Hydrolysis is a chemical reaction that lead to the breaking of a complex compound into a simple molecule on reaction with water. The word Hydrolysis is composed of “hydro” and “lysis” which means water and breaking down. Hence, the meaning of hydrolysis is the breaking of a compound with the help of water via a chemical reaction. In these reactions, water is the key reagent that cleaves the bond and thus breaks the compound. Several examples of hydrolysis are hydrolysis of glucose, hydrolysis of ester and ether etc.

In this article, we will learn in detail about hydrolysis, its formula, types, and examples. We will also learn the comparison between Hydrolysis, hydration, and dehydration.

Hydrolysis

What is Hydrolysis?

Hydrolysis is a chemical reaction in which a compound reacts with water which ultimately leads breakage of bonds within that compound. This reaction creates two or more compounds which are simple ions. In hydrolysis, water splits into hydrogen ions (H⁺) and hydroxide ions (OH⁻) which then participate in the breaking of bonds within the compound itself.

The general formula for hydrolysis can be represented as

AB + H₂O → AH + BOH

Where AB is the compound producing hydrolysis and AH and BOH are the compounds formed after the reaction.

Hydrolysis Reaction

Hydrolysis is a chemical process by which a chemical compound interacts with water molecules, which causes the splitting of bonds between atoms within the molecule and new bond formation. This reaction partially affects the scission of a molecule during the addition of a water molecule.

Here’s a generalized equation for a hydrolysis reaction:

Compound + Water → Product 1 + Product 2

In this environment, water is regarded as a reagent; it can be added to the molecule in several ways, or the product can depend on the compound structure and reaction conditions.

Hydrolysis Mechanism

Water decomposition is a process employed by water molecules to break bonds between a compound’s atoms. Here’s a brief overview:

• Nucleophilic Attack: As a nucleophile, a water molecule forms a bond with a carbon located on the target compound’s electrophilic center.
• Bond Cleavage: The atom under the coordination attack and the adjacent atom shares a bond that is harmful to the former.
• Ionization: The initially created pieces can therefore either become ions or donate/withdraw protons, so as to form new species that will be more stable as the reaction intermediate is formed.
• Formation of Products: When there is an electrophilic attack, there is a cleavage of the bonds, hence creating new compounds by one part exhibiting hydroxyl group (-OH) and the other the hydrogen ion (H⁺).

Fundamentally, hydrolysis reactions are the reaction between water molecules to transform complex chemical compounds into simpler products through the breakdown of the molecules.

Degree of hydrolysis

Hydrolysis involves the concept of degree of hydrolysis (α) that defines the amount of the compound hydrolytically deconstructed. It shows the efficiency of the hydrolysis reaction and the result is usually directly proportional to the fraction/percentage of the hydrolysis.

Mathematically, the degree of hydrolysis (α) can be calculated as the ratio of the number of moles of the compound that have undergone hydrolysis to the total number of moles of the compound initially present:

α = total moles of compound initially / moles of hydrolyzed compound

In some instance, the degree of hydrolysis may be expressed in percentage as well by multiplying the ratio result with 100 (it gives 100%).

Types of Hydrolysis

Hydrolysis reactions are classified into types determined by the catalyst and the substances undergoing hydrolysis. The main types of hydrolysis include:

• Acid Hydrolysis
• Base Hydrolysis
• Enzymatic Hydrolysis
• Salt Hydrolysis

Acid Hydrolysis

In Acid Hydrolysis, chemical bonds of the compound are broken in the presence of an acidic catalyst which gives hydrogen ions, H. Being in acidic conditions the specific bonds cleavages takes place. Acid hydrolysis is a phenomenon that very often occurs in biological systems e.g. digestion of food in the stomach using hydrochloric acid which assists in breaking down proteins into amino acids.

Base Hydrolysis

Basic hydrolysis involves the use of primary hydroxide ion (OH⁻). Hydroxide ions from a base to react with a compound resulting into cleavage of bonds. Like acid hydrolysis base hydrolysis yields simpler compounds or ions. Saponification, is one of the most known examples of base hydrolysis. This is a reaction between fat and oil and a strong base—for example sodium hydroxide—which produces soap and glycerol.

Enzymatic Hydrolysis

Enzymatic hydrolysis is the process of using biological catalysts which are enzymes to promote hydrolysis of specific bonds in organic molecules. Enzymes are highly specific and usually the most efficient catalysts in hydrolysis reactions without being being depleted. Several enzymes catalyze hydrolysis reactions in the living organism including the digestive enzymes such as amylase, that breaks down starch into glucose molecules during digestion.

Salt Hydrolysis

Salt hydrolysis is the process of the reaction between water and the ions of a salt which gives a resulting solution that is either acidic or basic. This type of hydrolysis happens when either the cation or the anion of the salt goes through hydrolysis to produce hydrogen ions (H⁺) or hydroxide ions (OH^–). The pH of the obtained solution is dependent on the strength relation of the acid and the base formed through hydrolysis.

Example of Hydrolysis

Hydrolysis is a chemical reaction in which a compound reacts with water and split into two products. The common examples of hydrolysis are mentioned below:

Hydrolysis of Ester

Ester hydrolysis requires a series of reactions in which a water molecule breaks the ester bond, producing a carboxylic acid and an alcohol as the products. For example, the hydrolysis of ethyl acetate: For example, the hydrolysis of ethyl acetate:

CH₃COOCH₂H₅ + H₂O →CH₃COOH + C₂H₅

In this reaction, ethyl acetate reacts with water to form acetic acid and ethanol.

Sucrose Hydrolysis

Hydrolysis of sucrose involves in the breaking of the glycosidic bond present in sucrose which s done by the water molecules to give glucose and fructose. The catalyst acts on this reaction is the enzyme sucrase.

C₁₂H₂₂O₁₁ + H₂O → C₆H₁₂O₆ + C₆H₁₂O₆

In this reaction, sucrose reacts with water to form glucose and fructose.

Amide Hydrolysis

Amide hydrolysis involves a water molecule as a reactant and which is responsible for the breaking of an amide bond by water, resulting in the formation of a carboxylic acids and an amines. For example, the hydrolysis of acetamide:

CH₃CONH₂ + H₂O + CH₃COOH +NH₃

In this reaction, acetamide reacts with water to form acetic acid and ammonia.

Hydrolysis of Ether

Ether hydrolysis involves hydrolysis of the ether linkage by strong acids or bases. The results are the molecular conversion into alcohols and/or alkyl halides. An example involves the hydrolysis of ethyl ether in acidic conditions:

(C₂H₅)₂O + H₂O + H⁺ → 2C₂H₅OH

In this reaction, ethyl ether reacts with water and a proton (from the acid) to form ethanol.

Hydrolysis vs Dehydration

In hydrolysis and dehydration both involve water but they occur in different directions and the process either generates or breaks chemical bonds for various reasons.