Difference Between Soap and Detergent

All the important differences between soaps and detergents are explained in this article. Soaps are the potassium or sodium salts of long chain fatty acids and detergents are generally alkylbenzenesulfonates.

What are Soaps and Detergents?

Soaps

  • Soaps are potassium or sodium salts of a carboxylic acid having a long aliphatic chain attached to it.
  • They are surfactants (compounds that reduce the surface tension between a liquid and another substance) and therefore help in the emulsification of oils in water.
  • Soaps are generally prepared via the saponification of fats and oils.
  • The carboxylate end of the soap molecule is hydrophilic whereas the hydrocarbon tail is hydrophobic.

Detergents

  • Detergents are the potassium or sodium salts of a long alkyl chain ending with a sulfonate group.
  • They are soluble in hard water.
  • This solubility is attributed to the fact that the sulfonate group does not attach itself to the ions present in hard water.
  • Commonly, anionic detergents such as alkylbenzenesulfonates are used for domestic purposes.

Difference between Soap and Detergent

The key differences between soaps and detergents are tabulated below.

Difference Between Soap and Detergent
Soaps Detergents
Consist of a ‘-COONa’ group attached to a fatty acid having a long alkyl chain. Consist of a ‘-SO3Na’ group attached to a long alkyl chain.
They are not effective in hard water and saline water They do not lose their effectiveness in hard water and saline water.
Soaps are completely biodegradable Detergents containing a branched hydrocarbon chain are non-biodegradable
They have a tendency to form sum in a hard water environment. These compounds do not form scum.
They are derived from natural sources such as vegetable oils and animal fats. Detergents are synthetic derivatives.
Soaps are environment-friendly products since they are biodegradable. These compounds can form a thick foam that causes the death of aquatic life.
Examples of soaps: sodium palmitate and sodium stearate. Examples of detergents: deoxycholic acid and sodium lauryl sulfate.

Preparation of Soap

The most commonly used soap making process is the saponification of oils and fats.

This process involves heating oils and fats reacting them with a liquid alkali to produce soap plus water plus glycerine.

Saponification

The other soapmaking process is with the neutralization of fatty acids with an alkali. Oils and fats are hydrolyzed with high-pressure steam to yield glycerine and crude fatty acids.

Saponification

The fatty acids are later purified by the method of distillation and neutralized with an alkali to produce water and soap.

Preparation of Soap

Alkali like sodium hydroxide produces sodium soap which is hard. Potassium soaps are soft. They are used in shaving creams and some liquid hand soaps.

The carboxylate end of the soap molecule is a hydrophilic end. The grease and oil attract the hydrocarbon chain and repel water. This is known as the hydrophobic end.

To learn more about soaps and detergents, register with BYJU’S and download the mobile application on your smartphone.


Practise This Question

Toluene on oxidation with dilute HNO3 and alkaline KMnO4 gives