Question

Write any 4 characteristic features of homologous series of an organic compound.

Answer 1

Hint: The functional group present in the homologous series is the same. They must show a gradation in the properties of a respective homologous series. They also have some structural properties.

Complete step by step answer:
To simplify and to systematize the study of organic chemistry, all the organic compounds have been grouped into families called homologous series.
In other words, a family or group of structurally similar compounds all the members of which has the same functional group, show a gradation in physical and similarity in chemical properties. Each member of a homologous series is called homologs and the phenomenon is called homology.
For example, alkane is a homologous series. The first six members of this series are:
\[\text{C}{{\text{H}}_{\text{4}}}\text{(methane) }{{\text{C}}_{\text{2}}}{{\text{H}}_{\text{6}}}\text{(ethane) }{{\text{C}}_{\text{3}}}{{\text{H}}_{\text{8}}}\text{(propane) }{{\text{C}}_{\text{4}}}{{\text{H}}_{\text{10}}}\text{(butane) }{{\text{C}}_{\text{5}}}{{\text{H}}_{\text{12}}}\text{(pentane) }{{\text{C}}_{\text{6}}}{{\text{H}}_{\text{14}}}\text{(hexane)}\]
Some other examples of homologous series are alkenes, alkynes, ketones, aldehydes, esters, etc.
Characteristics of a Homologous series:
1. Each homologous series can be represented by a general formula. For example, is the general formula of carboxylic acids.
2. All the members of a given homologous series have the same functional group in their carbon chain. For example, the functional group of alcohol is –OH.
3. The individual members of a homologous series can be prepared by the general method of preparation.
4. The physical properties such as density, boiling point, the melting point of the members of a homologous series show a regular gradation with a rise in molecular mass.

Note:
The chemical properties of the members of a homologous series similar though the first member may vary considerably from the rest of the members. The successive members of a homologous series differ by a \[C{{H}_{2}}\] group or by 14 mass units.