Freons

Freons are organic compounds of chlorine and fluorine -- chlorofluorocarbons, or CFCs -- and are commonly used as refrigerants. The most common representative is dichlorodifluoromethane (Freon-12); others in everyday use include chlorodifluoromethane (R-22, also mentioned in section 10.7.2 as a product made from chloroform) and trichlorofluoromethane (R-11), among others. Freons are used as refrigerants in refrigerators and air-conditioning systems, as propellants in aerosol products, and as solvents; they are also used as blowing agents in making foams and packing materials. Despite this wide range of everyday uses, chlorofluorocarbons are responsible for depleting the ozone layer in the stratosphere: when ultraviolet radiation strikes a CFC molecule such as CFCl3, the carbon-chlorine bond breaks to release a highly reactive chlorine atom, which then reacts with an ozone molecule (O3) to regenerate itself while destroying the ozone -- a catalytic chain reaction in which a single chlorine atom can go on to destroy up to 100,000 ozone molecules before it is finally …