1,1-Dichlorotetrafluoroethane Explained

1,1-Dichlorotetrafluoroethane is a chlorofluorocarbon also known as CFC-114a or R114a by American Society of Heating, Refrigerating, and Air Conditioning Engineers.[1] It has two chlorine atoms on one carbon atom and none on the other. It is one of two isomers of dichlorotetrafluoroethane, the other being 1,2-dichlorotetrafluoroethane, also known as CFC-114.

Formation

1,1-Dichlorotetrafluoroethane can be made free from other isomers by reacting trichlorotrifluoroethane (CFC-113 or CFC-113a) with antimony pentachloride.[2] Trichlorotrifluoroethane can also be reacted with sulfur tetrafluoride or dichlorodifluoromethane with aluminium fluoride catalyst to yield 1,1-dichlorotetrafluoroethane. The use of aluminium in the catalyst favours the asymmetric molecules.[3]

It can also be made in a reaction of tetrachloroethylene with hydrogen fluoride and chlorine, but this results in a mixture.[2]

Fluorinating 1,2-dichlorodifluoroethylene with fluorine produces a small amount of 1,1-dichlorotetrafluoroethane, but mostly tetrachlorotetrafluorobutene and some other chloroflurocarbons, so is not a good way.[4]

Properties

1,1-Dichlorotetrafluoroethane has a close boiling point (3.6°C) to the isomer 1,2-dichlorotetrafluoroethane (3.8°C), and so is difficult to separate by distillation.[5] Also in a gas chromatograph, it is hard to distinguish from the symmetric 1,2 isomer.[5]

Critical properties include critical temperature 145.7°C, critical pressure 4.92 Mpa and critical density of 0.82 g/ml.[6]

1,1-Dichlorotetrafluoroethane does not ignite in air.[6]

Reactions

1,1-Dichlorotetrafluoroethane reacts with hydrogen when heated at 300 to 600°C with a palladium catalyst in a hydrodechlorination. The main reaction product is 1,1,1,2-tetrafluoroethane, but also 1-chloro-1,2,2,2-tetrafluoroethane (CF3CHClF) and 1,1,1-trifluoroethane are formed.[7]

1,1-Dichlorotetrafluoroethane reacts with alkali metals, alkaline earths and aluminium.[6]

When heated with hydrogen over a nickel catalyst, 1,1-dichlorotetrafluoroethane is dechlorinated with replacement by hydrogen to yield a mixture of CF3CHClF and the dimer CF3CClFCClFCF3.[8]

Use

CFC-114a was used in aerosol propellants, blowing agents, and in polyolefin foams. There was also use in refrigerants. Production was banned in by the Montreal Protocol.

CFC-114a is a possible intermediate in the production of HFC-134a which can be produced by hydrogenation.[9]

Atmosphere

The ozone depletion potential of 1,1-dichlorotetrafluoroethane is 0.72.[10] The estimated lifetime in the atmosphere is about 100 years.[10] The radiative efficiency is 0.28 Wm−2ppb−1.[10] Global warming potential in 20 years is 6750.[10] The atmospheric concentration of CFC-114a is not usually measured separately from CFC-114 due to difficulties in distinguishing them apart.[10]

In 1978 atmospheric levels of CFC-114a were 0.35 ppt. By 2020 the level was up to 1.13 ppt.[11] CFC-114a appears to be emitted into the atmosphere is South East Asia.[12]

The atmospheric natural destruction of CFC-114a is by reaction with atomic oxygen, or breakup by ultraviolet light.[12] As of 2014 about 250 tons per year of CFC-114a were being put into the atmosphere.[12]

