Detergents: Types of Detergents, Formula, Properties, Uses

Detergents: Detergent, is any of several surfactants (surface-active agents) that are especially effective at dislodging foreign matter from soiled surfaces and keeping it suspended. The term typically refers to a synthetic substance that is not made by saponifying fats and oils (as is soap). 

The primary applications of detergents with a liquid bath are dishwashing and clothing laundering. Detergents are also used as emulsifiers in a variety of applications. Dispersing agents added to lubricating oils used in automotive engines to prevent the accumulation of varnishlike deposits on the cylinder walls, gasoline to prevent the buildup of gummy residues in the carburettor, and dry-cleaning solvents to facilitate the removal of soil from garments are examples of nonaqueous detergents. In this article, we will know more about soaps and detergents.

The ability of a substance to remove unwanted substances termed ‘soils’ from a substrate is called Detergency. A detergent is a surfactant or a mixture of surfactants which has cleansing properties when present in dilute solutions.There are a several types of detergents. However, most common detergents are the sodium salts of long chain alkyl hydrogen sulphate or a long chain of benzene sulphonic acid such as alkylbenzene sulfonates. Detergents are primarily used for dishwashing and fabric laundering. Moreover, they are also used as emulsifiers in many applications. Different types of detergent are used based on the type of laundry, the amount of dirt in them, the hardness of stains or as per the requirements of the fabric. This article discusses the nature, classification, functions and applications of detergents in detail. Read on to learn more.

What Are Detergents?

A detergent is a non-soapy cleaning agent that cleans a substance in solution by using a surface-active ingredient.

Soapless soaps are a term used to describe detergents. They are effective even in hard or saltwater, unlike soaps, because they do not develop scum. These are better cleansing agents because they do not form insoluble calcium and magnesium salt in hard water. Detergents were first introduced in the United States and the United Kingdom in the 1920s. Although detergents were introduced in India in1960, it was not until 1970 that they became the common person’s washing substance.

A detergent is a sodium salt of long-chain benzene sulphonic acid or sodium salt of long-chain alkyl hydrogen sulfate, which has cleansing properties in water. Like soaps, they contain anionic groups such as sulphonate groups or sulphate groups and long-chain hydrocarbon, a non-ionic group. These are also called soapless soaps, detergents, Syndets, or non-soapy detergents. You will more information on soaps and detergents in this post.

Soaps and Detergents – Preparation of Detergents

Synthetic detergents are made by reacting petroleum hydrocarbons with concentrated sulphuric acid and converting them to their sodium salt. Long-chain alcohols are treated with strong sulphuric acid and then neutralized sulfate with alkali to make synthetic detergents.

For example, Sodium lauryl sulfate, Sodium dodecylbenzene sulphonate, and so forth.

Soaps and Detergents – Chemical Formula of Detergents

Detergents are either sodium salt of alkyl hydrogen sulfates or sodium salt of long-chain alkyl benzene sulphonic acids.

Soaps and Detergents – Types of Detergents

A detergent molecule is made up of two parts: an oil-soluble hydrocarbon and a water-soluble polar group \({\rm{S}}{{\rm{O}}_3}{\rm{Na}}\) or \({\rm{OS}}{{\rm{O}}_3}{\rm{Na}}{\rm{.}}\) The detergents have been divided into three groups based on the charge on the polar head.

Classification of Detergent

(i) Anionic Detergent

Anionic detergents contain an anionic hydrophilic group that is engaged in the cleansing process. These are sodium salts of sulfonated long-chain alcohols or hydrocarbons.

There are two types of anionic detergents:

(I) Sodium alkyl sulfates: These are obtained from long-chain alcohols containing \(12 – 18\) carbon atoms. Long-chain alcohols are treated with strong sulphuric acid to produce high molecular mass alkyl hydrogen sulfates, which are subsequently neutralized with alkali to form a salt.

