs}}{l 	imes c}$$

Question 12

Which statement about meso compounds is correct?

Accepted Answer

They are optically inactive due to an internal plane of symmetry.

Question 13

Which of the following best explains why the D/L system is limited in its application?

Accepted Answer

It is based on the relationship to glyceraldehyde and does not describe absolute configuration.

Question 14

A molecule has two chiral centers and is found to be a meso compound. What is the expected optical activity?

Accepted Answer

It will not rotate plane-polarized light.

Question 15

Which of the following is the correct sequence for assigning priorities in the Cahn-Ingold-Prelog system?

Accepted Answer

Assign priorities based on atomic number, with the highest atomic number receiving priority 1.

Question 16

Which projection is most useful for visualizing the stereochemistry of sugars and amino acids?

Accepted Answer

Fischer projection

Question 17

If a chiral molecule has the configuration shown as S in a Fischer projection, what will be the configuration after a single swap of two groups?

Accepted Answer

It will become R.

Question 18

Which of the following is true about the relationship between D-glyceraldehyde and L-glyceraldehyde?

Accepted Answer

They are enantiomers.

Question 19

Which of the following is the correct way to assign R/S configuration using a Newman projection?

Accepted Answer

View down the bond from the chiral center to the lowest priority group and assign priorities to the other three groups.

Stereochemistry: Chirality, Fischer Projections, and the R/S System

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