| Fluoroform | |
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Trifluoromethane |
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Other names
Fluoroform, Carbon trifluoride, Methyl trifluoride, Fluoryl, Freon 23, Arcton 1, HFC 23, R-23, FE-13, UN 1984 |
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| Identifiers | |
| CAS number | 75-46-7 |
| PubChem | 6373 |
| ChemSpider | 21106179 |
| UNII | ZJ51L9A260 |
| EC number | 200-872-4 |
| ChEBI | CHEBI:24073 |
| RTECS number | PB6900000 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | CHF3 |
| Molar mass | 70.01 g/mol |
| Appearance | Colorless gas |
| Melting point |
-155.2 °C (117.95 K) |
| Boiling point |
-82.1°C (191.05 K) |
| Solubility in water | 1 g/l |
| 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 | |
| S-phrases | S38 |
| Main hazards | Nervous system depression |
| NFPA 704 |
0
2
0
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| Flash point | Non-flammable |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox 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). Fluoroform is used in diverse niche applications and is produced as a by-product of the manufacture of Teflon. It is also generated biologically in small amounts apparently by decarboxylation of trifluoroacetic acid.[1]
Contents |
Fluoroform was first obtained by Maurice Meslans in the violent reaction of iodoform with dry silver fluoride in 1894.[2] The reaction was improved by Otto Ruff by substitution of silver fluoride by a mixture of mercury fluoride and calcium fluoride.[3] 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.[3]
CHF3 is used in the semiconductor industry in plasma etching of silicon oxide and silicon nitride. Known as R-23 or HFC-23, it is 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.
CHF3 is a reagent to generate sources of "CF3-" by deprotonation. The molecule is weakly acidic with a pKa = 25–28. It is a precursor to CF3Si(CH3)3[4]
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. More recent work (IPCC, 2007) suggests that this equivalency, also called a 100-yr global warming potential, is slightly larger at 14,800 for HFC-23.[5] The atmospheric lifetime is 270 years.[5]
According to the 2007 IPCC climate report, 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).
Data reported to the United Nations Framework Convention on Climate Change (UNFCCC) greenhouse gas emissions databases [6] indicate substantial decreases 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.[7] 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.
| 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 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 |
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