From nitriles and amides

Alkyl or aryl nitriles, on acid hydrolysis with a dilute mineral acid (dilute H2SO4 or dilute HCl), FIRST give an amide -- via a short-lived imine intermediate, R-C(=NH)-OH -- and that amide, on FURTHER acid hydrolysis, gives the corresponding carboxylic acid: R-C#N + H2O gives the imine intermediate, which becomes R-CO-NH2 (the amide); this amide, with H2O and dilute HCl, gives R-COOH plus ammonia (isolated as NH4Cl on workup). Written as one overall equation: R-C#N + 2 H2O + dilute HCl, heated, gives R-COOH + NH4Cl -- so hydrolysing a nitrile all the way to the acid gen …