Question 1

Which of the following statements best explains why the first step of electrophilic aromatic substitution (EAS) is rate-determining?

Accepted Answer

The first step is highly endothermic and involves the loss of aromaticity, which is energetically unfavorable.

Question 2

During the halogenation of benzene, what is the role of the Lewis acid (such as $$\mathrm{$$FeBr_3$$}$$)?

Accepted Answer

It generates a more electrophilic halogen species by polarizing the halogen molecule.

Question 3

Which of the following is the correct electrophile in the nitration of benzene?

Accepted Answer

$$\mathrm{NO_2$^+} ($$nitronium ion)

Question 4

Why does Friedel-Crafts alkylation often lead to polyalkylation of the aromatic ring?

Accepted Answer

The first alkyl group introduced activates the ring toward further substitution.

Question 5

Which of the following substituents is a strong deactivator and meta-director in electrophilic aromatic substitution?

Accepted Answer

$$\mathrm{NO_2$} ($$nitro group)

Question 6

A student attempts to synthesize tert-butylbenzene via Friedel-Crafts alkylation using 1-chlorobutane and benzene. Which major product is most likely formed?

Accepted Answer

sec-Butylbenzene, due to carbocation rearrangement.

Question 7

Which of the following best describes the effect of an alkyl group on the reactivity and orientation of electrophilic aromatic substitution?

Accepted Answer

Activates the ring and directs substitution to the ortho and para positions.

Question 8

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

Accepted Answer

Polyacylation does not occur because the acyl group deactivates the ring.

Question 9

What is the major product when toluene is treated with N-bromosuccinimide (NBS) and light?

Accepted Answer

Benzyl bromide ($$\mathrm{C_6H_5CH_2Br})$$

Question 10

Which of the following best explains why benzylic and allylic halides are more reactive in $$\mathrm{S_N1}$$ and $$\mathrm{S_N2}$$ reactions than simple alkyl halides?

Accepted Answer

The benzylic and allylic carbocations and transition states are stabilized by resonance.

Question 11

Which of the following is the correct order of reactivity for the halogenation of benzene under standard conditions?

Accepted Answer

$$\mathrm{F_2$} \u003e \mathrm{Cl_2$} \u003e \mathrm{Br_2$} \u003e \mathrm{I_2$}$$

Question 12

A chemist wants to synthesize p-nitroaniline from aniline. Which of the following strategies is most appropriate?

Accepted Answer

Protect the amino group by acetylation, nitrate, then hydrolyze to regenerate the amino group.

Question 13

Which of the following best describes the effect of a nitro group ($$\mathrm{NO_2$}) on $$the orientation and reactivity of a benzene ring in EAS?

Accepted Answer

Deactivates the ring and directs substitution to the meta position.

Question 14

Which of the following is the correct sequence of steps in the mechanism of sulfonation of benzene?

Accepted Answer

Generation of $$\mathrm{SO_3$}$$, attack by benzene to form arenium ion, deprotonation to restore aromaticity.

Question 15

Which of the following statements about the Clemmensen reduction is correct?

Accepted Answer

It reduces aryl ketones to alkylbenzenes using zinc amalgam and hydrochloric acid.

Question 16

Which of the following best explains why polyacylation does not occur in Friedel-Crafts acylation?

Accepted Answer

The acyl group deactivates the aromatic ring toward further substitution.

Question 17

Which of the following is the major product when ethylbenzene is oxidized with hot $$\mathrm{$$KMnO_4$$}$$?

Accepted Answer

Benzoic acid ($$\mathrm{C_6H_5COOH})$$

Question 18

Which of the following best describes the resonance stabilization of the arenium ion intermediate in EAS?

Accepted Answer

The positive charge is delocalized over three carbon atoms of the ring.

Reactions of Aromatic Compounds: Electrophilic Aromatic Substitution

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