Tetrafluoromethane 2375338 225837261 2008-07-15T17:04:24Z Evolauxia 100838 [[Category:Greenhouse gases]] {{Chembox new | ImageFileL1 = Tetrafluoromethane-2D.png | ImageSizeL1 = | ImageFileR1 = Tetrafluoromethane-3D-vdW.png | ImageSizeR1 = 110px | IUPACName = Tetrafluoromethane<br/>Carbon tetrafluoride | OtherNames = Perfluoromethane, Tetrafluorocarbon, Freon 14, Halon 14, Arcton 0, CFC 14, PFC 14, R 14, UN 1982 | Section1 = {{Chembox Identifiers | CASNo = 75-73-0 | EINECS = 200-896-5 | PubChem = 6393 | SMILES = C(F)(F)(F)F | InChI = 1/CF4/c2-1(3,4)5 | RTECS = FG4920000 }} | Section2 = {{Chembox Properties | Formula = CF<sub>4</sub> | MolarMass = 88.00 g/mol | Appearance = Colorless odorless gas | Density = 3.72 g/l, gas (15 °C) | MeltingPt = -183.6 °C (89.6 K) | BoilingPt = -127.8 °C (145.4 K) | Solubility = 0.005 %<sub>V</sub> at 20 °C 0.0038 %<sub>V</sub> at 25 °C | VaporPressure = 3.65 MPa at 15 °C 106.5 kPa at -127 °C }} | Section3 = {{Chembox Structure | CrystalStruct = | Coordination = | MolShape = Tetrahedral }} | Section3 = {{Chembox Hazards | MainHazards = | RPhrases = None | SPhrases = None | NFPA-H = 1 | NFPA-F = 0 | NFPA-R = 0 | NFPA-O = | FlashPt = Non flammable | Autoignition = > 1100 °C }} }} '''Tetrafluoromethane''', also known as '''carbon tetrafluoride''', '''Freon-14''' and '''R 14''', is a [[carbon]] [[fluoride]] (CF<sub>4</sub>). It can be considered either a [[haloalkane]], [[halomethane]], [[perfluorocarbon]] or an [[inorganic]] compound. At a temperature of -198 °C, it has [[Monoclinic crystal system|monoclinic]] structure with [[lattice constants]] ''a'' = 8.597, ''b'' = 4.433, ''c'' = 8.381 (.10<sup>-1</sup> nm), β = 118.73°<ref name="chtas">F. Brezina, J. Mollin, R. Pastorek, Z. Sindelar. ''Chemicke tabulky anorganickych sloucenin'' (''Chemical tables of inorganic compounds''). SNTL, 1986.</ref>. == Additional physical properties == {| class="wikitable" ! Property ! Value |- | [[Density]] (ρ) at -196 °C (solid) | 1.943 g.cm<sup>-3</sup> |- | [[Density]] (ρ) at -183 °C | 1.89 g.cm<sup>-3</sup> |- | [[Density]] (ρ) at -127.8 °C (liquid) | 1.603 g.cm<sup>-3</sup> |- | [[Density]] (ρ) at -80 °C (gas) | 1.317 kg.m<sup>-3</sup> |- | [[Density]] (ρ) at 15 °C (gas) | 3.72 kg.m<sup>-3</sup> |- | [[Density]] (ρ) at 21 °C (gas) | 3.858 kg.m<sup>-3</sup> |- | [[Triple point]] temperature (T<sub>t</sub>) | -183.7 °C (89.4 K) |- | [[Critical temperature]] (T<sub>c</sub>) | -45.5 °C (227.6 K) |- | Critical pressure (p<sub>c</sub>) | 3.793 MPa (37.43 bar) |- | Critical volume (V<sub>c</sub>) | 0.142 dm<sup>3</sup>.mol<sup>-1</sup> |- | Critical compressibility (Z<sub>c</sub>) | 2.77 |- | [[Latent heat of fusion]] (l<sub>f</sub>) at triple point | 8.09 kJ.kg<sup>-1</sup> |- | [[Latent heat of vaporization]] (l<sub>v</sub>) at -127.8 °C | 135.7 kJ.kg<sup>-1</sup> |- | [[Specific heat capacity]] at constant pressure (c<sub>p</sub>) at 30 °C | 58 J.mol<sup>-1</sup>.K<sup>-1</sup> |- | [[Specific heat capacity]] at constant pressure (c<sub>p</sub>) at -145 °C | 80.08 J.mol<sup>-1</sup>.K<sup>-1</sup> |- | [[Specific heat capacity]] at constant volume (c<sub>v</sub>) at 30 °C | 49 J.mol<sup>-1</sup>.K<sup>-1</sup> |- | [[Heat capacity ratio]] (κ) at 30 °C | 1.178571 |- | [[Compressibility|Compressibility Factor]] (Z) at 15 °C | 0.9981 |- | [[Acentric factor]] (ω) | 0.177 |- | [[Dipole moment]] | 0 D |- | [[Viscosity]] (η) at 0 °C | 16.1 μPa.s (0.0161 cP) |- | [[Viscosity]] (η) at -60.3 °C | 17.0 μPa.s (0.0170 cP) |- | [[Surface tension]] (σ) at -80 °C | 6.4 mN.m<sup>-1</sup> |- | [[Thermal conductivity]] (λ) at 0 °C | 15.03 mW.m<sup>-1</sup>.K<sup>-1</sup> |- |} == Chemistry<ref name="chemelem">N. N. Greenwood, A. Earnshaw. ''Chemie prvku'' (''Chemistry of the Elements''). Informatorium, Prague, 1993.