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Fluoroform

Fluoroform
Fluoroform.svg
Fluoroform-3D-vdW.png
Names
IUPAC name
Trifluoromethane
Other names
Fluoroform, Carbon trifluoride, Methyl trifluoride, Fluoryl, Freon 23, Arcton 1, HFC 23, R-23, FE-13, UN 1984
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.000.794
EC Number 200-872-4
RTECS number PB6900000
UNII
Properties
CHF3
Molar mass 70.01 g/mol
Appearance Colorless gas
Density 2.946 kg·m−3 (gas, 1 bar, 15 °C)
Melting point −155.2 °C (−247.4 °F; 118.0 K)
Boiling point −82.1 °C (−115.8 °F; 191.1 K)
1 g/l
Solubility in organic solvents Soluble
Vapor pressure 4.38 MPa at 20 °C
0.013 mol.kg−1.bar−1
Acidity (pKa) 25 - 28
Structure
Tetrahedral
Hazards
Main hazards Nervous system depression
S-phrases (outdated) S38
NFPA 704
Flammability code 0: Will not burn. E.g. waterHealth code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored diamond
0
2
0
Flash point Non-flammable
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Fluoroform is the chemical compound with the formula CHF3. It is one of the "haloforms", a class of compounds with the formula CHX3 (X = halogen) with C3v symmetry. Fluoroform is used in diverse applications in organic synthesis. It is not an ozone depleter but is a greenhouse gas.[1]

Synthesis

About 20M kg/y are produced industrially as both a by-product of and precursor to the manufacture of Teflon.[1] It is produced by reaction of chloroform with HF:[2]

CHCl3 + 3 HF → CHF3 + 3 HCl

It is also generated biologically in small amounts apparently by decarboxylation of trifluoroacetic acid.[3]

Historical

Fluoroform was first obtained by Maurice Meslans in the violent reaction of iodoform with dry silver fluoride in 1894.[4] The reaction was improved by Otto Ruff by substitution of silver fluoride by a mixture of mercury fluoride and calcium fluoride.[5] The exchange reaction works with iodoform and bromoform, and the exchange of the first two halogen atoms by fluorine is vigorous. By changing to a two step process, first forming a bromodifluoro methane in the reaction of antimony trifluoride with bromoform and finishing the reaction with mercury fluoride the first efficient synthesis method was found by Henne.[5]

Industrial applications

CHF3 is used in the semiconductor industry in plasma etching of silicon oxide and silicon nitride. Known as R-23 or HFC-23, it is also a useful refrigerant, sometimes as a replacement for chlorotrifluoromethane (cfc-13) and is a byproduct of its manufacture.

When used as a fire suppressant, the fluoroform carries the DuPont trade name, FE-13. CHF3 is recommended for this application because of its low toxicity, its low reactivity, and its high density. HFC-23 has been used in the past as a replacement for Halon 1301[cfc-13b1] in fire suppression systems as a total flooding gaseous fire suppression agent.

Organic chemistry

Fluoroform is weakly acidic with a pKa = 25–28 and quite inert. Attempted deprotonation results in defluorination to generate F and difluorocarbene (CF2). Some organocopper and organocadmium compounds have been developed as trifluoromethylation reagents.[6]

Fluoroform is a precursor of Ruppert's reagent CF3Si(CH3)3, which a source of the nucleophilic CF3 anion.[7][8]

Greenhouse gas

CHF3 is a potent greenhouse gas. A ton of HFC-23 in the atmosphere has the same effect as 11,700 tons of carbon dioxide. This equivalency, also called a 100-yr global warming potential, is slightly larger at 14,800 for HFC-23.[9] The atmospheric lifetime is 270 years.[9]

HFC-23 was the most abundant HFC in the global atmosphere until around 2001, which is when the global mean concentration of HFC-134a (1,1,1,2-tetrafluoroethane), the chemical now used extensively in automobile air conditioners, surpassed those of HFC-23. Global emissions of HFC-23 have in the past been dominated by the inadvertent production and release during the manufacture of the refrigerant HCFC-22 (chlorodifluoromethane).

