CIE A Level Chemistry (9701) 2019-2021

Revision Notes

7.5.4 Reactions of Acyl Chlorides

Reactions of Acyl Chlorides

  • Acyl chlorides are reactive organic compounds that undergo many reactions such as addition-elimination reactions
  • In addition-elimination reactions, the addition of a small molecule across the C=O bond takes place followed by elimination of a small molecule
  • Examples of these addition-elimination reactions include:
    • Hydrolysis
    • Reaction with alcohols and phenols to form esters
    • Reaction with ammonia and amines to form amides

Hydrolysis

  • The hydrolysis of acyl chlorides results in the formation of a carboxylic acid and HCl molecule
  • This is an addition-elimination reaction
    • A water molecule adds across the C=O bond
    • A hydrochloric acid (HCl) molecule is eliminated
  • An example is the hydrolysis of propanoyl chloride to form propanoic acid and HCl

 

Carboxylic Acids & Derivatives - Overall Hydrolysis Acyl Chlorides, downloadable AS & A Level Chemistry revision notes

Acyl chlorides are hydrolysed to carboxylic acids

Formation of esters

  • Acyl chlorides can react with alcohols and phenols to form esters
    • The reaction with phenols requires heat and a base
  • Esters can also be formed from the reaction of carboxylic acids with phenol and alcohols however, this is a slower reaction as carboxylic acids are less reactive and the reaction does not go to completion (so less product is formed)
  • Acyl chlorides are therefore more useful in the synthesis of esters
  • The esterification of acyl chlorides is also an addition-elimination reaction
    • The alcohol or phenol adds across the C=O bond
    • A HCl molecule is eliminated

Carboxylic Acids & Derivatives - Esterification of Acyl Chlorides, downloadable AS & A Level Chemistry revision notes

Acyl chlorides undergo esterification with alcohols and phenols to form esters

Formation of amides

  • Acyl chlorides can form amides from their condensation reaction with amines and ammonia
  • The nitrogen atom in ammonia and amines has a lone pair of electrons which can be used to attack the carbonyl carbon atom in the acyl chlorides
  • The product is a non-substituted amide (when reacted with ammonia) or substituted amide (when reacted with primary and secondary amines)
  • This is also an example of an addition-elimination reaction as
    • The amine or ammonia molecule adds across the C=O bond
    • A HCl molecule is eliminated

Carboxylic Acids & Derivatives - Condensation of Acyl Chlorides, downloadable AS & A Level Chemistry revision notes

Acyl chlorides undergo condensation reactions with ammonia and amines to form amides

Author: Francesca

Fran has taught A level Chemistry in the UK for over 10 years. As head of science, she used her passion for education to drive improvement for staff and students, supporting them to achieve their full potential. Fran has also co-written science textbooks and worked as an examiner for UK exam boards.
Close

Join Save My Exams

Download all our Revision Notes as PDFs

Try a Free Sample of our revision notes as a printable PDF.

Join Now
Already a member?
Go to Top