What are the Main Sources of Organic Compounds – Chemistry

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 Berzelius gave vital force theory in 1809 .

According to ‘Vital Force Theory’

1.Organic compounds are prepared only inside the bodies of living organisms by a super natural force called vital force. 2.It is impossible to synthesize organic compounds in laboratory.

Rejection of Vital Force theory:

In 1828, Friedrich Wohler (a German chemist) rejected the vital force theory.

He prepared Urea (an organic compound) in a laboratory by heating Ammonium cyanate (inorganic compound).

It proved the vital force theory to be wrong. 

Preparation of First Organic Compound in Laboratory:

Urea was the first organic compound which was prepared in the laboratory. Therefore, the vital force theory is discarded.

so organic compounds can be obtained from living organisms and also synthesized in a laboratory.

When when the living organisms died and the dead living organisms were buried under the earth’s crust for millions of years, they due to different bacterial and chemical reactions under high temperatures converted to major commercial sources of organic compounds (coal, petroleum and natural gas ).

Major Sources of Organic Compounds:

  1. Coal

2. Petroleum

3. Natural gas

These are called fossil fuels.

What are Fossil Fuels? 

Fossil Fuels:

The dead remains of living organisms (animals and plants) are called fossil fuels.

The major sources of organic compounds (Coal, Petroleum, Natural Gas and Plants) are called fossil fuels because these are formed fossil remains of buried plants and animals inside the earth’s crust by the anaerobic (without oxygen) decomposition.


Coal is an important solid fossil fuel.

It is a black mineral of plant origin found under the earth’s crust.

Formation of Coal

 Plants, which were buried under the earth’s crust millions of years ago, due to different bacterial and chemical reactions first converted into peat which under high temperature and pressure was slowly converted to coal.

Uses of coal:

  1. Coal is used as domestic as well as industrial fuel to minimize the use of petroleum and natural gas.

2. It is also used as fuel to generate electricity. 

3. Coal is also a source of a large number of organic compounds, especially aromatic compounds.


 The word Petroleum is derived from two Latin words

          Petra means rock and oleum mean oil.

 So the word petroleum means rock oil.

It is also sometimes called mineral oil or liquid gas.

Petroleum is a thick sticky viscous

 liquid of black colour that seeps out of the ground.

Petroleum is a complex mixture of hydrocarbons (mostly alkanes, cycloalkanes and aromatic hydrocarbons) whose composition varies according to its place of occurrence.

Petroleum is produced by the decay of living organisms buried in the earth’s crust millions of years ago.

Crude oil:

Petroleum in unrefined form is called crude oil.

Important Products prepared from Petroleum:

Methane (CH4)

Ethylene (CH2=CH2)


Benzene C6H6

Toluene (C6H5CH3 )

Xylene C6H4 (CH3)2

Natural Gas

It is a mixture of low boiling hydrocarbons.

Natural gas is a mixture of methane, ethane, propane and butane. A major portion of natural gas is methane (CH4 about 85%)

Other gases include ethane, propane, and butane.

Why Natural gas is also known as Sui gas?

The first biggest deposit of natural gas was obtained at sui in Baluchistan. Therefore, it is also called sui gas.

Natural gas is usually found above petroleum reservoirs.

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