Alkaline hydrolysis usually refers to types of nucleophilic substitution reactions in which the attacking nucleophile is a hydroxide ion. The best known type is saponification: cleaving esters into carboxylate salts and alcohols. In ester hydrolysis and amide hydrolysis the hydroxide ion nucleophile attacks the carbonyl carbon in a nucleophilic acyl substitution reaction. This mechanism is supported by isotope labeling experiments. For example, when ethyl propionate with an oxygen-18 labeled ethoxy group is treated with sodium hydroxide (NaOH), the oxygen-18 is completely absent from the sodium propionate product and is found exclusively in the ethanol formed.
The reaction is often used to solubilize solid organic matter. Chemical drain cleaners take advantage of this method to dissolve hair and fat in pipes. The reaction is also used to dispose of human and other animal remains as an alternative to traditional burial or cremation.