First two members of homologous series having functional group - Cl are :-
1. CH₃Cl - Chloromethane
2. C₂H₅Cl - Chloroethane
These series have a difference of -CH₂- unit
In organic chemistry, a homologous series is a series of compounds with the same general formula usually varying by a single parameter.This can be the length of a carbon atom.The homologous series of straight-chained alkanes begins methane (CH4), ethane(C2H6), propane(C3H8), butane (C4H10).