Alkanes

Aliphatic, Saturated hydrocarbons are called Alkanes. Alkanes have open chain of carbon atoms. All the carbon atoms are joined by single covalent bonds.

                         General formula for Alkanes CnH2n+2,

               Where n is the number of carbon atoms (n= 1,2,3, ....)

Physical Properties of Alkanes 

1. No color and odour
2. Non polar compounds
3. Insoluble in water
4. Less dense than than water
5. Dissolve in organic solvent
6. Low melting and boiling point

Classification  

Straight chain alkanes - All carbon atoms in a straight continuous chain.

                    Example - butane C4H10

Branched chain alkanes - All Carbon atoms are not in a straight chain.

                    Examples - isoalkanes and Neo alkanes

Alkanes Preparation Method 

1)   From Alkene (unsaturated hydrocarbon)

When Ethene is reacted with Nickel agent by hydrogenation  it gives the formation of Ethane.

  

2)    From Sodium salts of fatty acid

      When Sodium Acetate is reacted with Sodium Hydroxide (NaOH) by decarboxylation it gives the formation of Methane.

3)     From Alkyl halide

     Methyl chloride is reacted with Nickel agent by hydrogenation it gives the formation of Methane.

                                             

    4)     Wartz reaction

      

              when the condensation of two molecules of alkyl halide i.e methyl chloride is reacted with two molecules of sodium it gives the formation of Ethane

                  

 Chemical Properties of Alkane

    

      1)    Action of halgoan (Cl₂,Br₂,F₂)

                When Methane is reacted with chlorine molecule in presence of UV light it gives the formation of methyl chloride.

     2)    Pyrolysis / craking Process

                 When Ethane is strongly heated it gives the formation of Ethene

        

                

     3)    Action O2 (Oxidation)

      

         When Methane is reacted with oxygen it gives the formation of carbon Dioxide.

4 4) Action of HNO₃

         

             When Methane is reacted with concentrated nitric acid it gives the formation of nitro methane.

               

             

Isomerism

A Compound have same molecular formula but different structural formula is called isomar the phenomenon is called isomerism.

Example - 

  

 C₄H₁₀

      Electronic structure and dash structure -

  

  Use of alkanes 

   

1.     Alkanes are used as a source of hydrogen.
2.     Alkanes have a high heat of combustion, hence, they are used as a fuels.example LPG and kerosene are  domestic fuels whereas Petrol, Diesel and CNG are used as fuels for automobiles.
3.      Higher alkanes are viscous liquids and used as a lubricants
4.      Solid alkanes are constituents of paraffin wax used in making candles
5.      Liquid alkanes are used as solvents.