1. Leaving Certificate Chemistry
Organic Chemistry
11 – The Alkenes
Leaving Certificate Chemistry

2. Carbon-Carbon double Bond Only
The Alkenes: CnH2n
Ethene: C2H4
Carbon-Carbon double Bond Only
2 Carbon Longest Chain H H C C H H
2 planar carbons

3. These compounds are not soluble in water
The Alkenes: CnH2n
These are also constituents of crude oil
The first member is ethene
2002 Q. 6 (a) (8)
These compounds are not soluble in water
Ethene – C2H4

4. Carbon-Carbon double Bond Only
The Alkenes: CnH2n
Propene: C3H6
Carbon-Carbon double Bond Only
Tetrahedral
carbon
3 Carbon Longest Chain H H H C C C H H H
2 planar carbons
2005 Q. 4 (i) (6)

5. Carbon-Carbon double Bond Only
The Alkenes: CnH2n
Butene: C4H8
Carbon-Carbon double Bond Only
Tetrahedral
carbon
4 Carbon Longest Chain H H H H C C C C H H H H
2 planar carbons

6. These compounds are not soluble in water
The Alkenes: CnH2n
These are also constituents of crude oil
The first member is ethene
2002 Q. 6 (a) (8)
These compounds are not soluble in water
Ethene – C2H4

7. The Alkenes Functional Group: C = C
All of these molecules are unsaturated molecules – They will decolourise bromine water and acidified potassium permanganate solution
2008 Q. 9 (c) (6)
2004 Q. 2 (d) (6)

8. 3 Isomers of C4H8 H H CH3 H H H C C C C H H H H
2008 Q. 9 (b) (12)
2006 Q. 9 (d) (12)
Methyl Group H H
CH3 H H 1 2 3 H C C C C H H H H
2 – methylprop – 1 - ene
But – 2 - ene
But – 1 - ene

9. Isomers of butene
But-1-ene
But-2-ene
2-methylpropene

10. Mandatory Experiment
Preparation of Ethene

11. Aluminium Oxide [catalyst]
Preparation of Ethene
2006 Q. 9 (b) (6)
Aluminium Oxide [catalyst]
Al2O3
Ethanol
C2H5OH

12. Ethanol Structural Formulae
Ethanol: C2H5OH
Other Uses
-OH Group Present
2 Carbon Longest Chain H H
C6H12O6 2
C2H5OH + 2
CO2 H C C OH
Glucose
Ethanol H H
Produced in industry by fermentation
Fuel
Solvent
Thermometer

13. Balanced Equation Ethene Ethanol Water H H H H C C H C C OH H H H H
Aluminium Oxide [catalyst]
Al2O3
Ethene H H
Ethanol
This is an elimination reaction
Formation of an unsaturated compound
Loss of a small molecule like water
H2O
Water
2007 Q. 8 (a) (6)

14. Balanced Equation for the Synthesis of Ethene
Preparation of Ethene
Balanced Equation for the Synthesis of Ethene
C2H5OH
Al2O3
C2H4
H2O +
Ethanol
Ethene
Water

15. Preparation of Ethene
Aluminium Oxide is placed halfway along the boiling tube
Ethanol soaked in glass wool
Heating the catalyst using a Bunsen
Collecting ethene by the downward displacement of water

16. Preparation of Ethene
2006 Q. 9 (b) (3)
2004 Q. 2 (a) (5)
The ethanol is soaked in glass wool with the glass wool being placed in after the ethanol so as to ensure that all of the liquid is soaked up.

17. Preparation of Ethene
The first couple of test tubes collected are usually discarded as they contain displaced air from the reaction boiling tube.

18. Remove the delivery tube from the boiling tube
Preparation of Ethene
Be careful of suckback
If this occurs:
Remove the delivery tube from the boiling tube
Apply heat

19. Colourless Pink Colourless Yellow Preparation of Ethene Ethene is
Ethene Reaction with acidified potassium permanganate
Colourless
Pink
Ethene Reaction with bromine water
Colourless
Yellow
These tests prove that ethene is an unsaturated compound

20. Ethene burns with a luminous flame
Preparation of Ethene
Ethene is
Ethene burns with a luminous flame
Burning any hydrocarbon produces carbon dioxide and water vapour
Balanced Equation for the Combustion of Ethene
C2H4 + 3 O2 2
CO2 + 2
H2O
Turns blue cobalt chloride paper pink
Turns Limewater Milky

21. The uses of Ethene
Ethene is commonly used in industry to ripen fruit and produce the useful plastic polythene

22. Chemical Reactions of The Alkenes
Ethene is
Chemical Reactions of The Alkenes

23. ADDITION OF hYDROGEN

24. Important Industrial Reaction
Addition of Hydrogen
Important Industrial Reaction
Used to convert vegetable oils, which are unsaturated, into solid saturated materials used in margarine and dairy products.

