Given the ban on producing chlorofluorocarbons, it is actually important not to produce 1,1-dichlorotetrafluoroethane intentionally or unintentionally.
1,1-Dichlorotetrafluoroethane can be made free from other isomers by reacting trichlorotrifluoroethane (CFC-113 or CFC-113a) with antimony pentachloride.[3] 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.[4]
It can also be made in a reaction of tetrachloroethylene with hydrogen fluoride and chlorine, but this results in a mixture.[3]
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.[5]
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.[6] Also in a gas chromatograph, it is hard to distinguish from the symmetric 1,2 isomer.[6]
Critical properties include critical temperature 145.7°C, critical pressure 4.92 Mpa and critical density of 0.82 g/ml.[7]
1,1-Dichlorotetrafluoroethane does not ignite in air.[7]
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.[8]
1,1-Dichlorotetrafluoroethane reacts with alkali metals, alkaline earths and aluminium.[7]
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.[9]
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.[10]
CFC-114a is a possible intermediate in the production of HFC-134a[10] which can be produced by hydrogenation.[11]
Atmosphere
Mixing ratio of CFC-114a in air (red). Also CFC-114 in black
The ozone depletion potential of 1,1-dichlorotetrafluoroethane is 0.72.[12] The estimated lifetime in the atmosphere is about 100 years.[12] The radiative efficiency is 0.28 Wm−2ppb−1.[12] Global warming potential in 20 years is 6750.[12] The atmospheric concentration of CFC-114a is not usually measured separately from CFC-114 due to difficulties in distinguishing them apart.[12]
In 1978 atmospheric levels of CFC-114a were 0.35 ppt. By 2020 the level was up to 1.13 ppt.[13] CFC-114a appears to be emitted into the atmosphere is South East Asia.[10]
The atmospheric natural destruction of CFC-114a is by reaction with atomic oxygen, or breakup by ultraviolet light.[10] As of 2014 about 250 tons per year of CFC-114a were being put into the atmosphere.[10]
^Deiters, Ulrich K (May 1997). "Some remarks on the nomenclature of refrigerants". Fluid Phase Equilibria. 132 (1–2): 265–270. doi:10.1016/S0378-3812(96)03232-3.
^Bozorgzadeh, H; Kemnitz, E; Nickkho-Amiry, M; Skapin, T; Winfield, J.M (January 2001). "Conversion of 1,1,2-trichlorotrifluoroethane to 1,1,1-trichlorotrifluoroethane and 1,1-dichlorotetrafluoroethane over aluminium-based catalysts". Journal of Fluorine Chemistry. 107 (1): 45–52. doi:10.1016/S0022-1139(00)00350-X.
^Haszeldine, R. N. (1952). "849. Fluoro-olefins. Part I. The synthesis of hexafluorobuta-1 : 3-diene". Journal of the Chemical Society (Resumed): 4423. doi:10.1039/JR9520004423.
^ abChen, Limin; Makide, Yoshihiro; Tominaga, Takeshi (1994). "Determination of 1,2-dichlorotetrafluoroethane (CFC-114) Concentration in the Atmosphere". Chemistry Letters. 23 (3): 571–574. doi:10.1246/cl.1994.571.
^Suh, Dong Jin; Park, Tae-Jin; Lee, Byung-Gwon; Park, Kun-You (January 1996). "Synthesis of HFC-134a by isomerization and hydrogenation". Korean Journal of Chemical Engineering. 13 (1): 75–81. doi:10.1007/BF02705892. S2CID97614597.
