Hydrolysis: Definition and Examples

Definition: Hydrolysis is a type of decomposition reaction where one of the reactants is water; and typically, water is used to break chemical bonds in the other reactant.

Hydrolysis may be considered the reverse of a condensation reaction, in which two molecules combine with each other, producing water as one of the products.

Origin: The term comes from the Greek prefix hydro- (water) and lysis (to break apart).

General formula of a hydrolysis reaction is:

AB + H₂O → AH + BOH

Organic hydrolysis reactions involve the reaction of water and an ester:
RCO-OR' + H₂O → RCO-OH + R'-OH

(The hyphen on the left side denotes the covalent bond that is broken during the reaction.)

Hydrolysis Examples

The first commercial application of hydrolysis was in the making of soap. The saponification reaction occurs when a triglyceride (fat) is hydrolyzed with water and a base (usually sodium hydroxide, NaOH, or potassium hydroxide, KOH). Fatty acids react with the base to produce glycerol and salts (which becomes soap).

Salt

Dissolving a salt of a weak acid or base in water is an example of a hydrolysis reaction. Strong acids may also be hydrolyzed. For example, dissolving sulfuric acid in water yields hydronium and bisulfate.

Sugar

Hydrolysis of a sugar has its own name: saccharification. For example, the sugar sucrose may undergo hydrolysis to break into its component sugars: glucose and fructose.

Acid-Base

Acid-base catalyzed hydrolysis is another type of hydrolysis reaction. An example is the hydrolysis of amides.

Catalyzed Hydrolysis

In biological systems, hydrolysis tends to be catalyzed by enzymes. A good example is the hydrolysis of the energy molecule adenosine triphosphate, or ATP. Catalyzed hydrolysis is also used for digestion of proteins, carbohydrates, and lipids.