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Friedel–Crafts **acylation** is generally preferred over alkylation for installing a $-R$ group onto benzene because
Aacylation works without a Lewis acid
Bacylation gives no polysubstitution and no carbocation rearrangement
Calkylation requires a metal catalyst
Dacylation uses cheaper reagents
Answer & Solution
Correct answer: B. acylation gives no polysubstitution and no carbocation rearrangement
Two big issues with Friedel–Crafts alkylation: (1) primary carbocations rearrange to more stable secondary/tertiary, and (2) the alkyl product is more activated than the starting arene, so polysubstitution. Acylation produces an acylium ion (no rearrangement) and gives a *deactivated* ketone product (no polysubstitution). Subsequent Clemmensen/Wolff–Kishner reduces $>C=O$ to $-CH_2-$ giving the desired alkylbenzene cleanly.
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