Question 1

Which of the following statements best describes the difference between conformational and configurational isomers?

Accepted Answer

Conformational isomers interconvert by rotation around single bonds, while configurational isomers require breaking and reforming bonds to interconvert.

Question 2

Which of the following compounds can exhibit cis-trans isomerism?

Accepted Answer

$$\mathrm{CH_3CH=$$CHCH_3$$}$$

Question 3

Why is rotation around a double bond restricted, leading to the existence of cis and trans isomers?

Accepted Answer

Because the pi bond must be broken to allow rotation, which requires significant energy.

Question 4

Which of the following objects is chiral?

Accepted Answer

A left hand

Question 5

How many stereoisomers are possible for a molecule with three asymmetric centers (assuming no meso forms)?

Accepted Answer

$$2^3 = 8$

Question 6

Which of the following statements about enantiomers is correct?

Accepted Answer

Enantiomers rotate plane-polarized light in opposite directions.

Question 7

A solution of (R)-2-methyl-1-butanol has a specific rotation of $$+5.75. $$What is the specific rotation of its enantiomer, (S)-2-methyl-1-butanol?

Accepted Answer

$$-5.75$$

Question 8

Which of the following compounds is optically inactive?

Accepted Answer

A racemic mixture of (R)- and (S)-2-butanol

Question 9

Which of the following best describes a meso compound?

Accepted Answer

A compound with asymmetric centers that is optically inactive due to a plane of symmetry

Question 10

A sample contains 70% of one enantiomer and 30% of the other. What is the enantiomeric excess (ee)?

Accepted Answer

$$ee = 40\%$$

Question 11

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

Accepted Answer

Enantiomers can be separated by using a chiral column in chromatography.

Question 12

Which of the following molecules does NOT have a stereocenter?

Accepted Answer

$$\mathrm{CH_3CH_2CH_2CH_3}$$

Question 13

Which of the following is true about diastereomers?

Accepted Answer

They are stereoisomers that are not mirror images.

Question 14

Which of the following is required for a molecule to exhibit optical activity?

Accepted Answer

It must be chiral.

Question 15

A compound has two asymmetric centers and is found to be optically inactive. Which of the following best explains this observation?

Accepted Answer

The compound is a meso compound.

Question 16

Which of the following statements about amine inversion is correct?

Accepted Answer

Amines with a lone pair undergo rapid inversion, preventing separation of enantiomers.

Question 17

Which of the following best describes the R/S system for naming enantiomers?

Accepted Answer

Groups are ranked by decreasing atomic number, and the configuration is determined by the direction of rotation from highest to next highest priority with the lowest priority group oriented away from the viewer.

Question 18

Which of the following is true about the physical properties of enantiomers?

Accepted Answer

They have identical physical properties except for their interaction with plane-polarized light.

Question 19

Which of the following best describes a stereocenter?

Accepted Answer

An atom at which the interchange of two groups produces a stereoisomer.

Isomers: The Arrangement of Atoms in Space (Stereochemistry)

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