Let’s face facts: alkanes don’t have many uses.  In real life, they are non-polar solvents, larger-chain ones can be used to make wax, and they are good for burning/they make good fuels.  As far as organic chemistry goes, alkanes are very boring.  They have only three uses in your class:

1)      Solvents: Alkanes are very good non-polar solvents.


2)      Halogenation: Alkanes can be reacted with bromine or chlorine under free-radical conditions to obtain an alkyl halide.


3)      Combustion: This is the fuel part.  Complete combustion is an alkane reaction with oxygen to obtain CO2 and water, as shown in the following example:  C3H8 +5O2 –> 3CO2 + 4H2O + Heat


There is only a small possibility that you will see a combustion reaction on one of your exams.  Therefore, the only real uses for alkanes in your undergraduate organic chemistry class will be as a solvent or in a halogenation reaction.  Hence, if you have an alkane in one of your exam reactions, it should be very simple to determine its role.  If there is a halogen (usually either Br2 or Cl2) , then beware of a halogenation reaction.  Otherwise, it is most likely safe to say that if you have an alkane in your reaction, it is a solvent and does not participate as a reactant.