Chlorofluorocarbons
Definition and meaning of Chlorofluorocarbons in chemistry.
Chlorofluorocarbons (CFCs) are a class of synthetic organic compounds made up entirely of carbon, chlorine, and fluorine atoms, once widely used as refrigerants, aerosol propellants, and industrial solvents.
In more detail
CFCs are chemically stable, nonflammable, and non-toxic in the lower atmosphere, which made them ideal industrial chemicals for decades. In the stratosphere, however, ultraviolet radiation breaks their carbon-chlorine bonds, releasing chlorine radicals that catalytically destroy ozone (O3) molecules in a repeating chain reaction, since one chlorine atom can destroy thousands of ozone molecules before it is removed. This process drives the seasonal Antarctic ozone hole, and it led to the 1987 Montreal Protocol, which phased out CFC production worldwide in favor of less ozone-damaging substitutes.
Key facts
| Formula (example) | CCl3F (CFC-11), CCl2F2 (CFC-12) |
|---|---|
| Field | Organic Chemistry |
| Key mechanism | UV photolysis releases Cl radicals that destroy stratospheric ozone |
| Regulation | Phased out globally under the Montreal Protocol (1987) |
CFC-11 (trichlorofluoromethane, CCl3F) was a common refrigerant and foam-blowing agent before international bans took effect.
Frequently asked questions
Why are CFCs harmful to the ozone layer?
UV light in the stratosphere breaks the carbon-chlorine bond, releasing a chlorine radical. This radical reacts with ozone (O3) to form ClO and O2, and the resulting ClO can regenerate the chlorine radical, allowing a single chlorine atom to destroy thousands of ozone molecules in a catalytic chain reaction.
What replaced CFCs?
Hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) were adopted as transitional and long-term substitutes because they have little or no chlorine to reach the stratosphere intact, though HFCs are now being phased down for their high global warming potential.