- Fluoroform
-
Fluoroform 
TrifluoromethaneOther namesFluoroform, Carbon trifluoride, Methyl trifluoride, Fluoryl, Freon 23, Arcton 1, HFC 23, R-23, FE-13, UN 1984Identifiers CAS number 75-46-7 
PubChem 6373 ChemSpider 21106179 UNII ZJ51L9A260 EC number 200-872-4 ChEBI CHEBI:24073 RTECS number PB6900000 Jmol-3D images Image 1 - FC(F)F
- InChI=1S/CHF3/c2-1(3)4/h1H
Key: XPDWGBQVDMORPB-UHFFFAOYSA-N
InChI=1/CHF3/c2-1(3)4/h1H
Key: XPDWGBQVDMORPB-UHFFFAOYAM
Properties Molecular formula CHF3 Molar mass 70.01 g/mol Appearance Colorless gas Melting point -155.2 °C (117.95 K)
Boiling point -82.1°C (191.05 K)
Solubility in water 1 g/l Solubility in organic solvents Soluble Vapor pressure 4.38 MPa at 20 °C kH 0.013 mol.kg-1.bar-1 Acidity (pKa) 25 - 28 Hazards S-phrases S38 Main hazards Nervous system depression NFPA 704 
020Flash point Non-flammable 
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)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). Fluoroform is used in diverse niche applications and is produced as a by-product of the manufacture of Teflon. It is also generated biologically in small amounts apparently by decarboxylation of trifluoroacetic acid.[1]
Contents
Synthesis
Fluoroform was first obtained by Maurice Meslans in the violent reaction of iodoform with dry silver fluoride in 1894.[2] The reaction was improved by Otto Ruff by substitution of silver fluoride by a mixture of mercury fluoride and calcium fluoride.[3] 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.[3]
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
CHF3 is a reagent to generate sources of "CF3-" by deprotonation. The molecule is weakly acidic with a pKa = 25–28. It is a precursor to CF3Si(CH3)3[4]
Greenhouse gas
CHF3 is a potent greenhouse gas. The secretariat of the Clean Development Mechanism estimates that a ton of HFC-23 in the atmosphere has the same effect as 11,700 tons of carbon dioxide. More recent work (IPCC, 2007) suggests that this equivalency, also called a 100-yr global warming potential, is slightly larger at 14,800 for HFC-23.[5] The atmospheric lifetime is 270 years.[5]
According to the 2007 IPCC climate report, 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).
Data reported to the United Nations Framework Convention on Climate Change (UNFCCC) greenhouse gas emissions databases [6] indicate substantial decreases in developed or Annex 1 countries HFC-23 emissions from the 1990s to the 2000s (UNFCCC greenhouse gas emissions databases). 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.[7] 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.
References
- ^ Kirschner, E., Chemical and Engineering News 1994, 8.
- ^ Meslans M. M. (1894). "Recherches sur quelques fluorures organiques de la série grasse". Annales de chimie et de physique 7 (1): 346–423. http://gallica.bnf.fr/ark:/12148/bpt6k34901c/f344.table.
- ^ a b Henne A. L. (1937). "Fluoroform". Journal of the American Chemical Society 59 (7): 1200–1202. doi:10.1021/ja01286a012.
- ^ Rozen, S.; Hagooly, A. "Fluoroform" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. doi: 10.1002/047084289
- ^ 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.". Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter2.pdf.
- ^ http://unfccc.int/di/FlexibleQueries.do
- ^ http://ozone.unep.org/Data_Reporting/Data_Access/
Literature
- McBee E. T. (1947). "Fluorine Chemistry". Industrial & Engineering Chemistry 39 (3): 236–237. doi:10.1021/ie50447a002.
- Oram D. E., Sturges W. T., Penkett S. A., McCulloch A., Fraser P. J. (1998). "Growth of fluoroform (CHF3, HFC-23) in the background atmosphere". Geophysical Research Letters 25 (1): 236–237. doi:10.1029/97GL03483. http://www.agu.org/pubs/crossref/1998.../97GL03483.shtml.
- McCulloch A. (2003). "Fluorocarbons in the global environment: a review of the important interactions with atmospheric chemistry and physics". Journal of Fluorine Chemistry 123 (1): 21–29. doi:10.1016/S0022-1139(03)00105-2.
External links
- International Chemical Safety Card 0577
- MSDS at Oxford University
- MSDS at mathesontrigas.com
- Coupling of fluoroform with aldehydes using an electrogenerated base
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 density (ρc) 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 Halomethanes Monosubstituted Disubstituted Trisubstituted Categories:- Organofluorides
- Halomethanes
- Refrigerants
- Fire suppression agents
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