Dichlorodifluoromethane CCl₂F₂, - This compound, also known as Freon 12, is the primary CFC that has been linked to the greenhouse effect. Even though the compound is found in very small concentrations, its properties make it a significant factor in stratospheric chemistry. CCl₂F₂ absorbs UV light in the upper stratosphere where it arrives decades after being released in the troposphere. CFCs, which were originally created by Dupont corporation, were used as refrigerants for everything from air conditioning to home refrigerators because they are non-toxic and extremely unreactive (in the troposphere). It is this unreactivity that makes them such a problem for the atmosphere, because they are able to last long enough to make it to the stratosphere, where they cause so many problems. CCl₂F₂ production, along with all CFCs, has been banned since the mid 90s, but some scientists believe that the damage has already been done. For further reading see the term Greenhouse Effect.
[Crutzen, Paul and T.E. Graedel. Atmospheric Change. W.H. Freeman and Co. NY, 1993, page 45.] 
Atmospheric Chemistry Glossary