In this topic “CHEMICAL REACTIONS OF ORGANIC COMPOUNDS”focus area based topics are given below

1 Substitution Reactions
2 Addition Reactions
3 Polymerisation
4 Combustion of Hydrocarbons
5 Thermal Cracking

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1 Substitution Reactions

A reaction in which an atom or a group in a compound is replaced
by another atom or a group is called substitution reaction

methane -chloromethane

2.Addition Reactions

Reactions in which unsaturated organic compounds with double bond or triple bond react with other molecules to form saturated compounds are called addition reactions


Polymerisation is the process in which a large number of simple molecules combine under suitable conditions to form complex molecules. The product molecules are called polymers

ethene polyethene
vinyl chloride PVC

The simple molecules which combine in this manner are called monomers.
We use a number of natural and man – made polymers in our daily life.
PVC (Polyvinyl Chloride) is a polymer commonly used for making pipes. It is formed by the polymerisation of a large number of chloroethene (Vinyl chloride) molecules.

4.Combustion of Hydrocarbons

When hydrocarbons burn they combine with the oxygen in the air to form CO2 and H2O along with heat and light. This process is called combustion

Eg; CH4+ 2O2 → CO2 + 2H2O + Heat

Thermal Cracking

Some hydrocarbons with high molecular masses, when heated in the absence of air undergo decomposition to form hydrocarbons with lower molecular masses. This process is called Thermal cracking.A number of products are made in this way Propane is one of the simplest hydrocarbons which can undergo thermal cracking.

When hydrocarbons with larger number of carbon atoms undergo thermal cracking, the carbon chain can undergo cleavage or breaking in a number of ways. The products formed as a result of thermal cracking depend on the nature of the hydrocarbons getting cracked, temperature and pressure.
When saturated hydrocarbons are subjected to thermal cracking the products formed contain both saturated and unsaturated hydrocarbons.
Plastic wastes, which are polymers can be converted to simpler molecules by thermal cracking.


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