Sources of organic compounds-coal, plants and animals, natural gas


In this article, the author has explained Sources of organic compounds such as coal, plants, animals, and petroleum products.

Sources of organic compounds

 Organic compounds are everywhere. The rich source of organic compounds in plants and animals. Due to the importance of organic compounds in the modern world, these are also being synthesized in laboratories on a large scale. There are four main sources of organic compounds.

  • Plants and animals
  • Coal
  • Natural gas
  • Petroleum

 Let us discuss the main sources one by one in detail.

Related: Fundamental principles of organic chemistry

 1: Plants and animals

 First of all we will discuss about plants and animals

 Plants and animals which are directly available to us are also a good source of the organic compound.  Moreover, organic synthesis also helps us to have some new compounds.  Plant and animal are the major sources of organic compounds from nature.

 2: Coal

 Let us know what is coal?

 Coal is found in the Earth crust in the form of black deposits.  These deposits are the remains of vegetable matter.  This vegetable was buried under the surface of Earth millions of years ago. 

Above 500 million years ago,  due to high pressure and temperature, the vegetable matter changed into coal deposits.  This happened due to the loss of moisture and elimination of gas like Hydrogen and oxygen.

 What elements are present in the Coal?

In addition to carbon hydrogen and oxygen coal contains minor amounts of Nitrogen and sulfur.  Some amount of water and mineral impurities are also there.  Due to the bacterial and chemical action on wood it was converted into peat. 

 Various types of folds are as follows.

Elements present in coal
Elements present in coal

 Classification of coal

 Based on the percentage of carbon coal has been classified into four categories.


 Anthracite black in color consists of 95% of carbon with a hard texture.  Due to the high percentage of carbon, it is utilized as a fuel.

 Bituminous coal

 This is the most used full form of coal and is the most abundant one.  When this coal is fractionally distilled it give 5 fractions.

Sub-bituminous coal

This form of coal is used in power generating stations


 Lignite coal brown in colour consists of  50 to 60% of carbon with high moisture content and soft texture. 

Carbonization of coal or destructive distillation of coal

At first stage Bituminous coal is stored in iron retorts.  It is heated in the absence of air between 2000 degree centigrade to 1400 degree centigrade.  Following Chief products are obtained as a result.

Products from destructive distillation of coal
Products from destructive distillation of coal

 Composition of Coal Tar

 It is a liquid component of coal.  It contains about 215 aromatic compounds.  It is subjected to fractional distillation again and gives for fractions.

Composition of coal tar
Composition of coal tar

  3: Natural gas

 Natural gas is also found under the earth’s crust.

 Composition of natural gas

 Natural mostly consists of methane.  The presence of Methane is 80 to 95%.  It also contains a lot of Ethane propane and butane.  These three hydrocarbons are also gases at room temperature.  Moreover natural gas also contains CO2,  H2S, and N2 gas.

 How Natural gas is formed?

 Natural gas is formed from the remains of the sea animals and plants.  It is always associated with Petroleum.  It is found in porous rocks in the earth crust.

 Applications of natural gas

  •  Natural gas is mostly used as a fuel around the world
  •  It is used to produce carbon black which is a filler in the manufacturing of tires.
  •  It is one of the raw materials for the manufacturing of urea.
  •  It is utilized as an electricity source in the cement and Fertilizer industry
  • It is used as a domestic fuel

4: Petroleum

 Petroleum is a naturally occurring Brown and greenish-black viscous oily liquid which is obtained from the earth’s crust.

The word petroleum is derived from a Latin word which means Rock oil. 

Chemical nature of Petroleum 

Petroleum is a mixture of saturated hydrocarbon from C-1 to C-40.  Anyhow small amounts of the same other compounds are also present.  This compound contains nitrogen Sulfur and oxygen.

 Origin of Petroleum

 Petroleum is found in some parts of the world below The crust of the earth.  Many theories have been proposed to explain the origin of petroleum in nature.  Anyhow, none of the theories is complete in itself.  Two old theories are as follows

 Carbide theory

 Organic theory

 Modern theory about the origin of petroleum

 According to the modern theory it is believed that petroleum has biological origin.  Petroleum is found due to the decay and decomposition of marine animals. The vegetable organisms of the Prehistoric forest have also been decayed and decomposed. 

It is thought that the Prehistoric forest and sea animals got buried underground.  This biological matter found very high pressure and temperature in the interior of earth for millions of years.  This process is responsible for the composition under the influence of radioactive substances or by bacterial  agents. 

Deposition of Petroleum

 The petroleum that produce gradually moved through the porous rocks under great pressure.  Then it reach dude areas under the earth where it was surrounded by non porous rocks.  Here it was selected as large reservoir. 

The petroleum floats on water and is held under pressure along the natural gas.

Further at industrial scale cracking of petroleum results in different hydrocarbons for different uses.