Cleaning Agents

5.2

Cleaning Agents

Definition of Soap

Sodium or potassium fatty acid salts.

Introduction to Soap

Soaps are sodium or potassium fatty acid salts.
Soaps are produced from the neutralisation reaction between fatty acids and alkalis.
Fatty acids are long-chain carboxylic acids.
Sources of fatty acids can be obtained from natural esters in animal fats or vegetable oils.
The general formula for soap is \(RCOO−Na^+\) or \(RCOO−K^+\).
R is an alkyl group containing at least 8 carbon atoms.
However, this alkyl group usually contains 12 to 20 carbon atoms.
R consists of saturated or unsaturated hydrocarbons.

Examples of Soap
Soap	Chemical Formula	Fatty Acid	Source
Sodium laurate	CH₃(CH₂)₁₀COONa	CH₃(CH₂)₁₀COOH Asid laurik	Coconut oil
Sodium palmitate	CH₃(CH₂)₁₄COONa	CH₃(CH₂)₁₄COONa Asid palmitik	Palm oil

Detergent

Definition

Detergents are sodium salts of sulphonic acids.

Raw Material

Petroleum.

Preparation

The production of detergents began during the second world war owing to the lack of animal fats and vegetable oils.
Detergents are non-soap cleaning agents.
Detergents are sodium salts of sulphonic acids.
Two types of sulphonic acids used to make detergents are alkyl sulphonic acid and alkylbenzene sulphonic acid.
Detergents are usually made from synthetic sources, such as petroleum fractions.

Example of Detergents
Alkyl Sulphonic Acid	Alkylbenzene Sulphonic Acid

Prepartion of Soap

Soaps can be prepared from natural sources through hydrolysis of oils or fats in sodium hydroxide, \(NaOH\) or potassium hydroxide, \(KOH\) solutions.
This reaction is called saponification, which is the process of hydrolysis of oils or fats by alkalis.
Oils or fats react with concentrated alkalis to produce glycerol and fatty acid salts, which is soap.
Oils and fats are natural esters known as triglycerides.

General Equation of Saponification Reaction

Oil/Fat + Concentrated alkali → Soap + Glycerol

Prepartion of Detergents

Detergents are usually made from petroleum fractions and sulphuric acid, \(H_2SO_4\).
They are produced through two processes which are:
- Sulphonation
- Neutralisation

Preparation of Sodium Alkylbenzene Sulphonate

(i) Sulphonation of Alkylbenzene

Alkylbenzene reacts with concentrated sulphuric acid, \(H_2SO_4\) to form alkylbenzene sulphonic acid.

(ii) Neutralisation

Alkylbenzene sulphonic acid will be neutralised by sodium hydroxide, NaOH solution to produce alkylbenzene sulphonate salt, which is detergent.

The image shows a chemical reaction. On the left side, there is alkylbenzene sulphonic acid reacting with sodium hydroxide (NaOH). The product on the right side is sodium alkylbenzene sulphonate and water (H2O). The reaction involves the replacement of the hydrogen atom in the sulphonic acid group with a sodium atom from sodium hydroxide, forming the sulphonate salt and water.

Preparation of Sodium Alkyl Sulphate

(i) Sulphonation of Alcohol

Long chain alcohol reacts with concentrated sulphuric acid, \(H_2SO_4\) to form alkyl sulphonic acid.

This image depicts a chemical reaction. On the left side, a long-chain alcohol (CH₃(CH₂)nCH₂OH) reacts with sulfuric acid (H₂SO₄). The reaction produces an alkyl sulfonic acid (CH₃(CH₂)nCH₂OSO₃H) and water (H₂O). The reaction arrow points from the reactants to the products, indicating the direction of the reaction

(ii) Neutralisation

Alkyl sulphonic acid will be neutralised by sodium hydroxide, NaOH solution to produce sodium alkyl sulphate, which is detergent.

Cleansing Action of Soap and Detergent

Basically, the cleansing action of soap and detergent is the same.
Soaps and detergents act as emulsifying agents because soap and detergent molecules are soluble in oil or grease and water.
When soap or detergent is dissolved in water, soap or detergent molecules dissolve to form:
- sodium ion, \(Na^+\) or potassium ion, \(K^+\).
- soap anion or detergent anion.

Anion and Detergent Anion

Soap \(\xrightarrow[]{Water}\) Soap anion + Sodium ion

Detergent \(\xrightarrow[]{Water}\) Detergent anion

Structural Formula for Soap Anion and Detergent Anion

The structures of soap anion and detergent anion consist of two parts, namely:
- hydrophilic part that is soluble in water.
- hydrophobic part that is soluble in oil or grease.
Both of these properties make soap and detergent effective cleaning agents.

