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.
Fluoroform, carbon trifluoride, methyl trifluoride, Fluoryl, Freon 23, Arcton 1, HFC 23, R-23, FE-13, UN 1984
3D model (JSmol)
CompTox Dashboard (EPA)
|Molar mass||70.01 g/mol|
|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)|
|Solubility in organic solvents||Soluble|
|Vapor pressure||4.38 MPa at 20 °C|
|Main hazards||Nervous system depression|
|NFPA 704 (fire diamond)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
- CHCl3 + 3 HF → CHF3 + 3 HCl
Fluoroform was first obtained by Maurice Meslans in the violent reaction of iodoform with dry silver fluoride in 1894. The reaction was improved by Otto Ruff by substitution of silver fluoride by a mixture of mercury fluoride and calcium fluoride. 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.
CHF3 is used in the semiconductor industry in plasma etching of silicon oxide and silicon nitride. Known as R-23 or HFC-23, it was 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.
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.
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. The atmospheric lifetime is 270 years.
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). 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.
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- "Archived copy". Archived from the original on 2011-07-21. Retrieved 2010-04-03.CS1 maint: archived copy as title (link)
- Profits on Carbon Credits Drive Output of a Harmful Gas August 8, 2012 New York Times
- Subsidies for a Global Warming Gas
- 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.
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Additional physical propertiesEdit
|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|