Chemistry in the Service to Mankind

Some of the Chemistry in the service to mankind

Polymer

Polymers are compounds of high molecular mass formed by the combination of a large number of simple molecules. The simple molecules which combine to give a polymer are called monomers. The process of formation of polymer from monomer is called polymerization.

Monomer \xrightarrow{Polymerization}Polymer

Classification of polymers

Based on types of monomers

1. Homopolymer: The polymer formed by only one type of monomer is called a homopolymer. eg. polyethene, PVC, Teflon, etc.

2. Copolymer: The polymer formed by more than one type of monomer is called a copolymer—eg Nylon-6,6, bakelite, etc.

On the basis of mode of synthesis

1. Addition polymer: A polymer formed by addition of monomers without elimination of any molecule is called addition polymer. eg. polyethene, PVC, teflon,etc.
   
2. Condensation polymer: A polymer formed by addition of monomers with elimination of smaller molecule like water is called condensation polymer. eg. nylon-6,6, bakelite, etc.

On the basis of molecular force

1. Elastomers: The polymers in which the molecular chains are held together by weak intermolecular force are called elastomers. eg. vulcanized rubber.
   
2. Fibres: The polymers in which the molecular chains are held together by strong intermolecular force are called elastomers. eg. Nylon-6,6, polystyrene, etc.

On the basis of source of origin

1. Natural polymer: The polymers formed in the body of plants and animals are natural polymers. eg. protein, starch, cellulose, etc.
   
2. Synthetic polymer: The polymers which are prepared in the laboratory are called synthetic polymers. eg. polyethene, PVC, nylon, bakelite, etc.

Some synthetic polymers are given below:

1. Polyethene

It is obtained by polymerization of ethene in presence of Ziegler nata catalyst [Al(C₂H₅)₃ + TiCl₄].

Uses

• Manufacture of bottle, bucket, dustbin, tube.

2. Polyvinyl chloride (PVC)

It is obtained by the polymerization of vinyl chloride.

Uses

• Manufacture of raincoats, blood bags, credit cards, etc.

3. Teflon

It is obtained by the polymerization of tetrafluoro ethene.

Uses

• Manufacture of seals, gaskets, valve, etc.

4. Polystyrene

It is obtained by the polymerization of styrene.

Uses

• Manufacture of refrigerator, TV cabinets , plastic cups, etc

5. Nylon-6,6

It is obtained by the condensation of hexamethylene diamine and adipic acid.

Uses

• Manufacture of carpets, brushes, fabrices, etc

6. Bakelite

It is obtained by the reaction of phenol and formaldehyde in a basic medium.

Uses

• Manufacture of combs, fountain pens, plugs , switches, etc.

Dyes

Dyes are coloured substances used to impart colour to textiles, silk, wool, leather, etc.

Character of dyes

• It should have suitable colour.
• It should be able to fix itself.
• It should be fast to light.
• It should be resistant to the action of water, dilute acids and alkalis and various organic solvents.

A dye is made up of two kinds of parts, chromophore and auxochrome. Chromophores are unsaturated groups that give colour to the dye. eg. >C=O (carbonyl group), -N=N- (azo group), -NO₂ (nitro group), etc. Auxochrome are saturated groups that increase the colour of dye. eg. -OH, -SO₃H, -COOH, -NH₂, etc.

Classification of dyes

On the basis of source

1. Natural dyes: They are extracted from plants and animals. eg. Indigo (blue dye), Alizardin ( red dye), etc.

2. Synthetic dyes: They are synthesized in the laboratory. eg. methyl orange, malachite green, etc.

On the basis of structure

They possess a specific structural unit in them. Some are given below:

On the basis of methods of application

1. Vat dyes: These are insoluble in water. They are reduced into colourless soluble form (leuco) when reacted with sodium bisulphite and they are oxidized in air. When exposed in air, insoluble dye is regenerated in the fabric. Such dying was done in woolen vats, so called vat dyes. eg. Indigo.

2. Direct dyes: These are directly applied to the fabric in hot aqueous solution. They may be acidic or basic in nature. These can form hydrogen bond and used for silk, nylon, rayon, etc. eg. napthol, martious yellow, etc are acidic whereas aniline yellow, malachite green, etc are basic.

3. Mordant dyes: These dyes donot dye the fabric directly and fixed to the fabric with the help of basic salts of metals like Al, Cr, Fe, etc. which are called mordants. The mordant forms an insoluble coordination complex between the fabric and the dye. If the dye is basic, acidic mordant like tannic acid is used. They are used for dying wool. The same dye may give different colour depending upon the mordant used. eg. Alizardin gives red with Al, violet black with Fe, brown violet with Cr and blue with Ba.

4. Disperse dyes: They are insoluble in water and dispersed in water in a colloidal form. When fabric is immersed in the colloidal form of dye, fine particles are absorbed in the crystal structure of the fabrics. These dyes are used for dying synthetic fibres like nylons, polysters and hence these dyes are also called synthetic fiber dyes.

5. Azoic dyes: These are water insoluble azo dyes which are formed on the fibre. The fabric is immersed in the solution of the coupling reagents like phenol, aniline, naphthol,etc. and then immersed into appropriate diazonium salts.

