Saponification

The word 'sapo' in the term saponification is actually a Latin word that means soap. Saponification is the general term for the process of making soap. Soaps are long chains of fatty acid sodium and potassium salts. In chemistry, saponification is defined as the reaction of an ester with water and a base such as NaOH or KOH to produce alcohol and the sodium or potassium salt of an acid. Saponified oils are oils that have undergone the saponification reaction. Saponified oils are dissolved in a solution of sodium hydroxide and water. 

Saponification Reaction in General: 

Saponification =  Ester + Water + Base Soap (Sodium or Potassium Salts of Fatty Acids) + Alcohol 

During a saponification reaction, the ester group reacts with water and base (mostly NaOH) to form carboxylate ions and alcohol. The carboxylate ion is converted to carboxylic acid. Saponification is named after the fact that soap has long been made by the hydrolysis of fats (esters). 

Reaction to Saponification (in detail) 

The saponification reaction involves the reaction of sodium or potassium hydroxides with triglycerides (esters) to produce glycerol (alcohol) and potassium or sodium fatty acid salts. Soaps are the fatty acid salts of potassium or sodium. 

The Mechanism of Saponification 

The saponification reaction mechanism consists of three steps: 

Step one 

Hydroxide ion nucleophilic attack: The nucleophile hydroxide ion attacks the ester group and forms an orthoester. 

Step two

The leaving group, i.e., alkoxide, is removed, and the orthoester splits into a carboxylic acid (RCOOH) and an alkoxide group. 

Step three 

Deprotonation: Alcohol and carboxylate ions are formed when carboxylic acid and alkoxide deprotonate. 

Saponification value 

Saponification value, also known as saponification number, is the amount of base required to saponify one gramme of fat under specific conditions. It's written in terms of KOH or NaOH. It denotes the amount of KOH or NaOH used in saponification expressed in milligrams. 

The Importance of Saponification Value 

1. It informs you of the length of the carbon chain in the fatty acid used for saponification. 

2. The saponification value of fatty acids with a long carbon chain is generally low. 

3. Fats with a short carbon chain will have a higher saponification value. For example, the saponification value of butter is 230–240, whereas that of human fat is 195–200. 

4. It provides a rough estimate of the average molecular weight of the fat or oil used in saponification. 

Saponification Applications 

1. It's found in fire extinguishers. Burning oils are converted into non-combustible salts that aid in fire extinguishment. Because this reaction is endothermic, it lowers the temperature of the surrounding environment. 

2. The saponification reaction damages oil paintings. 

3. Saponification is the chemical reaction that produces soap. Soaps are extremely useful in a variety of applications. They are used for cleaning, lubrication, laundry, and other purposes. 

We use soap on a daily basis and  soap making is very common at home. People love to make soaps at home of their own choice. Being a science student, have you ever thought of which reaction is involved in soap making? If yes and didn’t get an answer yet, then in this article we are going to explain to you the reactions involved in soap making. Saponification definition, saponification reaction, saponification value are some of the important topics for your CBSE Class 10 Board Exam perspective also. You will perform soap making practical as well in the Chemistry lab of your school in Class 10. 

Saponification 

The hydrolysis of an ester with NaOH or KOH yields alcohol and the sodium or potassium salt of the acid, Soap is now a necessary daily item that is valued in everyday life. But how does soap get made? Saponification is the process of creating soap. The soap-making process, also known as saponification, is discussed in detail and in an easy-to-understand manner here. 

What exactly is Saponification? 

Saponification is the process of creating soap. Soaps are nothing more than potassium or sodium salts of long-chain fatty acids. Ester reacts with an inorganic base to produce alcohol and soap during saponification.

In general, it happens when triglycerides react with potassium or sodium hydroxide (lye) to produce glycerol and fatty acid salts, also known as 'soap.' 

Reactions to Saponification 

Triglycerides are commonly found in animal fats and vegetable oils. When they react with sodium hydroxide, they form a hard form of soap. This is where potassium enters the picture, resulting in a softer version of the soap. 

The equation is as follows: 

Base + Ester ————–> Soap + Alcohol 

Saponification Reaction Examples: 

A base (for example, sodium hydroxide) reacts with any fat to form glycerol and soap molecules in a saponification reaction. 

Triglyceride reacts with sodium hydroxide (a strong base) to produce glycerol (an acid) as well as soap (sodium palmitate). Similarly, potassium soap can be formed by reacting a strong potassium base (such as KOH) with an ester. 

It should be noted that only potassium and sodium soaps are used for cleaning. Soaps are classified as hard or soft depending on the base used. Potassium soaps are generally soft, whereas sodium soaps are hard. 

Saponification Step One & Saponification Step Two 

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

The steam hydrolysis of the triglyceride, on the other hand, yields glycerol and carboxylic acid in the two-step saponification process (rather than its salt). Alkali neutralises fatty acid in the second step to produce soap.

Value of Saponification 

The amount of base required to saponify a fat sample is referred to as the saponification value or saponification number. Saponification values are typically listed in KOH, so saponification value can also be defined as the number of milligrammes required to saponify one gramme of fat under the specified conditions. 

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

Saponification's Effects 

Saponification can have either desirable or undesirable effects. The following points discuss some of the effects of saponification. 

One of the most beneficial effects of saponification can be seen in fire extinguishers. Wet chemical fire extinguishers use saponification to convert burning fats and oils into non-combustible soap, which aids in fire extinguishment. Furthermore, the reaction is endothermic, which means it absorbs heat from the surroundings and lowers the temperature of the flames. 

In the worst-case scenario, saponification destroys oil paintings. Heavy metals used in pigments react with the oil containing free fatty acids to form soaps in oil paintings. As a result, the paintings deteriorate gradually. 

Soaps formed are used in everyday life, such as sodium soaps for laundry, potassium soaps for cleaning, and lithium soaps as lubricating greases. Other types of soap are used for a variety of purposes. 

Example 

in the presence of a conc. sulphuric acid, ethanolic acid reacts with alcohols to form esters. 

 C₂H₅OH + CH₃COOH → CH₃COOC₂H₅ + H₂O 

The ester is converted back to alcohol and the sodium salt of carboxylic acid when it is treated with a base such as NaOH. Saponification is the name given to the reaction because it is used to make soap. 

  CH₃COOC₂H₅ + NaOH → C₂H