2 John 1:12

1,1,2-Trichloro-1,2,2-trifluoroethane

Trichlorotrifluoroethane, also called 1,1,2-Trichloro-1,2,2-trifluoroethane or CFC-113 is a chlorofluorocarbon. It has the formula Cl2FC-CClF2.

CFC-113 is a very unreactive chlorofluorocarbon, that will stay in the atmosphere for a great deal of time if it is released. CFC-113 will stay in the atmosphere long enough that it will cycle out of the troposphere and into the stratosphere. In the stratosphere, CFC-113 can be broken up by ultraviolet radiation, creating chlorine radicals, which can in turn react with ozone molecules to form molecular oxygen (O2), leading to the overall depletion of stratospheric ozone. The amount of CFC-113 in the atmosphere has stayed relatively stable, at about 80 parts per trillion, since the early 1990s.

History

CFC-113 was originally used as a coolant in air conditioners and refrigerators because of its low boiling point and relative inertness. CFC-113 was also formerly used as a solvent with which to clean electronics, especially phones. It is estimated that in 1988, 360 million pounds of CFC-113 were being used, accounting for 17% of the total amount of chlorofluorocarbons produced globally. The Montreal Protocol in 1987 called for the phase out of all CFC’s, including CFC-113 by 2010.

Chemistry

CFC-113 has two constitutional isomers: 1,1,1-trichlorotrifluoroethane and 1,1,2-trichlorofluoroethane. Both have a two-carbon backbone. The first isomer has all three chlorines attached to one carbon, and all three fluorines attached to the other. 1,1,2-trichlorotrifluoroethane has two chlorines and one fluorine attached to one carbon, and one chlorine and two fluorines bonded to the other carbon. The molecular weight of CFC-113 is 187.375 g/mol. The mean residence time of CFC-113 is approximately 90 years. This long mean residence time means that it will stay in the atmosphere long enough that it will make its way into the stratosphere and can begin to deplete the stratospheric ozone.

Uses

CFC-113 was one of the many forms of CFCs that were made to eliminate toxic and flammable substances in the areas that they were used. It has been used as a cooling agent in refrigerants and air conditioners, aerosol propellant, and a cleansing agent for electrical and electronic components. CFC-113 is one of the three most popular CFCs, along with CFC-11 and CFC-12 and saw much use in its time. CFC-113 has a unique property that makes it perfect for cooling systems. When it is in a gas form and compressed, it heats up, when it is expanded, it cools. This makes them ideal for the vapor compression cycle systems. They were also very desirable because of their low toxicity, non-flammability, thermophysical properties, and normal boiling point. CFC-113 also has a flexible form so it was used in the production of plastics, packaging material, insulation, foams for cushioning, and things like the soles of your shoes. CFC-113 has such a low flammability and low toxicity that it was also used as a cleaner for delicate electrical equipment, fabrics, and even metals. Because it would not warm the product it was cleaning, catch fire with a spark or react to and other chemicals it was ideal for this purpose. CFC-113 in laboratory analytics has been replaced by other solvents.

Environmental effects

Ozone destruction

CFC-113 has a great negative affect on the environment because of how well it breaks down the ozone in the stratosphere. It has a long lifetime of about 90 years so it has time to make its way into the stratosphere and when up there it gets broken down by the UV radiation that is up there. Most CFCs accumulate at about 25km in altitude. They photodissociate by many different short wavelength solar radiation in the range of 190-225 nm. These wavelengths usually do not break through the stratosphere because of ozone. CFC-113 can only be photochemically broken down by this radation by the following example:

CCl2F2 + UV (<220nm) => Cl + CClF2
This reaction releases Chlorine (Cl) which is the main decomposer of the ozone. This is harmful to the earth because 90% of the earth’s ozone [Molina, Mario J. Role of chlorine in the stratospheric chemistry. Pure and Applied chemistry. 1996.] is in the stratosphere and now can potentially be broken up by the presence of Chlorine through this cycle:
Cl + O3 => ClO + 02
This will occur in only half a second and is then followed by:
ClO + O => Cl + O2
which is only a few minute process. But the end reaction shows how Cl destroys the ozone and is then liberated, from the O that it was carrying. This is called a free radical chain meaning it can go on and on to keep breaking down more O3. This whole process continues for the atmospheric lifetime of Cl, about one to two years. In this lifetime it can destroy 100,000 ozone molecules. This ozone depletion is harmful because without ozone humans can become blind or acquire skin cancer due to the new penetrating UV light that is no longer being stopped by the ozone.

References

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