Chlorofluorocarbon - Wikipedia, The Free Encyclopedia

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ChlorofluorocarbonFrom Wikipedia, the free encyclopedia

A chlorofluorocarbon (CFC) is an organic compound that contains only carbon, chlorine, and fluorine,

produced as a volatile derivative of methane and ethane. They are also commonly known by the DuPont brand

name Freon. The most common representative is dichlorodifluoromethane (R-12 or Freon-12). Many CFCs

have been widely used as refrigerants, propellants (in aerosol applications), and solvents. The manufacture of

such compounds hasbeen phased out (and replaced with products such as R-410A) by the Montreal Protocol

because they contribute to ozone depletion in the upper atmosphere.

Contents

1 Structure, properties and production

2 Reactions

3 Applications4 Classes of compounds, nomenclature

4.1 Commercial names

4.2 Numbering system

5 History

5.1 Commercial development and use of CFCs and related compounds

5.2 Regulation

5.2.1 Regulatory gap

5.2.2 Regulation and DuPont

5.3 Phase out of CFCs

5.4 Development of alternatives for CFCs

6 Environmental impacts

7 Tracer of ocean circulation

7.1 CFC and SF6 Tracer-Derived Age of Ocean Water

7.1.1 Partial pressure and ratio dating techniques

8 Safety

9 References

10 External links

Structure, properties and production

Main article: Organofluorine chemistry

As in simpler alkanes, carbon in the CFCs and the HCFCs is tetrahedral. Since the fluorine and chlorine atoms

differ greatly in size from hydrogen and from each other, the methane derived CFCs deviate from perfect

tetrahedral symmetry.[1]

The physical properties of the CFCs and HCFCs are tunable by changes in the number and identity of thehalogen atoms. In general they are volatile, but less so than parent alkane. The decreased volatility is attributed

to the molecular polarity induced by the halides and the polarizability of halides, which induces intermolecular

interactions. Thus, methane boils at 161 C whereas the fluoromethanes boil between 51.7 (CF2H2) and
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128 C (CF4). The CFCs have still higher boiling points because the chloride is even more polarizable than

fluoride. Because of their polarity, the CFCs are useful solvents. The CFCs are far less flammable than methane,

in part because they contain fewer C-H bonds and in part because, in the case of the chlorides and bromides,

the released halides quench the free radicals that sustain flames.

The densities of CFCs are invariably higher than the corresponding alkanes. In general the density of these

compounds correlates with the number of chlorides.

CFCs and HCFCs are usually produced by halogen exchange starting from chlorinated methanes and ethanes.

Illustrative is the synthesis of chlorodifluoromethane from chloroform:

HCCl3 + 2 HF HCF2Cl + 2 HCl

The brominated derivatives are generated by free-radical reactions of the chlorofluorocarbons, replacing C-H

bonds with C-Br bonds. The production of the anesthetic 2-bromo-2-chloro-1,1,1-trifluoroethane ("halothane")

is illustrative:

CF3CH2Cl + Br2 CF3CHBrCl + HBr

Reactions

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

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-B

radiation, 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

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.

Billions of kilograms of chlorodifluoromethane are produced annually as a precursor to tetrafluoroethylene, the

monomer that is converted into Teflon.[2]

Classes of compounds, nomenclature

Chlorofluorocarbons (CFCs): when derived from methane and ethane these compounds have the

formulae CClmF4-m and C2ClmF6-m, where m is nonzero.

Hydrochlorofluorocarbons (HCFCs): when derived from methane and ethane these compounds have theformulae CClmFnH4-m-n and C2ClxFyH6-x-y, where m, n, x, and y are nonzero.

Bromochlorofluorocarbons and bromofluorocarbons have formulae similar to the CFCs and HCFCs but

also bromine.
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Hydrofluorocarbons (HFCs): when derived from methane, ethane, propane, and butane, these

compounds have the respective formulae CFmH4-m, C2FmH6-m, C3FmH8-m, and C4FmH10-m, where m is

nonzero.

Commercial names

Freon is DuPont's brand name for CFCs, HCFCs and related compounds. Other commercial names from

around the world are Algofrene, Arcton, Asahiflon, Daiflon, Eskimo, FCC, Flon, Flugene, Forane, Fridohna,Frigen, Frigedohn, Genetron, Isceon, Isotron, Kaiser, Kaltron, Khladon, Ledon, Racon, and Ucon.

Numbering system

Main article: refrigerant#Refrigerants by class

A numbering system is used for fluorinated alkanes, prefixed with Freon-, R-, CFC-, and HCFC-. The

rightmost value indicates the number of fluorine atoms, the next value to the left is the number of hydrogen atoms

lus 1, and the next value to the left is the number of carbon atoms less one (zeroes are not stated). Remaining

atoms are chlorine. Thus, Freon-12 indicates a methane derivative (only two numbers) containing two fluorine

atoms (the second 2) and no hydrogen (1-1=0). It is therefore CCl2F2.

