The functional group present in the following molecules are encircled.
Common functional groups and their families of compound
A homologous series is a family of organic compounds containing a particular characteristic group and exhibiting similar properties. For example, the compounds given below belong to the alcohol family.
CH3OH methyl alcohol (methanol)CH3CH2CH2OH propyl alcohol (1-propanol)
CH3CH2.CH2.CH2OH butyl alcohol (1-butanol)
Characteristics of a Homologous Series
All members of a homologous series exhibit some common characteristics. They are:
- All the members of a homologous series can be represented by a common general formula, as they have the same functional group. For example, alkanes can be represented by the formula CnH2n+2.
CH4 C2H5 C3H8 C4H10Methane Ethane Propane Butane
- Each member of a homologous series has a common difference of -CH2 from the next higher or lower member.
- Common general methods of preparation exist for all members of the series.
- All members exhibit similar chemical behavior.
- An increase in molecular mass of members within a homologous series show a similar regular gradation of the physical properties, such as, physical state, melting and boiling points etc.