Detergent
(Short Note)
Definition
Detergents are the salts of alkyl
sulphate or aryl sulphate that improves the cleaning action of solvents,
particularly ionic solvents.
Explaination
Detergents are long chain molecules,
which when dissolve in water dissociate into positive and negative ions, these
ions react with the ions of dirt and grease to produce soluble compounds with
are readily carried away by the water molecules.
General
Formula
Detergents are sodium or potassium
salts of alkyl sulphate or aryl sulphate.
R-OSO3-Na+ Sodium Alkyl Sulphate
R-OSO3-Na+ Sodium Alkyl Sulphate
Where R is an alkyl group containing
7 to 18 carbon atoms. Soaps are sodium or potassium salts of long chain fatty
acids.
R – COO-Na+
Composition of Detergents
Detergents are composed of two main
parts namely.
1. Hydrophobic Part
2. Hydrophilic Part
1.
Hydrophobic Part
It is a water repelling part of
detergent, which consist of long hydrocarbon chain. The hydrocarbon chain being
non-polar attracts dirt particles, which are normally non polar, i.e. greasy or
oily molecules. Therefore, this part of detergent removes dirt particles from
thing being washed and water takes away the dirt particles with it.
2.
Hydrophilic Part
Hydrophilic part of the detergent is
water attracting part. It consists of small ionic groups such as sulphonate
(SO3) and sulphate (-SO3-). The hydrophilic group being ionic gets attracted by
the polar water molecules and in this way, this part of the detergent removes
the ionic dirt particles.
Advantage of
Detergents
Detergents can act in hard water,
since the calsium and magnesium salts of detergents are soluble in water.
Whereas, the corresponding salts of soap are insoluble in water. Thus
detergents are better cleaning agents than soaps.
Disadvantages of Detergents
One disadvantage of detergent over
soap is that hydrocarbon chain, unlike those of soaps, which are derived from
food substances (fats and oil) cannot be broken down by bacteria and
dispersads. Therefore, it causes water pollution.
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