Another, easier equation that can be applied to get the correct molecular formula of the CFC/R/Freon class

compounds is this to take the numbering and add 90 to it. The resulting value will give the number of carbons as

the first numeral, the second numeral gives the number of hydrogen atoms, and the third numeral gives the

number of fluorine atoms. The rest of the unaccounted carbon bonds are occupied by chlorine atoms. The value

of this equation is always a three figure number. An easy example is that of CFC-12, which gives: 90+12=102 -

> 1 carbon, 0 hydrogens, 2 fluorine atoms, and hence 2 chlorine atoms resulting in CCl2F2. The main advantage

of this method of deducing the molecular composition in comparison with the method described in the paragraphabove, is that it gives the number of carbon atoms of the molecule.

Freons containing bromine is signified by four numbers. Isomers, which are common for ethane and propane

derivatives, are indicated by letters following the numbers.
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Principal CFCs

Systematic nameCommon/trivial

name(s), code

Boiling

point (C)Formula

Trichlorofluoromethane Freon-11, R-11, CFC-11 23 CCl3F

Dichlorodifluoromethane Freon-12, R-12, CFC-12 29.8 CCl2F2

Chlorotrifluoromethane Freon-13, R-13, CFC-13 81 CClF3Chlorodifluoromethane R-22, HCFC-22 40.8 CHClF2

Dichlorofluoromethane R-21, HCFC-21 8.9 CHCl2F

Chlorofluoromethane Freon 31, R-31, HCFC-31 -9.1 CH2ClF

Bromochlorodifluoromethane BCF, Halon 1211, H-1211, Freon 12B1 CBrClF2

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

trifluoroethane

Freon 113, R-113, CFC-113, 1,1,2-

Trichlorotrifluoroethane47.7 Cl2FC-CClF2

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

Freon 113a, R-113a, CFC-113a 45.9 Cl3C-CF3

1,2-Dichloro-1,1,2,2-

tetrafluoroethane

Freon 114, R-114, CFC-114,

Dichlorotetrafluoroethane3.8 ClF2C-CClF2

1-Chloro-1,1,2,2,2-

pentafluoroethane

Freon 115, R-115, CFC-115,

Chloropentafluoroethane38 ClF2C-CF3

2-Chloro-1,1,1,2-

tetrafluoroethaneR-124, HCFC-124 12 CHFClCF3

1,1-Dichloro-1-fluoroethane R-141b, HCFC-141b 32 Cl2FC-CH3

1-Chloro-1,1-difluoroethane R-142b, HCFC-142b 9.2 ClF2C-CH3

Tetrachloro-1,2-difluoroethane Freon 112, R-112, CFC-112 91.5 CCl2FCCl2F

Tetrachloro-1,1-difluoroethane Freon 112a, R-112a, CFC-112a 91.5 CClF2CCl3

1,1,2-Trichlorotrifluoroethane Freon 113, R-113, CFC-113 48 CCl2FCClF2

1-Bromo-2-chloro-1,1,2-

trifluoroethaneHalon 2311a 51.7 CHClFCBrF2

2-Bromo-2-chloro-1,1,1-trifluoroethane

Halon 2311 50.2 CF3CHBrCl

1,1-Dichloro-2,2,3,3,3-

pentafluoropropaneR-225ca, HCFC-225ca 51 CF3CF2CHCl2

1,3-Dichloro-1,2,2,3,3-

pentafluoropropaneR-225cb, HCFC-225cb 56 CClF2CF2CHClF

History

Carbon tetrachloride (CCl4) was used in fire extinguishers and glass "anti-fire grenades" from the late nineteenth

century until around the end of World War II. Experimentation with chloroalkanes for fire suppression on

military aircraft began at least as early as the 1920s.Freon is a trade name for a group of CFCs which are used
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primarily as refrigerants, but also have uses in fire-fighting and as propellants in aerosol cans. Bromomethane is

widely used as a fumigant. Dichloromethane is a versatile industrial solvent.

The Belgian scientist Frdric Swarts pioneered the synthesis of CFCs in the 1890s. He developed an effective

exchange agent to replace chloride in carbon tetrachloride with fluoride to synthesize CFC-11 (CCl3F) and

CFC-12 (CCl2F2).

In the late 1920s, Thomas Midgley, Jr. improved the process of synthesis and led the effort to use CFC as

refrigerant to replace ammonia (NH3), chloromethane (CH3Cl), and sulfur dioxide (SO2), which are toxic but

were in common use. In searching for a new refrigerant, requirements for the compound were: low boiling point,

low toxicity, and to be generally non-reactive. In a demonstration for the American Chemical Society, Midgley

flamboyantly demonstrated all these properties by inhaling a breath of the gas and using it to blow out a candle [3]

in 1930.[4][5]

Commercial development and use of CFCs and related compounds

During World War II, various chloroalkanes were in

standard use in military aircraft, although these earlyhalons suffered from excessive toxicity. Nevertheless,

after the war they slowly became more common in civil

aviation as well. In the 1960s, fluoroalkanes and

bromofluoroalkanes became available and were quickly

recognized as being highly effective fire-fighting

materials. Much early research with Halon 1301 was

conducted under the auspices of the US Armed Forces,

while Halon 1211 was, initially, mainly developed in the

UK. By the late 1960s they were standard in many applications where water and dry-powder extinguishers

posed a threat of damage to the protected property, including computer rooms, telecommunications switches,

laboratories, museums and art collections. Beginning with warships, in the 1970s, bromofluoroalkanes also

progressively came to be associated with rapid knockdown of severe fires in confined spaces with minimal risk

to personnel.

