Same chapter3 marksDifficulty: Medium
Why is benzene unusually stable and why does it prefer substitution to addition?
Hydrocarbons
3 marksDifficulty: Medium
Name three electrophilic substitution reactions of benzene with the reagent used in each.
Original Khojo Papers practice question — not from a past board paper.
Answer
Nitration with a mixture of concentrated nitric and sulphuric acids. Halogenation with chlorine or bromine in the presence of anhydrous aluminium chloride or iron(III) bromide. Friedel-Crafts alkylation or acylation with an alkyl or acyl halide and anhydrous aluminium chloride. Sulphonation with fuming sulphuric acid is a fourth.
No citable source has been recorded for this record. Treat it as practice material, not as fact.
Explanation
In each case an electrophile attacks the delocalised pi system and a proton is lost, so the ring survives.
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