A synthetic detergent is the sodium salt of sulphonic acid which has cleansing properties in water.

 

 

                Structure Of Molecule Of Detergent

The structure of a synthetic detergent is similar to that of soaps. It consists of a long hydrocarbon chain which is hydrophobic and a short ionic part which is hydrophilic. The cleansing action of detergent is considered to be more effective than soap in hard water because a detergent does not give precipitate with salts of calcium and magnesium present in hard water.

Cleansing Action of Detergents

When detergents are dissolved in water, its hydrocarbon part attaches itself to grease and oil particles whereas its ionic part remains attached to water. Therefore, when dirty clothes are agitated in solution of detergents then dirt particles sticks to the hydrocarbon part of detergents and at the same time the water loving ionic part pulls away this dirt from clothes.

Advantages of Synthetic Detergents over Soaps

 Synthetic detergents have following advantages over soaps:

1. Synthetic detergents can be used even in hard water, while soaps cannot be used in hard water.
2. Synthetic detergents are prepared from petroleum. So, the use of synthetic detergents helps us to save vegetable oils.
3. These have a stronger cleansing action than soaps.
4. These are more soluble in water than soaps.

Disadvantages of Synthetic Detergents

The main disadvantage of synthetic detergents is that some detergents are not biodegradable and hence cause water pollution in lakes and rivers after accumulating there.

How synthetic detergents cause water pollution?

Synthetic detergents are non-biodegradable. So, these remain in water bodies for a long time and make water unfit for drinking by aquatic animals. Synthetic detergents also cause rapid growth of algae in water bodies like rivers and lakes which leads to reduction of oxygen in water bodies. Due to reduction of oxygen in water the aquatic animals feel suffocation and can die.

Test your understanding and answer these questions:

1. How synthetic detergents cause water pollution?
2. Explain cleansing action of detergents.
3. What are advantages of using detergents over soaps?
4. What are disadvantages of using detergents?

Detergents

Any substance which has cleansing action in water is called a detergent. It is of two types: Soaps and Synthetic detergents

Soaps

Soaps are sodium or potassium salts of higher fatty acids such as oleic acid (C₁₇H₃₃COOH), stearic acid (C₁₇H₃₅COOH) and palmitic acid (C₁₅H₃₁COOH). These acids are present in the form of their esters, with glycerol an alcohol containing 3 hydroxyl groups. Soaps are effective cleansing agents only in soft water. Thus, these are not effective in hard water because hard water contains salts of magnesium and calcium. When soap is dissolved in hard water, it reacts with salts of calcium and magnesium to produce water insoluble precipitates called scum. Due to formation of scum the efficiency of soap reduces drastically. So, if we will use soap for washing clothes then a lot of soap will go waste in reacting with salts of magnesium and calcium present in hard water.

Preparation of Soap

Take about 20 ml of castor oil or cottonseed oil in a beaker and add an equal volume of conc. sodium hydroxide in it. Heat the mixture with a continuous stirring for a few minutes, till a thick paste of soap is formed. Now, add 5-10 gm of common salt to it. Stir the mixture and allow it to cool. Ultimately, a pale yellow solid cake will separate out as soap.

 

 

Saponification

The process of making soap by the hydrolysis of fats and oils with sodium hydroxide is called saponification.

Working of Soap

A soap molecule is made up of two parts a long hydrocarbon part and a short ionic part containing – COO^–Na⁺.

 

 

                          Structure Of Soap Molecule

The long hydrocarbon part is hydrophobic (water repelling) in nature, whereas the ionic part of soap is hydrophilic (water loving) in nature. So, when soap is dissolved in water, its hydrocarbon part attaches itself to grease and oil particles whereas its ionic part remains attached to water. Therefore, when dirty clothes are agitated in soap solution then dirt particles sticks to the hydrocarbon part of soap and at the same time the water loving ionic part pulls away this dirt from clothes.

Micelles

When soap is dissolved in water, the soap molecules cluster together in the form of micelles. In a micelle the hydrocarbon part remains directed towards the centre while the ionic part remains directed outwards.

Test your understanding and answer these questions:

1. Define detergents.
2. Define soap.
3. What is saponification?
4. What is a micelle?
5. What is structure of soap molecule?

1) Rubber: Rubber occurs in nature as well as it is obtained by synthetic methods.

Natural Rubber

Natural rubber is obtained as latex from rubber trees. The monomer of natural rubber is isoprene. There may be as many as 11000 to 20000 isoprene units in a polymer chain of natural rubber.

 

Properties of Natural Rubber
It is soft and sticky material which is insoluble in water. When a rubber piece is stretched, its length increases greatly. And on releasing the stretched rubber piece, it returns to its original size.