By the early 1980s, bromofluoroalkanes were in common use on aircraft, ships, and large vehicles as well as in

computer facilities and galleries. However, concern was beginning to be expressed about the impact of

chloroalkanes and bromoalkanes on the ozone layer. The Vienna Convention for the Protection of the Ozone

Layer did not cover bromofluoroalkanes as it was thought, at the time, that emergency discharge of extinguishing

systems was too small in volume to produce a significant impact, and too important to human safety for

restriction.

Regulation

Since the late 1970s, the use of CFCs has been heavily regulated because of their destructive effects on the

ozone layer. After the development of his electron capture detector, James Lovelock was the first to detect the

widespread presence of CFCs in the air, finding a mole fraction of 60 ppt of CFC-11 over Ireland. In a self-

funded research expedition ending in 1973, Lovelock went on to measure CFC-11 in both the Arctic and

Antarctic, finding the presence of the gas in each of 50 air samples collected, and concluding that CFCs are not

hazardous to the environment. The experiment did however provide the first useful data on the presence ofCFCs in the atmosphere. The damage caused by CFCs was discovered by Sherry Rowland and Mario Molina

who, after hearing a lecture on the subject of Lovelock's work, embarked on research resulting in the first

publication suggesting the connection in 1974. It turns out that one of CFCs' most attractive featurestheir low
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NASA projection of stratospheric ozone, in

Dobson units, if chlorofluorocarbons had not

been banned. Right-click: animate, to see

animated version.

Ozone-depleting gas trends

reactivity is key to their most destructive effects. CFCs' lack of reactivity gives them a lifespan that can

exceed 100 years, giving them time to diffuse into the upper stratosphere. Once in the stratosphere, the sun's

ultraviolet radiation is strong enough to cause the homolytic cleavage of the C-Cl bond.

By 1987, in response to a dramatic seasonal depletion of the

ozone layer over Antarctica, diplomats in Montreal forged a

treaty, the Montreal Protocol, which called for drastic

reductions in the production of CFCs. On March 2, 1989, 12

European Community nations agreed to ban the production of

all CFCs by the end of the century. In 1990, diplomats met in

London and voted to significantly strengthen the Montreal

Protocol by calling for a complete elimination of CFCs by the

ear 2000. By the year 2010 CFCs should have been

completely eliminated from developing countries as well.

Because the only

CFCs available to

countries adhering tothe treaty is from

recycling, their prices

have increased

considerably. A

worldwide end to

production should

also terminate the

smuggling of this material. However, there are current CFC smuggling

issues, as recognized by UNEP (United Nations Environmental

Programme) in a 2006 report titled "Illegal Trade in Ozone DepletingSubstances". UNEP estimates that between 16,00038,000 tonnes

of CFCs passed through the black market in the mid-1990s. The

report estimated between 7,000 and 14,000 tonnes of CFCs are

smuggled annually into developing countries. Asian countries are those

with the most smuggling; China, India and South Korea were found to account for around 70% of global CFC

production.[6] Possible reasons for continued CFC smuggling were also examined: the report noted that many

banned CFC producing products have long lifespans and continue to operate. The cost of replacing the

equipment of these items is sometimes cheaper than outfitting them with a more ozone-friendly appliance.

Additionally, CFC smuggling is not considered a significant issue so the perceived penalties for smuggling are

low. While the eventual phaseout of CFCs is likely, efforts are being taken to stem these current non-compliance problems.

By the time of the Montreal Protocol it was realised that deliberate and accidental discharges during system tests

and maintenance accounted for substantially larger volumes than emergency discharges, and consequently halons

were brought into the treaty, albeit with many exceptions.

Regulatory gap

While the production and consumption of CFCs are regulated under the Montreal Protocol, emissions from

existing banks of CFCs are not regulated under the agreement. As of 2002, there were an estimated 5,791

kilotons of CFCs in existing products such as refrigerators, air conditioners, aerosol cans and others. [7]
http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-7http://en.wikipedia.org/wiki/Montreal_Protocolhttp://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-6http://en.wikipedia.org/wiki/Londonhttp://en.wikipedia.org/wiki/European_Communityhttp://en.wikipedia.org/wiki/Montreal_Protocolhttp://en.wikipedia.org/wiki/Montrealhttp://en.wikipedia.org/wiki/Antarcticahttp://en.wikipedia.org/wiki/Homolysis_(chemistry)http://en.wikipedia.org/wiki/Ultraviolethttp://en.wikipedia.org/wiki/Stratospherehttp://en.wikipedia.org/wiki/File:Ozone_cfc_trends.pnghttp://en.wikipedia.org/wiki/File:Future_ozone_layer_concentrations.gifhttp://en.wikipedia.org/wiki/Dobson_unithttp://en.wikipedia.org/wiki/File:Future_ozone_layer_concentrations.jpg


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Approximately one-third of these CFCs are projected to be emitted over the next decade if action is not taken,

posing a threat to both the ozone layer and the climate.[8] A proportion of these CFCs can be safely captured

and destroyed.

