Freon
Freon is a trademark belonging to the E. I. du Pont company for a series of chlorofluorocarbons (CFCs). CFCs are organic compounds composed primarily of chlorine, fluorine, carbon, and hydrogen. These compounds are chemically stable, nontoxic, and nonflammable. Due to their high density, low boiling point, and low viscosity they are especially useful for use as refrigerants, aerosol propellants, solvents, and expansion agents in polyurethane foams. Since the 1970s, CFC use has declined due to concerns about their effects on the ozone layer.
The compounds that would become known as Freon were discovered in the 1930s by researchers for General Motors led by Thomas Midgley, Jr. They discovered that chlorine and fluorine atoms could be positioned along a hydrocarbon backbone to form molecules that functioned as efficient refrigerants. The first material they made was dichlorodifluoromethane, a compound that contains one carbon, two chlorine, and two fluorine atoms. This material is now referred to as Freon F-12. Other similar compounds followed shortly thereafter, including trichlorofluoromethane, dichlorotetrafluoroethane,and chlorodifluoromethane. These chemicals were given Freon names based on their structure and molecular weight. Freon molecules based on methane(CH3) are designated with numbers below 100; those based on ethane (C2H5) are given numbers between 100 and 200. Freon F-11 and F-12 are the most common.
The number of applications for Freon compounds grew tremendously between the 1930s and the 1960s. Increased production of these CFCs allowed widespread manufacture of refrigerators and air conditioners. Other applications for CFCs were discovered as well, for example, they are used as blowing agents in polystyrene foam.
In 1972, two scientists from the University of California, F. Sherwood Rowland and Mario Jose Molino, found that certain Freon materials could persist in the atmosphere long enough to reach the stratosphere where they could be broken down by ultraviolet radiation. When this occurs the CFCs release chlorine which can affect ozone production in the upper atmosphere. This discovery set the stage for fervent public contention regarding the continued use of CFCs. By the mid-1970s, the United States government banned the CFCs as aerosol propellants but it resisted a total ban for all industries. Instead, countries and industries began negotiating the process of phasing out CFCs. As CFC use is allowed in fewer and fewer applications, a black market has been growing for the chemical. In 1997, the Environmental Protection Agency, Customs Service, State Dept., Justice Dept., IRS and the FBI initiated enforcement actions to prevent (CFC) smuggling in the US.
Many CFCs have been replaced with related materials known as hydrochlorofluorocarbons (HCFCs) which reportedly do not interfere with the ozone layer. These are used principally in large air conditioning installations and while they are believed to be less damaging than CFCs, they are are not free from controversy. A 1997 Belgian health officials report indicate hydrochlorofluorocarbon-123 may be responsible for a rise in acute hepatitis among workers of a smelting plant. Liver damage found in nine workers is believed to be caused by a leaking refrigerant pipe in the workers' cabin. However, the U.S. Environmental Protection Agency, disputes these findings.
Meanwhile, the search for the perfect Freon replacement continues. In Europe scientists have had some success with butane mixtures as refrigerants in some European refrigerator models, but the explosive nature of the gas could create a dangerous situation if used in the frost-free models popular in the U.S.
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