. What is meant by homologous series of organic compounds
Write the chemical formulae of two members of a homologous series and state which part determines the (i) physical properties, (ii) chemical properties, of these compounds
Ans. A homologous series is a group of organic compounds having similar structures and
similar chemical properties in which the successive compounds differ by CH2 group. Example: The general formula of the homologous series of alkenes is CnH2n+2 where n is the number of carbon atoms.
1st member is CH4,
2nd member is C2H6
(1) The members of a homologous series show a gradual change in their physical properties with increase in molecular mass, e.g., as the number of carbon atoms increases, the melting points, boiling points and densities of its members increase gradually.
(ii) All the compounds of homologous series show similar chemical properties because the basic structure of all the members of a homologous series is similar.