CFC

CFC

A chlorofluorocarbon (CFC) is an organic compound that contains only carbon, chlorine, hydrogen and fluorine, produced as a volatile derivative of methane and ethane. They are also commonly known by the DuPont brand name Freon. The most common representative is dichlorodifluoromethane (R-12 or Freon-12). Many CFCs have been widely used as refrigerants, propellants (in aerosol applications), and solvents. The manufacture of such compounds has been phased out (and replaced with products such as R-410A) by the Montreal Protocol because they contribute to ozone depletion in the upper atmosphere.

Reactions

The most important reaction of the CFCs is the photo-induced scission of a C-Cl bond:

CCl₃F → CCl₂F^. + Cl^.

The chlorine atom, written often as Cl^., behaves very differently from the chlorine molecule (Cl₂). The radical Cl^. is long-lived in the upper atmosphere, where it catalyzes the conversion of ozone into O₂. Ozone absorbs UV-B radiation, so its depletion allows more of this high energy radiation to reach the Earth's surface. Bromine atoms are even more efficient catalysts, hence brominated CFCs are also regulated.