Nitriles hydrolyze in acidic media, under heating, becoming carboxylic acids and ammonium salts. The hydrolysis of nitriles is an irreversible process.

hidrolisis-acida-nitrilos
The reaction mechanism consists of the following stages:
Stage 1. Protonation of the nitrile
hidrolisis-acida-nitrilos
Stage 2. Nucleophilic attack of water
hidrolisis-acida-nitrilos
Stage 3. Deprotonation of water
hidrolisis-acida-nitrilos
Stage 4. Tautomerism
hidrolisis-acida-nitrilos
The amide hydrolyzes in the acid medium to carboxylic acid. The mechanism can be found in the section e amides.
hidrolisis-acida-nitrilos
Due to the higher reactivity of the nitrile on the amide, working under mild conditions, the hydrolysis to the amide can be stopped.