Alkanes

• Alkanes have the general formula CnH2n+2.
• Alkanes are the main components of natural gas and crude oil.
• Alkanes are very stable as the C-H bonds are very strong non-polar covalent bonds that contain sigma bonds.
• Alkanes are saturated hydrocarbons, meaning they contain only single bonds between carbon atoms.
• Alkanes are a tetrahedral shape with angle of 109.5 degrees surrounded by four electron pairs. The sigma bond acts as an axis which the atoms can rotate clearly around.
• As the length of the chain increases, so does the boiling point due to the larger amount of London forces. Branched chains have lower boiling points due to the less contact points, therefore less contact points.
• Complete combustion gives out heat by burning with excess oxygen, alkanes burn completely to make H2O and CO2.
• Incomplete combustion is when there isn't enough oxygen present to fully react with all the fuel, this produces carbon monoxide (CO) and unburnt hydrogen (H).
• Alkanes react with halogens in the presence of UV light, which provides additional energy needed for reaction to take place.
• Free-radical substitution is when a species contains an unpaired electron and is able to donate it to another species.
• The initiation step of free-radical substitution is the production of free radicals by homolytic fission of a covalent bond.
• The propagation step of free-radical substitution is the reaction of a free-radical with a molecule to produce anther free radical.
• The termination step of free-radical substitution is the combination of two free-radicals to form a single molecule.
• Limitations of free-radical substitution are that they are only useful when making haloalkanes as this is the only product. There can also be impurities.
• Further substitution can occur when a free-radical is hit cy another halogen radical creating a multi-substituted haloalkane.