25. Addition of Hydrogen Propene Hydrogen Propane H H H C C C H H H H H H

26. Addition of Hydrogen Hydrogen Butene Butane H H H H H2 C C C C H H H H

27. Uses of hydrogenation reactionsions
Saturated fats
Unsaturated fats

28. ADDITION OF cHLORINE

29. Important Industrial Reaction
Addition of Chlorine
Important Industrial Reaction
1, 2 – Dichloroethane is used to produce chloroethene which is used to produce the very important plastic PVC

30. 1,2 dichloroethane is used to make PVC

31. Addition of Chlorine Propene Chlorine 1, 2 -dichloropropane H H H C C
Cl2 Cl Cl H
Chlorine
1, 2 -dichloropropane

32. Addition of Chlorine Chlorine Butene H H H H H Cl2 C C C C H H H H H H
1, 2 - dichlorobutane H C C C C H Cl Cl H H

33. ADDITION OF bROMINE

34. Important Industrial Reaction
Addition of Bromine
Important Industrial Reaction
1, 2 – Dibromoethane is used to prevent poisonous lead accumulating in cars

35. Addition of Bromine Propene Bromine 1, 2 -dibromopropane H H H C C C H

36. Addition of Bromine Bromine Butene 1, 2 - dibromobutane H H H H Br2 C

37. ADDITION OF WATER

38. Addition of Water Important Industrial Reaction
Used to produce the important solvent ethanol

39. Addition of Water Propene Water Propanol H H H C C C H H H H H H H C C
2002 Q. 6 (d) (6) H H
Propene H H H H C C C OH
H2O H H H
Water
Propanol

40. Addition of Water Water Butene Butanol H H H H H2O C C C C H H H H H HOH H H H H

41. Uses of Hydration reactions
Used to make alcohols, which are useful solvents for chemical reactions

42. ADDITION OF Hydrogen
chloride

43. Addition of Hydrogen Chloride
HCl

44. Addition of Hydrogen Chloride
Ethene H Cl
Chloroethane
HCl
Hydrogen Chloride

45. Chloroethane – used as a binding agent in paint

46. Addition of Hydrogen Chloride
Propene H H H Cl C C C H
HCl H H H
Hydrogen Chloride
chloropropane

47. Addition of Hydrogen Chloride
HCl C C C C H
Hydrogen Chloride H
Butene H H
chlorobutane H H H H H C C C C H Cl H H H

48. Polymerisation of EtheneC C C C H H H H
Ethene
Ethene H H H H
2008 Q. 9 (e) (6) C C C C
Polythene H H H H n

49. Polymerisation of ethene
Important Industrial Reaction
Used to produce the very important plastic polythene

50. Polymerisation of PropeneH H H H C C C C H
CH3 H
CH3
Propene
Propene H H H H C C C C
Polypropene H
CH3 H
CH3 n

51. Using Polymerisation to make Polyvinylchloride PVC – step 1
Ethene H H H C C H
Cl2 Cl Cl
Chlorine
1, 2 -dichloroethane

52. Using Polymerisation to make Polyvinylchloride PVC – step 2Cl C C H C C H H H Cl Cl
chloroethene
1, 2 -dichloroethane

53. Using Polymerisation to make Polyvinylchloride PVC – step 3Cl Cl C C C C H H H H H H H H C C C C
PVC Cl H Cl H n

54. PVC WINDOWS

55. The Alkanes - H2 The Chloroalkanes + H2 The Alkenes + HCl , + Cl2
Substitution
using UV Light
Ethane C2H6
- H2
The Chloroalkanes
+ H2
Chloroethane C2H5Cl
The Alkenes
+ HCl , + Cl2
Ethene C2H4
+ H2O
The Alcohols
Ethanol C2H5OH
- H2O
Aluminium Oxide Catalyst
The Polymers
Polythene & Polypropene