Notes and References

  1. Deiters . Ulrich K . Some remarks on the nomenclature of refrigerants . Fluid Phase Equilibria . May 1997 . 132 . 1–2 . 265–270 . 10.1016/S0378-3812(96)03232-3.
  2. Web site: Gumprecht . William Henry . Longoria . John Mark . Christoph . Frank J. . Process for manufacture of 1,1-dichlorotetrafluoroethane . en . 8 May 1991.
  3. Bozorgzadeh . H . Kemnitz . E . Nickkho-Amiry . M . Skapin . T . Winfield . J.M . Conversion of 1,1,2-trichlorotrifluoroethane to 1,1,1-trichlorotrifluoroethane and 1,1-dichlorotetrafluoroethane over aluminium-based catalysts . Journal of Fluorine Chemistry . January 2001 . 107 . 1 . 45–52 . 10.1016/S0022-1139(00)00350-X.
  4. Haszeldine . R. N. . 849. Fluoro-olefins. Part I. The synthesis of hexafluorobuta-1 : 3-diene . Journal of the Chemical Society (Resumed) . 1952 . 4423 . 10.1039/JR9520004423.
  5. 10.1246/cl.1994.571 . Determination of 1,2-dichlorotetrafluoroethane (CFC-114) Concentration in the Atmosphere . 1994 . Chen . Limin . Makide . Yoshihiro . Tominaga . Takeshi . Chemistry Letters . 23 . 3 . 571–574 .
  6. Book: Bruno . Thomas J. . Spectroscopic Library for Alternative Refrigerant Analysis . 1990 . U.S. Department of Commerce, National Institute of Standards and Technology . en. 25–27.
  7. Karpinski . Zbigniew . Early . Kintu . d'Itri . Julie L. . Catalytic Hydrodechlorination of 1,1-Dichlorotetrafluoroethane by Pd/Al2O3 . Journal of Catalysis . December 1996 . 164 . 2 . 378–386 . 10.1006/jcat.1996.0394.
  8. Tomioka . Satoshi . Mori . Tohru . Ueda . Wataru . Morikawa . Yutaka . Ikawa . Tsuneo . A Novel Hydrodechlorinative Dimerization of Chlorofluorocarbons over Supported Ni Catalysts . Chemistry Letters . October 1991 . 20 . 10 . 1825–1826 . 10.1246/cl.1991.1825.
  9. Suh . Dong Jin . Park . Tae-Jin . Lee . Byung-Gwon . Park . Kun-You . Synthesis of HFC-134a by isomerization and hydrogenation . Korean Journal of Chemical Engineering . January 1996 . 13 . 1 . 75–81 . 10.1007/BF02705892. 97614597 .
  10. Davis . Maxine E. . Bernard . François . McGillen . Max R. . Fleming . Eric L. . Burkholder . James B. . UV and infrared absorption spectra, atmospheric lifetimes, and ozone depletion and global warming potentials for CCl<sub>2</sub>FCCl<sub>2</sub>F (CFC-112), CCl<sub>3</sub>CClF<sub>2</sub> (CFC-112a), CCl<sub>3</sub>CF<sub>3</sub> (CFC-113a), and CCl<sub>2</sub>FCF<sub>3</sub> (CFC-114a) . Atmospheric Chemistry and Physics . 1 July 2016 . 16 . 12 . 8043–8052 . 10.5194/acp-16-8043-2016. 2016ACP....16.8043D . 102078043 . free . 1983/df193a7b-14de-427c-a539-238701f9e3b3 . free .
  11. Western . Luke M. . Vollmer . Martin K. . Global increase of ozone-depleting chlorofluorocarbons from 2010 to 2020 . Nature Geoscience . 3 April 2023 . 309–313 . 16 . 4 . 10.1038/s41561-023-01147-w . 2023NatGe..16..309W . 257941769 . 1. 1983/9e103fef-e61c-49c7-a1a3-902540ec1d7c . free .
  12. Laube . Johannes C. . Mohd Hanif . Norfazrin . Martinerie . Patricia . Gallacher . Eileen . Fraser . Paul J. . Langenfelds . Ray . Brenninkmeijer . Carl A. M. . Schwander . Jakob . Witrant . Emmanuel . Wang . Jia-Lin . Ou-Yang . Chang-Feng . Gooch . Lauren J. . Reeves . Claire E. . Sturges . William T. . Oram . David E. . Tropospheric observations of CFC-114 and CFC-114a with a focus on long-term trends and emissions . Atmospheric Chemistry and Physics . 9 December 2016 . 16 . 23 . 15347–15358 . 10.5194/acp-16-15347-2016. 2016ACP....1615347L . 54195362 . free .

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