Sodium lauryl sulfate \(\left( {{{\rm{C}}_{{\rm{11}}}}{{\rm{H}}_{{\rm{23}}}}{\rm{C}}{{\rm{H}}_{\rm{2}}}{\rm{OSO}}_{\rm{3}}^{\rm{ – }}{\rm{N}}{{\rm{a}}^{\rm{ + }}}} \right)\) and sodium stearyl sulfate \(\left( {{{\rm{C}}_{{\rm{17}}}}{{\rm{H}}_{{\rm{35}}}}{\rm{C}}{{\rm{H}}_{\rm{2}}}{\rm{OSO}}_{\rm{3}}^{\rm{ – }}{\rm{N}}{{\rm{a}}^{\rm{ + }}}} \right)\) are common examples of this type of detergent.

For example,

(II) Sodium alkyl benzene sulphonates: These are sodium salts of long-chain alkyl sulphonic acids. For example, to make sodium p-(dodecyl) benzene sulphonate, dodecylbenzene is treated with concentrated \({{\rm{H}}_{\rm{2}}}{\rm{S}}{{\rm{O}}_{\rm{4}}}\) to generate p-dodecylbenzene sulphonic acid, which is then neutralized with \({\rm{NAOH}}{\rm{.}}\)

Uses of Anionic Detergent

Anionic detergents are used in a variety of situations. The cleaning activity of anionic detergents is regulated by the anionic portion of the molecules.

1. Anionic detergents are commonly used in the home, such as to wash clothes.
2. Anionic detergents are also used in toothpaste.

(ii) Cationic Detergent

Cationic detergents are chlorides, bromides, or acetates that are quarter-nary ammonium salts. These detergents are costly and are used only infrequently. Some of these detergents are used as germicides because they contain germicidal properties. Cationic detergents are also used as fabric softeners and hair conditioners.

For example, the most common cationic Detergent is cetyltrimethylammonium bromide and Sapamine.

(iii) Non-ionic Detergent

Non-ionic detergents are those that have a neutral group in their molecule that can form hydrogen bonds with water as their surface-active group. Non-ionic detergents are monoesters of polyhydric alcohols or polyethers derived from ethylene oxide.

Some non-ionic detergents are pentaerythrityl stearate and polyether.

Uses of Non-ionic Detergent

Non-ionic detergents are very effective for dishwashing and other situations where inorganic ions are not allowed.

Soaps and Detergents – List of Detergents

Laundry detergent is a type of Detergent that is added for cleaning laundry. The main types of detergents are powder, liquid, tablets, non-toxic, conventional, and pod detergents. Some of the laundry detergents are given below:

Soaps and Detergents – Cleansing Action of Detergents

A molecule of any detergent is made up of the following two parts:

1. A polar part consists of an anionic or cationic group and is called the polar end.
2. A non-polar part consisting of a long chain of twelve to eighteen carbon atoms is called a hydrocarbon end.

Cleansing Action of Detergents

The polar end of a detergent molecule is water-soluble, whereas the hydrocarbon part is water repellent and oil soluble. When an oily piece of cloth is dipped into a detergent solution, the Detergent’s hydrocarbon end bonds to the oily drop and the polar end orients itself towards the water, resulting in the production of a micelle. The oily dirt is entrapped by the negatively charged micelle that has formed. The ions in the solution arrange themselves around the micelles. The negatively charged micelles repel each other due to the electrostatic repulsion. As a result, the tiny oily dirt particles do not come together and get washed away in the water.

Soaps and Detergents – Properties of Detergents

1. Synthetic detergents are unaffected by the ions in hard water. As a result, synthetic detergents have no trouble forming lather with hard water, indicating that hard water does not affect their efficacy.
2. With hard water, synthetic detergents do not generate insoluble calcium or magnesium salts. As a result, less amount of synthetic Detergent is used for washing.
3. Synthetic detergents can be used in acidic and seawater, as they are the salts of strong acid and are not decomposed in an acidic medium.
4. Some of the synthetic detergents are non-biodegradable.
5. Synthetic detergents are prepared from the hydrocarbons of petroleum.

What are Detergents – Advantages of Soaps and Detergents

The advantages of Soaps & detergents are discussed below:

1. Advantage of soaps: Soaps are biodegradable, so they do not produce pollution.
2. Disadvantages of soaps: Soaps do not lather or froth properly in hard water and do not wash well. Calcium, magnesium, or iron ions present in hard water generate scum, an intractable sticky grey-colored precipitate limiting soap’s cleansing effect and making washing more difficult. The resulting sludge hardens and discolours the fabric. As a result, much soap is wasted, and cleaning is ineffective.
   
