Homologous Series

A homologous series is a family of organic compounds with the same functional group and the same general formula.Each member differs from the next by a CH₂ group. For example, the alkanes methane CH₄, ethane C₂H₆ and propane C₃H₈ all fit the general formula C_nH_2n+2.Members of a homologous series have similar chemical properties because they have the same functional group.They show a gradual trend in physical properties. For example, boiling point increases as the chain gets longer, because the larger molecules have stronger van der Waals forces between them.Other examples are the alkenes (C_nH_2n) and the alcohols (C_nH_2n+1OH).