What is a homologous series? Explain with examples.

A homologous series is a series of carbon compounds in which the consecutive compounds differ by a formula of − CH 2 or an atomic mass of 14 amu. The compounds of a particular series have the same functional group which leads to identical chemical properties. But, as the compounds have different masses, a slight gradation in physical properties is observed. For example, methane, ethane, propane, butane, etc., are all members of the alkane homologous series. The general formula of the alkane series is C n H 2 n + 2 . So, the formula for methane is CH 4 , ethane is CH 3 CH 3 and propane is CH 3 CH 2 CH 3 . They differ by a − CH 2 unit. The chemical properties of these compounds are similar.