Regulation and DuPont

In 1978 the United States banned the use of CFCs such as Freon in aerosol cans, the beginning of a long series

of regulatory actions against their use. The critical DuPont manufacturing patent for Freon ("Process forFluorinating Halohydrocarbons", U.S. Patent #3258500) was set to expire in 1979. In conjunction with other

industrial peers DuPont sponsored efforts such as the "Alliance for Responsible CFC Policy" to question anti-

CFC science, but in a turnabout in 1986 DuPont, with new patents in hand, publicly condemned CFCs. [9]

DuPont representatives appeared before the Montreal Protocol urging that CFCs be banned worldwide and

stated that their new HCFCs would meet the worldwide demand for refrigerants.[9]

Phase out of CFCs

Use of certain chloroalkanes as solvents for large scale application, such as dry cleaning, have been phased out,for example, by the IPPC directive on greenhouse gases in 1994 and by the volatile organic compounds (VOC)

directive of the EU in 1997. Permitted chlorofluoroalkane uses are medicinal only.

Bromofluoroalkanes have been largely phased out and the possession of equipment for their use is prohibited in

some countries like the Netherlands and Belgium, from 1 January 2004, based on the Montreal Protocol and

guidelines of the European Union.

Production of new stocks ceased in most (probably all) countries as of 1994.[citation needed] However many

countries still require aircraft to be fitted with halon fire suppression systems because no safe and completely

satisfactory alternative has been discovered for this application. There are also a few other, highly specializeduses. These programs recycle halon through "halon banks" coordinated by the Halon Recycling Corporation[10]

to ensure that discharge to the atmosphere occurs only in a genuine emergency and to conserve remaining

stocks.

The interim replacements for CFCs are hydrochlorofluorocarbons (HCFCs), which deplete stratospheric ozone,

but to a much lesser extent than CFCs.[11] Ultimately, hydrofluorocarbons (HFCs) will replace HCFCs. Unlike

CFCs and HCFCs, HFCs have an ozone depletion potential (ODP) of 0. DuPont began producing

hydrofluorocarbons as alternatives to Freon in the 1980s. These included Suva refrigerants and Dymel

propellants.[12] Natural refrigerants are climate friendly solutions that are enjoying increasing support from large

companies and governments interested in reducing global warming emissions from refrigeration and airconditioning. Hydrofluorocarbons are included in the Kyoto Protocol because of their very high Global

Warming Potential and are facing calls to be regulated under the Montreal Protocol[13] due to the recognition of

halocarbon contributions to climate change.[14]

On September 21, 2007, approximately 200 countries agreed to accelerate the elimination of

hydrochlorofluorocarbons entirely by 2020 in a United Nations-sponsored Montreal summit. Developing

nations were given until 2030. Many nations, such as the United States and China, who had previously resisted

such efforts, agreed with the accelerated phase out schedule.[15]

Development of alternatives for CFCs
http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-15http://en.wikipedia.org/wiki/Global_warming_controversyhttp://en.wikipedia.org/wiki/People%27s_Republic_of_Chinahttp://en.wikipedia.org/wiki/United_Stateshttp://en.wikipedia.org/wiki/Montrealhttp://en.wikipedia.org/wiki/United_Nationshttp://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-14http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-A_Novel_Tactic_in_Climate_Fight_Gains_Some_Traction.2C_NY_Times-13http://en.wikipedia.org/wiki/Montreal_Protocolhttp://en.wikipedia.org/wiki/Global_Warming_Potentialhttp://en.wikipedia.org/wiki/Kyoto_Protocolhttp://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-1930:_Freon.2C_DuPont_Heritage-12http://en.wikipedia.org/wiki/Haloalkanes#Hydro_fluoro_compounds_.28HFC.29http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-11http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-10http://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Montreal_Protocolhttp://en.wikipedia.org/wiki/European_Unionhttp://en.wikipedia.org/wiki/Volatile_organic_compoundshttp://en.wikipedia.org/wiki/Greenhouse_gashttp://en.wikipedia.org/wiki/Integrated_Pollution_Prevention_and_Controlhttp://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-Ethics-9http://en.wikipedia.org/wiki/Montreal_Protocolhttp://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-Ethics-9http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-8


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Work on alternatives for chlorofluorocarbons in refrigerants began in the late 1970s after the first warnings of

damage to stratospheric ozone were published. The hydrochlorofluorocarbons (HCFCs) are less stable in the

lower atmosphere, enabling them to break down before reaching the ozone layer. Nevertheless, a significant

fraction of the HCFCs do break down in the stratosphere and they have contributed to more chlorine buildup

there than originally predicted. Later alternatives lacking the chlorine, the hydrofluorocarbons (HFCs) have an

even shorter lifetimes in the lower atmosphere. One of these compounds, HFC-134a, is now used in place of

CFC-12 in automobile air conditioners. Hydrocarbon refrigerants (a propane/isobutane blend) are also used

extensively in mobile air conditioning systems in Australia, the USA and many other countries, as they haveexcellent thermodynamic properties and perform particularly well in high ambient temperatures. One of the

natural refrigerants (along with Ammonia and Carbon Dioxide), hydrocarbons have negligible environmental

impacts and are also used worldwide in domestic and commercial refrigeration applications, and are becoming

available in new split system air conditioners.[16] Various other solvents and methods have replaced the use of

