Halogens & Alkanes (Edexcel IGCSE Chemistry)
Revision Note
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Chemistry Lead
Halogens & Alkanes
- 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
Exam Tip
CFC stands for chlorofluorocarbon, an important class of halogenoalkanes, previously used in fridges and air conditioners, but gradually being phased out because of the damage they cause to the ozone layer.
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