Question

Identify the compounds below that cannot be made via a direct friedel-crafts alkylation but can be made via acylation followed by a clemmensen reduction (to avoid carbocation rearrangements). select all that apply.

Answer 1

Let suppose you want to synthesize Propyl Benzene, and for addition of alkyl group on benzene we do Friedal Craft Alkylation. So, 1-chloropropane is treated with Lewis acid to generate electrophile and reacted with benzene.
But, doing so we get two products, a Major one is Cumene (isopropylbenzene) and the Minor product is propylbenzene. This happened due to rearrangement of carbocation propan-1-ylium to propan-2-ylium which is secondary and more stable.

In order to overcome this drawback, FC Acylation is done by reacting benzene with propionyl chloride in the presence of Lewis acid and propiophenone is formed which on reduction yields propylbenzene as a mojor product.
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