Tetrachloro-1,1-difluoroethane or 1,1,1,2-tetrachloro-2,2-difluoroethane, Freon 112a, R-112a, or CFC-112a is an asymmetric chlorofluorocarbon isomer of tetrachloro-1,1-difluoroethane with formula CClF₂CCl₃. It contains ethane substituted by four chlorine atoms and two fluorine atoms. With a boiling point of 91.5°C it is the freon with second highest boiling point. Tetrachlorodifluoroethane as made is a mixture of the symmetrical and asymmetric isomers.

Preparation

Tetrachloro-1,1-difluoroethane can be prepared in 40% yield by reacting

1,1,2-trichloro-1,2,2-trifluoroethane 1,1,2-Trichloro-1,2,2-trifluoroethane, also called trichlorotrifluoroethane (often abbreviated as TCTFE) or CFC-113, is a chlorofluorocarbon. It has the formula . This colorless, volatile liquid is a versatile solvent. Production CFC-113 can be pr ...

(freon 113) with

aluminium chloride Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula . It forms a hexahydrate with the formula , containing six water molecules of hydration. Both the anhydrous form and the hexahydrate are col ...

at 60°C. It can also be made in a reaction with hydrogen fluoride with

hexachloroethane Hexachloroethane (perchloroethane) is an organochlorine compound with the chemical formula . Its structure is . It is a white or colorless solid at room temperature with a camphor-like odor. It has been used by the military in smoke compositions, ...

tetrachloroethane Tetrachloroethane () may refer to either of two isomeric chemical compounds: * 1,1,1,2-Tetrachloroethane (R-130a) * 1,1,2,2-Tetrachloroethane (R-130) See also * Tetrachloroethene * Trichloroethane * Tetrafluoroethane * Tetrabromoethane 1,1,2,2-Te ...

with extra chlorine. This reaction occurs with an aluminium fluoride catalyst at 400°C. unsymmetrical trichlorotrifluoroethane (CCl₂FCClF₂) is also produced along with other chlorofluorocarbons. Separation of the symmetrical and unsymmetrical isomer is difficult.

Properties

Tetrachloro-1,1-difluoroethane is non-combustible. It has a critical pressure of 4.83 MPa and a critical temperature of 279.2°C. At the critical point the density is 0.754 g/cm³. Tetrachloro-1,1-difluoroethane in liquid form is miscible with

perfluorocarbon Fluorocarbons are chemical compounds with carbon-fluorine bonds. Compounds that contain many C-F bonds often have distinctive properties, e.g., enhanced stability, volatility, and hydrophobicity. Several fluorocarbons and their derivatives are ...

Reactions

Tetrachloro-1,1-difluoroethane reacts with

zinc Zinc is a chemical element; it has symbol Zn and atomic number 30. It is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic tabl ...

ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound with the chemical formula . It is an Alcohol (chemistry), alcohol, with its formula also written as , or EtOH, where Et is the ps ...

at 60°C to yield unsymmetrical dichlorodifluoroethylene ().

Uses

Tetrachlorodifluoroethane (CFC-112a), as with most high boiling point CFCs, has various uses as a non-flammable and clean agent solvent. It has historically been used as an extractant in liquid-liquid extraction and dry cleaning processes. CFC-112 and CFC-112a have also been used as feedstock chemicals in the manufacturing of fluorovinyl ethers. CFC-112a and its isomers are attractive organic solvents, as they have many important properties: they are nonflammable, clean drying, and have lower toxicity than common chlorinated organic solvents. Tetrachlorodifluoroethane (mixture of isomers) has a niche application as a veterinary medicine to treat parasites (''

Fasciola hepatica ''Fasciola hepatica'', also known as the common liver fluke or sheep liver fluke, is a parasitism, parasitic trematode (fluke (flatworm), fluke or flatworm, a type of helminth) of the class (biology), class Trematoda, phylum Platyhelminthes. It ...

'').

Atmosphere

Tetrachloro-1,1-difluoroethane was first detected in air collected from

Cape Grim Cape Grim, officially Kennaook / Cape Grim, is the northwestern point of Tasmania, Australia. The Peerapper name for the cape is recorded as ''Kennaook''. It is the location of the Cape Grim Baseline Air Pollution Station and of the Cape Gri ...

, Tasmania in the

Cape Grim Air Archive The Cape Grim Air Archive (CGAA) also "Kennaook/Cape Grim" is a facility of the Australian Bureau of Meteorology's Cape Grim Baseline Air Pollution Station, Tasmania, that aims to collect air samples starting from 1978. The archive is a facility ...

, and later from air bubbles in snow from Greenland. The substance made its first appearance around 1965, and increased in level until around 2000. In 2000 Earth's atmosphere contained 0.08 parts per trillion of Freon 112a. Level slightly declined to 0.07 ppt by 2012. Estimated lifetime in the stratosphere is 44 years. By 2014 3,600 tons of Freon 112a had been put into the atmosphere. As of 2023, levels have been rising in the Earth's atmosphere. As a greenhouse gas its radiative efficiency is 0.25 Wm⁻²ppb⁻¹.

References

Extra reading

* * *{{cite journal , last1=Kakáč , first1=B. , last2=Hudlický , first2=M. , title=Organic compounds of fluorine. VII. Spectrophotometric study in the series of halofluoroethanes , journal=Collection of Czechoslovak Chemical Communications , date=1965 , volume=30 , issue=3 , pages=745–751 , doi=10.1135/cccc19650745 Chlorofluorocarbons Atmosphere of Earth Chlorofluoroalkanes