Chloroflourocarbons


Chloroflourocarbons were discovered in the 1920\'s by Thomas Midgley, an
organic chemist at General Motors Corporation. He was looking for inert, non-
toxic, non-flammable compounds with low boiling points that could be used as
refrigerants. He found what he was looking for in the form of two compounds:
dichlorodifluoromethane (CFC-12) and trichloromonoflouromethane (CFC-11). In
both compounds, different amounts of chlorine and fluorine are combined with
methane, which is a combination of carbon and hydrogen. These two CFCs were
eventually manufactured by E.I. du Pont de Nemours and company, and, under the
trade name “freon,” constituted 15% of the market for refrigerator gases.
CFCs were the perfect answer for cooling refrigerators and air
conditioners. They were easily turned into liquid at room temperature with
application of just a small amount of pressure, and they could easily then be
turned back into gas. CFCs were completely inert and not poisonous to humans.
They became ideal solvents for industrial solutions and hospital sterilants.
Another use found for them was to blow liquid plastic into various kinds of
foams.
In the 1930\'s, household insecticides were bulky and hard to use, so CFCs
were created because they could be kept in liquid form and in an only slightly
pressurized can. Thus, in 1947, the spray can was born, selling millions of
cans each year. Insecticides were only the first application for CFC spray cans.
They soon employed a number of products from deodorant to hair spray. In 1954,
188 million cans were sold in the U.S. alone, and four years later, the number
jumped to 500 million. CFC filled cans were so popular that, by 1968, 2.3
billion spray cans were sold in America.
The hopes of a seemingly perfect refrigerant were diminished in the late
1960\'s when scientists studied the decomposition of CFCs in the atmosphere.
What they found was startling. Chlorine atoms are released as the CFCs
decompose, thus destroying the Ozone (O3) atoms in the high stratosphere. It
became clear that human usage of CF2Cl2 and CFCl3, and similar chemicals were
causing a negative impact on the chemistry of the high altitude air.
When CFCs and other ozone-degrading chemicals are emitted, they mix with
the atmosphere and eventually rise to the stratosphere. CFCs themselves do not
actually effect the ozone, but their decay products do. After they photolyzed,
the chlorine eventually ends up as “reservoir species” - they do not themselves
react with ozone- such as Hydrogen Chloride, HCL, or Chlorine Nitrate, ClONO2.
These than further decompose into ozone hurting substances. The simplest is as
follows: (How do CFCs Destroy the Ozone) Cl + O3 -----> ClO + O2 ClO + O
------> Cl + O2 O3 + O -------> 2 O2
The depletion of the ozone layer leads to higher levels of ultraviolet
radiation reaching Earth\'s surface. Therefore, this can lead to a greater
number of cases of skin cancer, cataracts, and impaired immune systems, and is
expected to reduce crop yields, diminish the productivity of the oceans, and
possibly contribute to the decline of amphibious populations that is occurring
in the world. Besides CFCs, carbon tetrachloride methyl bromide, methyl
chloroform, and halons also destroy the ozone.
In 1985, the degradation of the ozone layer was confirmed when a large hole
in the layer over Antarctica was reported. The hole\'s existence is due to
industrial chemicals which were manufactured there. During September/October of
1985, up to 60 percent of the ozone had been destroyed. Since then, smaller yet
significant stratospheric decreases have been seen over more populated regions
of the Earth.
Worldwide monitoring has shown that stratospheric ozone has been
decreasing for more than 20 years. The average loss across the globe totaled
about five percent since the mid-1960\'s with cumulative losses of about ten
percent in the winter and spring. A five percent loss occurs in the summer and
autumn over North America, Europe, and Australia.
The world has been forced to address this issue. Thus, the major powers
of the world created a global treaty, the Vienna Convention for the Protection
of the Ozone Layer. The agreement was put into affect in 1988 and the
subsequent Montreal Protocol on Substances that Deplete the Ozone layer went
into effect in 1989. To date, 140 countries are acknowledging the Montreal
Treaty. The countries decided on a timetable for countries to reduce and to end
their production and consumption of eight major halocarbons. The timetable was
accelerated in 1990 and 1992. Various amendments were adopted in response to
scientific evidence that stratospheric ozone is depleting at a much faster rate
than was predicted.
On the home front, the U.S. Environmental Protection Agency (EPA), under
authority of the