Step	Explanation
1	Adding soap or detergent into water will reduce the surface tension of water. This increases the water’s ability to wet the surface of the cloth.
2	Soap or detergent will ionise in water to produce free moving soap anions or detergent anions.
3	The hydrophilic parts of soap anions or detergent anions dissolve in water. The hydrophobic parts dissolve in grease.
4	Movement of water during scrubbing and agitation causes grease to pull away from the surface of the cloth.
5	The hydrophilic parts of soap anions or detergent anions surround the grease. Grease floats to the surface of the water.
6	Grease will break into small droplets. The small droplets will not reattach to the surface of the cloth due to the repulsion of negative charges of the hydrophilic parts on the surface of the grease. The droplets are suspended in water, forming an emulsion. Rinsing with water causes the surface of the cloth to become clean because the grease droplets are left in the water.

Cleansing Action of Soap and Detergent

Grease Broken into Droplets of Emulsion

Comparison of Cleansing Action of Soap and Detergent

Water containing calcium ions, \(Ca^{2+}\) and magnesium ions, \(Mg^{2+}\) is called hard water.
Soap anions combine with the cations to form insoluble salts called scum.
The formation of scum causes wastage of soap because more soap will be needed for the cleansing action.
Detergent anions also combine with the cations to form soluble salts in water.
Therefore, the effectiveness of the detergent’s cleansing action is not affected by hard water.
The comparison of cleaning action of soap and detergent is as shown below:

Aspect	Soap	Detergent
Effectiveness in soft water	Effective.	Effective.
Effectiveness in hard water	Less effective	More effective.
Effectiveness in acidic water	Not effective due to the formation of insoluble organic acid.	Effective because the organic acid formed is soluble.

Additives in Detergent
Additives	Function	Example
Biological enzyme	To remove protein stains, such as blood, milk and sugar.	Amylase, protease, cellulase and lipase.
Whitening agent	To change dirt to colourless substance.	Sodium perborate and Sodium hypochlorite.
Optical whitener	To make clothes become whiter and brighter.	Fluorescent dyes.
Water softener and builder	To enhance the effectiveness of the detergent by softening the water.	Sodium tripolyphosphate.
Foam control agent	To control the foam formed by the detergent.	Alkyl monoethanolamide.
Anti suspension agent	To prevent the removed dirt from redepositing to the clothes.	Sodium carboxylmethyl-cellulose.
Fragrances	To enhance the fragrance of the detergent and fabric.	Jasmine and lavender.
Drying agent	To ensure that the detergent powder is always dry in its container.	Sodium sulphate and sodium silicate.

Cleaning Agents

5.2

Cleaning Agents

Definition of Soap

Sodium or potassium fatty acid salts.

Introduction to Soap

Soaps are sodium or potassium fatty acid salts.
Soaps are produced from the neutralisation reaction between fatty acids and alkalis.
Fatty acids are long-chain carboxylic acids.
Sources of fatty acids can be obtained from natural esters in animal fats or vegetable oils.
The general formula for soap is \(RCOO−Na^+\) or \(RCOO−K^+\).
R is an alkyl group containing at least 8 carbon atoms.
However, this alkyl group usually contains 12 to 20 carbon atoms.
R consists of saturated or unsaturated hydrocarbons.

Examples of Soap
Soap	Chemical Formula	Fatty Acid	Source
Sodium laurate	CH₃(CH₂)₁₀COONa	CH₃(CH₂)₁₀COOH Asid laurik	Coconut oil
Sodium palmitate	CH₃(CH₂)₁₄COONa	CH₃(CH₂)₁₄COONa Asid palmitik	Palm oil

Detergent

Definition

Detergents are sodium salts of sulphonic acids.

Raw Material

Petroleum.

Preparation

The production of detergents began during the second world war owing to the lack of animal fats and vegetable oils.
Detergents are non-soap cleaning agents.
Detergents are sodium salts of sulphonic acids.
Two types of sulphonic acids used to make detergents are alkyl sulphonic acid and alkylbenzene sulphonic acid.
Detergents are usually made from synthetic sources, such as petroleum fractions.

Example of Detergents
Alkyl Sulphonic Acid	Alkylbenzene Sulphonic Acid

Prepartion of Soap

Soaps can be prepared from natural sources through hydrolysis of oils or fats in sodium hydroxide, \(NaOH\) or potassium hydroxide, \(KOH\) solutions.
This reaction is called saponification, which is the process of hydrolysis of oils or fats by alkalis.
Oils or fats react with concentrated alkalis to produce glycerol and fatty acid salts, which is soap.
Oils and fats are natural esters known as triglycerides.

