Question

Synthetic detergents have advantage over usual soaps as far as cleansing power is concerned. But the use of synthetic detergents over a long time creates environmental pollution. How can the pollution caused by synthetic detergents be minimized? Classify the detergents according to their chemical nature.

Answer 1

Minimization of the pollution caused by synthetic detergents:

Synthetic detergents are actually cleansing agents and have stronger cleansing power than soaps, though having similar properties to 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.

So, steps that are taken nowadays are:

• The branching of hydrocarbon chains is being controlled and kept as low as possible.
• Instead of heavily branched chains, straight-chain alkyl groups should be used in the manufacturing of synthetic detergents. Unbranched chains can be biologically degraded easily and hence pollution can be prevented to a certain degree.

Classification of detergents

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

Anionic detergents (containing anionic hydrophilic groups)
These are actually sodium salts of sulphonated long-chain alcohols or hydrocarbons.



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

(ii) Cationic detergents

Cationic detergents (containing cationic hydrophilic group)

These are actually quaternary (central atoms having 4 groups) ammonium salts of amines with acetate, chlorides or bromides as the anionic part.

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

For example:



Cationic detergents generally have germicidal properties.

(iii) Non-ionic detergents (neutral in nature)
These kinds of detergents do not possess any ionic part in their constitution.
They contain non-ionic polar groups that can make hydrogen bonds with water.
Such detergents are formed when Stearic acid reacts with Polyethylene glycol.



Maximum of these types of detergents resemble soaps.