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Saponification-Definition, Saponification value, Mechanism of Saponification, Examples, Applications, Practice Problems, FAQs

While watching programs on television, all of you must have seen advertisements for soaps which are fascinating to watch. Isn’t it! Many of you may find your favorite celebrities promoting any particular brand. You get influenced by these advertisements and at the same time, you decide to bring that product to your home. 

Have you imagined how these soaps are made of? There is a chemical process known as saponification. There is a wide variety of soaps available in the market, some are for washing dishes and some for toilet uses. 

Have you visited any factory where large-scale soap production happens? Ask your parents to take you on a visit to such factories to get a better and wider picture.

There is a wide range of soaps and similarly, there are wide uses of soap. It is important for us to study how this is carried out and let's study this soap-making process in detail!

TABLE OF CONTENTS:

  • What is saponification?
  • Saponification value
  • Mechanism of Saponification
  • Examples of saponification
  • Application of saponification
  • Esterification vs Saponification
  • Practice problems
  • Frequently asked questions-FAQs

What is saponification?

Saponification is the procedure used to create soaps. Triglycerides are commonly used to prepare soaps, which are long carbon chains of fatty acids formed when they are combined with sodium or potassium hydroxides. The process of turning oils and fats into soaps by the action of aqueous alkalis is known as saponification. Alcohol and fatty acid salts are produced using alkalis like and . The following generic equation represents the saponification reaction:

Saponification is a hydrolysis process, according to the aforementioned reaction. In the process of saponification, a hydroxide breaks the ester link between fatty acids and the triglyceride glycerol, resulting in the creation of free fatty acids and glycerol.

Triglycerides in fat and oil are transformed into soap and glycerol when they interact with aqueous or . This process is known as esters' alkaline hydrolysis. The Saponification Process is the name given to this reaction since it results in the production of soap.

Saponification value:

The quantity of base, such as or , needed to saponify 1 mg of fat under specific circumstances is known as the saponification value. The term "saponification number" also refers to the saponification value. The average molecular mass of all the fatty acids found in the given triglyceride sample is used to compute it. The amount of base needed decreases with increasing glyceride molecular mass. Similar to this, a shorter chain length and higher saponification values go hand in hand.

The below mentioned saponification values of different compounds:

Oil/fat Saponification value ()
Olive oil 184 – 196
Soybean oil        187 – 195
Coconut oil 248 – 265
Cottonseed oil 189 – 207
Sunflower oil 189 –195
Canola oil 182 –193
Palm oil 190 – 209
     Castor oil       176 – 187
       Palm kernel oil        230 – 254

Significance of saponification value:

  • The molecular mass of glycerides has an inverse relationship with the saponification value. The saponification value increases with decreasing molecular weight.
  • Saponification value aids in calculating the necessary amount of base.
  • The chain length can be calculated using the saponification value.
  • It offers details on how to calculate the number of fatty acids in fats or oils.

Mechanism of Saponification:

The process of nucleophilic carbonyl substitution that constitutes saponification's mechanism is described in the following steps.

Step 1. The ester group is being attacked by the nucleophilic hydroxide ion to create an intermediate.

Step 2. Carboxylic acid and an alkoxide are formed when the intermediate rearranges by releasing the leaving group.

Step 3. The carboxylic acid undergoes deprotonation to produce a carboxylate ion and alcohol when the hydrogen is removed.

Examples of Saponification:

  • Sodium Stearate: The sodium salt of stearic acid ( is called sodium stearate It serves as a detergent and a soap. It plays a big role in soaps and has both a hydrophobic and a hydrophilic component. It is created when aqueous sodium hydroxide 
    ( hydrolyzes the glyceryl tristearate , the triglyceride of stearic acid.
     
  • Sodium Palmitate: The sodium salt of fatty palmitic acid () is called sodium palmitate . It can be found in detergents and soaps. Glyceryl palmitate can be saponified using sodium hydroxide () in the form of caustic soda, lye, or lime to produce it.
     
  • Methyl Salicylate: When sodium hydroxide () and methyl salicylate ( combine, sodium salicylate ( solidifies into a thick, white solid.
     
