- A series of compounds with similar chemical properties, in which members differ from one another by the possession of an additional CH2 group, is called a homologous series.
- Each homologous series must have the following four characteristics:
- Every member in the homologous series can be represented by a common formula. For example:
- Alkane: CnH2n+2
- Alkene: CnH2n
- Alcohol: CnH2n+1OH
- Carboxylic acid : CnH2n+1COOH
- Ester: CnH2n+1COOCmH2m+1
- Every member differ from others by the group -CH2- which has the relative mass 14. For example:
- Members of the same homologous series can be prepared through one common method. For examples, All alkenes can be prepared by dehydration of relevant alcohols. Preparing Ethene (Dehydration of ethanol):
- Members of the homologous series have the same chemical properties. For example:All alkenes show addition reaction as added into bromine.
C2H5OH → C2H4 + H2O
Preparing Propene (Dehydration of propanol)
C3H7OH → C3H8 + H2O