Freon

Freon [trade name], any one of a special class of chemical compounds that are used as refrigerants, aerosol propellants, and solvents. These compounds are haloalkanes, i.e., halogen derivatives of saturated hydrocarbons (see alkane). Every Freon contains at least some fluorine in its molecule, and most contain chlorine or bromine as well. Freons are generally colorless, odorless, nontoxic, noncorrosive, nonflammable, and chemically unreactive. The most commonly used is Freon-12, or dichlorodifluoromethane (CCl₂F₂), which boils at -29.8°C; and is thus a gas at ordinary temperatures and pressures. It is prepared by the reaction of carbon tetrachloride with hydrogen fluoride in the presence of a catalyst. There are a number of other Freons. Some of those containing bromine in their molecules are used in fire extinguishers. See also chlorofluorocarbons.

Trademark for any of several organic compounds containing fluorine (fluorocarbons) and sometimes chlorine (chlorofluorocarbons, or CFCs). Nonflammable, nontoxic, and noncorrosive, they have low boiling points, which makes them useful as refrigerants. By the mid-1970s they were in wide use in refrigeration and air conditioning systems, as blowing agents for plastic foams, as fire-extinguishing agents, and in aerosol sprays. Evidence has accumulated that decomposition of CFCs in the stratosphere destroys ozone there (see ozone layer), so most of their uses have been banned. International agreements signed by most of the industrialized countries have called for the phasing out of CFC use.

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Freon is DuPont's trade name for its odorless, colorless, nonflammable, and noncorrosive chlorofluorocarbon and hydrochlorofluorocarbon refrigerants, which are used in air conditioning and refrigeration systems.

History

Freon was initially developed in the early 20th century as an alternative to the toxic gases that were previously used as refrigerants, such as ammonia, chloromethane, and sulfur dioxide. Freon, in this case dichlorodifluoromethane, was invented by Thomas Midgley, Jr. with co-inventor Charles Kettering. Each Freon product is designated by a number; for instance, Freon-11 is trichlorofluoromethane, while Freon-12 is dichlorodifluoromethane.

Controversy

In the 1990s, most uses of Freon chlorofluorocarbons (CFCs) were phased out due to the negative effects that CFCs have on the Earth's ozone layer. DuPont began to phase out its production of Freon CFCs in the 1980s after federal regulatory agencies banned their use. The interim replacements for CFCs are hydrochlorofluorocarbons (HCFCs), which contain chlorine that depletes stratospheric ozone, but to a much lesser extent than CFCs. Ultimately, hydrofluorocarbons (HFCs) will replace HCFCs with essentially no ozone destruction, yet they are classed as greenhouse gases. DuPont began producing hydrofluorocarbons as alternatives to Freon in the 1980s. These included Suva refrigerants and Dymel propellants. Any of these gases that are used as refrigerants are designated by an "R-" number and colloquially known as "Freon", whether they are made by DuPont or another supplier.

Footnotes

See also

• Haloalkane, a group of chemical compounds
• List of refrigerants