JEE Main · 2019 · 08 Apr 2019 · Shift 2 · Hydrocarbons

Polysubstitution is a major drawback in:

(A)Friedel Craft's alkylation✓ Correct
(B)Reimer Tiemann reaction
(C)Acetylation of aniline
(D)Friedel Craft's acylation

Answer: (A)

Solution

Polysubstitution is the drawback of Friedel-Crafts alkylation. Once one alkyl group is on the ring, its electron-donating inductive effect makes the ring even more reactive towards the electrophile, so further alkyl groups add and the reaction is hard to stop at one substitution. Acylation does not suffer this, because the acyl group it installs is electron-withdrawing and deactivates the ring. So polysubstitution is the major drawback in Friedel-Crafts alkylation.

JEE Main · 2019 · 08 Apr 2019 · Shift 2 · Single correct option

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