2. What is an Alkene?
❏ An alkene is an unsaturated hydrocarbon that contains a double bond.
❏ The double bond in the carbon chain cannot rotate freely as the single bonds in an alkane
can.
❏ The molecular geometry around the C=C bond in an alkene is linear. Since the molecular
geometry is linear the bond angle around the double bond is 180 degrees.
❏ The double bond is made up of one sigma bond and one pi bond.
❏ This diagram shows why the double bond in C=C does not rotate freely. The sigma bond
connects the to carbons and the pi bonds connect the hydrogens making it very difficult
for the bond to rotate.
3. Ethene
❏ Ethene has a double bond between two
carbons.
❏ The two carbons are both bonded to two
hydrogens.
4. Propene
❏ Propene contains three carbons and six
hydrogens.
❏ There is a double bond between the first
and second carbon
❏ The first carbon is attached to two
hydrogens.
❏ The second carbon is attached to one
hydrogen.
❏ The third carbon is attached to three
hydrogens.
6. Alkenes Fun Fact
❏ Alkenes can act as monomers because they
contain a double bond. They can join end to
end in a reaction called addition
polymerisation
❏ Monomers are small molecules that when
put together make polymers.
❏ Example: Multiple Chloroethene combine to
become Polychloroethene, also known as
PVC.
