What are synthetic detergents? Explain their types.

(N/A) Synthetic detergents are cleansing agents which have all the properties of soaps,but which actually do not contain any soap.
These can be used both in soft and hard water as they give foam even in hard water. Some of the detergents give foam even in ice cold water.
Synthetic detergents are mainly classified into three categories:
$i$. Anionic detergents
$ii$. Cationic detergents
$iii$. Non-ionic detergents
$i$. Anionic Detergents:
Anionic detergents are sodium salts of sulphonated long chain alcohols or hydrocarbons.
Alkyl hydrogensulphates formed by treating long chain alcohols with concentrated sulphuric acid are neutralised with alkali to form anionic detergents.
Similarly,alkyl benzene sulphonates are obtained by neutralizing alkyl benzene sulphonic acids with alkali.
In anionic detergents,the anionic part of the molecule is involved in the cleansing action. Sodium salts of alkylbenzenesulphonates are an important class of anionic detergents. They are mostly used for household work. Anionic detergents are also used in toothpastes.
$ii$. Cationic Detergents:
These are quaternary ammonium salts of amines with acetates,chlorides,or bromides as anions. The cationic part possesses a long hydrocarbon chain and a positive charge on the nitrogen atom. Hence,these are called cationic detergents. Cetyltrimethylammonium bromide is a popular cationic detergent and is used in hair conditioners.
$iii$. Non-ionic Detergents:
These detergents do not contain any ion in their constitution. One such detergent is formed when stearic acid reacts with polyethylene glycol.
$CH_3(CH_2)_{16}COOH + HO(CH_2CH_2O)_nCH_2CH_2OH \rightarrow CH_3(CH_2)_{16}COO(CH_2CH_2O)_nCH_2CH_2OH$
Liquid dishwashing detergents are non-ionic type.