Vulcanization of Rubber

The process of heating natural rubber with Sulphur to improve its properties is called vulcanization of rubber. Vulcanization of rubber makes the rubber hard, strong and more elastic and loses its sticky properties.

Hardening of Rubber

Rubber is hardened by adding carbon black in it.

Synthetic Rubber
Synthetic rubber means artificial rubber. It is superior to natural rubber. The two important synthetic rubbers are:

1. Neoprene rubber, and
2. Thiokol

a Neoprene Rubber
The monomer of neoprene rubber is chloroprene. It was prepared in 1931.

Uses of Neoprene Rubber
Following are the uses of neoprene rubber:

1. It is used for making insulation of electric wires.
2. It is used for making belts in industry and coal mines.
3. It is used for making hoses for petrol delivery and transporting oil.

b) Thiokol Rubber
The monomer of Thiokol rubber is ethylene polysulphide.

2) Polythene
Polythene is formed by heating ethene at temperature of 460 K to 480 K and applying high pressure.

Uses of Polythene
Following are the uses of polythene:

1. It is used for insulation of electric wires.
2. It is used in manufacture of bags, toys and pipes.

3) Polypropene
Polypropene is formed by polymerization of propene.

Uses of Polypropene
Following are the uses of polypropene:

1. It is used for making carpets, ropes and fishing nets.
2. It isused for making seat covers.

4)Buna-S-Rubber
It is prepared by polymerization of 1, 3–Butadiene and Styrene in the presence of sodium.

 

This rubber is called Buna-S-Rubber because in it Bu stands for butadiene, na for Sodium and S for Sulphur.
Uses of Buna-S-Rubber

1. It is used for making rubber tyres and footwear.
2. It is also used for making belts.

5) Teflon or Polytetrafluoroethane or (PTFE)
Teflon is prepared by polymerization of tetrafluoroethane.

 

Uses of Teflon

1. It is used for making non-stick cooking utesnsils.
2. It is used for making gaskets, pump packings and seals.

6) Nylon
Nylon is a polyamide fibre. A polyamide fibre is made when a carbon compound containing two carboxylic acid groups is reacted with another carbon compound containing two amino groups.

Nylon is formed by polymerization of hexamethylene diamine with adipic acid.

 

Uses of Nylon

1. It is used for making fibres and ropes.
2. It is used for making footwears and bristles of tooth brushes.

7) Polyesters
A polyester fibre is prepared by polymerization of a dicarboxylic acid with dihydric alcohols. An important example of polyester is terylene.

8) Terylene
Terylene is prepared by polymerization of terephthalic acid with ethylene glycol.

 

 Uses of Polyester Fibres

1. These are used for making clothes, sarees, dress materials and curtains.
2. These are used for making conveyor belts.
3. These are used for making sails of sail boats.

Test your understanding and answer these questions:

1. What is nylon? How is it manufactured?
2. What is teflon? How is it manufactured?
3. What is thiokol rubber?
4. What is polyester? give examples.
5. What is terylene? name its monomer units.
6. What is neoprene rubber?
7. What is polythene?
8. what is isoprene rubber?

Polymers can be classified in two ways as give below:

1. Classification based on source of availability.
2. Classification based on method of synthesis.

1. Classification based on source of availability

According to this classification polymers are of two types:

1. Natural polymers
2. Synthetic polymers

Natural Polymers

The polymers obtained from nature are called natural polymers. For example, starch, cellulose, natural rubber, proteins and nucleic acids etc. are common examples of natural polymers.

Synthetic Polymers

The polymers which are prepared in the laboratories are called synthetic polymers. These are also known as man-made polymers. Examples of synthetic polymers are nylon, teflon, terylene, polyvinyl chloride and synthetic rubber.

2. Classification of polymers on the basis of method of synthesis

On the basis of method of synthesis, the polymers are also of two types:

1. Addition polymers
2. Condensation polymers

1. Addition Polymers

A polymer formed by direct addition of repeated monomers without the elimination of any molecule is called addition polymer. The addition polymers are generally prepared from unsaturated compounds. For example natural rubber is obtained as latex from rubber trees. The monomer of natural rubber is isoprene. There may be as many as 11000 to 20000 isoprene units in a polymer chain of natural rubber.

 

2. Condensation Polymers

These polymers are formed by the condensation of two or more monomers with the elimination of simple molecules like water and alcohol. Following are the examples of two important condensation polymers:

1. Nylon
2. Polyester

Test your understanding and answer these questions:

1. What are addition polymers? give examples.
2. What are condensation polymers? give examples.
3. What do you understand by natural and synthetic polymers. give examples.

