1. Hydrocarbons…
Hydrocarbons are a class of compounds which contain ONLY hydrogen and carbon.
There are a number of different types but we will be concentrating on:
Alkanes
Alkenes

2. Hydrocarbons… Alkanes are a homologous series where:
No double bonds present (SATURATED)
General Formula = CnH2n+2
Compounds are non-polar

3. Hydrocarbons…
What shape does a carbon and its surrounding bonds have in an alkane
(Use VSEPR)
Tetrahedral
109.5o

4. Hydrocarbons… Why are the following not isomers?
Rotation around the C-C single bond means that they are all identical
H3C H C Cl
H3C Cl C H
H3C H C Cl

5. Hydrocarbons…
What happens to the boiling point of alkanes as the chain length increases? [4 marks]
Increased contact between the hydrocarbon chains
Increased Instantaneous dipole – induced dipole
Increased energy required to overcome IM forces
Increased boiling point

6. Hydrocarbons…
Which has the higher boiling point, heptane or 2,4-dimethylpentane? Explain your answer.
There is more contact between the chains of heptane as less BRANCHING
More contact means higher IM forces
Heptane has the higher b.p.

7. Hydrocarbons… Alkenes undergo the following types of reaction:
Combustion:
Complete
Incomplete
Radical Substitution:
Halogenation
We will look at these in greater detail in a couple of lessons

8. Hydrocarbons… Alkenes are a homologous series where:
Double bonds present (UNSATURATED)
General Formula = CnH2n
Exhibit stereoisomerism

9. Hydrocarbons…
What shape does a carbon and its surrounding bonds have in a double bond (Use VSEPR)
Trigonal Planar
120o

10. Hydrocarbons…
Double bonds consist of two different types of electron sharing:
Sigma ()
Pi ()

11. Hydrocarbons…
Sigma bonds are caused by s-orbitals overlapping directly between two nuclei 

12. Hydrocarbons…
Pi bonds are caused by p-orbitals overlapping both above and below the sigma bond
The -bond prevents rotation   

13. Hydrocarbons… Alkenes undergo the following reactions: Hydrogenation
Electrophilic addition
Halogenation
Hydrogen halides
Hydration
Polymerisation

14. Hydrocarbons…
Alkanes and alkenes will both react with Br2 (aq) to form dihaloalkanes
C2H4 + Br2 C2H4Br2
C2H6 + Br2 C2H4Br2 + H2
However, alkanes require an extra input of energy, in the form of strong UV light, for the reaction to proceed. UV

15. Hydrocarbons…
Use this information to design an experiment to determine which samples are alkenes.
You will be given:
Reference Alkane
Reference Alkene
Bromine water (Br2 (aq))
Unlabelled hydrocarbons
You need to produce:
Method
Results table