Question 1

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

Accepted Answer

Constitutional isomers have the same molecular formula but different connectivity of atoms; stereoisomers have the same connectivity but different arrangement in space.

Question 2

Maleic acid and fumaric acid are examples of which type of isomerism, and what is a key physical property that differs between them?

Accepted Answer

They are geometric (cis-trans) isomers; their melting points differ significantly.

Question 3

Which of the following best explains why geometric isomers (such as cis- and trans-alkenes) exist?

Accepted Answer

Restricted rotation around double bonds leads to different spatial arrangements of substituents.

Question 4

Consider the cyclohexane chair conformations. Which factor most strongly determines the stability of a given chair conformation?

Accepted Answer

The presence of torsional and steric strain, especially from bulky substituents in axial positions.

Question 5

Which of the following molecules is chiral?

Accepted Answer

CHClBrF

Question 6

A molecule has two chiral centers. Which of the following statements is true?

Accepted Answer

It can have up to $$2^2 = 4$ stereoisomers.

Question 7

Which of the following best describes an enantiomer?

Accepted Answer

A stereoisomer that is a non-superimposable mirror image of another molecule.

Question 8

Which of the following is the correct method for assigning priority to substituents on a chiral center according to the Cahn-Ingold-Prelog rules?

Accepted Answer

Assign priority based on the atomic number of the atoms directly attached to the chiral center.

Question 9

Which of the following statements about biomolecules is correct?

Accepted Answer

Chirality is common in biomolecules, and most are chiral.

Question 10

Which of the following best describes the relationship between ethanol ($$C_2H_6O) $$and isopropanol ($$C_3H_8O$$)?

Accepted Answer

They are not isomers.

Question 11

Which of the following is true about the E/Z (cis/trans) nomenclature for alkenes?

Accepted Answer

E-isomers have the higher priority groups on opposite sides of the double bond.

Question 12

Which of the following is a necessary condition for a carbon atom to be a chiral center?

Accepted Answer

It must be bonded to four different substituents.

Question 13

Which of the following best explains why the left and right hands are considered chiral objects?

Accepted Answer

They are non-superimposable mirror images due to their asymmetry.

Question 14

Which of the following is true about the stability of cyclohexane chair conformations with bulky substituents?

Accepted Answer

Bulky substituents prefer the equatorial position to minimize steric strain.

Question 15

Which of the following is true about the rotation around bonds in organic molecules?

Accepted Answer

Rotation around double bonds is restricted due to the presence of a pi bond.

Question 16

Which of the following is a correct statement about the assignment of R/S configuration to a chiral center?

Accepted Answer

The lowest priority group should be oriented away from the observer.

Question 17

Which of the following is true about the relationship between enantiomers?

Accepted Answer

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

Question 18

Which of the following is a real-world consequence of chirality in biomolecules?

Accepted Answer

Only one enantiomer of a chiral drug may be biologically active, while the other may be inactive or toxic.

Question 19

Which of the following best describes the difference between a chiral and an achiral object?

Accepted Answer

A chiral object cannot be superimposed on its mirror image; an achiral object can.

Lecture 5 Part 1 Stereochemistry and Isomerism in Organic Chemistry

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