Question 1

Which of the following best describes the first step in the mechanism of electrophilic aromatic substitution (EAS) for benzene?

Accepted Answer

A slow addition of an electrophile to the benzene ring, forming a carbocation intermediate.

Question 2

In the bromination of benzene, what is the role of FeBr$$_3$$?

Accepted Answer

It acts as a Lewis acid to generate the bromonium ion (Br$$^+) $$from Br$$_2.$$

Question 3

Why does benzene undergo substitution rather than addition when reacting with Br$$_2 in $$the presence of FeBr$$_3$$?

Accepted Answer

Addition would disrupt aromaticity, resulting in a less stable product.

Question 4

Which of the following is the correct energy profile for the bromination of benzene?

Accepted Answer

The reaction has two transition states, with the first being rate-limiting, and is overall exothermic.

Question 5

Which reagent is required for the iodination of benzene?

Accepted Answer

Nitric acid (HNO$$_3) as an $$oxidizing agent

Question 6

What is the major product when toluene undergoes nitration?

Accepted Answer

Ortho- and para-nitrotoluene

Question 7

Which of the following substituents is both activating and ortho/para-directing in electrophilic aromatic substitution?

Accepted Answer

$$-CH_3$

Question 8

Why are halogens considered deactivating but ortho/para-directing in EAS reactions?

Accepted Answer

They donate electrons by resonance but withdraw by induction, stabilizing the sigma complex at ortho/para positions.

Question 9

Which of the following groups is meta-directing and deactivating in EAS?

Accepted Answer

$$-NO_2$

Question 10

What is the best method to convert a nitro group on a benzene ring to an amino group?

Accepted Answer

Reduction with Zn, Sn, or Fe in dilute acid

Question 11

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

Accepted Answer

Carbocation rearrangements can occur during the reaction.

Question 12

Why is Friedel-Crafts acylation preferred over alkylation for synthesizing monoacylated products?

Accepted Answer

Acyl groups deactivate the ring, preventing further substitution.

Question 13

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

Accepted Answer

It cannot occur on benzene rings with substituents more deactivating than halogens.

Question 14

What is the product of the following reaction: benzene + acetyl chloride + AlCl$$_3$$?

Accepted Answer

Acetophenone

Question 15

Which of the following statements about sulfonation of benzene is true?

Accepted Answer

Sulfonation is reversible; the sulfonic acid group can be removed by heating in dilute acid.

Question 16

Which of the following best explains why anisole ($$C_6H_5OCH_3) $$undergoes nitration much faster than benzene?

Accepted Answer

The methoxy group donates electrons by resonance, stabilizing the sigma complex.

Question 17

Which of the following is the correct order of reactivity for aryl halides in nucleophilic aromatic substitution (NAS)?

Accepted Answer

$$Ar-F \u003e Ar-Cl \approx Ar-Br \approx Ar-I$$

Question 18

Which of the following is required for nucleophilic aromatic substitution (addition-elimination) to occur on an aryl halide?

Accepted Answer

An electron-withdrawing group (such as $$NO_2) $$ortho or para to the halogen.

Question 19

Which of the following best describes the product of the Birch reduction of benzene?

Accepted Answer

A nonconjugated 1,4-cyclohexadiene.

Question 20

What is the major product when ethylbenzene is brominated with Br$$_2$$ and FeBr$$_3$$?

Accepted Answer

Ortho- and para-bromoethylbenzene

Reactions of Aromatic Compounds: Electrophilic Aromatic Substitution and Related Mechanisms

Study Guide - Practice Questions