Alkenes

                 Aliphatic unsaturated hydrocarbons containing one or more double bonds are called alkenes (olefins)

                            Example: CH₂=CH₂

                General formula of alkenes is CnH₂n.

Where 'n' is a number of carbon atoms.

Classification of Alkenes

            1) Symmetrical Alkenes

            2) Unsymmetrical Alkenes

 1) Symmetrical Alkenes

The alkenes in which similar group s or atoms are attached to the carbon atoms joined by double bonds, are called as symmetrical alkenes.

                         Example: Ethene  CH₂ = CH₂

2) Unsymmetrical Alkenes

The alkenes in which different atoms or groups of atoms are attached to the carbon atoms joined by double bond are called on unsymmetrical Alkenes.

                       Example: propene CH₃-CH=CH₂

Physical properties of alkenes

1. Alkenes are nonpolar compounds. Insoluble in water.
2. Soluble in a nonpolar organic solvents.
3. They are less dense than water.

Method of Preparation of Alkenes

1) From Alkyl halide 

When Ethyl chloride is reacted with Potassium hydroxide (alco-KOH) it gives the formation of Ethene.

2)   From Alcohol

when Ethyl alcohol is reacted with conc. sulphuric acid (H2SO4) it gives the formation of Ethene.

3) From Vicinal dihalide

Two halogen compounds can be attached neighbouring carbon atoms is called Vicinal dihalide.

when Ethylene dichloride is reacted with zinc it gives the formation of ethene

4)  From Alkyne 

When Ethyne is reacted with Nickel agent by hydrogenation it gives the formation of ethene.

Properties of Alkenes 

1) Action of halogen (Vicinal Di halide)

When ethene is reacted with chlorine halogen it gives the formation of Ethylene dichloride.

2) Alkyl halide (Action of halo-acid)

When ethene is reacted with Hydrochloric acid (HCl) it gives the formation of Ethyl chloride.

3) Ozonolysis (Aldehyde or ketone)

When Ethene is reacted with ozone (O3) to form an Ozonide,then undergoes hydrolysis it gives the formation of two molecules of formaldehyde.

4) Reducing agent(Alkane)

When Ethene is reacted with Nickel agent (Ni) by hydrogenation gives the formation of Ethane.

5) Action Of KmNO₄  (Oxidising agent) (Ketone/Carboxylic acid)

When ethene is reacted with oxidizing agent KmNO₄ it gives the formation of formaldehyde.

6)Action Of H₂SO₄ (Alcohol)

When Ethene is reacted with sulphuric acid H2SO4 to form ethyl hydrogen sulphate then undergoes hydrolysis it gives the formation of Ethyl alcohol.

Alkenes example -

1. Propene C3H6 CH3-CH=CH2
2. Butene C4H8 CH3-CH2-CH=CH2
3. Pentene C5H10 CH3-CH2-CH2-CH=CH2