Functional Groups and their Formulae (CIE AS Chemistry)

• Functional groups determine the physical and chemical properties of molecules
• The table below shows a summary of common functional groups found in compounds
• R is any other atom or group of atoms (except for hydrogen)

Functional groups found in compounds table

• The general formula is a formula that represents a homologous series of compounds using letters and numbers
  • Eg. the general formula of alkanes is C_nH_2n+2
  • A homologous series is a group of organic compounds that have the same functional group, the same general formula and the same chemical properties

• The structural formula is a formula that shows how the atoms are bonded to each carbon atom in a molecule
• The displayed formula is a 2D representation of an organic molecule showing all its atoms (by their symbols) and their bonds (by single, double or triple bonds)
• The skeletal formula is a simplified displayed formula with all the carbon and hydrogen (C-H) bonds removed

Overview of the formulae of organic compounds table

Worked example: Drawing skeletal formulae of molecules

Worked example: Drawing displayed formulae of molecules