Fluoroform

Fluoroform
IUPAC name	Trifluoromethane
Other names	Fluoroform, Carbon trifluoride, Methyl trifluoride, Fluoryl, Freon 23, Arcton 1, HFC 23, R-23, FE-13, UN 1984
Identifiers
CAS number	75-46-7 Y
PubChem	6373
EC number	200-872-4
ChEBI	24073
RTECS number	PB6900000
SMILES	C(F)(F)F
InChI	1/CHF3/c2-1(3)4/h1H
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
NFPA 704	0 2 0
Flash point	Non-flammable
Y(what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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]

Synthesis

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]

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 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 is also used as a replacement for Halon 1301[cfc-13b1] in fire suppression systems as a total flooding gaseous fire suppression agent.

Organic chemistry

CHF₃ is a reagent to generate sources of "CF₃^-" by deprotonation. The molecule is weakly acidic with a pK_a = 25–28. It is a precursor to CF₃Si(CH₃)₃^[4]

Greenhouse gas

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.^[5] According to researchers, it is the most abundant of hydrofluorocarbons (HFCs). Its usage has been regulated since December 1997 at Kyoto climate conference. To mitigate its impact, CHF₃ can be destroyed with electric plasma arc technologies or by high temperature incineration.

References

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. doi:10.1029/97GL03483. http://www.agu.org/pubs/crossref/1998.../97GL03483.shtml. 
• 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. 

External links

• International Chemical Safety Card 0577
• MSDS at Oxford University
• MSDS at mathesontrigas.com
• Coupling of fluoroform with aldehydes using an electrogenerated base

Additional physical properties