CFCs in laboratory analytics.[17]

Applications and replacements for CFCs

Application Previously used CFC Replacement

Refrigeration& air-

conditioning

CFC-12 (CCl2F2); CFC-11(CCl3F);

CFC-13(CClF3); HCFC-22 (CHClF2);

CFC-113 (Cl2FCCClF2); CFC-114

(CClF2CClF2); CFC-115 (CF3CClF2);

HFC-23 (CHF3); HFC-134a (CF3CFH2); HFC-507 (a

1:1 azeotropic mixture of HFC 125 (CF3 CHF2) and

HFC-143a (CF3CH3)); HFC 410 (a 1:1 azeotropic

mixture of HFC-32 (CF2H2) and HFC-125 (CF3CF2H))

Propellants

in medicinal

aerosols

CFC-114 (CClF2CClF2) HFC-134a (CF3CFH2); HFC-227ea (CF3CHFCF3)

Blowing

agents for

foams

CFC-11 (CCl3F); CFC 113

(Cl2FCCClF2); HCFC-141b

(CCl2FCH3)

HFC-245fa (CF3CH2CHF2); HFC-365 mfc

(CF3CH2CF2CH3)

Solvents,

degreasing

agents,

cleaning

agents

CFC-11 (CCl3F); CFC-113

(CCl2FCClF2)None

Environmental impacts

As previously discussed, CFCs were phased out via the Montreal Protocol due to their part in ozone depletion.

However, the atmospheric impacts of CFCs are not limited to its role as an active ozone reducer. This

anthropogenic compound is also a greenhouse gas, with a much higher potential to enhance the greenhouse

effect than CO2.

Infrared bands trap heat from escaping earth's atmosphere. In the case of CFCs, the strongest of these bands

are located at the spectral region referred to as an atmospheric window due to the relative transparency of the

atmosphere within this region.[18] The strength of CFC bands and the unique susceptibility of the atmosphere, at

which the compound absorbs and emits radiation, are two factors that contribute to CFCs' "super" greenhouse

effect.[19] Another such factor is the low concentration of the compound. Because CO2 is close to saturation

with high concentrations, it takes more of the substance to enhance the greenhouse effect. Conversely, the lowconcentration of CFCs allow their effects to increase linearly with mass.[19]

Tracer of ocean circulation
http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-Ramanathan_2009_37.E2.80.9350-19http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-Ramanathan_2009_37.E2.80.9350-19http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-18http://en.wikipedia.org/wiki/Greenhouse_gashttp://en.wikipedia.org/wiki/Montreal_Protocolhttp://en.wikipedia.org/wiki/Pentafluoroethanehttp://en.wikipedia.org/wiki/Azeotropehttp://en.wikipedia.org/wiki/Fluoroformhttp://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-17http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-16http://en.wikipedia.org/wiki/HFC-134ahttp://en.wikipedia.org/wiki/Stratospherehttp://en.wikipedia.org/wiki/Stratosphere


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Since the time history of CFC concentrations in the atmosphere is relatively well known, they have provided an

important constraint on ocean circulation. CFCs dissolve in seawater at the ocean surface and are subsequently

transported into the ocean interior. Since CFCs are conservative, their concentration in the ocean interior

reflects simply the convolution of their atmospheric time evolution and ocean circulation and mixing.

CFC and SF6 Tracer-Derived Age of Ocean Water

Chlorofluorocarbons (CFCs) are anthropogenic compounds which have been released into the atmospheresince the 1930s in various applications such as in air-conditioning, refrigeration, blowing agents in foams,

insulations and packing materials, propellants in aerosol cans, and as solvents.[20] The entry of CFCs into the

ocean makes them extremely useful as transient tracers to estimate rates and pathways of ocean circulation and

mixing processes.[21] However, due to production restrictions of CFCs in the 1980s, atmospheric

concentrations of CFC-11 and CFC-12 have stopped increasing, and the CFC-11 to CFC-12 ratio in the

atmosphere have been steadily decreasing, making water dating of water masses more problematic.[21]

Incidentally, production and release of sulfur hexafluoride (SF6) have rapidly increased in the atmosphere since

the 1970s.[21] Similar to CFCs, SF6 is also an inert gas and is not affected by oceanic chemical or biological

activities.[22]

Thus, using CFCs in concert with SF6 as a tracer resolves the water dating issues due todecreased CFC concentrations.

