Editing Hydrolysis (section)

===Esters and amides===
{{Main|Ester hydrolysis}}
Acid–base-catalysed hydrolyses are very common; one example is the hydrolysis of [[amide]]s or [[ester]]s. Their hydrolysis occurs when the [[nucleophile]] (a nucleus-seeking agent, e.g., water or hydroxyl ion) attacks the carbon of the [[carbonyl|carbonyl group]] of the [[ester]] or [[amide]]. In an aqueous base, hydroxyl ions are better nucleophiles than polar molecules such as water. In acids, the carbonyl group becomes protonated, and this leads to a much easier nucleophilic attack. The products for both hydrolyses are compounds with [[carboxylic acid]] groups.

Perhaps the oldest commercially practiced example of ester hydrolysis is [[saponification]] (formation of soap). It is the hydrolysis of a [[triglyceride]] (fat) with an aqueous base such as [[sodium hydroxide]] (NaOH). During the process, [[glycerol]] is formed, and the [[fatty acid]]s react with the base, converting them to salts. These salts are called soaps, commonly used in households.<ref name=":0">{{Cite book |last=Clayden |first=Johnathan |title=Organic Chemistry |last2=Greeves |first2=Nick |last3=Warren |first3=Stuart |publisher=Oxford University Press |year=2025 |isbn=978-0-19-927029-3 |edition=2nd |publication-date=23 March 2012 |pages=212-213}}</ref>

In addition, in living systems, most biochemical reactions (including ATP hydrolysis) take place during the catalysis of [[enzyme]]s. The catalytic action of enzymes allows the hydrolysis of [[protein]]s, fats, oils, and [[carbohydrate]]s. As an example, one may consider [[protease]]s (enzymes that aid [[digestion]] by causing hydrolysis of [[peptide bond]]s in [[protein]]s). They catalyze the hydrolysis of interior peptide bonds in peptide chains, as opposed to [[exopeptidase]]s (another class of enzymes, that catalyze the hydrolysis of terminal peptide bonds, liberating one free amino acid at a time).

However, proteases do not catalyze the hydrolysis of all kinds of proteins. Their action is stereo-selective: Only proteins with a certain tertiary structure are targeted as some kind of orienting force is needed to place the amide group in the proper position for catalysis. The necessary contacts between an enzyme and its substrates (proteins) are created because the enzyme folds in such a way as to form a crevice into which the substrate fits; the crevice also contains the catalytic groups. Therefore, proteins that do not fit into the crevice will not undergo hydrolysis. This specificity preserves the integrity of other proteins such as [[hormone]]s, and therefore the biological system continues to function normally.
[[File:Acid-CatAmideHydrolMarch.png|thumb|upright=1.7|Mechanism for acid-catalyzed hydrolysis of an amide.]]

Upon hydrolysis, an [[amide]] converts into a [[carboxylic acid]] and an [[amine]] or [[ammonia]] (which in the presence of acid are immediately converted to ammonium salts). One of the two oxygen groups on the carboxylic acid are derived from a water molecule and the amine (or ammonia) gains the hydrogen ion. The hydrolysis of [[peptide bond|peptides]] gives [[amino acid]]s.<ref name=":0" />

Many [[polyamide]] polymers such as [[nylon 6,6]] hydrolyze in the presence of strong acids. The process leads to [[depolymerization]]. For this reason nylon products fail by fracturing when exposed to small amounts of acidic water. Polyesters are also susceptible to similar [[polymer degradation]] reactions. The problem is known as [[environmental stress cracking]].