Homologous Series (Cambridge (CIE) IGCSE Co-ordinated Sciences (Double Award)): Revision Note
Homologous series
A homologous series is a family of organic compounds that have similar features and chemical properties due to them having the same functional group
The functional group is a group of atoms which are bonded in a specific arrangement that is responsible for the characteristic reactions of each member of a homologous series
Table of compounds & their functional groups
Examiner Tips and Tricks
Make sure you can identify the functional group for each homologous series.
General characteristic of homologous series
Extended tier only
All members of a homologous series have:
The same general formula
Same functional group
The difference in the molecular formula between one member and the next is CH2
These characteristics are shown below for ethanol and propanol, which belong to homologous series, alcohols
Table of characteristics of ethanol and propanol
| Ethanol | Propanol |
|---|---|---|
Molecular formula | CH3CH2OH | CH3CH2CH2OH |
General formula | CnH2n+1OH | CnH2n+1OH |
Functional group | -OH | -OH |
Boiling point (oC) | 78 | 97 |
Examiner Tips and Tricks
Make sure you learn the general formula for each homologous series.
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