Using CFCs or SF6 as a tracer of ocean circulation allows for the derivation of rates for ocean processes due to

the time-dependent source function. The elapsed time since a subsurface water mass was last in contact with the

atmosphere is the tracer-derived age.[23] Estimates of age can be derived based on the partial pressure of an

individual compound and the ratio of the partial pressure of CFCs to each other (or SF6).[23]

Partial pressure and ratio dating techniques

The age of a water parcel can be estimated by the CFC partial pressure (pCFC) age or SF6 partial pressure

(pSF6) age. The pCFC age of a water sample is defined as:

pCFC = [CFC]/F(T,S)

where [CFC] is the measured CFC concentration (pmol kg-1) and F is the solubility of CFC gas in seawater as

a function of temperature and salinity.[24] The CFC partial pressure is expressed in units of 10-12 atmospheres

or parts-per-trillion (ppt).[25] The solubility measurements of CFC-11 and CFC-12 have been previously

measured by Warner and Weiss[25] Additionally, the solubility measurement of CFC-113 was measured by Bu

and Warner[26] and SF6 by Wanninkhof et al.[27] and Bullister et al.[28] Theses authors mentioned above have

expressed the solubility, F, at a total pressure of 1 atm as:

ln F = a1 + a2(100/T) + a3ln(T/100) + a4(T/100)2 + S[b1 + b2(T/100) + b3(T/100)

2]

where F = solubility expressed in either mol l-1 or mol kg-1 atm-1 T = absolute temperature S = salinity in parts

per thousand (ppt) a1, a2, a3, b1, b2, and b3 are constants to be determined from the least squares fit to the

solubility measurements.[26] This equation is derived from the integrated van't Hoff equation and the logarithmic

Setchenow salinity dependence.[26]

It can be noted that the solubility of CFCs increase with decreasing temperature at approximately 1% per

degree Celsius.[23]
http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-Fine-23http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-BuWarner-26http://en.wikipedia.org/wiki/Van%27t_Hoff_equationhttp://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-BuWarner-26http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-28http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-27http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-BuWarner-26http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-MinWarner-25http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-MinWarner-25http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-WarnerWeiss-24http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-Fine-23http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-Fine-23http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-22http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-BullisterWisegraver-21http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-BullisterWisegraver-21http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-BullisterWisegraver-21http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-PlummerBusenberg-20


10/12



Once the partial pressure of the CFC (or SF6) is derived, it is then compared to the atmospheric time histories

for CFC-11, CFC-12, or SF6 in which the pCFC directly corresponds to the year with the same measurement.

The difference between the corresponding date and the collection date of the seawater sample is the average

age for the water parcel.[23] The age of a parcel of water can also be calculated using the ratio of two CFC

partial pressures or the ratio of the SF6 partial pressure to a CFC partial pressure.[23]

SafetyAccording to their material safety data sheets, CFCs and HCFCs are colourless, volatile, toxic liquids and gases

with a faintly sweet ethereal odour. Overexposure at concentrations of 11% or more may cause dizziness, loss

of concentration, central nervous system depression and/or cardiac arrhythmia. Vapors displace air and can

cause asphyxiation in confined spaces. Although non-flammable, their combustion products include hydrofluoric

acid, and related species.[29] It is important to note that normal occupational exposure is rated at 0.07% and

does not pose any serious health risks.[30]

References

1. ^ Gnter Siegemund, Werner Schwertfeger, Andrew Feiring, Bruce Smart, Fred Behr, Herward Vogel, Blaine

McKusick "Fluorine Compounds, Organic" Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH,

Weinheim, 2002. doi:10.1002/14356007.a11_349 (http://dx.doi.org/10.1002%2F14356007.a11_349)

2. ^ M. Rossberg et al. "Chlorinated Hydrocarbons" in Ullmann's Encyclopedia of Industrial Chemistry 2006,

Wiley-VCH, Weinheim. doi:10.1002/14356007.a06_233.pub2

(http://dx.doi.org/10.1002%2F14356007.a06_233.pub2)

3. ^ Inventors (http://inventors.about.com/library/inventors/blfreon.htm) accessed December 21, 2007

4. ^ Carlisle, Rodney (2004). Scientific American Inventions and Discoveries, p. 351. John Wiley & Songs, Inc.,

New Jersey. ISBN 0-471-24410-4.5. ^ McNeill, J. R. Something New Under the Sun: An Environmental History of the Twentieth-Century World

(2001) New York: Norton, xxvi, 421 pp. (as reviewed in the Journal of Political Ecology

(http://dizzy.library.arizona.edu/ej/jpe/volume_9/1101bess.html))

6. ^ "Illegal Trade in Ozone Depleting Substances" (http://www.mea-

ren.org/files/publications/Illegal%20Trade%20in%20ODS.pdf) UNEP, 2007. Web. 3 Apr. 2011.

7. ^ IPCC/TEAP Special Report on Ozone and Climate (http://www1.ipcc.ch/pdf/special-reports/sroc/sroc11.pdf)

8. ^ Chlorofluorocarbons: An Overlooked Climate Threat, EESI Congressional Briefing

(http://www.eesi.org/100209_cfc). Eesi.org. Retrieved on 2011-09-24.

9. ^ ab "Ethics of Du Pont's CFC Strategy 19751995", Smith B. Journal of Business Ethics, Volume 17, Number

5, April 1998, pp. 557568(12)

10. ^ Welcome to the Halon Corporation (http://www.halon.org/). Halon.org. Retrieved on 2011-09-24.

11. ^ "Ozone Layer Depletion", U.S. Environmental Protection Agency (http://www.epa.gov/ozone/defns.html)

accessed June 25, 2008

12. ^ Freon : 1930. In Depth

(http://www2.dupont.com/Heritage/en_US/1930_dupont/1930_freon/1930_freon_indepth.html). dupont.com

(2009-01-30). Retrieved on 2011-09-24.

