Question

What is an homologous series? Explain with an example.

Answer 1

A homologous series is a series of compounds with the same general formula, usually varying by a single parameter such as the length of a carbon chain. Compounds within a homologous series typically have a fixed set of functional groups that gives them similar chemical and physical properties.

For example, methane, ethane, propane, butane, etc. are all part of the alkane homologous series. The general formula of this series is $C_n{H}_{2n+2}$.

Methane $C{H}_4$

Ethane $C{H}_{3}C{H}_3$

Propane $C{H}_{3}C{H}_{2}C{H}_3$

Butane $C{H}_3­C{H}_{2}C{H}_{2}C{H}_3$

It can be noticed that there is a difference of $-C{H}_2$ unit between each successive compound.