S3.2.3 Homologous series

Definition and Characteristics of Homologous Series
📌 A homologous series is a series of organic compounds within the same family that differ by a common structural unit.
🧪 Members of the same series share the same functional group (e.g., the hydroxyl (-OH) group) and differ sequentially by a $\text{CH}_2$ unit.
✍️ Compounds in a homologous series share the same general formula.

Chemical and Physical Trends
🔥 Members exhibit similar chemical properties; for instance, all alkanes burn in excess oxygen to produce $\text{CO}_2$ and $\text{H}_2\text{O}$.
🌡️ They display a gradation (gradual increase) in physical properties, such as an increasing boiling point as the molecular weight increases within the series.

Key Points & Insights
➡️ A homologous series is defined by a constant difference of a $\text{CH}_2$ unit between successive members.
➡️ A key characteristic is having the same general formula and similar chemical reactions.
➡️ Physical properties, like boiling point, show a gradual trend across the series.

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