DETERGENTS-STRUCTURE OF DETERGENTS-STRUCTURE OFSOAP-HYDROPHILIC-HYDROPHOBIC

DETERGENTS

DEFINITION

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Detergents are soap-like compounds which are used for cleaning purpose. They are sodium salts of long chain alkyl benzene sulphonic acids or sodium salts of long chain alkyl hydrogen sulphate, whereas, soaps are sodium salts of long chain carboxylic acids. The general formulae of soaps and detergents are:

Detergents may be used in hard water without the formation of scum. This is the advantage of a detergent over soap which gives curdles when used with hard water.

STRUCTURE OF DETERGENTS

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A detergent consists of two parts:

Hydrophilic part (water soluble)

Hydrophobic part (oil soluble)

Hydrophilic part

Hydrophilic part is sodium salt which is readily soluble in water. e.g. –SO₃^-^,–OSO₃^-, OH^- or NR_4.
This part of a detergent is ionic and is attracted by polar water molecules.

Hydrophobic part
hydrocarbon part of detergent is called hydrophobic part. It is non-polar . Hydrophobic part is insoluble in water but it is soluble in oil. This part consists of a hydrocarbon segment and can dissolve oil or grease.

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CLEANING ACTION

When a greasy cloth is put into aqueous solution of a detergent, The hydrophilic part of detergent is dissolved in water while hydrophobic part dissolves grease or oil like substances on the cloth. On slight agitation grease is readily removed from the cloth.

ADVANTAGE OF DETERGENT

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See difference between soap and detergent.

DISADVANTAGE OF DETERGENT

Hydrocarbon chain of detergent does not broken by bacteria and bacteria remain in the solution.

DIFFERENCE BETWEEN SOAP AND DETERGENT
SOAP	DETERGENT
Soaps are sodium salts of long chain carboxylic acids.	Detergents are sodium salts of long chain alkyl benzene sulphonic acids or alkyl sulphate.
It is obtained by natural resources i.e. fats and oils.	Detergents are synthetic materials.
Calcium and magnesium salts of soaps are insoluble in water.	Calcium and magnesium salts of detergents are soluble in water.
In hard water it produces scum which affect its cleaning action.	Hard water does not affect its cleaning action.

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