   (I) Ordinary soaps are unsuitable for fabrics such as silks, wool, and other natural fibres. This is because the alkalis in them cause havoc on the fibre.
   (II) Soaps cannot be used for cleaning if the water is slightly acidic. This is because soaps are converted to carboxylic acid in acid media, rendering their action useless.

What are Detergents – Advantages of Detergents Over Soaps

1. Synthetic detergents can be used even in hard water, whereas some of the soap gets wasted if the water is hard. 
2. Synthetic detergents can be used even in an acidic medium as they are the salts of strong acids and are not decomposed in an acidic medium.
3. Synthetic detergents have a stronger cleansing action than soaps. 
4. Synthetic detergents are more soluble in water than soaps. 
5. Synthetic detergents are prepared from the hydrocarbons obtained from petroleum. 
6. Some synthetic detergents give foams even in ice-cold water.

What are Detergents – Disadvantages of Detergents

1. Some of the first synthetic detergents were non-biodegradable, meaning bacteria could not break them down. As a result, they polluted the water and land. Effluents containing such detergents end up in rivers, ponds, and other bodies of water. These detergents remain in the water after sewage treatment and generate foaming in rivers, ponds, and other bodies of water.
2. They tend to produce stable foams in rivers that extend over several hundred meters of the river water. This is due to the effects of surfactants used in their preparation. Thus, they become a danger to aquatic life.
3. They tend to inhibit the oxidation of organic substances present in wastewaters because they form an envelope around them.

Uses of Detergents

Powder and liquid detergent can be used for other purposes besides cleaning clothes or dishes.

1. These are mostly used as cleaning agents in the laundry and dishwashing.
2. Tiles, floors, worktops, tubs, and toilets may all be cleaned with either type of Detergent.
3. Oil spilled on a garage floor or the street can be absorbed by powdered Detergent.
4. The detergents increase the softness of the water.
5. On moss growing in the cracks of your steps, sidewalk, or driveway, sprinkle powdered Detergent. Allow it to be brown for a few days before brushing it out of the gaps with a broom.
6. These are also used for solubilizing and crystallizing membrane proteins, as well as preventing non-specific binding.
7. Detergents are used for cell permeabilization, cell lysis, gel electrophoresis, and other procedures in laboratories.

Detergents – Summary

From this article, we can conclude that detergents have a more decisive cleansing action than soaps. Therefore, this property of detergents makes its use in our day-to-day life as well as in the industrial and commercial fields.

Frequently Asked Questions On Detergents

Q.1: What are high-efficiency detergents?
Ans: High-efficiency laundry detergent is designed especially for high-efficiency washing machines, which use less water. Detergent provides an excellent clean in a small amount of water. 

Q.2: What are examples of Detergents?
Ans: Laundry and fabric softeners, all-purpose cleaners, and combinations for soaking(pre-washing), rinsing, or bleaching are examples of common detergent products.

Q.3: What is meant by detergents in chemistry?
Ans: A detergent is a sodium salt of long-chain benzene sulphonic acid or sodium salt of long-chain alkyl hydrogen sulfate, which has cleansing properties in water.

Q.4. What are detergents made up of?
Ans: Synthetic detergents are made by reacting petroleum hydrocarbons with concentrated sulphuric acid and converting them to their sodium salt.

Q.5. Advantages of detergents?
Ans: Following are the Advantages of Detergents:
a. Synthetic detergents can be used even in hard water, whereas some of the soap gets wasted if water is hard. 
b. Synthetic detergents can be used even in an acidic medium as they are the salts of strong acids and are not decomposed in an acidic medium.
c. Synthetic detergents have a stronger cleansing action than soaps. 
d. Synthetic detergents are more soluble in water than soaps. 
e. Synthetic detergents are prepared from the hydrocarbons obtained from petroleum. 
f. Some synthetic detergents give foams even in ice-cold water.