</ref> == Pure tetrafluoromethane was first synthesised in [[1926]]. Tetrafluoromethane can be prepared in the laboratory by the reaction of silicon carbide with fluorine: : SiC + 2 F<sub>2</sub> → CF<sub>4</sub> + Si or by the [[fluorination]] of [[carbon dioxide]], [[carbon monoxide]] or [[phosgene]] with [[sulfur tetrafluoride]]. Commercially it is manufactured by the aggressive reaction of [[fluorine]] with [[dichlorodifluoromethane]] or [[chlorotrifluoromethane]]; it is also produced during the [[electrolysis]] of metal [[fluoride|fluorides]] MF, MF<sub>2</sub> using a carbon electrode. Tetrafluoromethane, as other fluorinated hydrocarbons, is very stable due to the strength of C-F [[bonds]] with [[bonding energy]] of 515 kJ.mol<sup>-1</sup> (see Environmental effects). As a result, it is inert to acids and hydroxides. However, it reacts explosively with [[alkali metal]]s. Thermal decomposition of CF<sub>4</sub>produces toxic gases ([[carbonyl fluoride]] and [[carbon monoxide]]) and in the presence of water will also yield [[hydrogen fluoride]]. It is very slightly soluble in water (about 20 mg.l<sup>-1</sup>), but miscible with [[ethanol]], [[ether]], [[benzene]]. == Uses == Tetrafluoromethane is sometimes used as a low temperature [[refrigerant]]. It is used in [[electronics]] [[microfabrication|microprocessing]] alone or in combination with [[oxygen]] as a [[plasma etching|plasma etchant]] for [[silicon]], [[silicon dioxide]], and [[silicon nitride]].<ref name=williams>K. Williams, K. Gupta, M. Wasilik. ''Etch Rates for Micromachining Processing - Part II'' J. Microelectromech. Syst., vol. 12, pp. 761-777, Dec. 2003.</ref> == Environmental effects == Tetrafluoromethane is a potent [[greenhouse gas]] that contributes to the [[greenhouse effect]]. It is very stable, has an atmospheric lifespan of 50,000 years, and a high [[greenhouse warming potential]] of 6500 ([[carbon dioxide|C0<sub>2</sub>]] has a factor of 1), however, the low amount in the atmosphere restricts the overall [[radiative forcing]] effect.{{fact|date=July 2008}} Although structurally similar to [[chlorofluorocarbons]] (CFCs), tetrafluoromethane does not [[Ozone depletion|deplete the ozone layer]]. This is because the depletion is caused by the chlorine atoms in CFCs, which dissociate when struck by UV radiation. Carbon-fluorine bonds are stronger and less likely to dissociate.{{fact|date=July 2008}} == Health risks == Inhalation of tetrafluoromethane can cause, depending on concentration, headache, nausea, dizziness and damage to the [[cardiovascular system]] (mainly the heart). Long-term exposure can cause severe heart damage. Due to its density, tetrafluoromethane can displace air, creating an [[asphyxiation]] hazard in inadequately ventilated areas. == References == {{reflist}} == See also == * [[Haloalkane]] * [[Halomethane]] * [[Tetrahalomethane]] * [[Fluoromethane]] * [[Difluoromethane]] * [[Fluoroform]] * [[Carbon tetrachloride]] (Tetrachloromethane) * [[Tetrabromomethane]] * [[Carbon tetraiodide]] (Tetraiodomethane) * [[Hexafluoroethane]] * [[Octafluoropropane]] * [[Silicon tetrafluoride]] == External links == *{{ICSC|0575|05}} *[http://www.npi.gov.au/database/substance-info/profiles/44.html National Pollutant Inventory - Flouride and compounds fact sheet] *[http://encyclopedia.airliquide.com/Encyclopedia.asp?GasID=61 Data from Air Liquide] *[http://encyclopedia.airliquide.com/images_encyclopedie/VaporPressureGraph/Tetrafluoromethane_Vapor_Pressure.GIF Vapor pressure graph at Air Liquide] *[http://ptcl.chem.ox.ac.uk/MSDS/CA/carbon_tetrafluoride.html MSDS at Oxford University] *[http://www.climatevision.gov/sectors/aluminum/pdfs/tms_protocol.pdf Protocol for measurement of tetrafluoromethane and hexafluoroethane from primary aluminium production] *[http://www.cheric.org/kdb/kdb/hcprop/listcmp.php?cmpclass=48 Chemical and physical properties table] [[Category:Inorganic carbon compounds]] [[Category:Fluorides]] [[Category:Nonmetal halides]] [[Category:Organofluorides]] [[Category:Halomethanes]] [[Category:Refrigerants]] [[Category:Greenhouse gases]] [[de:Tetrafluormethan]] [[fr:Perfluorométhane]] [[hu:Tetrafluor-metán]] [[ja:四フッ化炭素]] [[ru:Тетрафторметан]] [[zh:四氟甲烷]]