CONCEPTS

What is hydrolysis?

We explain what hydrolysis is and what this chemical reaction consists of. In addition, the types of hydrolysis that exist.

  1. What is hydrolysis?

It is known as hydrolysis to a specific chemical reaction , in which water molecules divide into their component atoms (H2O: hydrogen and oxygen) and form different bonds with some other substance involved, altering it in the process. This is what happens, in other words, when water is used as a solvent.

The specific name of this reaction comes from the Greek words  hydro  (“water”) and  lýsis  (“rupture”), which shows that it is a form of breakage of a particular molecule of solute , by reacting it with water. In terms of organic chemistry, it is the process exactly opposite to the condensation reaction, which is the junction of two organic molecules that byproducts a water molecule .

There are three main forms of hydrolysis, depending on the substances that are reacted with water:

Acid-base hydrolysis . In this reaction the water is divided into a hydroxyl ion (OH-) and a proton (H +) that is immediately hydrated to form hydronium (H3O +), in the presence of substances such as salts, whose ions are combined with the above, depending on the degree of dissolubility that these salts have with respect to water. This can lead to four different scenarios:

  • Salt hydrolysis of strong acid-strong base . In this case almost hydrolysis does not occur, since cations and anions are not very reactive, since they are weak. The pH in this case will be neutral.
  • Hydrolysis of weak acid salt – strong base . In this case the weakness of the acid (and hence of the anion) will generate hydroxyl ions, while the cation, being strong, will not react. The resulting pH will be basic.
  • Hydrolysis of strong acid salt – weak base . Otherwise, the weakness of the base (and hence the cation) will generate hydronium (hydroxonium) ions, while the anions will not react. The resulting pH will be acidic.
  • Hydrolysis of weak acid salt-weak base . The high reactivity of both the cations and the anions, so there will be a greater or lesser balance in the reaction and both hydroxyl and hydronium ions will be produced. The pH of this reaction will be neutral.

Hydrolysis of amides and esters . In the case of this type of organic substances, the presence of water or a hydroxide ion reacts with the carbon atoms, breaking them down into their constituent elements: the amides are broken down into amines and carboxylic acids, and the esters into alcohols and carboxylic acids . In fact, this is what happens in the practice of saponification (hydrolysis of triglycerides and obtaining soaps).

Polysaccharide hydrolysis . Various sugars such as disaccharides or polysaccharides can be broken down when dissolved in water, when the hydrogen of the latter binds to the oxygen at the end of the sugar molecule, while the hydroxyl ion (OH-) binds to the rest of it. In this way, sugar is simplified, which allows to carry complex molecules to similar ones much simpler, and is a process carried out regularly by life forms.

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