chloroflourocarbons

Chlorofluorocarbons (CFC) are found in cars, refrigerators, and were used as aerosol propellants. Originally CFCs replace NH3 and SO2 because those chemicals were used as a refrigerant but were found to be very toxic and corrosive. But now, CFCs are no longer used because it has been found that they are harmful to the environment. Despite not having CFCs in use today, CFCs are very inert (they don't react), so they could survive in the environment for up to 120 years, which is bad because then they go further out to reach the stratosphere. CFCs represent the major source of anthropogenic halogen in the atmosphere which has bad effects. CFCs work as a cataylst in the stratosphere breaking Ozone into dioxide and monoxide. This is detrimental because the Ultra Violet radiatin that is normally used to break the bonds in Ozone is able to make it the surface. The Montreal Protocal reduced and worked to permanently ban the use of CFCs around the world. CFCs have been replaced by HCFCs, which are better because they are more reactive, but there is still risk of HCFCs potentially contributing to the depletion of the ozone. Another replacement for CFCs has been HFCs, which are more reactive and don't contain chlorine, which is good because chlorine is a main contributed to the breakdown of ozone.

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

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-radiation better than O2 does, 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.

Applications exploit the low toxicity, low reactivity, and low flammability of the CFCs and HCFCs. Every permutation of fluorine, chlorine, and hydrogen based on methane and ethane has been examined and most have been commercialized. Furthermore, many examples are known for higher numbers of carbon as well as related compounds containing bromine. Uses include refrigerants, blowing agents, propellants in medicinal applications, and degreasing solvents.
 * Applications:**

Billions of kilograms of chlorodifluoromethane are produced annually as a precursor to tetrafluoroethylene, the monomer that is converted into Teflon.

The CFC Diagram: