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Fluoroform
Fluoroform.svg
Fluoroform-3D-vdW.png
IUPAC name
Other names Fluoroform, Carbon trifluoride, Methyl trifluoride, Fluoryl, Freon 23, Arcton 1, HFC 23, R-23, FE-13, UN 1984
Identifiers
CAS number 75-46-7 Yes check.svgY
PubChem 6373
EC number 200-872-4
ChEBI 24073
RTECS number PB6900000
SMILES
InChI
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
NFPA 704
NFPA 704.svg
0
2
0
 
Flash point Non-flammable
 Yes check.svgY (what is this?)  (verify)
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 tons for HFC-23.[5] The atmospheric lifetime is 260 years.[6]
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 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. 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

  1. ^ Kirschner, E., Chemical and Engineering News 1994, 8.
  2. ^ 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.  
  3. ^ a b Henne A. L. (1937). "Fluoroform". Journal of the American Chemical Society 59 (7): 1200–1202. doi:10.1021/ja01286a012.  
  4. ^ 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
  5. ^ 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://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_Ch02.pdf.  
  6. ^ "Refrigerant Data Summary". Engineered Systems 18: 74–88. 2001.  

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







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