Definition:

The branch of chemistry which deals with the study of hydrocarbons and their derivatives is known as Organic Chemistry.

Importance:

• Organic compounds are famous for their Due to large number and diverse behaviour. 
• Several million organic compounds are known to exist naturally or have been synthesized in the laboratory. 
• Organic compounds are large and more complex in nature. 
• They include biomolecules like proteins, enzymes, carbohydrates, lipids, vitamins and nucleic acids, pharmaceuticals, and synthetic fibres, etc.

The element carbon is so important due to the following reasons:

• The element carbon is present at the centre of the periodic table and it is generally not possible for it to gain or lose electrons to form ionic bonds.
• Therefore, it forms four covalent bonds. Because of its small size, these covalent bonds are short and strong. This enables carbon to form strong and stable bonds with itself and with hydrogen, oxygen and nitrogen.
• The self linking property of carbon is called catenation. And due to this it forms long, straight and branched chains and rings.
• Carbon atom mostly forms covalent bonds with other carbon, hydrogen, oxygen, nitrogen and halogens.
• Compounds in which carbon forms single bonds with other atoms are called saturated compounds.
• These compounds are generally represented by their structural formulas. 
  Methane, a saturated compound, is represented by the following structural formula

            H
             |
      H - C - H  
             |
            H            or its condensed form is CH₄

• A structural formula thus shows the symbols for the atoms present in the compound connected by short lines which represent the bonds present in them.
• Other Examples of Saturated Compounds are C₂H₆, CH₃Cl, CH₃OH, CH₃NH₂ , etc.

In alkanes, C-C single bond is very strong and non-reactive. So it does not behave as a functional group. While in alkenes, C=C double bond is reactive and gives addition reactions. That’s why it is called a functional group.

Electron Cross and Dot Structures of Alkanes:

Methane:

Structural Formula:

          H
           |
    H - C - H
           |
          H

Electron Dot Structure:    

          H
          x
    H x C x H
          x
          H

Ethane:

Structural Formula:

                   H   H
                     |   |
              H - C - C - H
                      |   |
                     H   H

Electron Dot Structure:

                    H   H
                     x   x
              H x C . . C x H
                     x   x
                    H   H

Propane:

Structural Formula:

                H   H   H
                  |   |   |
         H - C - C - C - H
                  |   |    |
                H   H  H

Electron Dot Structure:

                H   H   H
                  x   x   x
          H x C . C . C x H
                 x   x    x
                H   H   H

Butane:
Structural Formula:

                        H   H   H   H
                          |     |    |    |
                   H - C - C - C - C - H
                          |     |    |     |
                         H   H   H   H

Electron Dot Structure:

                  H   H   H   H
                   x   x   x     x
            H x C . C . C .  C x H
                    x   x   x    x
                  H   H   H   H

Alkanes burn in oxygen or air to form CO₂ and H₂O with the evolution of large amount of heat. The reaction is called combustion.

Examples:

Methane:

CH₄​(g)+2O₂​(g) ⟶ CO₂(g)+2H₂O(g)+heat

Ethane:

2C₂​H₆​(g)+7O₂​(g) ⟶ 4CO₂​(g)+6H₂O(g)+heat

Uses of Alkanes:

• Natural gas, which is chiefly methane, is used as domestic fuel.
•  Compressed natural gas (CNG) is used as automobile fuel.
• These gases are used in the manufacture of chemicals such as carbon black, methyl alcohol, ethyl alcohol, chloroform, carbon tetrachloride etc.

The self-linking property of carbon called catenation. Due to this, it forms long, straight and branched chains and rings.

When natural gas, mainly methane is oxidized under controlled conditions, it gives following products:

• Methanol 
• Formaldehyde 
• Formic Acid 

Fractional distillation of petroleum gives naphtha which consists of a mixture of liquid hydrocarbons. It is then heated at around 500°C in the presence of catalyst called zeolite to give hydrocarbons which have five carbon atoms.

            Naphtha ---- heatzeolite​ ---->Alkanes and Alkenes

(mixture of hydrocarbons)                   (containing 5 to 10 carbon atoms)

Molecular, structural and condensed structural formula for Iso-Butane :

Because these compounds are part of everything from food we eat to the various items we use in daily life to fulfill our needs.

Uses:

• As Food: Carbohydrates, Proteins, Fats, Vitamins
• As Clothing: Cotton, Wool, Silk, Synthetic fibers
• As Shelter/Houses: Wood, Plastic, Paint
• As Fuel: Petrol, Diesel, LPG, Natural Gas, Coal
• As Medicines: Aspirin, Antibiotics, Vitamins
• As Raw Material: Plastics, Soap, Cosmetics, Dyes

 Five Naturally Occurring Organic Compounds are:

• Vitamins
• Enzymes
• Lipids/Fats
• Carbohydrates
• Proteins

IUPAC name of the given compound is 2-Methylbutane.

The melting and boiling points of alkanes increase regularly with the increase of molecular size. This is because of increase of attractive forces between the molecules of alkanes.