Question 1

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

Accepted Answer

Formation of the resonance-stabilized carbocation by addition of the electrophile

Question 2

In the halogenation of benzene using Br$$_2$$ and FeBr$$_3$$, what is the role of FeBr$$_3$$?

Accepted Answer

Acts as a Lewis acid to polarize Br$$_2$$ and generate a better electrophile

Question 3

Which of the following is NOT a suitable starting material for Friedel-Crafts alkylation?

Accepted Answer

Vinyl halide

Question 4

During Friedel-Crafts alkylation, why do 1$$^	ext{st}$$ and 2$$^	ext{nd}$$ degree carbocations often undergo rearrangement?

Accepted Answer

To form more stable carbocations via 1,2-hydride or methyl shifts

Question 5

Which reagent combination is used to reduce an acyl group on a benzene ring to an alkyl group without carbocation rearrangement?

Accepted Answer

Zn(Hg), HCl, heat or NH$$_2NH$_2$$, KOH, heat

Question 6

What is the product when ethylbenzene is treated with Br$$_2$$ under radical conditions (h$$
u or $$ROOR)?

Accepted Answer

Benzylic bromide (1-bromo-2-phenylethane)

Question 7

Which of the following statements about nitration of benzene is correct?

Accepted Answer

The electrophile is generated by mixing HNO$$_3$$ and H$$_2SO$_4 to $$produce NO$$_2^+$$

Question 8

Which group is considered an electron-donating group (EDG) and activates the benzene ring toward EAS?

Accepted Answer

Alkyl group (R)

Question 9

What is the directing effect of a halogen substituent (e.g., Cl) on a benzene ring during EAS?

Accepted Answer

Ortho/para-directing and deactivating

Question 10

Which of the following is the correct sequence for the mechanism of sulfonation of benzene?

Accepted Answer

Formation of SO$$_3H$^+$$, attack by benzene, deprotonation to restore aromaticity

Question 11

Which of the following statements about the oxidation of alkyl groups on benzene is correct?

Accepted Answer

KMnO$$_4$$ oxidizes all alkyl groups to carboxylic acids except tertiary benzylic positions

Question 12

Which mechanism explains why benzylic radicals are stabilized during benzylic bromination?

Accepted Answer

Resonance delocalization of the radical over the aromatic ring

Question 13

What is the product of reducing nitrobenzene with Fe/HCl?

Accepted Answer

Aniline (C$$_6H$_5NH$_2)$$

Question 14

Which of the following substituents is meta-directing and deactivates the benzene ring toward EAS?

Accepted Answer

Nitro group (NO$$_2)$$

Question 15

Why is the aromaticity temporarily lost during the formation of the carbocation intermediate in EAS?

Accepted Answer

The addition of the electrophile disrupts the delocalized $$\pi$$ system

Question 16

Which of the following is a plausible method to temporarily block a position on a benzene ring during synthesis?

Accepted Answer

Sulfonation with SO$$_3/H$_2SO$_4$$

Question 17

Which statement best explains why Friedel-Crafts acylation does not suffer from carbocation rearrangement?

Accepted Answer

The acylium ion formed is resonance-stabilized and does not rearrange

Question 18

Which of the following is true about the resonance effects of electron-donating groups (EDGs) on benzene?

Accepted Answer

EDGs place a negative charge on benzene carbons, increasing nucleophilicity

Question 19

Which of the following is the correct product of Friedel-Crafts alkylation of benzene with 1-chloropropane and AlCl$$_3$$?

Accepted Answer

Isopropylbenzene (due to carbocation rearrangement)

Electrophilic Aromatic Substitution and Substituent Effects in Aromatic Chemistry

Study Guide - Practice Questions