Fluoroform

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Template:Chembox ECNumberTemplate:Chembox E numberTemplate:Chembox SolubilityInWater
Fluoroform
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
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RTECS number PB6900000
Properties
CHF3
Molar mass 70.01 g/mol
Appearance Colorless gas
Melting point
Boiling point
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
Main hazards Nervous system depression
S-phrases S38
Flash point {{{value}}}
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and 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). CHF3 is used in diverse niche applications. It is produced as a by-product of the manufacture of Teflon. CHF3 is generated biologically in small amounts apparently by decarboxylation of trifluoroacetic acid.[1]

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) 4.87 MPa
Critical temperature (Tc) 25.7 °C (299 K)
Critical densityc) 7.52 mol/l
Compressibility factor (Z) 0.9913
Acentric factor (ω) 0.263
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

Industrial applications

CHF3 is used in the semiconductor industry in plasma etching of silicon oxide and silicon nitride.

As a refrigerant, CHF3 is known as R-23 or HFC-23.

HFC-23 is also used as a replacement for Halon 1301[cfc-13b1] in fire suppression systems as a total flooding gaseous fire suppression agent. It is also used as a low temperature refrigerant (replacement for Chlorotrifluoromethane (cfc-13). It is a byproduct of its manufacture. When used as a fire suppressant, the chemical 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.

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. The atmospheric lifetime is 260 years.[2] According to researchers, it is the most abundant of hydrofluorocarbons (HFCs). Its usage has been regulated since December 1997 at Kyoto climate conference.

Chemistry

It was first obtained by Meslans in the violent reaction of iodoform with dry silver fluoride in 1894. [3] The reaction was improved by Otto Ruff by substitution of silver fluoride by a mixture of mercury fluoride and calcium fluoride.[4] 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 methode was found by Henne.[5]

Organic chemistry

CHF3 is a reagent to generate CF3- reagents by deprotonation. The molecule is weakly acidic with a pKa = 25–28. It is a precursor to CF3Si(CH3)3[6]

See also

References

  1. Kirschner, E., Chemical and Engineering News 1994, 8.
  2. "Refrigerant Data Summary". Engineered Systems. 18: 74–88. 2001.
  3. Meslans M. M. (1894). Annales de chimie et de physique. 7 (1): 346–423 http://gallica.bnf.fr/ark:/12148/bpt6k34901c/f344.table |url= missing title (help).
  4. Henne A. L. (1937). "Fluoroform". Journal of the American Chemical Society. 59 (7): 1200–1202. doi:10.1021/ja01286a012.
  5. Henne A. L. (1937). "Fluoroform". Journal of the American Chemical Society. 59 (7): 1200–1202. doi:10.1021/ja01286a012.
  6. 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


External links

de:Fluoroform


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