13. ^ John M. Broder (November 9, 2010). "A Novel Tactic in Climate Fight Gains Some Traction"

(http://www.nytimes.com/2010/11/09/science/earth/09montreal.html?ref=earth). The New York Times. p. A9.

Retrieved 2013-02-05.

14. ^ Velders et al.,PNASMarch 20, 2007 vol. 104 no. 12 48144819 [1]

(http://www.pnas.org/content/104/12/4814.abstract) "The importance of the Montreal Protocol in protectingclimate"

15. ^ HCFC Phaseout Schedule (http://www.epa.gov/ozone/title6/phaseout/hcfc.html). Epa.gov (2006-06-28).

Retrieved on 2011-09-24.

16. ^ "Greenpeace, Cool Technologies" (http://www.greenpeace.org/raw/content/china/en/campaigns/stop-climate-

chan e/climate-friendl -coolin /cool-technolo ies- art-1. df . PDF . Retrieved on 2011-09-24.
http://www.greenpeace.org/raw/content/china/en/campaigns/stop-climate-change/climate-friendly-cooling/cool-technologies-part-1.pdfhttp://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-16http://www.epa.gov/ozone/title6/phaseout/hcfc.htmlhttp://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-15http://www.pnas.org/content/104/12/4814.abstracthttp://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-14http://www.nytimes.com/2010/11/09/science/earth/09montreal.html?ref=earthhttp://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-A_Novel_Tactic_in_Climate_Fight_Gains_Some_Traction.2C_NY_Times_13-0http://www2.dupont.com/Heritage/en_US/1930_dupont/1930_freon/1930_freon_indepth.htmlhttp://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-1930:_Freon.2C_DuPont_Heritage_12-0http://www.epa.gov/ozone/defns.htmlhttp://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-11http://www.halon.org/http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-10http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-Ethics_9-1http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-Ethics_9-0http://www.eesi.org/100209_cfchttp://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-8http://www1.ipcc.ch/pdf/special-reports/sroc/sroc11.pdfhttp://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-7http://www.mea-ren.org/files/publications/Illegal%20Trade%20in%20ODS.pdfhttp://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-6http://dizzy.library.arizona.edu/ej/jpe/volume_9/1101bess.htmlhttp://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-McNeill_5-0http://en.wikipedia.org/wiki/Special:BookSources/0471244104http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-4http://inventors.about.com/library/inventors/blfreon.htmhttp://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-3http://dx.doi.org/10.1002%2F14356007.a06_233.pub2http://en.wikipedia.org/wiki/Digital_object_identifierhttp://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-Ullmann_2-0http://dx.doi.org/10.1002%2F14356007.a11_349http://en.wikipedia.org/wiki/Digital_object_identifierhttp://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-1http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-30http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-29http://en.wikipedia.org/wiki/Cardiac_arrhythmiahttp://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-Fine-23http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_note-Fine-23


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17. ^ Use of Ozone Depleting Substances in Laboratories. TemaNord 516/2003

(http://www.norden.org/pub/ebook/2003-516.pdf). Norden.org (2003-01-01). Retrieved on 2011-09-24.

18. ^ Ramanathan, V (1975). "Greenhouse Effect Due to Chlorofluorocarbons: Climatic Implications". Science,

New Series19: 5052. JSTOR 1740877 (http://www.jstor.org/stable/1740877).

19. ^ ab Ramanathan, V; Y. Feng (2009). "Air pollution, greenhouse gases and climate change: Global and regional

perspectives".Atmospheric Environment43: 3750. doi:10.1016/j.atmosenv.2008.09.063

(http://dx.doi.org/10.1016%2Fj.atmosenv.2008.09.063).

20. ^ Plummer LN and Busenberg E. 2006. "Chlorofluorocarbons in aquatic environments" (chapter 1), p. 1-8. In

IAEA (ed.), Use of chlorofluorocarbons in hydrology A guidebook: Vienna, International Atomic Energy

Agency.

21. ^ abc Bulister JL and Wisegarver DP. 2008. "The shipboard analysis of trace levels of sulfur hexafluoride,

chlorofluorocarbon-11 and chlorofluorocarbon-12 in seawater". Deep-Sea Res I; 55:1063-74.

22. ^ Watanabe YW, Shimamoto A, and Ono T. 2003. "Comparison of time-dependent tracer ages in the Western

North Pacific: oceanic background levels of SF6, CFC-11, CFC-12, and CFC-113". J Oceanogr.; 59:719-29.

23. ^ abcde Fine RA. 2011. "Observations of CFCs and SF6 as ocean tracers". Ann Rev Mar Sci.; 3:173-95.

24. ^ Warner MJ and Weiss RF. 1985. "Solubility of chlorofluorocarbons 11 and 12 in water and seawater".Deep-

Sea Res.; 32:1485-97.

