Acyl chlorides
Cambridge A-Level Chemistry (9701) · Unit 33: Carboxylic acids and derivatives (A Level) · 8 flashcards
Acyl chlorides is topic 33.3 in the Cambridge A-Level Chemistry (9701) syllabus , positioned in Unit 33 — Carboxylic acids and derivatives (A Level) , alongside Carboxylic acids and Esters. In one line: Phosphorus trichloride (PCl₃) with heat, phosphorus pentachloride (PCl₅), or thionyl chloride (SOCl₂). These reagents replace the -OH group of the carboxylic acid with a chlorine atom.
Marked as A2 Level: examined at A Level in Paper 4 (A Level Structured Questions) and Paper 5 (Planning, Analysis and Evaluation). It is not tested on the AS-only papers (Papers 1, 2 and 3).
The deck below contains 8 flashcards — 6 definitions and 2 key concepts — covering the precise wording mark schemes reward. Use the 6 definition cards to lock down command-word answers (define, state), then move on to the concept and calculation cards to handle explain, describe, calculate and compare questions.
List three reagents that can be used to convert a carboxylic acid into an acyl chloride
Phosphorus trichloride (PCl₃) with heat, phosphorus pentachloride (PCl₅), or thionyl chloride (SOCl₂). These reagents replace the -OH group of the carboxylic acid with a chlorine atom.
What the Cambridge 9701 syllabus says
2025-2027 syllabus, in our words · A2 LevelWhat the syllabus expects you to be able to do in this topic, in plain English. For the exact wording, see the official syllabus (PDF).
- Recall the reagents and conditions for making acyl chlorides: (a) treating a carboxylic acid with PCl₅, with SOCl₂, or with PCl₃ and heat.
- Describe these acyl chloride reactions, all at room temperature and all also forming HCl: (a) hydrolysis with water to the carboxylic acid; (b) with an alcohol to an ester; (c) with phenol to an ester; (d) with ammonia to an amide; (e) with a primary or secondary amine to an amide.
- Describe the addition-elimination mechanism for each of the acyl chloride reactions (a) to (e) in the previous outcome.
- Explain why acyl chlorides, alkyl chlorides and aryl chlorides (halogenoarenes) differ in how easily they are hydrolysed.
Cambridge syllabus keywords to use in your answers
These are the official Cambridge 9701 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.
List three reagents that can be used to convert a carboxylic acid into an acyl chloride.
Phosphorus trichloride (PCl₃) with heat, phosphorus pentachloride (PCl₅), or thionyl chloride (SOCl₂). These reagents replace the -OH group of the carboxylic acid with a chlorine atom.
Write the general equation for the reaction of an acyl chloride with water.
RCOCl + H₂O → RCOOH + HCl. This hydrolysis reaction produces a carboxylic acid and hydrogen chloride gas.
What type of organic compound is produced when an acyl chloride reacts with an alcohol?
An ester is formed. The reaction is: RCOCl + R'OH → RCOOR' + HCl. Hydrogen chloride gas is also produced.
Write the general equation for the reaction of an acyl chloride with ammonia.
RCOCl + 2NH₃ → RCONH₂ + NH₄Cl. An amide is formed, along with ammonium chloride.
Describe the addition-elimination mechanism of acyl chloride reactions.
The nucleophile (
Outline the reaction of acyl chloride with phenol.
RCOCl + C₆H₅OH → RCOOC₆H₅ + HCl. An ester is formed, along with hydrogen chloride gas. Phenol is benzene ring with an -OH group.
Explain why acyl chlorides are more readily hydrolysed than alkyl chlorides or halogenoarenes.
The carbonyl carbon in acyl chlorides is more δ+ due to the electronegativity of both the oxygen and chlorine atoms. This makes it more susceptible to nucleophilic attack by water. Alkyl chlorides and halogenoarenes are less polarised and the C-Cl bond is stronger.
Write the general equation for the reaction of an acyl chloride with a primary amine.
RCOCl + 2R'NH₂ → RCONHR' + R'NH₃Cl. An N-substituted amide is formed, along with the amine salt.
More Chemistry flashcards
Browse every 9701 flashcard topic by syllabus area.
All Chemistry FlashcardsMore topics in Unit 33 — Carboxylic acids and derivatives (A Level)
Acyl chlorides sits alongside these A-Level Chemistry decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.
Key terms covered in this Acyl chlorides deck
Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.
How to study this Acyl chlorides deck
Start in Study Mode, attempt each card before flipping, then rate Hard, Okay or Easy. Cards you rate Hard come back within a day; cards you rate Easy push out to weeks. Your progress is saved in your browser, so come back daily for 5–10 minute reviews until every card reads Mastered.
Study Mode
Rate each card Hard, Okay, or Easy after flipping.