CIE IGCSE Chemistry

Revision Notes

14.1.3 Homologous Series

Homologous Series

  • This is a series or family of organic compounds that have similar features and chemical properties due to them having the same functional group
  • All members of a homologous series have:
    • The same general formula
    • Same functional group
    • Similar chemical properties
    • Gradation in their physical properties
    • The difference in the molecular formula between one member and the next is CH2
Extended Only

Characteristics, Formula & Structural Isomerism

Functional group

  • This 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

Names and structures of the functional groups

Names and structures of the functional groups table, IGCSE & GCSE Chemistry revision notes


Structural isomers

  • Compounds that have the same molecular formula but different structural formulae
  • This is due to the different arrangement of their atoms in space
  • There are two types: chain and position
  • In chain isomerism the structure of the carbon chain differs
  • In position isomerism, the position of the functional group differs

Example of chain isomerism

Example of chain isomerism table, IGCSE & GCSE Chemistry revision notes


Example of position isomerism

Position isomers - propanol, IGCSE & GCSE Chemistry revision notesPosition isomers of propanol: 1-propanol or propan-1-ol on the left and propan-2-ol on the right

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