Soaps and Detergents in Chemistry

Chemical compounds used as cleaning agents like soaps and detergents are made up of a variety of different components. Various fatty acid combinations are dissolved in water to form a soapy sodium or potassium salt. Because the term “detergent” refers to a cleaning agent and is unaffected by the hardness of the water, detergents are much preferable to cleaning solutions. Soap and other detergents are examples of cleaning agents. Soap has been around for more than 2,000 years. Soap is also a detergent, according to this definition.

Soaps

Soap is the sodium or potassium salt of long-chain carboxylic acids (fatty acids). Hard soaps are sodium salts of fatty acids, while soft soaps are potassium salts of fatty acids. The soap contains many non-ionic hydrocarbons and an ionic COO– Na+ group. Soap’s structure may be expressed as follows:

Where ~ denotes the negatively charged carboxyl group and represents the hydrocarbon group. Soaps include sodium stearate 

Preparation of Soaps

Oil or fat from plants or animals is heated with a concentrated sodium hydroxide solution. This mixture is then cooled and mixed with water to make soap (caustic soda solution). There is a process called saponification in which alkaline hydrolysis of oils and fats, or saponification. The sodium salt of fatty acids formed is used to make soap.

Soap molecule structure

Detergents are the salt of long-chain benzene sulphonic acid (or long-chain alkyl hydrogen sulphate) that can clean in water. Anionic groups like sulphonate, SO3–Na+ or SO4–Na+ can be found in detergents. A large non-ionic hydrocarbon group and an ionic group like SO4–Na+ make up detergents. Dodecyl sulphate and sodium n-dodecyl sulfonate are two examples of detergents, but many more. These are below:

Structure: Soaps and detergents are both made up of the same parts. Water-repelling (hydrophobic): A detergent molecule also has two parts: a long hydrocarbon chain that doesn’t like water and a short ionic part that likes water (hydrophilic).

Preparation of detergents

Chemicals from petroleum, like hydrocarbons, are mixed with sulfuric acid and turned into sodium salt. This is how synthetic detergents are made.

Cleansing action or mode of action of soap

Soaps and detergents are composed of two components: a lengthy hydrocarbon tail and a negatively charged head, which act together to clean the skin. In addition to being hydrophobic, the hydrocarbon tail is non-polar, making it insoluble in water (water-repelling).

On the other hand, because it is polar, the negatively charged head is soluble in water and is hence hydrophilic (water-attracting).

Water is used to dissolve the polar heads of soap and detergent molecules. The nonpolar tails of these molecules dissolve in each other when the soap or detergent is put into water. Soap or detergent generates spherical ionic micelles, clusters of around 100-200 molecules with their polar heads (shown by solid circles) on the cluster’s surface and non-polar chains (represented by wavy lines) towards the centre. Detergents work in a similar way to create ionic micelles as well. This colloid of micelles remains suspended in water due to the repulsion between the identical negative charges in the micelles, which prevents them from coming together and precipitating out.

• Since dirt is predominantly oily, it does not dissolve in water.
• The soap molecule comprises sodium or potassium salts of long-chain carboxylic acids. The illustration shows that the carbon chain dissolves in oil, and the ionic end dissolves in water.
• Micelles are formed as a result of this formation of soap molecules.
• The oil droplet is approached from one end, while the other, ionic, is approached from the opposite end.
• The result is that the dirt is dissolving due to an emulsion in the water.
• The soap molecules are arranged in a radial pattern in a soap micelle, with the hydrocarbon ends pointing towards the centre and the ionic ends pointing away.
• In the presence of oil or grease particles on the surface of the unclean fabric after it has been immersed in water containing dissolved soap, the hydrocarbon ends of the soap molecules in the micelle bind themselves to the oil or grease particles.
• On the other hand, Colloidal solutions are made up of the ionic ends of soap molecules that stay bonded to water in micelles.
• Several times rinsing in clean water entirely removes the oily and greasy particles that have accumulated on its surface and are captured by soap micelles.
• The soap solution produces a colloidal solution, which scatters light when exposed to sunlight.

Using mechanical means, such as a stone or a wooden paddle or agitating the fabric in a washing machine, the loosened oily dirt particles are removed from the filthy surface. The cloth is cleaned as a result of the mechanical cleaning. Because detergents reduce the surface tension of water to a larger extent than soaps, the cleaning power of detergents is significantly greater than that of soaps, as a result.

Properties of soaps and detergents

Properties of soaps

• Soaps are fatty acid salts soluble in water.
• They are formed of oils and fats.
• Heating fats and oils make them with a liquid alkali.
• Soaps react with mineral salts to generate scum or soap film.

Properties of detergent

• Even with hard water, detergents clean well.
• They tend to soften water.
• Laundry detergents generate micelles that include an organic chain of lipids and oils and an ionic section that contains dirt and dust.

Conclusion

Soaps and detergents are chemical compounds or mixtures of chemicals used as cleaning agents. Soap is a sodium salt or potassium salt of several combinations of fatty acids that have a cleansing activity in the water. However, detergent surfactants are far superior to cleaning solutions since they are unaffected by water hardness.