1^st part:

Minimization of the pollution caused by synthetic detergents : Synthetic detergents are actually cleansing agents and have stronger cleansing power that the soaps, though having similar properties like soap. This is mainly due to their usability in even hard water (soaps cannot be used in hard waters) over soaps.

• The major problem with the usage of these synthetic detergents is that if their hydrocarbon chains are highly branched, they become non-biodegradable and hence turns into a threat to nature. Slow degradation of such heavily branched detergents leads to causing foams in rivers, ponds and other water bodies & water gets polluted (this is due to their ability to make foam both in hard & soft water even in acidic medium also).

So steps that are taken in now-a-days are:

• The branching of hydrocarbon chains is being controlled and kept as minimum as possible.

• Instead of heavily branched chains straight chain alkyl groups are used in manufacturing of synthetic detergents.

• Unbranched chains can be biologically degraded easily and hence pollution can be prevented to a certain amount.

2^nd part:

According to their chemical nature , the detergents can be classified into 3 categories-

(i)Anionic detergents,(ii) Cationic detergents & (iii) non-ionic detergents.

(i)Anionic detergents(containing anionic hydrophilic groups)

These are actually sodium salts of sulphonated long chain alcohols or hydrocarbons

At first long-chain alcohols are treated with concentrated sulphuric acid then alkyl-hydrogen sulphates are formed

Then these alkyl-hydrogen sulphates that are formed are neutralized by alkali (NaOH solution) to form anionic detergents.

Similarly, alkyl benzene sulphonates are obtained by neutralizing alkyl benzene sulphonic acids by reaction with alkali.

In this type of detergents, the anionic part of the molecule is the actual cleansing agent.

Cationic detergents ( containing cationic hydrophilic group)

These are actually quaternary (four degrees, center atom having 4 groups ) ammonium salts of amines with acetates chlorides or bromides as the anionic part.

The cationic part contains long hydrocarbon chain and a positive charge on the central nitrogen atom.

Eg-

Cationic detergents generally have germicidal properties.

(ii) Non-ionic detergents( neutral in nature)

These kinds of detergents do not possess any ionic part in their constitution.

Instead, they contain non-ionic polar groups that can make hydrogen bonds with water.

Such detergents are formed when Stearic acid reacts with Polyethyl glycol.

Maximum of these types of detergents resembles that of soaps.