Hydrocarbons

The family of alkanes
Alkanes are a homologous series of saturated hydrocarbons. Saturatedhydrocarbons have single bonds between the carbon atoms in the molecule. All molecules in this series share the same formula CnH2n+2. A homologous series is composed of a series of compounds all sharing similar chemical properties where each compound differs by an -CH2 group from its neighbour.

The compounds in this homologous series are characterised by single covalent bonds between hydrogen and carbon. Atoms can rotate about a single covalent bond. Click to see an animation.

Alkanes are insoluble in water and react only under the right conditions. We are all familiar with petrol and its explosive properties in the presence of oxygen and a flame. Click to find out more about some of the reactions of alkanes.

Name
Molecular formula
Structural formula
Diagram
Methane
CH4

CH4

Click to see the symmetry of methane
Ethane
C2 H6
CH3CH3
Propane
C3H8

CH3CH2CH3  


Click to see a model of propane
n-butane
C4H10
CH3CH2CH2CH3

Click to see a model of butane
n-pentane
C5H12  
CH3CH2CH2CH2CH3

Click to see a model of n-pentane
n-hexane
C6H14
CH3CH2CH2CH2CH2CH3

Why do the molecules, represented diagrammatically, appear to be twisted?
What is the formula of n-heptane?
Look at n-butane. Are there any other ways of drawing this molecule? (look at isomers)
Below is a table of the properties of some of the alkanes. Explain any noticeable trends.

Name
Boiling point oC
Physical state at room temperature
Methane
-162
Gas
Ethane
-89
Gas
Propane
-43
Gas
Hexane
69
Liquid
Heptane
98
Liquid

Continue with the alkenes