1,1,1,2-Tetrafluoroethane (also known as norflurane ( INN ), R-134a , Freon 134a , Forane 134a , Genetron 134a , Florasol 134a , SuVA 134a , or HFC-134a ) is a hydrofluorocarbon (HFC) and haloalkane R-12 (dichlorodifluoromethane), a refrigerant with similar thermodynamic properties , but negligible ozone depletion potential and a lower 100-year global warming potential (1,430, 10,900 compared to R-12 ‘s GWP). [2]It has the formula CF 3 CH 2 F and a boiling point of -26.3 °C (-15.34 °F) at atmospheric pressure. R-134a cylinders are pale blue in color. [3] A phasing out and transition to HFO -1234yf and other refrigerants, with GWP similar to CO2 , within the automotive market began in 2012.
Use
1,1,1,2-Tetrafluoroethane is a non-flammable gas primarily used as a “high temperature” refrigerant for domestic refrigeration and automobile air conditioners. These devices began using 1,1,1,2-tetrafluoroethane in the early 1990s as a replacement for the more environmentally harmful R-12. Retrofit kits are available to convert units that were originally R-12-equipped.Boiling of tetrafluoroethane liquid when exposed to normal atmospheric pressure and temperature.
Other common uses include blowing plastic foam, as a cleaning solvent, a propellant for the delivery of pharmaceuticals (such as bronchodilators), wine cork remover, gas dusters (“canned air”), and air for removing moisture from compressed air. Dryer included. 1,1,1,2-tetrafluoroethane has also been used to cool the computer in some overclocking efforts. This is the refrigerant used in plumbing pipe freeze kits. It is also commonly used as a propellant for airsoft airguns. The gas is often mixed with silicone-based lubricants.
Aspiring and Niche Applications
1,1,1,2-tetrafluoroethane is also being considered as a suitable organic solvent for the extraction of flavor and aroma compounds as a potential alternative to other organic solvents and supercritical carbon dioxide. [5] [6] It can also be used as a solvent in organic chemistry, both in liquid and in supercritical liquid. [7] It is used in resistive plate chamber particle detectors at the Large Hadron Collider. [8] [9] It is also used for other types of particle detectors, such as some cryogenic particle detectors. [10] It can be used as a shielding gas as a substitute for sulfur hexafluoride in magnesium smelting. [11 1]
1,1,1,2-tetrafluoroethane is also being considered as a dielectric gas as an alternative to sulfur hexafluoride. [12] Its arc-quenching properties are poor, but its dielectric properties are quite good.
History and environmental impact
1,1,1,2-tetrafluoroethane first appeared in the early 1990s as a replacement for dichlorodifluoromethane (R-12), which has ozone depleting properties. [13] It has negligible ozone depletion potential (ozone layer) and negligible acidification potential (acid rain). It has a 100-year global warming potential of 1430 and an estimated atmospheric lifetime of 14 years. [2] Its concentration in the atmosphere and contribution to the radiation force has been increasing since its introduction. It is included in the IPCC list of greenhouse gases.
1,1,1,2-Tetrafluoroethane is subject to use restrictions. The Society of Automotive Engineers (SAE) has proposed that it be replaced by a new fluorochemical refrigerant HFO-1234yf (CF3CF =CH2 ) in automobile air conditioning systems. [15] The R-134A is to be banned from use in the European Union, starting with cars in 2011 and due to be banned entirely by 2030. [16] [17] By model year 2021, the United States will no longer use the R-134a in newly manufactured light-duty vehicles. [4]
California may also prohibit the sale of packaged R-134a to individuals to avoid unprofessional recharge of air conditioners. [18] From October 1994, ATCP 136 banned the sale of container sizes of 1,1,1,2-tetrafluoroethane less than 15 pounds in Wisconsin, but this restriction only applied if the chemical was intended. a refrigerant. However, the ban was lifted in Wisconsin in 2012. [19] While it was active, the Wisconsin-specific ban had flaws. For example, it was legal for a person to purchase a gas duster container with any amount of the chemical because the chemical is neither intended to be a refrigerant in that instance [19] nor is HFC-134a listed in a 7671a Class I has been included in. and class II substances.
production and reactions
Tetrafluoroethane is usually made by the reaction of trichloroethylene with hydrogen fluoride: [21]CHCl=CCl 2 + 4 HF → CF 3 CH 2 F + 3 HCl
It reacts with butyl lithium to give trifluorovinyl lithium: [22]CF 3 CH 2 F + 2 BuLi → CF 2 = CFLi + LiF + 2 BuH
Security
Gas mixtures with air 1,1,1,2-tetrafluoroethane are not flammable at atmospheric pressure and temperatures up to 100 °C (212 °F). However, mixtures containing high concentrations of air can be ignited at elevated pressures and/or temperatures. [23] Contact of 1,1,1,2-tetrafluoroethane with flames or hot surfaces above 250 °C (482 °F) can lead to vapor decomposition and the emission of toxic gases, including hydrogen fluoride and carbonyl fluoride. , [24] although decomposition temperatures have been reported above 370 °C. [25] 1,1,1,2-tetrafluoroethane in rats at 1,500 g/ m3It has an LD50 of LD50, which makes it relatively non-toxic, apart from the inherent dangers from inhalant abuse. Its gaseous form is denser than air and will displace air in the lungs. This can result in asphyxiation due to excessive breathing. [26] [27] It contributes to the majority of deaths from inhalant abuse.
Aerosol cans containing 1,1,1,2-tetrafluoroethane, when inverted, become effective freeze sprays. Under pressure, 1,1,1,2-tetrafluoroethane is compressed into a liquid, which upon vaporization absorbs a significant amount of thermal energy. As a result, it will greatly reduce the temperature of any object it comes into contact with when it evaporates.
medical use
For its medical uses, the generic name for 1,1,1,2-tetrafluoroethane is norflurane. It is used as a propellant for some metered dose inhalers. [28] It is considered safe for this use. [29] [30] [31] In combination with pentafluoropropane, it is used as a topical vapocoolant spray for numbing the boils before they corrode. [32] [33] It has also been studied as a potential inhalational anesthetic, [34] but it is nonanesthetic at the doses used in inhalers.