Polymers are very important products of chemical industry which have a great impact on our modern life. Plastics, synthetic fibres, synthetic rubber etc. are common examples of polymers. Polymers are also present in all living organisms. For example, proteins, carbohydrates. Natural rubber and wood are also polymers.
Polymers are compounds of very high molecular masses formed by the combination of a large number of simple molecules. Literally the word polymer consists of two words ‘poly’ and ‘mer’. In Greek language poly means ‘many’ and mer means ‘parts’. So, when a large number of parts combine with each other then the product formed is called polymer. Polythene and poly- vinyl chloride (PVC) are common examples of polymers.

Monomers

The simple molecules which combine to give polymers are called monomers. Ethene and vinyl chloride are common examples of monomers.

Polymerization

The process by which the simple molecules (monomers) are converted into polymers is called polymerization. For example, polythene is a polymer which is formed from its monomer ethene as given below:

 

Homopolymer and Copolymer
A polymer formed from one type of monomers is called homopolymer. For example, polythene is a homopolymer of monomer of ethene.  

A polymer formed from two or more different monomers is called copolymer. For example, nylon-66 is a copolymer because it is formed from two types monomers: hexamethylenediamine, and adipic acid

Test your understanding and answer these questions:

1. What are polymers?
2. Define monomers and polymers. give examples.
3. Define polymerization.

Esters () are the derivative of carboxylic acids in which the –OH group of the carboxylic acids has been replaced by –OR group. There general formula is C_nH_2n+1COOC_nH_2n+1. For example,

Name	Mol. Formula	Structural Formula
Methyl acetate	CH3COOCH3
Ethyle acetate	CH3COOC2H5

Preparation of Esters

Esters can be prepared by reacting acetic acid with ethanol in the presence of conc. H₂SO₄ as catalyst. This process is called esterification.

 

Uses of Esters: Following are the uses of esters:

1. Esters are used as artificial fruit flavours for making essences in cold drinks, ice-creams and sweets etc.
2. Esters are used as solvent for oils, fats and varnishes.
3. Esters are also used in making artificial perfumes.

Test your understanding and answer these questions:

1. What are esters? give examples.

Carboxylic acids are the compounds containing the carboxyl functional group    in their molecule. Their general formula is C_nH_2n+1COOH. The simplest carboxylic acid is methanoic acid (formic acid) having molecular formula HCOOH.

Fatty Acids

Fatty acids are the monocarboxylic acids which contain a long chain of carbon atoms. The minimum number of carbon atoms in fatty acids is 15. These are called as fatty acids because these are present mostly in fats and oils. For example, palmitic acid (C₁₅H₃₁COOH), oleic acid (C₁₇H₃₃COOH) and stearic acid (C₁₇H₃₅COOH).

Uses of Fatty Acids

Fatty acids are used in eatables, cold drinks, soaps and in medicines.

Nomenclature of carboxylic Acids

According to IUPAC system, the name of carboxylic acid is derived by replacing the terminal ‘e’ of the name of the corresponding alkane with ‘oic acid’.

Common Name	IUPAC Name	Molecular Formula
Formic acid	Methanoic acid
Acetic acid	Ethanoic acid
Propanic acid	Propanoic acid
Butric acid	Butanoic acid

Ethanoic Acid or Acetic Acid

Ethanoic acid can be prepared by following methods :

1. From Ethanol

 

 

Ethanoic acid can also be prepared by oxidation of ethanol in the presence of oxidizing agent K₂Cr₂O₇ and H₂SO₄.

 

 

2. From Methyl Cyanide

When water is added into methyl cyanide then upon hydrolysis ethanoic acid is produced.

 

 

Properties of Ethanoic Acid

Physical Properties

Following are the physical properties of ethanoic acid:

1. It is a colourless liquid with pungent odour.
2. It freezes below 16.5⁰C.
3. Its boiling point is 118⁰C.
4. It is soluble in water.

Chemical Properties

Following are the important chemical reactions of acetic acid :

1. Reaction with Alcohols or Esterification

When acetic acid reacts with ethanol in the presence of conc. H₂SO₄ as catalyst sweet smelling esters are formed. This process is called esterification.

 

 

2. Reaction with Sodium Metal

Acetic acid reacts with sodium metal to produce sodium acetate and hydrogen gas.

 

 

3. Decarboxylation Reaction or Reaction with Soda Lime

Loss of carbon dioxide from molecule of sodium or potassium salt of carboxylic acid is called decarboxylation. In this reaction, when sodium or potassium salts of carboxylic acids are heated after mixing with soda lime (NaOH + CaO) then methane gas is produced.

