Alkynes

 Aliphatic, unsaturated hydrocarbons containing atleast one triple bond are called alkynes. 

Example  

Ethyne

General formula of alkynes is CnH2n_2 

Where n is number of carbon atoms.

Physical properties of alkynes

1. Nonpolar
2. Insoluble in water
3. soluble in most organic solvents
4. boiling points are similar to alkanes of same size
5. less dense than water

Method of Preparation 

1) From Calcium Carbide (Ca.C2)

When calcium carbide is reacted with water molecule ( H2O) it gives the formation of Ethyne.

2) From Tetra-Halide

   When 1,1,2,2 Tetra chloro Ethane is reacted with zinc it gives the formation of Ethyne.

3)  Vicinal dihalide & geminal dihalide

   Two halogen compounds can be attached only one carbon compound is called geminal dihalide.

    When propyledien dichloride is reacted with alco KOH to form 2 Chloro-Propene. undergoes removal of HCl it gives the formation of Propyne.

     

  4) From Alkene

     When ethene is heated it gives the formation of ethyne

        

    Properties of Alkynes 

    1)  Action of Halogen 

        

               

    

   2) Action of Halo-acid 

      

       

   3) Ozonolysis 

     

      

    4) Action of Na Metal     

   5) Action of Reducing agent 

    

   6) Action of H2O

   7) Formation of benzene 

     

   8)  Action of H₂SO₄

    

    

Some example of alkynes