±«Óătv

Alkanes

The alkanes are a of . This means that they have similar chemical properties to each other and they have trends in physical properties. For example, as the chain length increases, their boiling point increases.

The alkanes share the same general formula.

CnH2n+2

The general formula means that the number of hydrogen in an alkane is double the number of carbon atoms, plus two. For example, methane is CH4 and ethane is C2H6.

Alkane can be represented by displayed formulae in which each atom is shown as its symbol (C or H) and the between them by a straight line.

Here are the names and structures of five alkanes:

Table containing the molecular formula and structural formula of methane, ethane, propane, butane and pentane.

Alkanes are saturated hydrocarbons. This means that their carbon atoms are joined to each other by single bonds. This makes them relatively unreactive, apart from their reaction with oxygen in the air – which we call burning or combustion.

[Higher tier only]

Like other homologous series, the alkanes show isomerism. This means that their atoms can be arranged differently to make slightly different with different properties. For example, an of butane is methylpropane.

Structural formula of butane and methylpropane.