Fluoroform
| |||
Names | |||
---|---|---|---|
IUPAC name
Trifluoromethane
| |||
Other names
Fluoroform, carbon trifluoride,[citation needed] methyl trifluoride, Fluoryl, Freon 23, Arcton 1
| |||
Identifiers | |||
3D model (
JSmol ) |
|||
Abbreviations | HFC 23, R-23, FE-13 , UN 1984
| ||
ChEBI | |||
ChemSpider | |||
ECHA InfoCard
|
100.000.794 | ||
EC Number |
| ||
PubChem CID
|
|||
RTECS number
|
| ||
UNII | |||
CompTox Dashboard (EPA)
|
|||
| |||
| |||
Properties | |||
CHF3 | |||
Molar mass | 70.014 g·mol−1 | ||
Appearance | Colorless gas | ||
Density | 2.946 kg/m3 (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) | ||
1 g/l | |||
Solubility in organic solvents | Soluble | ||
Vapor pressure | 4.38 MPa at 20 °C | ||
Henry's law
constant (kH) |
0.013 mol·kg−1·bar−1 | ||
Acidity (pKa) | 25–28 | ||
Structure | |||
Tetrahedral
| |||
Hazards | |||
Occupational safety and health (OHS/OSH): | |||
Main hazards
|
Nervous system depression | ||
GHS labelling:[1] | |||
Warning | |||
H280 | |||
P403 | |||
NFPA 704 (fire diamond) | |||
Flash point | Non-flammable | ||
Related compounds | |||
Related compounds
|
| ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|
Fluoroform, or trifluoromethane, is the
Synthesis
About 20 million kg per year are produced industrially as both a by-product of and precursor to the manufacture of
- CHCl3 + 3 HF → CHF3 + 3 HCl
It is also generated biologically in small amounts apparently by decarboxylation of trifluoroacetic acid.[4]
Historical
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]
Industrial applications
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
Organic chemistry
Fluoroform is weakly acidic with a pKa = 25–28 and quite inert. Attempted deprotonation results in defluorination to generate F− and
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
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
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]
The UNFCCC Clean Development Mechanism provided funding and facilitated the destruction of HFC-23.
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]
Additional physical properties
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 |
References
- ^ GHS: GESTIS 038260
- ^ .
- ISBN 978-3527306732.
- ^ Kirschner, E., Chemical and Engineering News 1994, 8.
- ^ Meslans M. M. (1894). "Recherches sur quelques fluorures organiques de la série grasse". Annales de chimie et de physique. 7 (1): 346–423.
- ^ .
- PMID 22136628.
- S2CID 206544170.
- ^ a b Forster, 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.
- S2CID 13583576.
- ^ "Data Access Centre". Archived from the original on 2011-07-21. Retrieved 2010-04-03.
- ^ Profits on Carbon Credits Drive Output of a Harmful Gas August 8, 2012 New York Times
- ^ Subsidies for a Global Warming Gas
- .
Literature
- McBee E. T. (1947). "Fluorine Chemistry". .
- 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". .
- McCulloch A. (2003). "Fluorocarbons in the global environment: a review of the important interactions with atmospheric chemistry and physics". .