Substantial decreases are evident in developed or Annex 1 countries HFC-23 emissions from the 1990s to the 2000s (UNFCCC greenhouse gas emissions databases).[10] The UNFCCC Clean Development Mechanism projects have provided funding and facilitated the destruction of HFC-23 co-produced from a portion of HCFC-22 produced in developing or non-Annex 1 countries since 2003. Developing countries have become the largest producers of HCFC-22 in recent years according to data compiled by the Ozone Secretariat of the World Meteorological Organization.[11][12][13] Emissions of all HFCs are included in the UNFCCCs Kyoto Protocol. To mitigate its impact, CHF3 can be destroyed with electric plasma arc technologies or by high temperature incineration.[14]

References

  1. ^ a b ShivaKumar Kyasa (2015). "Fluoroform (CHF3)". Synlett. 26 (13): 1911–1912. doi:10.1055/s-0034-1380924.
  2. ^ G. Siegemund, W. Schwertfeger, A. Feiring, B. Smart, F. Behr, H. Vogel, B. McKusick (2005). "Fluorine Compounds, Organic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a11_349.CS1 maint: multiple names: authors list (link)
  3. ^ Kirschner, E., Chemical and Engineering News 1994, 8.
  4. ^ Meslans M. M. (1894). "Recherches sur quelques fluorures organiques de la série grasse". Annales de chimie et de physique. 7 (1): 346–423.
  5. ^ a b Henne A. L. (1937). "Fluoroform". Journal of the American Chemical Society. 59 (7): 1200–1202. doi:10.1021/ja01286a012.
  6. ^ Zanardi, Alessandro; Novikov, Maxim A.; Martin, Eddy; Benet-Buchholz, Jordi; Grushin, Vladimir V. (2011-12-28). "Direct Cupration of Fluoroform". Journal of the American Chemical Society. 133 (51): 20901–20913. doi:10.1021/ja2081026. ISSN 0002-7863. PMID 22136628.
  7. ^ Rozen, S.; Hagooly, A. "Fluoroform" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. doi: 10.1002/047084289X.rn00522
  8. ^ Prakash, G. K. Surya; Jog, Parag V.; Batamack, Patrice T. D.; Olah, George A. (2012-12-07). "Taming of Fluoroform: Direct Nucleophilic Trifluoromethylation of Si, B, S, and C Centers". Science. 338 (6112): 1324–1327. Bibcode:2012Sci...338.1324P. doi:10.1126/science.1227859. ISSN 0036-8075. PMID 23224551.
  9. ^ a b Forster, P., V. Ramaswamy, P. Artaxo, T. Berntsen, R. Betts, D.W. Fahey, J. Haywood, J. Lean, D.C. Lowe, G. Myhre, J. Nganga, R. Prinn, G. Raga, M. Schulz and R. Van Dorland (2007). "Changes in Atmospheric Constituents and in Radiative Forcing." (PDF). Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change.CS1 maint: multiple names: authors list (link)
  10. ^ [unfccc.int]
  11. ^ [ozone.unep.org]
  12. ^ Profits on Carbon Credits Drive Output of a Harmful Gas August 8, 2012 New York Times
  13. ^ Subsidies for a Global Warming Gas
  14. ^ Han, Wenfeng; Li, Ying; Tang, Haodong; Liu, Huazhang (2012). "Treatment of the potent greenhouse gas, CHF3. An overview". Journal of Fluorine Chemistry. 140: 7-16. doi:10.1016/j.jfluchem.2012.04.012.CS1 maint: multiple names: authors list (link)

Literature

External links

Additional physical properties

Property Value
Density (ρ) at -100 °C (liquid) 1.52 g/cm3
Density (ρ) at -82.1 °C (liquid) 1.431 g/cm3
Density (ρ) at -82.1 °C (gas) 4.57 kg/m3
Density (ρ) at 0 °C (gas) 2.86 kg/m3
Density (ρ) at 15 °C (gas) 2.99 kg/m3
Dipole moment 1.649 D
Critical pressure (pc) 4.816 MPa (48.16 bar)
Critical temperature (Tc) 25.7 °C (299 K)
Critical densityc) 7.52 mol/l
Compressibility factor (Z) 0.9913
Acentric factor (ω) 0.26414
Viscosity (η) at 25 °C 14.4 μPa.s (0.0144 cP)
Molar specific heat at constant volume (CV) 51.577 J.mol−1.K−1
Latent heat of vaporization (lb) 257.91 kJ.kg−1