What are detergents? Give their scheme of classification. Why are detergents preferred over soaps?

Detergents are sodium salts of long chain sulphonates and sulphates.
Classification: They are two types:
(i) Sodium salts of long chain benzene sulphonic acid: These are obtained from derivatives of benzene sulphonic acid. The common example is sodium p-dodecyl benzene sulphonate.

(ii) Sodium salts of long chain alkyl hydrogen sulphate: These are sodium salts of sulphuric acid esters of long-chain alcohols containing usually 10-15 carbon atoms. These alcohols are obtained by the hydrogenolysis of oils and fats. For examples, sodium dodecyl sulphate or sodium lauryl sulphate and sodium cetyl sulphate.

Detergents are preferred our soaps for the following reasons:
(i) Synthetic detergents can be used even in the case of hard water whereas soaps fail to do so.
(ii) Synthetic detergents can be used in the acidic medium while soaps fail to do so because of their hydrolysis to free acids.
(iii) Synthetic detergents are more soluble in water and hence form more latter than soaps.
(iv) Synthetic detergents have a stronger cleansing action than soaps.