Functional Groups & their Formulae (Cambridge International A-Level Chemistry)

Functional Groups of Organic Compounds

• 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

Formulae of Organic Compounds

• 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 Draw the skeletal formula of the following molecules:

1. CH₃(CH₂)₃OH
2. (CH₃)₂CHCH₂OH
3. CH₃CH₂OCH₂CH₃

Answer:

Worked Example Draw the fully displayed formula of the following molecules:

Answer: