Acyl Chloride

Acyl chloride is a carboxylic acid derivative.
 Don’t forget the HCl when reacting with acyl chlorides.
 1) Preparing Acyl Chloride: Carboxylic acid and SOCl2 thionyl chloride.
Produces gases SO2 and HCl. Carry out in fume cupboard as products harmful.
 Reactions of Acyl Chloride: Acyl chlorides are very reactive.
– Acyl chlorides react with nucleophiles by losing chloride ion.
 2) Reaction of Acyl Chlorides with Alcohols to Form
Ester:

3) Reaction of Acyl Chlorides with Phenols to Form
Phenyl Ester: Carboxylic to reactive enough to react with phenols. No catalyst
needed.
 4) Reaction of Acyl Chlorides with Water to form
Carboxylic Acid:
Also produces hydrogen chloride fumes. Ethanoyl chloride shown below.
 5) Reaction of Acyl
Chlorides with
Ammonia/ Amines to Form Amide:
Ammonia and amines act as nucleophiles by donating lone pair of electrons on the nitrogen to
electron- deficient species.
Ammonia reacts to form primary amide- the N is attached to one C.
Primary amine reacts to form secondary amide- the N is attached to two C. Nmethylethanamide tells us that methyl group attached to nitrogen rather than main carbon
chain. Methyl group from primary amine.
 Reactions of Acid Anhydrides:
 Acid anhydrides also reactive but less reactive than acyl chlorides so reactions slower with acid
anhydrides. Acid anhydrides react in the same was as acyl chlorides with alcohols, phenols,
water and ammonia/ amines. However instead of HCl as a product, a carboxylic acid is formed. If
ethanoic anhydride used, then ethanoic acid formed.
 2(CH3CO)2O + C6H5OH -> CH3COOC6H5 + CH3COOH.
Ethanoic anhydride + phenol -> phenyl ethanoate +
ethanoic acid.

1) Reaction of Acid Anhydride with Alcohols to Form
Ester:
The red bit in acid anhydride AND hydrogen
from OH form a carboxylic acid. The rest of
acid anhydride and alcohol form an ester.
If ethanoic anhydride used, then ethanoic
acid and ethyl ethanoate formed.
 2) Reaction of Acid Anhydrides with Water to form
Carboxylic Acid:
 Anhydride to create an ester more favourable than alcohol + C.A. Better yield as irreversible
reaction. Only warm conditions required rather than heat/reflux/catalyst so cheaper.
 Anhydride and acyl chloride replace carboxylic acid in these reactions.
 Ethanoic anhydride doesn’t produce dangerous fumes of hydrogen chloride if used acyl
chlorides.
 Extension- nucleophilic reaction of acyl chloride.