Chemistry
Mechanistic Insights into Friedel–Crafts Acylation via Carbocation Intermediates
Quick fact
Friedel–Crafts acylation produces a ketone product that is less reactive towards further acylation, so the reaction typically stops after a single acyl group is added, unlike alkylation which can over-substitute.
Why this is interesting
You've probably seen benzene as a stable, unreactive ring. Yet chemists can attach an acyl group to it with surprising ease—how does that happen without disturbing the aromaticity?