Fluoroform

R-23 redirects here; for the Soviet air-to-air missile, see Vympel R-23

for the British airship, see R23

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]

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Additional physical properties

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 method 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

• Haloalkane
• Halomethane
• Trihalomethane
• Fluoromethane
• Difluoromethane
• Tetrafluoromethane
• Chloroform
• Bromoform
• Iodoform

References

1. ^ Kirschner, E., Chemical and Engineering News 1994, 8.
2. ^ (2001) "Refrigerant Data Summary". Engineered Systems 18: 74-88.
3. ^ Meslans M. M. (1894). ".". Annales de chimie et de physique 7 (1): 346-423.
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 10.1002/047084289

• 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.
• 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.