Q: Which of the following pairs are constitutional isomers?

$$\mathrm{CH_3CH_2OH}$$ \text{ and } $$\mathrm{CH_3OCH_3}$$

Q: Which of the following is the correct formula for calculating the specific rotation $$[\alpha]_D^T of a $$compound?

$$[\alpha]_D^T = \frac{\alpha_{\text{obs}}}{l \times c}$$

Question 1

Which of the following best explains why thalidomide caused severe birth defects when administered as a sedative to pregnant women in the 1950s and 1960s?

Accepted Answer

One enantiomer is an effective sedative, while the other is highly teratogenic, and interconversion occurs in the body.

Question 2

Which of the following pairs are constitutional isomers?

Accepted Answer

$$\mathrm{CH_3CH_2OH}$$ 	ext{ and } $$\mathrm{CH_3OCH_3}$$

Question 3

Which statement about conformational isomers is CORRECT?

Accepted Answer

They interconvert rapidly at room temperature and cannot be separated.

Question 4

Which of the following molecules is chiral?

Accepted Answer

A molecule with four different groups attached to a tetrahedral carbon and no plane of symmetry.

Question 5

How many stereoisomers are possible for a molecule with three chiral centers?

Accepted Answer

$$2^3 = 8$

Question 6

Which of the following statements about enantiomers is FALSE?

Accepted Answer

They can be separated by standard distillation techniques.

Question 7

A sample of (R)-2-bromobutane has a specific rotation of $$+23.1^\circ. $$What is the observed rotation if the sample is a racemic mixture?

Accepted Answer

$$0^\circ$$

Question 8

Which of the following best describes a meso compound?

Accepted Answer

A molecule with two or more chiral centers that is achiral due to a plane of symmetry.

Question 9

Which of the following is the correct formula for calculating the specific rotation $$[\alpha]_D^T of a $$compound?

Accepted Answer

$$[\alpha]_D^T = \frac{\alpha_{	ext{obs}}}{l 	imes c}$$

Question 10

Which of the following statements about the R/S system is TRUE?

Accepted Answer

The R/S designation is based on the priority of substituents around a chiral center.

Question 11

Which of the following pairs are diastereomers?

Accepted Answer

Two molecules with two chiral centers that are not mirror images.

Question 12

Which of the following is NOT a property of diastereomers?

Accepted Answer

They are nonsuperimposable mirror images.

Question 13

Which of the following best describes the difference between constitutional isomers and stereoisomers?

Accepted Answer

Constitutional isomers have different connectivities, while stereoisomers have the same connectivity but different spatial arrangements.

Question 14

Which of the following is a real-life example of the importance of stereochemistry in pharmaceuticals?

Accepted Answer

The (S)-isomer of naproxen sodium is an effective anti-inflammatory, while the (R)-isomer is inactive and toxic.

Question 15

Which of the following statements about optical activity is TRUE?

Accepted Answer

A chiral compound rotates plane-polarized light.

Question 16

A compound has two chiral centers and is found to be superimposable on its mirror image. What type of compound is this?

Accepted Answer

Meso compound

Question 17

Which of the following is the correct method for assigning priorities in the Cahn-Ingold-Prelog system when two substituents have the same atomic number?

Accepted Answer

Move to the next atom along the chain until a difference is found.

Question 18

Which of the following is a correct statement about Fischer projections?

Accepted Answer

The intersection represents a chiral center, with horizontal lines coming out and vertical lines going away.

Question 19

Which of the following is NOT a way to achieve conformers?

Accepted Answer

Breaking covalent bonds

Stereochemistry: The Three-Dimensional Structure of Organic Molecules

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