Mechanism of electrophilic aromatic substitution — NEET & JEE Questions

Question 1 · difficulty L1 · recall

In electrophilic aromatic substitution, the aromatic ring reacts with an

• A. electrophile
• B. nucleophile only
• C. free neutron
• D. alkoxide ion only

Question 2 · difficulty L2 · understanding

The key intermediate formed after electrophile attack on benzene is commonly called the

• A. sigma complex or arenium ion
• B. carbanion only
• C. free alkene
• D. diazonium ion in every EAS reaction

Question 3 · difficulty L2 · understanding

Aromaticity is restored in the final step of electrophilic aromatic substitution by

• A. loss of a proton from the sigma complex
• B. addition of another electrophile
• C. hydrogenation of the ring
• D. breaking the ring

Question 4 · difficulty L2 · understanding

The rate-determining step in many electrophilic aromatic substitution reactions is

• A. formation of the sigma complex
• B. final deprotonation
• C. diffusion of product away
• D. regeneration of aromaticity after all barriers are crossed

Question 5 · difficulty L3 · application

In nitration of benzene, the electrophile is

• A. $NO_2^+$
• B. $NO_3^-$
• C. $NH_2^-$
• D. $OH^-$

Question 6 · difficulty L3 · application

In bromination of benzene using $Br_2/FeBr_3$, the role of $FeBr_3$ is mainly to

• A. help generate a stronger electrophilic brominating species
• B. act as the final organic product
• C. reduce benzene to cyclohexane
• D. serve as a nucleophile

Question 7 · difficulty L3 · application

What happens to aromaticity when benzene first forms the sigma complex?

• A. It is temporarily lost
• B. It is strengthened
• C. It remains completely unchanged
• D. The ring becomes noncyclic

Question 8 · difficulty L3 · application

Why is the final deprotonation step favourable in EAS?

• A. It restores the aromatic system
• B. It destroys all resonance
• C. It creates a second sigma complex
• D. It removes the electrophile from the product

Question 9 · difficulty L4 · application

Which sequence best represents a typical EAS mechanism?

• A. Electrophile generation → ring attack/sigma complex → deprotonation/aromaticity restoration
• B. Nucleophile attack → elimination → radical rearrangement
• C. Hydrogenation → oxidation → cleavage
• D. Proton loss → electrophile generation → ring opening

Question 10 · difficulty L4 · application

Why is benzene less reactive toward simple electrophilic addition than an alkene?

• A. Addition would sacrifice aromatic stabilisation, whereas substitution can restore it
• B. Benzene has no pi electrons
• C. Alkenes are aromatic
• D. Benzene carbons cannot form sigma bonds