Product 'A' of following sequence of reactions is Ethylbenzene $$\xrightarrow[\substack{\text { (b) } \mathrm{Cl}_{2}, \Delta \\ \text { (c) alc. } \mathrm{KOH}}]{\text { (a) } \mathrm{Br}_{2}, \mathrm{Fe}}{ }^{\prime} \mathrm{A}^{\prime}$$ (Major product)

JEE Main · 2022 · 27 Jun 2022 · Shift 2 · Hydrocarbons

Product 'A' of following sequence of reactions is
Ethylbenzene

(a) Br_{2}, Fe (b) Cl_{2}, Δ (c) alc. KOH^{'} A^{'}

(Major product)

(A)(see structure)
(B)(see structure)
(C)(see structure)
(D)(see structure)
✓ Correct

Answer: (D)

Solution

The reaction sequence:
(a) Br₂/Fe performs electrophilic aromatic substitution, brominating the benzene ring at the para position (major product due to directing effect of ethyl group).
(b) Cl₂/Δ performs free radical halogenation at the benzylic position (α-carbon of ethyl group), replacing one H with Cl.
(c) Alcoholic KOH performs elimination (E2), removing HCl to form a double bond between the benzylic carbon and the ring, yielding p-bromostyrene.

The major product A is p-bromostyrene, option (D).

JEE Main · 2022 · 27 Jun 2022 · Shift 2 · Single correct option

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