Question 1

Which of the following statements best explains why benzene does not undergo typical addition reactions with Br$$_2$$ like cyclohexene does?

Accepted Answer

Benzene is stabilized by resonance and delocalization of its $$	ext{π}$$ electrons, making addition reactions energetically unfavorable.

Question 2

Which of the following compounds is aromatic according to Hückel’s rule?

Accepted Answer

Benzene ($$6$$ $$	ext{π}$$ electrons)

Question 3

What is the correct IUPAC name for the compound shown with OH at position 1 and Br at positions 3 and 5 on a benzene ring?

Accepted Answer

3,5-dibromophenol

Question 4

Which of the following best describes the molecular orbital (MO) arrangement in benzene?

Accepted Answer

Six atomic p-orbitals combine to form three bonding and three antibonding MOs, with six $$	ext{π}$$ electrons filling the bonding MOs.

Question 5

Which of the following is the correct formula for Hückel’s rule for aromaticity?

Accepted Answer

$$4n+2$$ $$	ext{π}$$ electrons, where $$n=0,1,2,3,...$$

Question 6

Which of the following best explains why cyclopentadiene is much more acidic than typical hydrocarbons?

Accepted Answer

Its conjugate base, the cyclopentadienyl anion, is aromatic and stabilized by delocalization of its lone pair.

Question 7

Which of the following is NOT a criterion for aromaticity?

Accepted Answer

The ring must contain only carbon atoms

Question 8

Which compound is aromatic: pyridine or pyrrole? Why?

Accepted Answer

Pyridine is aromatic because its lone pair is not part of the $$	ext{π}$$ system, and the ring contains $$6$$ $$	ext{π}$$ electrons.

Question 9

Which of the following best describes the effect of an electron-donating group on the regioselectivity of the Birch reduction of benzene?

Accepted Answer

Reduction occurs at carbons opposite to the electron-donating group.

Question 10

Which compound is antiaromatic according to MO theory and Hückel’s rule?

Accepted Answer

Cyclobutadiene ($$4$$ $$	ext{π}$$ electrons)

Question 11

Which of the following is a benzylic position?

Accepted Answer

A carbon directly attached to a benzene ring

Question 12

Which reagent can oxidize a benzylic position to a carboxylic acid, provided there is at least one proton on the benzylic carbon?

Accepted Answer

KMnO$$_4 ($$potassium permanganate)

Question 13

Which of the following best describes the difference between aromatic, antiaromatic, and nonaromatic compounds?

Accepted Answer

Aromatic compounds meet both criteria: fully conjugated ring and $$4n+2$$ $$	ext{π}$$ electrons; antiaromatic meet both but have $$4n$$ $$	ext{π}$$ electrons; nonaromatic fail at least one criterion.

Question 14

Which of the following is the correct order for naming benzene derivatives according to IUPAC rules?

Accepted Answer

Identify the parent, name substituents, number the ring, list substituents alphabetically (ignoring prefixes except iso)

Question 15

Which of the following best explains why the actual heat of hydrogenation for benzene is much less negative than expected?

Accepted Answer

Benzene is stabilized by resonance, so less energy is released upon hydrogenation.

Question 16

Which of the following is a polycyclic aromatic compound?

Accepted Answer

Naphthalene

Question 17

Which of the following best describes the role of heteroatoms in aromatic rings?

Accepted Answer

Heteroatoms can contribute lone pairs to the $$	ext{π}$$ system if necessary for aromaticity.

Question 18

Which of the following is the correct description of the Frost circle method?

Accepted Answer

Draw a circle, inscribe a polygon with one vertex at the bottom, draw a horizontal line through the center, and identify MO energies.

Aromatic Compounds: Structure, Nomenclature, Stability, and Reactions

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