What type of compounds does a homologous series include?

A homologous series is characterized by a group of compounds that share a common functional group, ensuring they exhibit similar chemical properties. The members of a homologous series have a gradual change in physical properties, such as boiling points or solubility, due to the variation in their carbon chain length.

While some homologous series can include saturated compounds, unsaturated compounds, or even both, the defining feature is the consistent functional group shared among all its members. For instance, alcohols (like ethanol and propanol) all possess the hydroxyl (-OH) group, while alkenes have the carbon-carbon double bond functional group.

This understanding of the structure and properties of compounds in a homologous series underlines the importance of recognizing the role of the functional group in determining chemical behavior, rather than focusing solely on whether they are saturated or part of a specific subclass like aromatic compounds.