Question 1

Which of the following best explains why electrophilic aromatic substitution (EAS) is favored over electrophilic addition in benzene?

Accepted Answer

The aromatic pi bond is more stable than the Nu-C sigma bond formed in addition.

Question 2

In the nitration of benzene, which reagent combination is used to generate the nitronium ion ($$\ce{NO2^+}$$)?

Accepted Answer

HNO3 and H2SO4

Question 3

What is the purpose of the iron catalyst in the halogenation of benzene?

Accepted Answer

To generate the halonium ion ($$\ce{X^+}) $$from the halogen molecule

Question 4

Which halogen is the most reactive in the halogenation of benzene?

Accepted Answer

Fluorine ($$\ce{F2})$$

Question 5

In Friedel-Crafts alkylation, why are primary alkyl halides less likely to form carbocations compared to secondary or tertiary alkyl halides?

Accepted Answer

Primary carbocations are less stable due to lack of alkyl group stabilization.

Question 6

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

Accepted Answer

Polyalkylation is difficult to prevent.

Question 7

What is the electrophilic center in the acylium ion ($$\ce{RCO^+}) $$used in Friedel-Crafts acylation?

Accepted Answer

The carbon atom of the carbonyl group

Question 8

Which reduction method is used to convert an aryl ketone to an alkylbenzene after Friedel-Crafts acylation?

Accepted Answer

Clemmensen reduction

Question 9

Why are ortho and para positions favored in the nitration of toluene?

Accepted Answer

The carbocation intermediate is stabilized by resonance with the methyl group.

Question 10

Which substituent is more activating towards electrophilic aromatic substitution: $$\ce{-NH2} or$$ $$\ce{-OH}$$? Why?

Accepted Answer

$$\ce{-NH2}$$, because it donates electrons more effectively through resonance and induction.

Question 11

Which of the following substituents is meta-directing and strongly deactivating in electrophilic aromatic substitution?

Accepted Answer

$$\ce{-COOH} ($$carboxylic acid)

Question 12

Halogens are deactivating substituents in EAS, but why do they direct new substituents to the ortho and para positions?

Accepted Answer

Halogens donate lone pair electrons to the ring, stabilizing ortho and para carbocations.

Question 13

In nucleophilic aromatic substitution (SNAr), what is the rate-determining step?

Accepted Answer

Loss of aromaticity during nucleophilic addition

Question 14

Which aryl halide would react fastest in SNAr with a nucleophile?

Accepted Answer

Aryl halide with ortho and para nitro groups

Question 15

Why do electron withdrawing groups (EWGs) increase the rate of SNAr reactions?

Accepted Answer

EWGs stabilize the negative charge in the intermediate by resonance and induction.

Question 16

A benzene ring with a trifluoromethyl group ($$\ce{-CF3}) $$and a nitro group ($$\ce{-NO2}) is $$subjected to bromination. Where will the major product form?

Accepted Answer

Meta to the $$\ce{-CF3}$$ group

Question 17

Which of the following best describes the mechanism of Friedel-Crafts acylation?

Accepted Answer

Formation of acylium ion, electrophilic attack, restoration of aromaticity

Question 18

Which of the following is NOT a limitation of Friedel-Crafts alkylation?

Accepted Answer

High yields and easy purification

Question 19

Which of the following groups is very strongly activating and ortho/para-directing in EAS?

Accepted Answer

$$\ce{-NH2} ($$amino)

Electrophilic Aromatic Substitution and Friedel-Crafts Reactions: Mechanisms, Substituent Effects, and Applications

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