Question 1

Which of the following statements best explains why benzene undergoes substitution rather than addition reactions under typical conditions?

Accepted Answer

Addition reactions would disrupt the aromatic stabilization of benzene, making the process highly endothermic.

Question 2

What is the correct IUPAC name for the compound shown below?

$$\mathrm{\begin{array}{c}
	ext{Benzene ring with methyl groups at positions 1 and 3}
\end{array}}$$

Accepted Answer

1,3-dimethylbenzene

Question 3

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

Accepted Answer

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

Question 4

During the bromination of benzene, what is the role of $$\mathrm{$$FeBr_3$$}$$?

Accepted Answer

It acts as a Lewis acid to generate the electrophilic $$\mathrm{Br^+}$$ species.

Question 5

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

Accepted Answer

$$\mathrm{-NH_2$} ($$amino group)

Question 6

A student treats toluene with concentrated $$\mathrm{$$HNO_3$$}$$ and $$\mathrm{H_2SO_4}. $$Which of the following is the major product?

Accepted Answer

Ortho- and para-nitrotoluene, with the ortho isomer being slightly more abundant.

Question 7

Which of the following best describes the rate-determining step in electrophilic aromatic substitution (EAS) reactions?

Accepted Answer

Formation of the sigma complex (arenium ion) by attack of the electrophile on the aromatic ring.

Question 8

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

Accepted Answer

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

Question 9

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

Accepted Answer

Carbocation rearrangements can lead to unexpected products.

Question 10

What is the product of the following reaction sequence?

Benzene $$\xrightarrow{SO_3$,\,H_2SO_4}$$ $$\xrightarrow{H_2O,\,100^\circ C}$$

Accepted Answer

Benzene (desulfonation)

Question 11

Which of the following best explains why halogens are ortho/para-directing but deactivating in EAS reactions?

Accepted Answer

Halogens withdraw electrons inductively but donate electrons by resonance at ortho and para positions.

Question 12

Which of the following is the correct order of reactivity towards electrophilic aromatic substitution (from most reactive to least reactive)?

Accepted Answer

Aniline $$\u003e$$ Toluene $$\u003e$$ Benzene $$\u003e$$ Nitrobenzene

Question 13

A benzene ring is substituted with a nitro group at position 1 and a methyl group at position 4. If the ring is further nitrated, where will the new nitro group most likely be introduced?

Accepted Answer

Meta to the methyl group and ortho to the nitro group (position 3)

Question 14

Which of the following is a correct statement about the mechanism of nucleophilic aromatic substitution (NAS) via the addition-elimination pathway?

Accepted Answer

A strong electron-withdrawing group must be ortho or para to the leaving group.

Question 15

Which reagent is commonly used to reduce a nitro group on a benzene ring to an amino group?

Accepted Answer

Zn/HCl (zinc in hydrochloric acid)

Question 16

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

Accepted Answer

It does not result in rearrangement of the acyl group.

Question 17

Which of the following best describes the effect of an electron-donating group (EDG) on the rate and orientation of EAS reactions?

Accepted Answer

Increases the rate and directs substitution to ortho and para positions.

Question 18

Which of the following is a common limitation of Friedel–Crafts alkylation and acylation reactions?

Accepted Answer

Poor yields with rings bearing strong electron-withdrawing groups.

Question 19

Which of the following best explains why phenol is much more reactive than benzene towards EAS reactions?

Accepted Answer

The hydroxyl group donates electron density to the ring via resonance, stabilizing the sigma complex.

Reactions of Aromatic Compounds: Nomenclature, Reactivity, and Mechanisms

Guida di studio - Domande di pratica

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