Fluoroform

Names

IUPAC name

Trifluoromethane

Other names

Fluoroform, carbon trifluoride,^{[citation needed]} methyl trifluoride, Fluoryl, Freon 23, Arcton 1

Identifiers

CAS Number

75-46-7^Y

3D model (JSmol)

Interactive image

Abbreviations

HFC 23, R-23, FE-13, UN 1984

ChEBI

CHEBI:24073^N

ChemSpider

21106179^Y

ECHA InfoCard

100.000.794

EC Number

200-872-4

PubChem CID

6373

RTECS number

PB6900000

UNII

ZJ51L9A260^Y

CompTox Dashboard (EPA)

DTXSID0026410

InChI

InChI=1S/CHF3/c2-1(3)4/h1H^Y
Key: XPDWGBQVDMORPB-UHFFFAOYSA-N^Y
InChI=1/CHF3/c2-1(3)4/h1H
Key: XPDWGBQVDMORPB-UHFFFAOYAM

SMILES

FC(F)F

Properties

Chemical formula

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)

Solubility in water

1 g/l

Solubility in organic solvents

Soluble

Vapor pressure

4.38 MPa at 20 °C

Henry's law
constant (k_H)

0.013 mol·kg⁻¹·bar⁻¹

Acidity (pK_a)

25–28

Structure

Molecular shape

Tetrahedral

Hazards

Occupational safety and health (OHS/OSH):

Main hazards

Nervous system depression

GHS labelling:^[1]

Pictograms

Signal word

Warning

Hazard statements

H280

Precautionary statements

P403

NFPA 704 (fire diamond)

Flash point

Non-flammable

Related compounds

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

N verify (what is ^YN ?)

Infobox references

Chemical compound

Fluoroform, or trifluoromethane, is the chemical compound with the formula CHF₃. It is a hydrofluorocarbon as well as being a part of the haloforms, a class of compounds with the formula CHX₃ (X = halogen) with C_3v symmetry. Fluoroform is used in diverse applications in organic synthesis. It is not an ozone depleter but is a greenhouse gas.^[2]

Synthesis

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]

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 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 pK_a = 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

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]

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 (p_c)	4.816 MPa (48.16 bar)
Critical temperature (T_c)	25.7 °C (299 K)
Critical density (ρ_c)	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 (C_V)	51.577 J.mol⁻¹.K⁻¹
Latent heat of vaporization (l_b)	257.91 kJ.kg⁻¹

References

^ GHS: GESTIS 038260
^ ^a ^b ShivaKumar Kyasa (2015). "Fluoroform (CHF3)". Synlett. 26 (13): 1911–1912. doi:10.1055/s-0034-1380924.
^ G. Siegemund; W. Schwertfeger; A. Feiring; B. Smart; F. Behr; H. Vogel; B. McKusick (2005). "Fluorine Compounds, Organic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a11_349. 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.
^ ^a ^b Henne A. L. (1937). "Fluoroform". Journal of the American Chemical Society. 59 (7): 1200–1202. doi:10.1021/ja01286a012.
^ 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. ISSN 0002-7863. PMID 22136628.
^ 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
^ Prakash, G. K. Surya; Jog, Parag V.; Batamack, Patrice T. D.; Olah, George A. (2012-12-07). "Taming of Fluoroform: Direct Nucleophilic Trifluoromethylation of Si, B, S, and C Centers". Science. 338 (6112): 1324–1327. Bibcode:2012Sci...338.1324P. doi:10.1126/science.1227859. ISSN 0036-8075. PMID 23224551. 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.
^ Montzka, S. A.; Kuijpers, L.; Battle, M. O.; Aydin, M.; Verhulst, K. R.; Saltzman, E. S.; Fahey, D. W. (2010). "Recent increases in global HFC-23 emissions". Geophysical Research Letters. 37 (2): n/a. Bibcode:2010GeoRL..37.2808M. doi:10.1029/2009GL041195. 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
^ 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.

Literature

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. Bibcode:1998GeoRL..25...35O. doi:10.1029/97GL03483.
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.