Question

Write a note on homologous series

Answer 1

Homologous series is a series of similarly constituted compounds in which the members possess the same functional group and have similar characteristics.The various members of the particular homologous series are called homologues.

Characteristics of homologous series:-

1.All the members can be represented by same general formula.

2.Any 2 consecutive members differ in their formula by a commom difference of -CH2.

3.Different members have common functional group.

4.Members of any particular family have almost identical chemical properties.Their physical properties show gradual gradation with increase in the molecular mass.

5.Members differ by molecular mass of 14.

6.The members can be prepared almost by the identical methods known as general methods of preparation.

For example:-

Homologous series of alkanes:-

Molecular General Name Differ by 

Formula Formula 

1. CH4 CnH2n+2 Methane 

2.C2H6 CnH2n+2 Ethane -CH2

3.C3H8 CnH2n+2 Propane -CH2

4.C4H10 CnH2n+2 Butane -CH2