Question

What is the specialty of detergent?

Answer 1

Hint: The detergents are the surfactants having the properties of cleansing. They are amphipathic molecules which contain hydrophilic or polar groups at the end of long lipophilic hydrocarbon groups.

Complete answer:
The detergents can be classified as the surfactants which are the amphipathic molecules which contain hydrophilic or polar groups at the end of long lipophilic hydrocarbon groups. The head is the charged hydrophilic group and tail is the long lipophilic hydrocarbon group. They have the ability to decrease the surface tension of the water.
There are three types of detergents:
i) Anionic Detergents: These are the sodium salts of sulphonated long chain alcohols or hydrocarbons. In this type of detergent, only the anionic part of the molecule is involved in the cleansing action. Sodium salts of alkyl benzene sulphonates are an important class of anionic detergents. These are used in toothpastes.
ii) Cationic detergents: These types of detergents have quaternary ammonium as the polar end instead of anionic sulfonate group. but they are however similar to anionic detergents, with the hydrophilic component.
iii) Non-ionic detergents: These types of detergents have no ion in their constitution. They are characterized by their uncharged, hydrophilic headgroups and are based on polyoxyethylene or glycoside.

The specialty of detergents is to form lather with both hard and soft water, as soap can only form lather with only soft water because when soap is used in hard water the scum is formed which is the solid substance because the calcium and magnesium particles present in the hard water reacts with the soap and form an insoluble substance but detergents do not form scum as detergents are more soluble than soap.

Note: There is the presence of $ - SO_3^ - N{a^ + }$ at the end of molecule of the detergent. This prevents the detergents from forming scum with the hard water and when scum forms the new substance dissolves into the water.