In Friedel–Crafts acylation of benzene with acetyl chloride, which species acts as the actual electrophile that attacks the ring?

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Multiple Choice

In Friedel–Crafts acylation of benzene with acetyl chloride, which species acts as the actual electrophile that attacks the ring?

In Friedel–Crafts acylation the species that actually attacks the aromatic ring is the acylium ion generated from the acyl chloride by the Lewis acid. When acetyl chloride meets AlCl3, the Lewis acid activates the acyl chloride and forms the acylium cation CH3CO+ (resonance-stabilized as R–C≡O+). This positively charged, highly electrophilic center is what the benzene ring attacks in an electrophilic aromatic substitution, giving the aryl ketone after workup. AlCl3 doesn’t itself act as the electrophile; it’s the catalyst that creates the active acylium species from the acetyl chloride.

In Friedel–Crafts acylation the species that actually attacks the aromatic ring is the acylium ion generated from the acyl chloride by the Lewis acid. When acetyl chloride meets AlCl3, the Lewis acid activates the acyl chloride and forms the acylium cation CH3CO+ (resonance-stabilized as R–C≡O+). This positively charged, highly electrophilic center is what the benzene ring attacks in an electrophilic aromatic substitution, giving the aryl ketone after workup. AlCl3 doesn’t itself act as the electrophile; it’s the catalyst that creates the active acylium species from the acetyl chloride.

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