 

 

Preparation of Soda Lime

Sodalime can be prepared for decarboxylation reaction by mixing 3 parts by volume of NaOH with 1 part by volume of CaO.

4. Reaction with Ammonia

Acetic acid reacts with ammonia to form acid amides.

 

 

Uses of Acetic Acid

Following are the uses of acetic acid:

1. It is used as a solvent and chemical reagent in laboratories.
2. It is used as a preservative.
3. It is used in preparation of acetone and acetic anhydride.
4. It is used in coagulation of latex of rubber.
5. It is used as vinegar in cooking.
6. It is used in manufacture of rayon and plastics.

Test your understanding and answer these questions:

1. What are caboxylic acids? give examples.

Ketones are the compounds which contain carbonyl group. The structure of ketone is:

 

 

Where R and R’ represents two alkyl groups which may be same or different. This functional group is also known as ketonic group. The general formula of ketone is C_nH_2n+1COC_nH_2n+1.

Nomenclature of Ketones

In IUPAC system of nomenclature following general rules are followed for naming ketones:

1. The longest chain carrying the carbonyl group is selected and the name is derived by replacing the terminal ‘e’ of the name of corresponding alkanes by the suffix ‘one’.
2. The parent chain is numbered in such a way that the keto group gets the lowest number. For example,

Molecular Formula	Common Name	IUPAC Name
	Dimethyl Ketone or Acetone	Propanone
	Ethyl methyl ketone	Butan-2-one
	Methyl Propyl Ketone	Pentan-2-one

Acetone

Acetone or propanone is the simplest ketone. Its molecular formula is CH3 – CO – CH3 and its structural formula is 

Preparation of Acetone

Acetone can be prepared by following methods:

1. From 2-Propanol

Acetone can be prepared by dehydrogenation of 2-Pronpanol in the presence of heated copper at a temperature of 573 K.

 

 

Acetone can be prepared by oxidation of isopropyl alcohol in the presence of oxidizing agent K₂Cr₂O₇ and sulphuric acid.

 

 

 

2. By Distillation of Calcium Salts of Acids

Acetone can be prepared by distilling the calcium salts of acids. For example,

 

 

Properties of Acetone

Physical Properties

Following are the physical properties of acetone:

1. Acetone is a colourless, volatile and highly inflammable liquid.
2. Its boiling point is 329 K.
3. It is miscible with water, alcohol and ether.
4. It has a pleasant smell.

Chemical Properties

       Following are the important chemical reactions of acetone:

1. Oxidation Reaction

Acetone can be oxidized by reacting with strong oxidizing agents like potassium dichromate and sulphuric acid to produce acetic acid, carbon dioxide and water as products.

 

 

2. Reduction Reaction

Acetone gives 2-Propanol (isopropyl alcohol) on catalytic hydrogenation in the presence of catalysts such as sodium borohydride (NaBH₄).

 

 

3. Reaction with Hydrogen Cyanide (HCN)

Acetone reacts with hydrogen to form propane cyanohydrin.

 

 

Uses of Acetone

1. It is very important solvent and is used in industries as a solvent.
2. It is used as nail polish remover.
3. It is used in preparation of chloroform and iodoform.
4. It is used in manufacture of plastics.

Test your understanding and answer these questions:

1. What are ketones? give examples.
2. What is acetone? give its use.

CARBONYL COMPOUNDS
The compounds containing carbonyl group () are called carbonyl compounds. The majority of biologically important compounds contain carbonyl group. For example,

Name	Structural Formula		Structural Formula
Aldehydes		or	RCHO
Ketones		or	RCOR’
Carboxylic acids		or	RCOOH
Esters		or	RCOOR

Where, R represents the alkyl group.

ALDEHYDES

Aldehydes are the compounds which contain carbonyl group. That is why; these compounds are also called carbonyl compounds. The structure of Aldehyde group is:

 

 

 

 

 

Where R represents the alkyl group and carbonyl group is attached to one hydrogen atom. The aldehyde (  CHO ) functional group is also called as aldehydic group. General formula of aldehydes is C_nH_2n+1CHO.

Nomenclature of Aldehydes

According to IUPAC nomenclature aldehydes are named by replacing ‘e’ in the name of parent alkane by ‘al’. For example,

Molecular Formula	Common Name	IUPAC Name
HCHO	Formaldehyde	Methanal
CH3CHO	Acetaldehyde	Ethanal
C2H5CHO	Propionaldehyde	Propanal
C3H7CHO	n – Butryaldehyde	Butanal

Formaldehyde is the simplest aldehyde and it is produced on commercial scale from methane gas which is main component of natural gas.

