Alkenes

Alkenes are hydrocarbons are formed only of Carbon and Hydrogen. They are contain a double carbon (C=C)  and are often known as unsaturated molecules (for information on saturated molecules visit the alkanes page)

Synthesis

Alkenes can be synthesised using two methods

  • Cracking of alkanes
  • Dehydration of alcohols

Reactions

Alkenes undergo many different reactions.

  • Addition
    • Hydrogenation
      Addition of hydrogen across the double bond
    • Halogenation
      Addition of halogens across the double bond
    • Hydration
      Addition of water across the double bond
  • Polymerisation
    • Opening of the double bond to form a large molecule known as a polymer.

Addition

Hydrogenation

Hydrogenation of ethene.H2

Hydrogenation of ethene to form ethane.
C2H4 + H2 -> C2H6

Halogenation

Hydration of ethene to form 1, 2-dichloroethaneC2H4 + Cl2 -> C2H4Cl2

Halogenation of ethene to form 1, 2-dichloroethane
C2H4 + Cl2 -> C2H4Cl2

Hydration

Hydration of ethene to form ethanolC2H4 + H2O -> C2H5OH

Hydration of ethene to form ethanol
C2H4 + H2O -> C2H5OH