Q: Which species acts as the electrophile in the nitration of benzene?

Nitronium ion ($$\text{NO}_2^+)$$

Question 1

Which of the following statements best explains why benzene does not undergo typical addition reactions like alkenes and alkynes?

Accepted Answer

Benzene's $$\pi$$ electrons are delocalized, creating a stable resonance structure that resists addition reactions.

Question 2

According to Hückel's Rule, which of the following compounds is aromatic?

Accepted Answer

A cyclic, planar, fully conjugated molecule with $$4n+2$$ $$\pi$$ electrons ($$n=1)$$

Question 3

Which physical property of benzene provides evidence for its resonance stabilization?

Accepted Answer

All C–C bond lengths in benzene are equal and intermediate between single and double bonds ($$1.40\ 	ext{Å}).$$

Question 4

Which of the following is the correct IUPAC name for a benzene ring with an ethyl group at position 1 and a propyl group at position 2, and a chlorine at position 4?

Accepted Answer

4-chloro-1-ethyl-2-propylbenzene

Question 5

In the electrophilic aromatic substitution mechanism, what is the role of the base in the second step?

Accepted Answer

It removes a proton from the carbon bonded to the electrophile, restoring aromaticity.

Question 6

Which of the following is the correct order of steps in the general mechanism of electrophilic aromatic substitution?

Accepted Answer

Addition of the electrophile to form a carbocation, then loss of a proton to restore aromaticity

Question 7

During the halogenation of benzene, why is a Lewis acid such as $$	ext{FeBr}_3$$ required?

Accepted Answer

To polarize the Br–Br bond, making Br a better electrophile.

Question 8

Which species acts as the electrophile in the nitration of benzene?

Accepted Answer

Nitronium ion ($$	ext{NO}_2^+)$$

Question 9

Which of the following statements about Friedel-Crafts alkylation is TRUE?

Accepted Answer

The reaction requires an alkyl halide and a Lewis acid such as $$	ext{AlCl}_3.$$

Question 10

Which of the following is NOT a requirement for a compound to be classified as aromatic according to Hückel's Rule?

Accepted Answer

The molecule must have $$4n$$ $$\pi$$ electrons.

Question 11

A student is asked to name a benzene ring with a methyl group at position 1 and a bromine at position 4. What is the correct name using common nomenclature?

Accepted Answer

p-bromotoluene

Question 12

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

Accepted Answer

Aromatic compounds have $$4n+2$$ $$\pi$$ electrons, antiaromatic have $$4n$$ $$\pi$$ electrons, and nonaromatic lack one or more criteria for aromaticity.

Question 13

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

Accepted Answer

$$	ext{SO}_3	ext{H}^+$$

Question 14

In Friedel-Crafts acylation, what is the reactive electrophile that attacks the benzene ring?

Accepted Answer

An acylium ion ($$	ext{RCO}^+)$$

Question 15

Which of the following best describes the resonance hybrid structure of benzene?

Accepted Answer

Benzene is a resonance hybrid with delocalized $$\pi$$ electrons above and below the plane of the ring.

Question 16

Which of the following is the correct product when benzene reacts with $$	ext{CH}_3	ext{Cl}$$ and $$	ext{AlCl}_3$$?

Accepted Answer

Toluene (methylbenzene)

Question 17

A compound is cyclic, planar, and fully conjugated, but contains 8 $$\pi$$ electrons. According to Hückel's Rule, how is this compound classified?

Accepted Answer

Antiaromatic

Question 18

Which of the following is the correct name for a benzene ring with three substituents: a methyl at position 1, a nitro at position 2, and a bromo at position 4?

Accepted Answer

1-methyl-2-nitro-4-bromobenzene (alphabetized: 4-bromo-2-nitro-1-methylbenzene)

Question 19

Which of the following statements about the Friedel-Crafts alkylation reaction is FALSE?

Accepted Answer

The reaction is suitable for introducing acyl groups onto the benzene ring.

Aromatic Hydrocarbons I: Structure, Nomenclature, and Reactions of Benzene

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