We have already learnt that when carboxylic acids are heated with P2O5 dehydration takes place to form acid anhydride.
Acid chlorides on heating with sodium salt of carboxylic acids gives corresponding anhydride.
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.