1. Leaving Certificate Chemistry
Organic Chemistry
10 – The Alkanes
Leaving Certificate Chemistry

2. Contents Chemical Structures of the Alkanes Saturated compounds Butane
Isomers
Butane
Propane
Physical Properties & Cyclohexane
Chemical Structure
Chemical Structure of Cyclohexane
Reactions of the Alkanes
Formation of a chloroalkane

3. Hydrocarbons 1. The Alkanes 2. The Alkenes 3. The Alkynes (Ethyne)
4. Aromatic

4. Objectives Today you should learn about.. What a homologous series is
What saturated means and how to test for it
What an isomer is and how to name isomers of alkanes

5. Homework From the worksheet: Questions 114 - 121
Learn the definitions of :
Homologous series, saturated and isomer

6. 2006 Q. 9 (a) (5)

7. The Alkanes: CnH2n+2 These are the main constituents of crude oil
The simplest member is methane
Methane – CH4

8. The First 8 Alkanes Methane: CH4 Ethane: C2H6 Propane: C3H8
Butane: C4H10

9. The First 8 Alkanes Pentane: C5H12 Hexane: C6H14 Heptane: C7H16
Octane: C8H18

10. The First 8 Alkanes Structural Formulae
Methane: CH4
Carbon-Carbon Single Bonds Only
1 Carbon-Long H H C H H

11. The First 8 Alkanes Structural Formulae
Ethane: C2H6
Used to produce the more useful ethene by catalytic cracking
Carbon-Carbon Single Bonds Only
2 Carbon Longest Chain H H H C C H H H

12. The First 8 Alkanes Structural Formulae
Propane: C3H8
Carbon-Carbon Single Bonds Only
3 Carbon Longest Chain
A constituent of liquid petroleum gas H H H H C C C H H H H H

13. The First 8 Alkanes Structural Formulae
Butane: C4H10
Carbon-Carbon Single Bonds Only
4 Carbon Longest Chain H H H H H C C C C H
A constituent of liquid petroleum gas H H H H

14. The First 8 Alkanes Structural Formulae
Pentane: C5H12
Carbon-Carbon Single Bonds Only
5 Carbon Longest Chain H H H H H H C C C C C H H H H H H

15. The First 8 Alkanes Structural Formulae
Hexane: C6H14
Carbon-Carbon Single Bonds Only
6 Carbon Longest Chain H H H H H H H C C C C C C H H H H H H H

16. The First 8 Alkanes Structural Formulae
Heptane: C7H16
Carbon-Carbon Single Bonds Only
7 Carbon Longest Chain H H H H H H H H C C C C C C H C H H H H H H H H

17. The First 8 Alkanes Structural Formulae
Octane: C8H18
Carbon-Carbon Single Bonds Only
8 Carbon Longest chain H H H H H H H H H C C C C C C C C H H H H H H H H H

18. The Alkanes
All of these molecules are saturated molecules – They will not decolourise bromine water or acidified potassium permanganate solution

19. Isomers

20. 2 Isomers of butane H H CH3 H H H H C C C C H H H H H 2 - methyl
Methyl Group
2002 Q. 8 (a) (6) H H
CH3 H H 1 2 3 H H C C C C H H H H H
2 - methyl
Butane
propane

21. Isomers of butane
Butane
2-Methylpropane

22. 3 Isomers of pentane 2 - methyl Pentane butane 2, 2 - dimethylpropane
2005 Q. 6 (b) (18)
2007 Q. 6 (a) (9)
Methyl Group H H
CH3 H H H 1 2 3 4 H H C C C C C H H H H
CH3 H H H
Methyl Group
2 - methyl
Pentane
butane
2, 2 - dimethylpropane

23. Isomers of pentane
Pentane
2, 2 - dimethylpropane
2-methylbutane

24. Cyclohexane H H H C H H C C H H C C H H C H H H
Cyclohexane: C6H12

25. Check your learning.. Do you know ? What a homologous series is
What saturated means and how to test for it
What an isomer is and how to name isomers of alkanes

26. Physical properties of the alkanes
Intramolecular Bonds present - Ionic, polar covalent or covalent?
Is the molecule polar overall?
( think of shape)
Soluble in a polar or a non polar solvent (like dissolves like)
Intermolecular bonds present?
Would it have a high boiling point or a low boiling point?
Solid gas or liquid at room temperature?

27. Physical Properties of the Alkanes
They are all excellent fuels
No taste
or smell
They all burn in air to produce carbon dioxide and water
-For Example Pentane
C5H O  CO H2O

28. chemical reactions of the alkanes
Reaction with Chlorine
Formation of the Chloroalkanes
2003 Q. 6 (b) (3)
2005 Q. 7(b) (3)
A substitution reaction involving ultraviolet light

29. The reaction of methane with chlorine
In the presence of ultraviolet light Cl Cl H C H
Hydrogen chloride
Chlorine H
Chloromethane
Methane

30. The reaction of ethane with chlorine
2003 Q. 6 (d) (9) H H
In the presence of ultraviolet light Cl Cl H C C H
Hydrogen chloride
Chlorine H H
Chloroethane
Ethane

31. The reaction of propane with chlorineCl Cl H H H
Hydrogen chloride
Chlorine H C C C H H H H
Propane
Chloropropane
In the presence of ultraviolet light

32. The reaction of butane with chlorineCl Cl H H H H
Hydrogen chloride
Chlorine H C C C C H H H H H
Chlorobutane
Butane
In the presence of ultraviolet light

33. The First 4 Chloroalkanes Structural Formulae
Chloromethane: CH3Cl
Single Bonds Only
Chlorine
1 Carbon-Long H
A toxic gas no longer found in consumer products H C Cl H
Functional group of atoms

34. The First 4 Chloroalkanes Structural Formulae
Chloroethane: C2H5Cl
Single Bonds Only
Chlorine
2 Carbons-Long H H
Aerosol spray propellant H C C Cl H H
2005 Q. 7 (a) (5)

35. The First 4 Chloroalkanes Structural Formulae
Chloropropane: C3H7Cl
Single Bonds Only
Chlorine
3 Carbons-Long H H H H C C C Cl H H H

36. The First 4 Chloroalkanes Structural Formulae
Chlorobutane: C4H9Cl
Single Bonds Only
Chlorine
4 Carbons-Long H H H H H C C C C Cl H H H H