 

 

 

 

Preparation of Methanal

Molecular formula of methanal is HCHO. It can be prepared by following two methods.

1. From Methanol

Methanal can be prepared by dehydrogenation process by passing methanol over copper or silver at temperature 573 K.

Methanal can also be prepared by oxidation of methanol with potassium dichromate and sulphuric acid.

2. From Distillation of Calcium Salts of Acids

Methanal can be prepared by distilling the calcium salts of the acids. For example,

 

 

 

 

 

1. Properties of Methanal

   Physical Properties
   Methanal is a colourless gas with pungent odour.

2. Its boiling point is 252 K.
3. Formaldehyde is soluble in water. Its 40% solution in water is called formalin. Formalin is very important preservative in biology because it is used for preserving biological specimens.

Chemical Properties

Following are the important chemical reactions of methanal:

1) Oxidation Reaction

Methanal can be easily oxidized into methanoic acid on treatment with common oxidizing agents like KMnO₄.

 

 

 

 

2) Reduction Reaction

Methanal gives methanol on catalytic hydrogenation in the presence of catalysts such as Ni, Pt or Pd.

 

3) Reaction with Hydrogen Cyanide

Methanal reacts with hydrogen cyanide to form methanal cyanohydrin.

 

 

4) Reaction with Tollen’s Reagent

Preparation of Tollen’s Reagent

Tollen’s reagent is ammoniacal solution of silver nitrate. Its chemical formula is [Ag(NH₃)₂]OH. Tollen’s reagent can be prepared by adding ammonium hydroxide (NH₄OH) to silver nitrate solution (AgNO₃).

 

 

 

The black precipitates of AgOH are dissolved in excess of NH₄OH by adding more NH₄OH in it, to produce [Ag(NH₃)₂]OH molecule which is Tollen’s reagent.

 

 

Reaction of Methanal with Tollen’s Reagent (Silver Mirror Test)

When methanal is heated with Tollen’s reagent then a bright silver mirror is produced on the inner side of the test tube.

 

5) Reaction with Fehling’s Solution

Preparation of Fehling’s Solution

Fehling’s solution is an alkaline solution of copper sulphate (also called Fehling solution A) and sodium potassium tartarate (also called Fehling solution B). The chemical formula of Fehling’s solution is [Cu(OH)₂ + NaOH]. It is prepared by mixing Fehling solution A and Fehling solution B in equal amount.

Reaction of Methanal with Fehling’s Solution

When methanal reacts with blue coloured Fehling’s solution, red precipitates of cuprous oxide (Cu₂O) are formed and the colour of Fehling’s solution changes from blue to red.

 

Uses of Methanal

1. Formaldehyde is used in the manufacture of synthetic polymers like bakelite and synthetic dyes.
2. Formaldehyde is used to preserve biological specimens in the form of formalin.
3. Formaldehyde is also used as an insecticide.
4. Formaldehyde is used in leather industry.
5. Formaldehyde is used for silver polishing of mirrors.

Test your understanding and answer these questions:

1. What are aldehydes? give examples.

Physical Properties

1. It is a colourless, volatile liquid with characteristic pleasant odour.
2. It has boiling point of 351 K. 

Chemical Properties

Following are the important chemical properties of ethanol.

1. Combustibility

Ethanol can easily burn in air to produce carbon dioxide and water.

 

 

2. Reaction with Na Metal

Ethanol Reacts With Sodium Metal To Produce Sodium Ethoxide And Hydrogen Gas

 

 

3. Dehydration of Ethanol

When ethanol is heated to 1600-1700C in the presence of sulphuric acid (H₂SO₄) then a molecule of water is liberated and ethene is formed.

 

 

4. Oxidation of Ethanol

The oxidation of alcohol involves the formation of a carbon-oxygen bond. These reactions are also called degradation reactions because these reactions involve loss of hydrogen from ethanol. The oxidation process can be carried out by a number of reagents such as potassium permanganate (KMnO₄) or chromic anhydride (CrO₃).

1) Oxidation by Chromic Anhydride

By chromic anhydride ethanol is converted into ethanal.

 

 

2) Oxidation by Potassium Permanganate

Ethanol can be converted into ethanoic acid by oxidation of KMnO4 as follows:

 

 

Esterification

Ethanol reacts with carboxylic acids in the presence of conc. H₂SO₄ as catalyst to form sweet smelling substance called esters having general formula (RCOOR). This process is called esterification.

 

 

Test your understanding and answer these questions:

1. Give properties of ethanol.