Question

What is homologous series? Give examples. What are the characteristics of homologous series?

Answer 1

A series of compounds having the same type of linkage between carbon atoms and differing by a ${\text{CH}}_2$ unit is called a homologous series.
Example: Alkane: ${\text{CH}}_4$ –methane, ${\text{C}}_2{\text{H}}_6$ – ethane, ${\text{C}}_3{\text{H}}_8$–propane.

Characteristics of homologous series-
$\bullet$They have the same general formula for all compounds with the same type of linkage between carbon atoms.
$\bullet$The members have identical chemical properties and physical properties such as melting point, boiling point, etc., show proper gradation with the increase in the molecular mass.
$\bullet$They have a difference of –${\text{CH}}_2$ between two successive members and the difference between their mass is 14 amu.