In the chemistry world, many organic compounds exist. They are further divided into sets or groups having the same general formula and related structures and properties.
Such a group of organic compound is called a homologous series.
Compounds in each set have the same little group of atoms called the functional group
Definition: A homologous series is a family of organic compounds with similar chemical properties.
Charateristics of Homologous Series
1. Members have the same general formula ( e.g. CnH2n + 2 for alkanes). Each member of the series differs from the next by a – CH2 – unit
2. Members have similar structures. They have the same functional group (e.g. Alcohol has hydroxyl functional group (-OH))
3. Members of the series can be prepared by using the same method
4. All members have the similar chemical properties due to same functional group but varying in reactivity
5. Physical properties vary gradually along the series. Melting and boiling points increase gradually as the number of carbon atoms in the molecle increases. Also, the viscosity increases as relative molecular mass and size increases.
Hydrocarbon: Alkane & Alkene 