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| Names | |||
|---|---|---|---|
| IUPAC names Tetrafluoromethane Carbon tetrafluoride | |||
| Other names Carbon tetrafluoride, Perfluoromethane, Tetrafluorocarbon, Freon 14, Halon 14, Arcton 0, CFC 14, PFC 14, R 14, UN 1982 | |||
| Identifiers | |||
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3D model (JSmol) | |||
| ChEBI | |||
| ChemSpider |
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| ECHA InfoCard | 100.000.815 | ||
| EC Number |
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| RTECS number |
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| UNII | |||
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| Properties | |||
| CF4 | |||
| Molar mass | 88.0043 g/mol | ||
| Appearance | Colorless gas | ||
| Odor | odorless | ||
| Density | 3.72 g/L, gas (15 °C) | ||
| Melting point | −183.6 °C (−298.5 °F; 89.5 K) | ||
| Boiling point | −127.8 °C (−198.0 °F; 145.3 K) | ||
| Critical point (T,P) | −45.55 °C (−50.0 °F; 227.6 K), 36.91 standard atmospheres (3,739.9 kPa; 542.4 psi)[1] | ||
| 0.005%V at 20 °C 0.0038%V at 25 °C | |||
| Solubility | soluble inbenzene,chloroform | ||
| Vapor pressure | 106.5 kPa at −127 °C | ||
Henry's law constant (kH) | 5.15 atm-cu m/mole | ||
Refractive index (nD) | 1.0004823[2] | ||
| Viscosity | 17.32 μPa·s[3] | ||
| Structure | |||
| Tetragonal | |||
| Tetrahedral | |||
| 0 D | |||
| Hazards | |||
| Occupational safety and health (OHS/OSH): | |||
Main hazards | Simple asphyxiant and greenhouse gas | ||
| NFPA 704 (fire diamond) | |||
| Flash point | Non-flammable | ||
| Safety data sheet (SDS) | ICSC 0575 | ||
| Related compounds | |||
Otheranions | Tetrachloromethane Tetrabromomethane Tetraiodomethane | ||
Othercations | Silicon tetrafluoride Germanium tetrafluoride Tin tetrafluoride Lead tetrafluoride | ||
Related fluoromethanes | Fluoromethane Difluoromethane Fluoroform | ||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Tetrafluoromethane, also known ascarbon tetrafluoride or R-14, is the simplestperfluorocarbon (CF4). As its IUPAC name indicates, tetrafluoromethane is the perfluorinated counterpart to the hydrocarbonmethane. It can also be classified as ahaloalkane orhalomethane. Tetrafluoromethane is a usefulrefrigerant but also a potentgreenhouse gas.[4] Although its atmospheric concentration is small, it persists in the atmosphere for 50,000 years, giving it a very highglobal warming potential.[5] It has a very high bond strength due to the nature of thecarbon–fluorine bond.
Because of the multiple carbon–fluorine bonds, and the highelectronegativity offluorine, the carbon in tetrafluoromethane has a significant positivepartial charge which strengthens and shortens the four carbon–fluorine bonds by providing additionalionic character. Carbon–fluorine bonds are the strongest single bonds inorganic chemistry.[6] Additionally, they strengthen as more carbon–fluorine bonds are added to the same carbon atom. In the one-carbonorganofluorine compounds represented by molecules offluoromethane,difluoromethane,trifluoromethane, and tetrafluoromethane, the carbon–fluorine bonds are strongest in tetrafluoromethane.[7] This effect is due to the increasedcoulombic attractions between the fluorine atoms and the carbon because the carbon has a positive partial charge of 0.76.[7]
Tetrafluoromethane is the product when any carbon compound, including carbon itself, is burned in an atmosphere of fluorine. With hydrocarbons,hydrogen fluoride is a coproduct. It was first reported in 1926.[8] It can also be prepared by thefluorination ofcarbon dioxide,carbon monoxide orphosgene withsulfur tetrafluoride. Commercially it is manufactured by the reaction ofhydrogen fluoride withdichlorodifluoromethane orchlorotrifluoromethane; it is also produced during theelectrolysis of metalfluorides MF, MF2 using a carbon electrode.
Although it can be made from a myriad of precursors and fluorine, elemental fluorine is expensive and difficult to handle. Consequently,CF
4 is prepared on an industrial scale usinghydrogen fluoride:[4]
Tetrafluoromethane andsilicon tetrafluoride can be prepared in the laboratory by the reaction ofsilicon carbide with fluorine.
Tetrafluoromethane, like other fluorocarbons, is very stable due to the strength of its carbon–fluorine bonds. The bonds in tetrafluoromethane have abonding energy of 515 kJ⋅mol−1. As a result, it is inert to acids and hydroxides. However, it reacts explosively withalkali metals.Thermal decomposition or combustion of CF4 produces toxic gases (carbonyl fluoride andcarbon monoxide) and in the presence of water will also yieldhydrogen fluoride.
It is very slightly soluble in water (about 20 mg⋅L−1), but highly soluble in organic solvents. When liquified, it is completely miscible in organic solvents.
Tetrafluoromethane is sometimes used as a low temperaturerefrigerant (R-14). It is used inelectronicsmicrofabrication alone or in combination withoxygen as aplasma etchant forsilicon,silicon dioxide, andsilicon nitride.[9] It also has uses in neutron detectors.[10]
Tetrafluoromethane is a potentgreenhouse gas that contributes to thegreenhouse effect. It is very stable, has anatmospheric lifetime of 50,000 years, and a highgreenhouse warming potential 6,500 times that of CO2.[11]
Tetrafluoromethane is the most abundantperfluorocarbon in the atmosphere, where it is designated as PFC-14. Its atmospheric concentration is growing:[12] its preindustrial concentration produced via radioactive oxidation offluorite and reaction with organic molecules was less than 40 parts per trillion.[13][a] As of 2019, the man-made gasesCFC-11 andCFC-12 continue to contribute a strongerradiative forcing than PFC-14.[14]
Although structurally similar tochlorofluorocarbons (CFCs), tetrafluoromethane does notdeplete the ozone layer[15] because the carbon–fluorine bond is much stronger than that between carbon and chlorine.[16]
Main industrial emissions of tetrafluoromethane besideshexafluoroethane are produced during production ofaluminium usingHall-Héroult process. CF4 also is produced as product of the breakdown of more complex compounds such ashalocarbons.[17]
Due to its density, tetrafluoromethane can displace air, creating anasphyxiation hazard in inadequately ventilated areas. Otherwise, it is normally harmless due to its stability.