25. ^ ab Min D, Warner MJ, and Bullister JL. 2010. "Estimated rates of carbon tetrachloride removal in the

thermocline and deep waters of the East Sea (Sea of Japan)". Mar Chem.; 121:100-11.26. ^ abc Bu X and Warner MJ. 1995. "Solubility of chlorofluorocarbon 113 in water and seawater". Deep-Sea

Res I.; 42:115161

27. ^ Wanninkhof R, Ledwell JR, and Watson AJ. 1991. "Analysis of sulfur hexafluoride in seawater". J Geophys

Res.; 96:873340

28. ^ Bullister JL, Wisegarver DP, and Menzia FA. 2002. "The solubility of sulfur hexafluoride in water and

seawater".Deep-Sea Res I.; 49:17587

29. ^ Material Safety Data Sheet (http://www.refrigerants.com/msds/r12.pdf). National Refrigerants

30. ^ WHO. "Fully Halogenated Chlorofluorocarbons"

(http://www.inchem.org/documents/ehc/ehc/ehc113.htm#SectionNumber:1.8). International Programme on

Chemical Safety. Retrieved 04/12/2012.

External links

Gas conversion table (http://www.mksinst.com/techinfo/GasConversionTable.aspx)

Nomenclature FAQ (http://www.faqs.org/faqs/sci/chem-faq/part3/section-1.html)

Numbering Scheme for Ozone-Depleting Substances and their Substitutes

(http://www.epa.gov/ozone/geninfo/numbers.html)

Class I Ozone-Depleting Substances (http://www.epa.gov/ozone/ods.html)

CFC Illegal Trade (http://www.american.edu/projects/mandala/TED/cfctrade.htm)Numbering Scheme for Ozone-Depleting Substances and their Substitutes

(http://www.epa.gov/ozone/geninfo/numbers.html)

Class I Ozone-Depleting Substances (http://www.epa.gov/ozone/ods.html)

Class II Ozone-Depleting Substances (HCFCs) (http://www.epa.gov/ozone/ods2.html)

History of Halon use by the US Navy (http://books.nap.edu/books/0309057825/html/63.html)

Ozone Loss: The Chemical Culprits (http://books.nap.edu/openbook.php?record_id=9042&page=5)

Process using pyrolysis in an ultra high temperature plasma arc for the elimination of CFCs

(http://www.plascon.com.au/destruction-of-ozone-depleting-substances.html)

[2] (http://www.eia-international.org) Environmental Investigation Agency: Reports etc. on illegal trade

and solutions.

[3] (http://www.eia-global.org) Environmental Investigation Agency in the USA: Reports etc. on illegal

trade and solutions.

Freon in Car A/C (http://www.carcare.org/car-care-articles/refrigerant)
http://www.greenpeace.org/raw/content/china/en/campaigns/stop-climate-change/climate-friendly-cooling/cool-technologies-part-1.pdfhttp://www.carcare.org/car-care-articles/refrigeranthttp://en.wikipedia.org/wiki/Environmental_Investigation_Agencyhttp://www.eia-global.org/http://en.wikipedia.org/wiki/Environmental_Investigation_Agencyhttp://www.eia-international.org/http://www.plascon.com.au/destruction-of-ozone-depleting-substances.htmlhttp://books.nap.edu/openbook.php?record_id=9042&page=5http://books.nap.edu/books/0309057825/html/63.htmlhttp://www.epa.gov/ozone/ods2.htmlhttp://www.epa.gov/ozone/ods.htmlhttp://www.epa.gov/ozone/geninfo/numbers.htmlhttp://www.american.edu/projects/mandala/TED/cfctrade.htmhttp://www.epa.gov/ozone/ods.htmlhttp://www.epa.gov/ozone/geninfo/numbers.htmlhttp://www.faqs.org/faqs/sci/chem-faq/part3/section-1.htmlhttp://www.mksinst.com/techinfo/GasConversionTable.aspxhttp://www.inchem.org/documents/ehc/ehc/ehc113.htm#SectionNumber:1.8http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-30http://www.refrigerants.com/msds/r12.pdfhttp://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-29http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-28http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-27http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-BuWarner_26-2http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-BuWarner_26-1http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-BuWarner_26-0http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-MinWarner_25-1http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-MinWarner_25-0http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-WarnerWeiss_24-0http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-Fine_23-4http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-Fine_23-3http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-Fine_23-2http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-Fine_23-1http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-Fine_23-0http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-22http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-BullisterWisegraver_21-2http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-BullisterWisegraver_21-1http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-BullisterWisegraver_21-0http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-PlummerBusenberg_20-0http://dx.doi.org/10.1016%2Fj.atmosenv.2008.09.063http://en.wikipedia.org/wiki/Digital_object_identifierhttp://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-Ramanathan_2009_37.E2.80.9350_19-1http://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-Ramanathan_2009_37.E2.80.9350_19-0http://www.jstor.org/stable/1740877http://en.wikipedia.org/wiki/JSTORhttp://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-18http://www.norden.org/pub/ebook/2003-516.pdfhttp://en.wikipedia.org/wiki/Chlorofluorocarbon#cite_ref-17http://www.greenpeace.org/raw/content/china/en/campaigns/stop-climate-change/climate-friendly-cooling/cool-technologies-part-1.pdf


12/12


Phase out of Halons in extinguishers (http://www.firesafe.org.uk/phase-out-of-halons/)

Retrieved from "http://en.wikipedia.org/w/index.php?title=Chlorofluorocarbon&oldid=557550468"

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Chlorofluorocarbon - Wikipedia, The Free Encyclopedia