Organic Reactions

Organic Reactions

Addition Reactions

  • Addition reactions occur when two reactants combine to form a single product. Often involves breaking of double or triple bonds in the reactants.
  • Examine the addition reaction between a halogen and an alkene. For example, the reaction between ethene and bromine forms 1,2-dibromoethane.
  • Note the electrophilic addition reaction where an electrophile reacts with the alkene to form an intermediate, followed by reaction with a nucleophile.
  • Examine the colour change in these reactions for possible colour by design applications: bromine water goes from orange to colourless when it reacts with an alkene.

Substitution Reactions

  • Substitution reactions involve replacement of an atom or a group of atoms by another atom or group of atoms in a molecule.
  • Examine the substitution of a hydrogen atom in a saturated hydrocarbon by a halogen atom. For example, the reaction between methane and chlorine under ultraviolet light to form chloromethane.
  • Consider the nucleophilic substitution reactions where an electron rich nucleophile replaces a leaving group.
  • The influence of different substituents on the colour of compounds should be examined.

Elimination Reactions

  • Elimination reactions involve the loss of atoms or groups of atoms from the reactant to form a double or triple bond in the product.
  • Examine the elimination of water (a dehydration reaction) from alcohols in the presence of an acid catalyst. For instance, the reaction of ethanol with sulfuric acid at 180°C forms ethene.
  • Note that elimination reactions are the reverse of addition reactions.
  • Understand how the creation or removal of double bonds can influence the colour of compounds in ways that could be used for design purposes.


  • Polymerisation is a process of reacting monomer molecules together to form polymer chains or three-dimensional networks.
  • Observe how some organic molecules, like ethene, can undergo addition polymerisation to form polyethene.
  • Appreciate the importance of polymers in the creation of colourful compounds and materials.

Oxidation Reactions

  • Oxidation reactions involve the loss of electrons from a substance or the addition of oxygen to it.
  • Both alcohols and aldehydes can be oxidised. For example, primary alcohols can be oxidised to aldehydes and then to carboxylic acids.
  • Recognise how the oxidation state of a molecule can affect its colour.
  • An understanding of how colourful oxidation reactions can be used in design, for instance in pigments or dyes, can also be beneficial.