Hydrocarbons: open-chain alkanes

• Have the general formula CnH2n+2
• Name ends in -ane
• Are saturated - all the bonds between carbon atoms are single bonds
• Are aliphatic - they have no ring structures

• Choose the longest carbon chain and name it
• Use prefixes in alphabetical order for any alkyl side chains
• Use di, tri and tetra before the prefix if the side chains are identical
• Show the position of any side chains by using numbers which are as low as possible, e.g. 2-methylbutane rather than 3-methylbutane
• Put a comma between numbers and a hyphen between a number and a letter, e.g. 2,2-dimethylhexane

The prefixes used in the alkanes are also used in naming other organic chemical compounds, so it is important for them to be learnt.

• Methane - CH4
• Ethane - C2H6
• Propane - C3H8
• Butane - C4H10
• Pentane - C5H12
• Hexane - C6H14
• Heptane - C7H16
• Octane - C8H18
• Nonane - C9H20
• Decane - C10H22

• Alkanes react completely with oxygen to produce carbon dioxide and water. This is called complete combustion.

C3H8 + 5O2  ->  3CO2 +4H2O

• Alkanes also undergo radical substitution reactions. (This is covered in Chemical Ideas 6.3 and Chemical Storylines A4)