Alkenes
Alkenes
• Unsaturated hydrocarbons
• Alkenes contain a C==C double bond
somewhere in the chain.
• Alkenes have the general formula CnH2n
– Where n is the number of carbon atoms
• The simplest alkene must contain 2 carbon
atoms.
Alkenes Burning
• Alkenes burn in oxygen to give carbon dioxide
and water vapour.
C2H4 + 3O2
2CO2 + 2H2O
Alkenes - Boiling Point
The double bond
• The double bond in
alkenes makes then much
more reactive than
alkanes.
• Other atoms can all to the
molecule when the
double bond breaks open.
• The double bond is the
functional group for
alkenes.
Chemical Test for Unsaturation –
Double Bond
• If the alkene is mixed with a solution of bromine.
The bromine loses it colour.
• http://www.youtube.com/watch?v=2C_6ax2TsV8
• Ethene + bromine
1,2-dibromoethane
Addition Reaction
Activity
• Complete the questions on page 292
• Make the following alkenes;
– Ethene
– Butene
– Pentene
– Hexene
– Propene