Question 1

Which of the following statements best describes constitutional isomers?

Accepted Answer

They have the same molecular formula but differ in the connectivity of their atoms.

Question 2

Which of the following compounds has a dipole moment of zero?

$$\mathrm{A: \ H_2C=CHCl}$$
$$\mathrm{B: \ ClHC=CHCl}$$
$$\mathrm{C: \ ClHC=CHCl}$$
$$\mathrm{D: \ Cl_2C=CH_2$}$$

Accepted Answer

B only

Question 3

Which of the following best explains why cis-trans isomers exist for some alkenes but not others?

Accepted Answer

Cis-trans isomerism requires each carbon of the double bond to have two different substituents.

Question 4

Which of the following is true about enantiomers?

Accepted Answer

They have identical physical properties except for their interaction with plane-polarized light and reactions in chiral environments.

Question 5

A compound with two asymmetric centers and the same four groups attached to each center can have how many stereoisomers?

Accepted Answer

Three: a pair of enantiomers and a meso compound.

Question 6

Which of the following best describes a meso compound?

Accepted Answer

A compound with asymmetric centers that is achiral due to an internal plane of symmetry.

Question 7

Which of the following compounds has an asymmetric center?

a. $$\mathrm{CH_3CH_2CHClCH_3}
b$$. $$\mathrm{CH_3CH_2CH(CH_3$)CH_3$}
c$$. $$\mathrm{CH_3CH_2CH_2CHBrCH_3}
d$$. $$\mathrm{CH_3CH_2OH}
e$$. $$\mathrm{CH_3CH_2CH_2CH_2Br}
f$$. $$\mathrm{CH_2$=CHCH(NH_2$)CH_3$}$$

Accepted Answer

a and c

Question 8

Which of the following statements about plane-polarized light and chirality is correct?

Accepted Answer

A chiral compound rotates plane-polarized light, while an achiral compound does not.

Question 9

Which of the following best describes the difference between a stereocenter and an asymmetric center?

Accepted Answer

An asymmetric center is always a stereocenter, but not all stereocenters are asymmetric centers.

Question 10

Which of the following pairs are diastereomers?

Accepted Answer

Stereoisomers that are not mirror images of each other.

Question 11

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

Accepted Answer

$$ee = 40\%$$

Question 12

Which of the following statements about the E/Z system of alkene nomenclature is correct?

Accepted Answer

E/Z nomenclature is based on the Cahn-Ingold-Prelog priority rules, assigning priority by atomic number.

Question 13

Which of the following is a real-world example of the importance of chirality in pharmaceuticals?

Accepted Answer

Thalidomide, where one enantiomer is a sedative and the other is teratogenic.

Question 14

Which of the following methods can be used to separate enantiomers in a laboratory?

Accepted Answer

Chromatography using a chiral stationary phase.

Question 15

Which of the following statements about amine inversion is correct?

Accepted Answer

Amines with a lone pair rapidly interconvert between enantiomers due to inversion.

Question 16

Which of the following best describes the relationship between R/S configuration and optical activity?

Accepted Answer

There is no direct relationship; R can be (+) or (−) and S can be (+) or (−).

Question 17

Which of the following is true about meso compounds?

Accepted Answer

They are optically inactive despite having asymmetric centers.

Question 18

Which of the following best describes the physical properties of diastereomers?

Accepted Answer

Diastereomers have different physical and chemical properties.

Question 19

Which of the following is a correct application of the Cahn-Ingold-Prelog priority rules for E/Z isomerism?

Accepted Answer

A deuterium (D) substituent has higher priority than a hydrogen (H) substituent.

Isomers: The Arrangement of Atoms in Space (Chirality and Stereochemistry)

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