Acid anhydride

Acid anhydride

Methods of preparation

1. Heating carboxylic acid with P₂O₅

We have already learnt that when carboxylic acids are heated with P₂O₅ dehydration takes place to form acid anhydride.

2. By reaction of acid halide with a salt of carboxylic acids.

Acid chlorides on heating with sodium salt of carboxylic acids gives corresponding anhydride.

Chemical properties

1. Hydrolysis

Acid anhydride are slowly hydrolysed, by water to form corresponding carboxylic acids.

2. Reaction with alcohol

Acid anhydride reacts with alcohols to form esters.

3. Reaction with ammonia

Acid anhydride reacts with ammonia to form amides.

4. Reaction with PCl₅

Acid anhydride reacts with PCl₅ to form acyl chlorides.