An alkane can get fluorinated/chlorinated/brominated by Free Radical Substitution.
Initiation: Break apart the Cl2 with UV light to make free radicals
Propagation: The Cl radical rips an H from the alkane, leaving it as an alkyl free radical. Then the alkyl free radical steals a Cl from another Cl2 molecule, leaving a Cl radical again, and this makes Cl radical a catalyst.
Termination: Two radicals combine to form a non-radical.
11 июл 2024