Saponification

Saponification

Soaps are an integral part to maintain good health and hygiene of the individuals. Soaps are essential to cleanse dirt and oil off the objects including skin surface. Soaps are widely used in bathing, cleaning, washing and in other household chores. Soap is now an essential everyday item and finds its importance in everyday life. But, how is soap made? The process of making soap is called saponification. Here, the soap making process or saponification is discussed in a detailed and easy way.

What is Saponification?

Saponification is simply the process of making soaps. Soaps are just potassium or sodium salts of long chain fatty acids. During saponification, ester reacts with an inorganic base to produce alcohol and soap. Generally, it occurs when triglycerides are reacted with potassium or sodium hydroxide (lye) to produce glycerol and a fatty acid salt, called ‘soap’. Triglycerides are generally animal fats and vegetable oils. When they are reacted with sodium hydroxide, a hard form of soap is created. This is where potassium comes and creates a softer version of the soap.
The equation can be written as:

Saponification reaction

Ester + Base ————–> Alcohol + Soap

Saponification Mechanism

Orthoester formation:

Saponification Mechanism

Expulsion of carboxylic acid and alkoxide:

Saponification Mechanism

Creation of alcohol:

Saponification Mechanism

Example of a Saponification Reaction:

In saponification reaction, a base (for example sodium hydroxide) reacts with any fat to form glycerol and soap molecules. One of the saponification reaction taking triglyceride as an ester and sodium hydroxide as the base is as follows:

Saponification

In this reaction, triglyceride reacts with sodium hydroxide (a strong base) and glycerol is produced (an acid) along with soap (sodium palmitate). Similarly, potassium soap can be formed if a strong potassium base (like KOH) is reacted with an ester. This reaction is as follows:

Saponification

It should be noted that for cleaning purposes, only potassium and sodium soaps are used. Based on the base used, soaps can either be hard soaps or soft soaps. In general, potassium soaps are soft and sodium soaps are hard. Visit cleansing action of soaps and detergents to know how dirt is removed from objects.

1-Step Saponification vs 2-Step Saponification :

There can be either one-step saponification or two-step saponification process to convert triglycerides to soaps. The examples mentioned above are one-step saponification process in which triglycerides, when treated with a strong base, splits from the ester bond to release glycerol and soaps (i.e. fatty acid salts).

On the other hand, in two-step saponification process, steam hydrolysis of the triglyceride yields glycerol and carboxylic acid (rather than its salt). In the second step, alkali neutralizes the fatty acid to produce soap.

Saponification Value:

Saponification value or saponification number refers to the amount of base that is required to saponify a fat sample. Generally, saponification values are listed in KOH and so, saponification value can also be defined as that value which represents the number of milligrams required to saponify 1 gram of fat under the specified conditions.

In case sodium hydroxide is used for saponification process, the saponification value must be converted from potassium to sodium by dividing the KOH values by the ratio of the molecular weights of KOH and NaOH (i.e. 1.403).

Effects of Saponification:

The effects of saponification can either be desirable or undesirable. Some of the effects of saponification are mentioned in the below-given points.

  • ● One of the major desirable effects of saponification is seen in fire extinguishers. Saponification is used by wet chemical fire extinguishers to convert burning fats and oils into non-combustible soap which helps in extinguishing the fire. Further, the reaction is endothermic and lowers the temperature of the flames by absorbing heat from the surroundings.
  • ● In an undesirable scenario, saponification damages oil paintings. In oil paintings, the heavy metals used in pigments react with the oil containing free fatty acids and forms soaps. This way, the paintings get damaged gradually.
  • ● Soaps formed are used in everyday life like sodium soaps are used for laundry, potassium soaps are used for cleaning and lithium soaps are used as lubricating greases. There are various other soaps which are used for different purposes.

Uses of saponification

  • Wet chemical fire extinguishers: To extinguish cooking oils and fats, we use a saponification reaction. This is because cooking oils and fats have a flash point which is above 37 degrees which render regular fire extinguishers useless.
  • Creating hard and soft soaps: By using different types of alkali in the process the type of the reaction product can be altered between hard and soft.
    • Using KOH: We can obtain soft soaps
    • Using NaOH: We can obtain hard soaps

This was all about the saponification process. This topic is one of the most crucial topics in chemistry and students are required to be thorough with the reactions and terms to be able to answer questions in the exam.

To learn more important chemistry topics in an easy and effective way, stay tuned with BYJU’S. At BYJU’S, students are provided with easy explanations of different topics, sample papers, question papers and effective preparation strategies to aide in chemistry preparation.


Practise This Question

CH3COOH(l) + C2H5OH(l)  CH3COOC2H5(l) + H2O(l)

In the above reaction, one mole of each of acetic acid and alcohol are heated in the presence of 

little conc. H2SO4. On equilibrium being attained