Halogens & Alkanes (Edexcel IGCSE Chemistry)

• In a substitution reaction, one atom is swapped with another atom
• Alkanes undergo a substitution reaction with halogens in the presence of ultraviolet radiation

In the presence of ultraviolet (UV) radiation, methane reacts with bromine in a substitution reaction

•  The equation for the reaction is

CH₄ + Br₂ → CH₃Br + HBr

methane + bromine → bromomethane + hydrogen bromide

• Chlorine will also react with alkanes to form chloromethane

CH₄ + Cl₂ → CH₃Cl + HCl

methane + chlorine → chloromethane + hydrogen chloride

• The products belong to a family called halogenoalkanes or haloalkanes
• Halogenoalkanes have many uses a solvents, refrigerants, propellants and pharmaceuticals