BRAINCAKEFree-Radical Substitution of Alkanes
Alkanes react with chlorine or bromine in ultraviolet (UV) light. A hydrogen atom is replaced by a halogen atom, so the reaction is a substitution. It happens by a free-radical mechanism with three stages.
CH4 + Cl2 → CH3Cl + HCl
1. Initiation
UV light provides the energy to break the Cl-Cl bond by homolytic fission, forming chlorine radicals:
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Key terms in this lesson
- radical
- A species with an unpaired electron, usually very reactive.
- homolytic fission
- The breaking of a covalent bond in which each atom keeps one electron from the shared pair, forming two radicals.
More in Alkanes
- Oxides of Sulfur
- Oxides of Nitrogen
- Catalytic Converters
- Alternative Fuels
- Biofuels
- Biofuels vs Fossil Fuels
- Bond Breaking
- Further Substitution
All 14 lessons in Alkanes · All Edexcel AS-level Chemistry topics