Why direct alkylation fails: make propylbenzene via acylation + Clemmenson reduction #chemistry

Added: 2026-05-05

[00:00:00]Direct Friedel-Crafts alkylation often [music] fails because of carbocation >> rearrangement. Let's look at a better way.

[00:00:07]>> [music] >> A primary carbocation >> can shift to a more stable secondary one, >> [music] >> giving you unwanted side products. Step one, Friedel-Crafts acylation. We react benzene with propanoyl chloride using an aluminum chloride catalyst. This forms propiophenone. Crucially, the acylium ion is resonance [music] stabilized and doesn't rearrange, giving us total control. Step two, Clemmensen reduction.

[00:00:32]Using a zinc-mercury amalgam and hydrochloric [music] acid, we reduce the carbonyl group. And there it is, pure propylbenzene. [music] Acylation plus reduction is the perfect strategy for controlled alkylation.