Characteristics of a homologous series
The compounds of the homologous series have some characteristics—they are as follows:
- General formula: All the members of a series can be represented by same general formula.
- Same functional group: All members of a series contain the same functional group i. e. alcohol has -OH group and amine has -NH2 group etc.
- Difference in molecular mass of two consecutive members of the series is 14 unit i.e. CH2.
- Preparative method: All the members of the series can be prepared by common methods — only in special cases different methods may be used.
- Identical chemical properties: Similar types of chemical properties are observed due to same functional group. However with increasing molar mass the chemical reactivity decreases to some extent.
- Regular order in physical property: With increase in molar mass there is a gradual change in physical properties. For example boiling and melting temperatures increase with molar mass-increment but solubility decreases.