Question 1

Which of the following statements best explains why benzene is classified as aromatic according to Hückel’s rule?

Accepted Answer

Benzene is cyclic, planar, and contains 6 π electrons, which fits the $$4n+2$$ rule with $$n=1.$$

Question 2

Which of the following is the correct mechanism for the bromination of benzene?

Accepted Answer

Benzene reacts with $$Br_2 in $$the presence of $$FeBr_3 to $$generate $$Br^+$$, which acts as the electrophile in an electrophilic aromatic substitution.

Question 3

Which of the following substituents is a strong activator and an ortho/para director on a benzene ring?

Accepted Answer

$$-OH$$

Question 4

A student wants to synthesize para-nitrotoluene from toluene. Which sequence of reactions will give the highest yield of the para isomer?

Accepted Answer

Nitration of toluene with $$HNO_3$$ and $$H_2SO_4.$$

Question 5

Which of the following best describes the effect of a nitro group ($$-NO_2$) on the reactivity and orientation of electrophilic aromatic substitution?

Accepted Answer

It is a strongly deactivating, meta-directing group.

Question 6

Which of the following is the correct order of acidity (from strongest to weakest) for the following compounds: benzenesulfonic acid, acetic acid, ethanol?

Accepted Answer

Benzenesulfonic acid $$\u003e$$ acetic acid $$\u003e$$ ethanol

Question 7

Which of the following statements about Friedel–Crafts alkylation is correct?

Accepted Answer

Carbocation rearrangement can occur, leading to unexpected products.

Question 8

A chemist wants to synthesize 1-bromo-3-nitrobenzene. Which sequence of reactions should be used starting from benzene?

Accepted Answer

Nitration first, then bromination.

Question 9

Which of the following is a necessary condition for a compound to be aromatic?

Accepted Answer

It must have a planar, cyclic structure with an uninterrupted cloud of $$\pi$$ electrons and $$4n+2$$ $$\pi$$ electrons.

Question 10

Which of the following best explains why sulfonation of benzene is reversible?

Accepted Answer

Heating benzenesulfonic acid in dilute acid causes the sulfonic acid group to be eliminated from the ring.

Question 11

Which of the following is the correct electrophile generated during the nitration of benzene?

Accepted Answer

The nitronium ion, $$NO_2$$^+$$

Question 12

Which of the following statements about the Friedel–Crafts acylation reaction is correct?

Accepted Answer

An acylium ion is generated as the electrophile, and a Lewis acid such as $$AlCl_3 is $$required.

Question 13

Which of the following is a real-world application of electrophilic aromatic substitution reactions?

Accepted Answer

The synthesis of aspirin (acetylsalicylic acid) from salicylic acid.

Question 14

Which of the following statements about the effect of substituents on the reactivity of benzene is correct?

Accepted Answer

Electron-donating groups increase the nucleophilicity of benzene and stabilize the carbocation intermediate.

Question 15

Which of the following is the correct product when ethylbenzene is oxidized with $$KMnO_4$$ under acidic conditions?

Accepted Answer

Benzoic acid

Question 16

Which of the following is a reason why Friedel–Crafts alkylation often leads to polyalkylation?

Accepted Answer

The alkylated product is more reactive than benzene toward further alkylation.

Question 17

Which of the following best describes the orientation of substitution for halogens on a benzene ring?

Accepted Answer

Halogens are weakly deactivating but direct new substituents to the ortho and para positions.

Question 18

Which of the following is a correct statement about nucleophilic aromatic substitution?

Accepted Answer

It requires a strongly electron-withdrawing group ortho or para to the leaving group.

Reactions of Benzene and Substituted Benzenes: Structure, Nomenclature, and Reactivity

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