Question 1

Which of the following criteria must a compound satisfy to be considered aromatic according to Hückel's rule?

Accepted Answer

It must be cyclic, planar, fully conjugated, and contain $$(4n+2)$$ $$\pi$$ electrons, where $$n is a $$non-negative integer.

Question 2

Which of the following molecules is antiaromatic?

Accepted Answer

Cyclobutadiene ($$C_4H_4)$$

Question 3

A compound is found to be cyclic, planar, fully conjugated, and contains 8 $$\pi$$ electrons. According to Hückel's rule, how would you classify this compound?

Accepted Answer

Antiaromatic

Question 4

Which of the following statements best explains why benzene is more stable than expected based on its heat of hydrogenation?

Accepted Answer

Benzene's $$\pi$$ electrons are delocalized over the ring, resulting in resonance stabilization.

Question 5

Which of the following heterocycles is aromatic due to the participation of a lone pair in the $$\pi-$$electron system?

Accepted Answer

Pyrrole

Question 6

Which of the following best describes the bond lengths in benzene?

Accepted Answer

All C–C bonds are equal and intermediate between single and double bonds

Question 7

Which of the following is the correct product of the complete oxidation of butylbenzene with $$KMnO_4$$?

Accepted Answer

Benzoic acid

Question 8

Why does benzene undergo electrophilic aromatic substitution (EAS) rather than addition reactions like alkenes?

Accepted Answer

Addition would disrupt the aromatic stabilization of the ring.

Question 9

Which of the following substituents is an ortho/para-director and an activator in electrophilic aromatic substitution?

Accepted Answer

$$-OH$$

Question 10

A student wants to synthesize m-chloroaniline from benzene. Which sequence of reactions would achieve this goal?

Accepted Answer

Chlorination, nitration, reduction

Question 11

Which of the following is a correct statement about the Friedel–Crafts alkylation of benzene?

Accepted Answer

It requires a Lewis acid catalyst such as $$AlCl_3.$$

Question 12

Which of the following best explains why halogens are ortho/para-directors but deactivators in EAS?

Accepted Answer

They donate electron density by resonance but withdraw by induction.

Question 13

Which of the following is NOT aromatic?

Accepted Answer

Cyclooctatetraene

Question 14

Which of the following is the correct order of reactivity toward electrophilic aromatic substitution (EAS)?

Accepted Answer

Toluene \u003e Benzene \u003e Nitrobenzene

Question 15

Which of the following best describes the role of $$FeBr_3 in $$the bromination of benzene?

Accepted Answer

It generates the electrophilic $$Br^+$$ species.

Question 16

Which of the following is a real-world example of an aromatic compound found in biological systems?

Accepted Answer

Serotonin

Question 17

Which of the following statements about the hydrogenation of benzene is correct?

Accepted Answer

The heat of hydrogenation of benzene is less negative than expected for three isolated double bonds.

Question 18

Which of the following best explains why pyrrole is aromatic?

Accepted Answer

The nitrogen atom's lone pair is in a p orbital and participates in the $$\pi$$ system, giving 6 $$\pi$$ electrons.

Question 19

Which of the following is the major product when toluene undergoes nitration?

Accepted Answer

o-Nitrotoluene

Question 20

Which of the following is a limitation of the Friedel–Crafts alkylation reaction?

Accepted Answer

Carbocation rearrangements can lead to unexpected products.

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