1. Alkanes and Alkenes

2. Property Alkane Alkene Reactions involve heterolytic fisson
Free Radical Substitution reaction
Formed during cracking reactions
Exist as Stereoisomers
Electrophilic addition reactions take place
Exist as Structural isomers
Exist as Cis/trans or E/Z isomers
Has 1 pi Molecular orbital
Has all single bonds
Decolourises bromine in absence of UV
Has sigma molecular orbitals
Reactions involve homolytic fisson
Substitution reactions occur
Addition reactions occur
Burn to give carbon dioxide and water in a good supply of air
Undergo polymerisation reactions

3. Processing Alkanes CRACKING, REFORMING, ISOMERISATION
How is it carried out?
C – Al2O3 and heat
R – Pt/Rh and heat
I – Pt separated by zeolyte catalyst and heat
What are the products?
C – Smaller Alkanes AND alkenes
R – Cyclic alkanes and hydrogen
I – Branched alkane isomers of original
Why is it carried out?
C – Smaller Alkanes used as fuels, alkenes used to make polymers
R – Lowers bp of alkane so more vapour at same temp so better ignition (Weaker VDW as smaller molecule)
I – Lowers bp of alkane so more vapour at same temp so better ignition (Weaker VDW as molecules pack together less well)

4. Free radical substitution
chlorination of methane
i.e. homolytic breaking of covalent bonds
Overall reaction equation
CH4 + Cl2
CH3Cl + HCl
Conditions
ultra violet light
excess methane
to reduce further substitution

5. Free radical substitution mechanism
ultra-violet
Cl2
Cl + Cl
initiation step
two propagation steps
CH4 + Cl
CH3 + HCl
CH3 + Cl2
CH3Cl + Cl
termination step
CH3 + Cl
CH3Cl
CH CH3
CH3CH3
minor termination step

6. Further free radical substitutions
Overall reaction equations
CH3Cl + Cl2
CH2Cl2 + HCl
CH2Cl2 + Cl2
CHCl3 + HCl
CHCl3 + Cl2
CCl4 + HCl
Conditions
ultra-violet light
excess chlorine

7. Electrophilic addition
bromine with ethene
Overall reaction equation
CH2=CH2
+ Br2
CH2BrCH2Br
1,2-dibromoethane
mechanism

8. Electrophilic addition mechanism
bromine with ethene H C H C Br +
carbocation δ+ δ- Br Br - H C Br Br
1,2-dibromoethane
reaction equation

9. Electrophilic addition 2
Hydrogen bromide with propene
Overall reaction equation
CH3CH2CH2Br
CH3CH=CH2
+ HBr
1-bromopropane or
CH3CHBrCH3
Conditions
DRY HBr in Ethanol
2-bromopropane
mechanism

10. Hydrogen bromide with Propene
Electrophilic addition mechanism
Hydrogen bromide with Propene H
CH3 C H
CH3 C + Br H δ+ δ- Br - H
CH3 C Br Br H δ+ δ-
1-bromopropane
reaction equation

11. Hydrogen bromide with Propene
Electrophilic addition mechanism
Hydrogen bromide with Propene H
CH3 C H
CH3 C + Br H δ+ δ- Br - H
CH3 C Br Br H δ+ δ-
2-bromopropane
reaction equation