1. Topics 3abc – Alkanes, alkenes and ethanol Topics 5bc – natural oil and gas and synthetic polymers

2. Crude oil (Petroleum)
A mixture of hydrocarbons (chemicals which contain only hydrogen and carbon atoms)

3. Fractional distillation
Separation of liquids with different boiling points

4. Fractional distillation
The mixture can be split into simpler fractions by fractional distillation

6. Welcome to a new family

7. The alkanes

8. Methane (CH4)

9. Ethane (C2H6)

10. Propane (C3H8)

11. Butane (C4H10)

12. The alkanes Methane CH4 Ethane C2H6 Propane C3H8 Butane C4H10
Pentane C5H12
Hexane C6H14
Octane C8H18

13. The alkanes CnH2n + 2 Methane CH4 Ethane C2H6 Propane C3H8
General formula
The alkanes CnH2n + 2
Methane CH4
Ethane C2H6
Propane C3H8
Butane C4H10
Pentane C5H12
Hexane C6H14
Octane C8H18
Homologous group – similar chemical properties, structures and functional groups

14. The alkanes CnH2n + 2 Methane CH4 Ethane C2H6 Propane C3H8
General formula
The alkanes CnH2n + 2
Methane CH4
Ethane C2H6
Propane C3H8
Butane C4H10
Pentane C5H12
Hexane C6H14
Octane C8H18
Homologous group – similar chemical properties, structures and functional groups
Generally unreactive, but burn exothermically. Longer chains burn less easily.

15. Structural formulae

16. Alkanes are saturated compounds
No double bonds

17. Tetrahedral bonds
In alkanes, the carbon bonds are tetrahedral

18. Chlorinated methane
Methane can be chlorinated. Trichloromethane is commonly known as chloroform.

19. Isomers Same formula, but different structures
We have slighty different physical properties (longer chains have higher boiling points)

20. Combustion

21. Combustion Hydrocarbons burn producing carbon dioxide and water
CH4 + 2O2 CO2 + 2H2O

22. Incomplete combustion
When there is insufficient oxygen, carbon monoxide is also formed
It reduces the blood’s oxygen carrying capability

23. Another family!

24. The alkenes CnH2n Ethene C2H4 Propene C3H6 Butene C4H8 Pentene C5H10
Hexene C6H12

25. The alkenes Unsaturated (contain a double bond) More reactive
Can “add” atoms – addition reactions

26. Alkenes - equilateral
The bonds on a double bonded carbon in an alkene point towards the corners of an equilateral triangle

27. Test for alkenes Decolourises bromine water Dibromoethane (colourless)
ethene
Bromine (yellow/orange)

28. Alcohols - ethanol

29. Alcohols Methanol CH3OH Ethanol C2H5OH Propanol C3H7OH Butanol C4H9OH
Pentanol C5H11OH
Hexanol C6H13OH

30. Alcohols Methanol CH3OH Ethanol C2H5OH Propanol C3H7OH Butanol C4H9OH
“functional group”
Methanol CH3OH
Ethanol C2H5OH
Propanol C3H7OH
Butanol C4H9OH
Pentanol C5H11OH
Hexanol C6H13OH

31. Ethanol
Can be made by the addition reaction of water to ethene – when you have plenty of oil
Phosphoric acid

32. Ethanol - Fermentation of sugars
You can make ethanol for industry this way when you have lots of sugar cane

33. Dehydration of Ethanol

34. Ethanol and sodium 2C2H5OH + 2Na 2C2H5ONa + H2
Hydrogen and sodium ethoxide formed

35. Oxidation of ethanol
Ethanol can be oxidised to form ethanoic acid (acetic acid = vinegar!)

36. Carboxylic acids Methanoic acid CHOOH Ethanoic acid C2H3OOH
Propanoic acid C3H5OOH
Butanoic acid C4H7OOH
Pentanoic acid C5H9OOH
Hexanoic acid C6H11OOH

37. Carboxylic acids Methanoic acid CHOOH Ethanoic acid C2H3OOH
“functional group”
Methanoic acid CHOOH
Ethanoic acid C2H3OOH
Propanoic acid C3H5OOH
Butanoic acid C4H7OOH
Pentanoic acid C5H9OOH
Hexanoic acid C6H11OOH

38. Ethanol + ethanoic acid acids
Ethanol + ethanoic acid ethyl ethanoate + water
An ester (they normally smell nice!)

39. Ethyl ethanoate – an “ester”

40. Polymers

41. Polymers – addition polymerisation
Molecules of ethene can be joined together to form polyethene
← monomers
← polymer

42. Polythene

43. Polypropylene – Strong and resistant to chemicals

44. poly(chloroethene) - PVC

45. Condensation polymers – Nylon Diamine + dicarboxylic acid
Reactive ends + + +
monomers
polymer
Small molecules given off (HCl)

46. Cracking!

47. Too many long molecules
Crude oil contains too many of the long (and not so useful molecules)

48. Cracking
Luckily we can break the long molecules into shorter ones by “cracking”
The long molecules are passed over hot broken pot (ceramic) and split up into smaller molecules. A catalyst can also be used

49. Cracking
Cracking an alkane produces smaller alkanes and also alkenes.