Why were CFCs banned for damaging the ozone layer?
Chlorofluorocarbons are so unreactive they drift up to the stratosphere intact.
Chlorofluorocarbons are so unreactive they drift up to the stratosphere intact. There, UV light breaks a C–Cl bond and releases chlorine free radicals. Each Cl radical then destroys ozone (O₃) in a chain reaction and is regenerated, so one chlorine atom can wreck thousands of ozone molecules. That catalytic destruction thinned the ozone layer, leading to the global CFC ban.
Key point
UV frees Cl radicals from CFCs, which catalytically destroy ozone in a chain reaction.
Common mistake
thinking CFCs react with ozone directly at ground level.
Memory tip
one Cl radical wrecks many O₃ molecules — catalytic chain damage.
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