About 20 million kg per year are produced industrially as both a by-product of and precursor to the manufacture of Teflon.[2] It is produced by reaction of chloroform with HF:[3]
Fluoroform was first obtained by Maurice Meslans in the violent reaction of iodoform with dry silver fluoride in 1894.[5] The reaction was improved by Otto Ruff by substitution of silver fluoride by a mixture of mercury fluoride and calcium fluoride.[6] 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 bromodifluoromethane in the reaction of antimony trifluoride with bromoform and finishing the reaction with mercury fluoride the first efficient synthesis method was found by Henne.[6]
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
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.[7]
Fluoroform is a precursor of the Ruppert-Prakash reagent CF3Si(CH3)3, which is a source of the nucleophilic CF−3 anion.[8][9]
Greenhouse gas
HFC-23 measured by the Advanced Global Atmospheric Gases Experiment (AGAGE) in the lower atmosphere (troposphere) at stations around the world. Abundances are given as pollution free monthly mean mole fractions in parts-per-trillion.Atmospheric concentration of HFC-23 vs. similar man-made gases (right graph), log scale.
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.[10]
The atmospheric lifetime is 270 years.[10]
HFC-23 was the most abundant HFC in the global atmosphere until around 2001, 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 in HFC-23 emissions by developed countries were reported from the 1990s to the 2000s: from 6-8 Gg/yr in the 1990s to 2.8 Gg/yr in 2007.[11]
Developing countries have become the largest producers of HCFC-23 in recent years according to data compiled by the Ozone Secretariat of the World Meteorological Organization.[12][13][14] 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.[15]
^Zanardi, Alessandro; Novikov, Maxim A.; Martin, Eddy; Benet-Buchholz, Jordi; Grushin, Vladimir V. (2011-12-28). "Direct Cupration of Fluoroform". Journal of the American Chemical Society. 133 (51): 20901–20913. doi:10.1021/ja2081026. ISSN0002-7863. PMID22136628.
^Rozen, S.; Hagooly, A. "Fluoroform" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. doi:10.1002/047084289X.rn00522
^ abForster, 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 & R. Van Dorland (2007). "Changes in Atmospheric Constituents and in Radiative Forcing."(PDF). Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change.
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.
