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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. Fluoroform is also generated biologically in small amounts apparently by decarboxylation of trifluoroacetic acid.[1]

Additional physical properties

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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

Industrial applications

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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

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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 method was found by Henne.[5]

Organic chemistry

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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

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References

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  1. ^ Kirschner, E., Chemical and Engineering News 1994, 8.
  2. ^ Refrigerant Data Summary. Engineered Systems. 2001, 18: 74–88. 
  3. ^ Meslans M. M. Recherches sur quelques fluorures organiques de la série grasse. Annales de chimie et de physique. 1894, 7 (1): 346–423. 
  4. ^ Henne A. L. Fluoroform. Journal of the American Chemical Society. 1937, 59 (7): 1200–1202. doi:10.1021/ja01286a012. 
  5. ^ Henne A. L. Fluoroform. Journal of the American Chemical Society. 1937, 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


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