Question 1

Which of the following statements best describes a meso compound?

Accepted Answer

A compound that has chiral centers but is optically inactive due to an internal plane of symmetry.

Question 2

A molecule has a $$C_2$$ axis of symmetry and a plane of symmetry. Which of the following is true about its optical activity?

Accepted Answer

It is always optically inactive.

Question 3

Which of the following is a necessary condition for a molecule to exhibit optical isomerism?

Accepted Answer

Absence of a plane of symmetry and presence of a chiral center.

Question 4

A solution of a pure enantiomer rotates plane-polarized light by $$+25^	ext{o}. $$What will be the observed rotation if an equal amount of its mirror image is added to the solution?

Accepted Answer

$$0^	ext{o}$$

Question 5

Which of the following best describes a racemic mixture?

Accepted Answer

A mixture containing equal amounts of both enantiomers, resulting in optical inactivity.

Question 6

Which of the following molecules is chiral?

Accepted Answer

A molecule with no plane of symmetry and at least one chiral center.

Question 7

A compound has two stereocenters and shows optical inactivity. Which of the following is the most likely explanation?

Accepted Answer

The compound is a meso compound.

Question 8

Which of the following is true about enantiomers?

Accepted Answer

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

Question 9

Which of the following is NOT a method for resolving a racemic mixture?

Accepted Answer

Distillation based on boiling point differences.

Question 10

A compound has the following Fischer projection:

$$\begin{array}{c}
\mathrm{CH}_3 \
| \
\mathrm{H} - \mathrm{C} - \mathrm{OH} \
| \
\mathrm{H} - \mathrm{C} - \mathrm{OH} \
| \
\mathrm{CH}_3
\end{array}$$

Which of the following statements is correct?

Accepted Answer

The compound is a meso compound and optically inactive.

Question 11

Which of the following best describes the D/L nomenclature system?

Accepted Answer

It is based on the configuration relative to glyceraldehyde.

Question 12

Which of the following molecules will NOT exhibit optical activity?

Accepted Answer

A meso compound with two chiral centers and a plane of symmetry.

Question 13

Which of the following is true about diastereomers?

Accepted Answer

They are stereoisomers that are not mirror images of each other.

Question 14

A molecule has an $$S_2$$ axis (alternate axis of symmetry). What does this imply about its optical activity?

Accepted Answer

It is always optically inactive.

Question 15

Which of the following is a correct statement about the relationship between plane of symmetry and chirality?

Accepted Answer

A molecule with a plane of symmetry is always achiral.

Question 16

A compound has the following structure:

$$\begin{array}{c}
\mathrm{Br} \
| \
\mathrm{C} - \mathrm{Br} \
| \
\mathrm{C} - \mathrm{Cl} \
| \
\mathrm{Cl}
\end{array}$$

Which of the following statements is correct?

Accepted Answer

The compound is achiral due to the presence of a plane of symmetry.

Question 17

Which of the following is the best method to separate enantiomers in a racemic mixture?

Accepted Answer

Resolution using a chiral resolving agent.

Question 18

A compound has the following configuration at its two chiral centers: (R,R). Which of the following is its enantiomer?

Accepted Answer

(S,S)

Question 19

Which of the following is a real-life application of optical isomerism?

Accepted Answer

Identifying the active form of a drug, as only one enantiomer may be biologically active.

Question 20

A compound has three chiral centers. How many possible stereoisomers can it have, assuming no meso forms?

Accepted Answer

$$2^3 = 8$

Optical Isomerism and Symmetry Elements in Organic Chemistry

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