A LITTLE LIGHTBULB MOMENT
Carboxylic acid derivatives, enolates and amines
Acyl chlorides are the most reactive common acyl donors
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Acyl chlorides are the hotheads of acyl substitution.
The idea behind the cue
Acyl chlorides are generally the most reactive common carboxylic acid derivatives in nucleophilic acyl substitution because chloride is an excellent leaving group and the carbonyl is strongly electrophilic. They sit at the top of the usual reactivity order.
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Short & simple
Acyl chlorides are the hotheads of acyl substitution.
Acronym
AC — Airborne Cats.
Story
A tiny chef drops a pizza labeled acyl chloride onto the counter. The chloride storm-cloud hops off first, leaving the carbonyl carbon wide open for the next hungry nucleophile.
Connect the pieces
- A (Airborne) → Acyl chloride: Most reactive common acyl donor in standard nucleophilic acyl substitution.
- C (Cats) → Chloride leaving: Chloride is an excellent leaving group, making the carbonyl very electrophilic.
- Airborne · Acyl chloride: Most reactive common acyl donor in standard nucleophilic acyl substitution.
- Cats · Chloride leaving: Chloride is an excellent leaving group, making the carbonyl very electrophilic.
Know the limits
This ranking describes common carboxylic acid derivatives in standard acyl substitution, not every acyl-containing compound.
Further reading · OpenStax Organic Chemistry ↗Check your understanding
Which carboxylic acid derivative is generally most reactive toward nucleophilic acyl substitution?
A. Acyl chloride
B. Amide
C. Ester
D. Carboxylate
Reveal explanation
Acyl chloride
Acyl chlorides have the best leaving group among these choices, so they are typically the most reactive.