What is the primary property of compounds within a homologous series?

Compounds in a homologous series are characterized by having similar chemical properties due to their identical functional groups and structural similarities. A homologous series consists of a group of organic compounds that share a common formula and have a gradual change in physical properties as the molecular size increases, but their chemical behavior remains consistently similar.

For example, in a series of alkanes, each member differs by a -CH2- unit, and while their physical properties like boiling points and densities vary, they all undergo similar types of chemical reactions, such as combustion and substitution reactions. This consistency across the members of a homologous series is what makes the concept significant in organic chemistry, where understanding the reactivity of compounds allows for predictions about their behavior in reactions.