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]]
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