Drugs

They are chemical substances used for the treatment of disease and for reducing suffering from pains.

Characters of drugs

• Non toxic
• Minimum side effect
• High effective
• Shouldnot injure host tissue

Classification

On the basis of source

1. Natural drugs: The drugs which are obtained from plants and animal bodies are called natural drugs. eg. Jatamansi, panchaule, bakaino, stem and leaf of garjo, leaves of neem, ginger, coriander, pudina, garlic, turmeric, aloe vera, etc. Natural drugs has valuable medicinal value and have been used against different diseases. Penicillin is one of the oldest natural drug.

2. Synthetic drugs: The drugs which are prepared by different chemical reactions in the laboratories in the form of tablets, capsules, liquids, etc. are called synthetic drugs. They are more effective and specific against diseases. The chemistry that deals with these drugs are called medicinal chemistry. These synthetic drugs are collectively called allophatic. eg. paracetamol, aspirin, iodol, etc.

On the basis of action against various pathogens or physiological effects

1. Antipyretic drugs: They are used to lower the body temperature during high fever. eg.

2. Analgesics: They are used to relieve pain without the loss of conciseness. They are known as pain killers. They are of two types:

• Narcotics drugs (habit forming): They induce sleeping as well as may cause unconsciousness if taken overdose. eg. morphine, heroin, etc.
• Non-narcotics drug (non-habit forming): They donot induce sleep and there is no loss of consciousness. eg. aspirin, brufen, novalgin, etc.

3. Antibiotics: They are chemical substances produced by a microorganism and can be used to kill other microorganisms. eg. penicillin, chloramphenicol, tetracyclin, streptomycin, etc. They are also called broad-spectrum antibiotics because they are used to prevent against several diseases.

4. Antiseptic and disinfectant drug: Antiseptics kill or prevent the growth of microorganisms. eg. Dettol, bithional, thymol, iodol, etc. Disinfectants are also used to kill microorganisms but they cannot be applied to living tissues. eg. chlorine water, phenol, SO₂, etc.

5. Sulpha drugs: They are used for the treatment of bacterial disease. eg. sulphadiazine, sulphapyridine, sulphathiazole, etc.

6. Anaesthetics: They bring the loss of sensation for a certain period of time. The use of anaesthetics has made surgery comfortable for patients and allowed surgeons more time in which they can work carefully and effectively. Generally, there are two types of anaesthetics:

• General or central anasthetics: They cause unconsciousness all over the body. eg. diethyl ether, ethene, chloroform, etc.
• Local anasthetics: They cause unconsciousness to a limited part of body. eg. ethyl chloride, benzocaine, procaine, etc.

7. Antacid: They neutralize excess acid in gastric juice. eg. sodium bicarbonate, aluminium hydroxide, magnesium hydroxide. A commercial eno contains a mixture of sodium bicarbonate, citric acid and anhydrous sodium carbonate.

8. Anti-diabetic drugs: They are used to treat diabetes by altering the glucose level in the blood. Diabetes is due to the defects in the metabolism of carbohydrates, protein and fat. This disease brings complications like degeneration of blood cells, blindness, renal and neurological disorders, etc.
Insulin is recommended to control type I diabetes and phenformin, metformin, carbutamide, etc. are used to cure type II diabetes.

9. Cardiovascular drugs: They are used to treat the disease of the heart. eg. amylnitrite, glycerol trinitrate, etc.

10. Antihistamines: They are used to treat many physiological conditions like itching, hypersecretion of stomach acid, etc. eg. avil, allerga, etc.

Habit forming drugs (Psycotropic drugs)

They are used for the treatment of mental disorders and bring calmness to the respective person. They act on the central nervous system to reduce anxiety. Most of them are habit-forming and their daily use leads to addiction. These drugs are also called tranquillizers and hypnotics. eg. equanil and barbituric acid. Charas and Hashish also belong to this habit-forming drug.

Drug adduction

It is a compulsory desire and dependence on an illegal drug or a medication despite the negative consequences. Once addiction develops, gene expression alters in the way that the brain looks and functions that affect human behaviour. It includes wild mood swings, depression, anxiety, paranoia, violence, decrease in pressure in daily life, a complication of mental illness, confusion, desire to engage in risky behaviour, etc. These brain changes interfere with an individual ability to make voluntary decisions, leading to compulsive drug craving, seeking and use. It creates many physical, physiological and psychological effects leading to serious problems in individual life, in family and in society. Many narcotic drugs like morphine, cocaine, heroin, etc. which were once used as analgesics are responsible for drug addiction.

Pesticides

The plants and animals which damage our agricultural economy are called pests and the chemicals used for killing them are called pesticides.

1. Insecticides: They are used for killing insects. eg. BHC (benzene hexachloride), DDT (dichlorodiphenyl trichloroethane),etc
2. Herbicides or weedicides: They are used for killing weed (undesired plant). eg. 2,4-D (2,4-dichlorophenoxy acetic acid).
3. Fungicides: They are used to kill or control fungi. eg. CuSO₄, Chloropicrin, aluminium phosphide,etc.