CFCs (Chlorofluorocarbons)





Cfcs Chlorofluorocarbons 3554
Photo by: ANK

Chlorofluorocarbons (CFCs), once described as "miracle chemicals," cause the breakdown of the ozone layer that protects the earth from the sun's ultraviolet (UV) radiation. CFCs have no significant natural sources. They were first manufactured in the 1930s, and industries soon found a wide variety of applications for them due to their chemical unreactivity and heat-absorbing properties. CFCs have been used as refrigerants in air conditioners and refrigerators, in aerosol spray cans, in manufacturing foams as industrial solvents , and as cleaning agents in the manufacture of electronics. One U.S. chemical industry gave them the trade name of "Freons," and the term has since become a household word.

Chemically, CFCs are a subset of the more general class of compounds known as halocarbons (carbon- and halogen-containing compounds). CFCs are halocarbons that contain only the elements carbon, chlorine, and fluorine. The most common CFCs are small molecules containing only one or two carbon atoms. For example, a common refrigerant has the chemical formula of CCl 2 F 2 , which in an industry-devised shorthand is noted as CFC-12.

Scientists initially believed that CFCs would be harmless in the earth's atmosphere because of their chemical inertness . This inertness, and their lack of solubility in water, give CFCs a long life span in the atmosphere (tens to hundreds of years, depending on the CFC). In the late 1970s, scientists began to realize that CFCs do break down in the upper atmospheric region known as the stratosphere, where the sun's UV waves are more intense. The UV-induced breakdown releases free, highly reactive chlorine and bromine atoms from the CFCs. Several subsequent chemical reactions are kick-started by this process, including the breakdown of the stratospheric ozone layer.

Chemical structure of CFCs.
Chemical structure of CFCs.
The ozone layer is important to humans and other life on earth because it absorbs harmful UV radiation (acting as a sort of UV "shield") Long-term effects on humans' excessive UV exposure include skin cancer, eye damage (cataracts), and suppression of the immune system.

CFCs are now recognized as harmful chemicals because of their ozone-depleting properties. As a consequence, an international agreement known as the Montréal Protocol was forged in 1987 and later strengthened by amendments to decrease and eventually end the use of these chemicals. CFCs are also potent greenhouse gases and are components of pending international agreements regarding greenhouse gases, the most notable being the Kyoto Protocol (1997).

SEE ALSO G LOBAL W ARMING ; G REENHOUSE G ASES ; M ONTRÉAL P ROTOCOL ; O ZONE .

Bibliography

World Meteorological Organization. (2003). Scientific Assessment of Ozone Depletion: 2002. Global Ozone Research and Monitoring Project, Report No. 47. Geneva: Author.


Internet Resources

National Oceanic and Atmospheric Administration, Climate Monitoring and Diagnostics Laboratory. "Chlorofluorocarbons." Available from http://www.cmdl.noaa.gov/noah/publictn/elkins/cfcs.html .

World Meteorological Organization. "Global Atmosphere Watch." Available from http://www.wmo.ch/web/arep/ozone.html .

Christine A. Ennis



User Contributions:

Natalie
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Aug 24, 2009 @ 5:05 am
This article managed to introduce CFCs in a succinct and relatively simple way; thus easy even for people who are unfamiliar with chemical terms to understand. Good!
Susan
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Sep 4, 2011 @ 4:16 pm
This article managed to introduce CFCs in a succinct and relatively simple way; thus easy even for people who are unfamiliar with chemical terms to understand. Good!

well said :D
Agit
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Sep 6, 2012 @ 12:00 am
October 7th, 2008 at 7:28 pmThe idea that the hole in the ozone layer is man-made is a myth. One must ask themselves this qoisteun: Why is the hole in the southern hemisphere when most of the poluting countries of the world (US/Europe/Russia/China) are in the Northern hemisphere? A very important qoisteun to ask. As a meteorologist, I can tell you that because of the way air flows on our planet that air in the northern hemisphere generally stays there and the same for the south.To understand why the hole is there you need to understand how ozone is created. Ozone is formed naturally in the upper stratosphere by short wavelength ultraviolet radiation. Wavelengths less than ~240 nanometers are absorbed by oxygen molecules (O2), which dissociate to give O atoms. The O atoms combine with other oxygen molecules to make ozone. The bottom line is that you need sunlight to create ozone. Mild levels of ozone are found at the earths surface in city streets all across the world especially toward the end of the day. About an hour after the sun sets the ozone at the surface is gone.Alright, now that you got that you need to ask yourself what the two poles don't have 6 months out of the year since the earth is tilted 23 1/2 degrees. Answer: Sunlight.The reason why a hole develops over the south pole is because there is no sunlight there during its winter. During the summer time the hole gets much smaller.So why isn't there a hole in the northern hemisphere if it gets dark there too? Good qoisteun. The main reason is because of the northern jet stream. The northern jet stream moves in a more North to South flow which is caused by all of the land masses the northern hemisphere has. Our jet stream dips deep down toward the equator at some points where there is a lot of ozone (because there is a lot of sunlight). It then transports that ozone into the north preventing it from developing a hole.The southern jet stream moves in a basic East to West direction since there is little land masses in the south to affect it. Because of this, the southern pole does not get the boost of ozone from the equator like the north does.I hope that this explanation helps some of you out there. We did not see a hole in the ozone develop. We discovered that a hole was there. I can assure you that man did not create it. Saying man is responsible for this hole would be like the first explorers to discover the Grand Canyon coming to the conclusion that it must have been something man did. The only other reason I can think of for this myth being perpetuated is that politicians like to use it to incite the public. Please feel free to look up these scientific claims for yourself.

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