General Equation of Saponification Reaction

Oil/Fat + Concentrated alkali → Soap + Glycerol

Prepartion of Detergents

Detergents are usually made from petroleum fractions and sulphuric acid, \(H_2SO_4\).
They are produced through two processes which are:
- Sulphonation
- Neutralisation

Preparation of Sodium Alkylbenzene Sulphonate

(i) Sulphonation of Alkylbenzene

Alkylbenzene reacts with concentrated sulphuric acid, \(H_2SO_4\) to form alkylbenzene sulphonic acid.

(ii) Neutralisation

Alkylbenzene sulphonic acid will be neutralised by sodium hydroxide, NaOH solution to produce alkylbenzene sulphonate salt, which is detergent.

Preparation of Sodium Alkyl Sulphate

(i) Sulphonation of Alcohol

Long chain alcohol reacts with concentrated sulphuric acid, \(H_2SO_4\) to form alkyl sulphonic acid.

(ii) Neutralisation

Alkyl sulphonic acid will be neutralised by sodium hydroxide, NaOH solution to produce sodium alkyl sulphate, which is detergent.

Cleansing Action of Soap and Detergent

Basically, the cleansing action of soap and detergent is the same.
Soaps and detergents act as emulsifying agents because soap and detergent molecules are soluble in oil or grease and water.
When soap or detergent is dissolved in water, soap or detergent molecules dissolve to form:
- sodium ion, \(Na^+\) or potassium ion, \(K^+\).
- soap anion or detergent anion.

Anion and Detergent Anion

Soap \(\xrightarrow[]{Water}\) Soap anion + Sodium ion

Detergent \(\xrightarrow[]{Water}\) Detergent anion

Structural Formula for Soap Anion and Detergent Anion

The structures of soap anion and detergent anion consist of two parts, namely:
- hydrophilic part that is soluble in water.
- hydrophobic part that is soluble in oil or grease.
Both of these properties make soap and detergent effective cleaning agents.

Step	Explanation
1	Adding soap or detergent into water will reduce the surface tension of water. This increases the water’s ability to wet the surface of the cloth.
2	Soap or detergent will ionise in water to produce free moving soap anions or detergent anions.
3	The hydrophilic parts of soap anions or detergent anions dissolve in water. The hydrophobic parts dissolve in grease.
4	Movement of water during scrubbing and agitation causes grease to pull away from the surface of the cloth.
5	The hydrophilic parts of soap anions or detergent anions surround the grease. Grease floats to the surface of the water.
6	Grease will break into small droplets. The small droplets will not reattach to the surface of the cloth due to the repulsion of negative charges of the hydrophilic parts on the surface of the grease. The droplets are suspended in water, forming an emulsion. Rinsing with water causes the surface of the cloth to become clean because the grease droplets are left in the water.

Cleansing Action of Soap and Detergent

Grease Broken into Droplets of Emulsion

Comparison of Cleansing Action of Soap and Detergent

Water containing calcium ions, \(Ca^{2+}\) and magnesium ions, \(Mg^{2+}\) is called hard water.
Soap anions combine with the cations to form insoluble salts called scum.
The formation of scum causes wastage of soap because more soap will be needed for the cleansing action.
Detergent anions also combine with the cations to form soluble salts in water.
Therefore, the effectiveness of the detergent’s cleansing action is not affected by hard water.
The comparison of cleaning action of soap and detergent is as shown below:

Aspect	Soap	Detergent
Effectiveness in soft water	Effective.	Effective.
Effectiveness in hard water	Less effective	More effective.
Effectiveness in acidic water	Not effective due to the formation of insoluble organic acid.	Effective because the organic acid formed is soluble.

Additives in Detergent
Additives	Function	Example
Biological enzyme	To remove protein stains, such as blood, milk and sugar.	Amylase, protease, cellulase and lipase.
Whitening agent	To change dirt to colourless substance.	Sodium perborate and Sodium hypochlorite.
Optical whitener	To make clothes become whiter and brighter.	Fluorescent dyes.
Water softener and builder	To enhance the effectiveness of the detergent by softening the water.	Sodium tripolyphosphate.
Foam control agent	To control the foam formed by the detergent.	Alkyl monoethanolamide.
Anti suspension agent	To prevent the removed dirt from redepositing to the clothes.	Sodium carboxylmethyl-cellulose.
Fragrances	To enhance the fragrance of the detergent and fabric.	Jasmine and lavender.
Drying agent	To ensure that the detergent powder is always dry in its container.	Sodium sulphate and sodium silicate.

Cleaning Agents

Cleaning Agents

Chapter : Consumers and Industrial Chemistry

Topic : Cleaning Agents

Related notes