9701 · 33.3
Acyl chlorides — FAQ
Frequently asked questions for 9701 Acyl chlorides. Direct answers first, then deeper explanation — then practise with marking.
Why do acyl chlorides 'fume' in moist air?
Acyl chlorides react very rapidly with water vapour present in the air in a hydrolysis reaction. This reaction produces the parent carboxylic acid and hydrogen chloride (HCl) gas. The HCl gas then appears as white, steamy fumes.
Why are two moles of an amine needed to react with one mole of an acyl chloride?
The first mole of the amine acts as a nucleophile, attacking the carbonyl carbon to form the amide. This reaction also produces one mole of HCl as a by-product. Since amines are bases, a second mole of the amine is required to react with and neutralise the acidic HCl, forming an ammonium salt (e.g., ).
Can I use an acyl chloride to make a tertiary amide?
No, you cannot make a tertiary amide (an amide where the nitrogen is bonded to three carbon atoms) using an acyl chloride and a tertiary amine. While a tertiary amine can act as a catalyst, it cannot form a stable amide product because it lacks an N-H bond. The final step of the mechanism involves the removal of a proton from the nitrogen atom, which is not possible for a tertiary amine.