  • Methyl Acetate: In the presence of sodium hydroxide (), methyl acetate ( saponified to sodium acetate (
     
  •  Methyl Benzoate: Methyl benzoate ( and aqueous sodium hydroxide ( combine to produce methanol and water-soluble sodium benzoate (miscible with water).

Applications of saponification:

  • making both hard and soft soaps: Saponification produces soaps with various characteristics. They are classed as hard and soft soaps as a result. The alkali that is utilized in the manufacturing of the soaps falling under these categories usually distinguishes them from one another. Hard soaps are those whose base ingredient is . The magnesium and calcium minerals in hard water make hard soaps beneficial as well. The ones made from are soft soaps.
     
  • Extinguishers for fire: Wet fire extinguishers can put out fires started by fats and oils used in cooking. These fire extinguishers work by utilizing saponification processes. The extremely flammable liquids are transformed into non-combustible soaps through saponification.
     
  • In the food sector: Saponification is important in the food sector in particular because it makes it easier to determine how much free fatty acid is contained in a given food product. The amount of alkali applied to the fat or oil to make it neutral can be used to identify the amount of free fatty acid.

Saponification Vs Esterification:

Acid and alcohol combine to create an ester and release water during esterification. Contrarily, saponification causes an ester's bonds to be broken, resulting in the formation of alcohol and a long-chained fatty acid derivative.

Example of Esterification:

The distinction between esterification and saponification is seen in the following table.

  Esterification    Saponification
Definition This process is used in the making of esters. This process is used in the making of soaps.
Process In the presence of strong sulfuric acid, carboxylic acid and alcohol react. Ester and aqueous alkali react.
Heat yes No
Catalyst Acid Base
Byproduct Water Alcohol

Practice problems:

Q1. Name the term that best describes saponification.

A. Breaking of ether molecules into alcohol and carboxylic acid
B. Two alkyl groups are synthesized to create an ether.
C. Breaking of ester molecules into alcohol and carboxylic acid
D. Salt hydrolysis with the addition of a weak acid

Answer: C
Strong bases are used to break the ester link and release fatty acid salts (soaps) and glycerol when the ester molecules are broken down into carboxylic acid and alcohol, which are triglycerides.

Q2. Which of the following oils or fats cannot be saponified?

A.Shea butter
B.Bee wax
C.Olive oil
D.Paraffin wax

Answer: D)
Unsaponifiables are substances found in oily (oil, fat, wax) mixtures that do not react with sodium hydroxide (lye) or potassium hydroxide to produce soap. Paraffin wax has an unsaponifiable value of about 100.

Q3. Which of the following compounds is produced industrially through saponification?

A. Sodium chloride
B. Sodium hydroxide
C. Glycerol
D. Potassium hydroxide

Answer: C)
A powerful base is used to treat the triglyceride, breaking the ester link and releasing glycerol and fatty acid salts (soaps). The primary industrial method for manufacturing glycerol also uses this process. In rare cases when manufacturing soap, the glycerol is left behind.

Q4. What chemical compound can be used to salt soap in order to precipitate it out?

A. Sodium chloride
B. Sodium hydroxide
C. Glycerol
D. Potassium hydroxide

Answer: A)
Soaps can be precipitated if necessary by salting them out with sodium chloride.

Frequently asked questions-FAQs

Q1. Who created the useful chemical known as "soap"?
Answer: The earliest people to create soap were the Babylonians around 2800 B.C. They found that mixing animal fats—specifically, animal fats—with wood ash produced a cleaner end result. Wool from the textile industry was washed with the first soap.

Q2. Why is fat used to make soap?
Answer: Sodium tallowate facilitates the mixing of water with oil and impurities for easier cleaning of your skin and hair. Animal fat-based homemade soaps frequently have fewer components than many commercial soaps.

Q3. Why does saponification need ?
Answer: NaOH is frequently used to make solid soap because it is not water-soluble. After the procedure, residues and residual fatty acids (oil) will form if the amount of needed for the saponification reaction.

Q4. What does science mean when it refers to saponification?
Answer: A "hydrolysis reaction in which free hydroxide dissolves the ester bonds between triglyceride fatty acids and glycerol, resulting in free fatty acids and glycerol," is what is meant by the term "saponification." Each of these components is soluble in aqueous solutions.

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