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 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 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 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.