Trifluoroacetic acid
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| Names | |||
|---|---|---|---|
| IUPAC name
2,2,2-Trifluoroethanoic acid | |||
| Other names
Perfluoroacetic acid Trifluoroethanoic acid TFA | |||
| Identifiers | |||
76-05-1  | |||
| ChEBI | CHEBI:45892  | ||
| ChEMBL | ChEMBL506259 | ||
| ChemSpider | 10239201 | ||
| Jmol interactive 3D | Image | ||
| PubChem | 6422 | ||
| RTECS number | AJ9625000 | ||
| UNII | E5R8Z4G708 | ||
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| Properties | |||
| C2HF3O2 | |||
| Molar mass | 114.02 g/mol | ||
| Appearance | colorless liquid | ||
| Density | 1.489 g/cm3, 20 °C | ||
| Melting point | −15.4 °C (4.3 °F; 257.8 K) | ||
| Boiling point | 72.4 °C (162.3 °F; 345.5 K) | ||
| miscible | |||
| Acidity (pKa) | 0.23 [1] | ||
| Hazards | |||
| Main hazards | Highly corrosive | ||
| Safety data sheet | External MSDS | ||
| R-phrases | R20 R35 R52/53 | ||
| S-phrases | S9 S26 S27 S28 S45 S61 | ||
| NFPA 704 | |||
| Related compounds | |||
| Related perfluorinated acids |
Perfluorooctanoic acid Perfluorononanoic acid | ||
| Related compounds |
Acetic acid Trichloroacetic acid | ||
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |||
| verify (what is ?) | |||
| Infobox references | |||
Trifluoroacetic acid (TFA) is an organofluorine compound with the chemical formula CF3CO2H. It is a colorless liquid with a sharp odor similar to vinegar, but stronger in acidity. TFA is an analogue of acetic acid with the three hydrogen atoms replaced by three fluorine atoms. The acidity of TFA is approximately 34,000 times stronger[2] than that of acetic acid due to the electronegativity of the trifluoromethyl group. TFA is widely used in organic chemistry for various purposes.
Synthesis
TFA is prepared industrially by the electrofluorination of acetyl chloride and acetic anhydride, followed by hydrolysis of the resulting trifluoroacetyl fluoride:[3]
- CH
3COCl + 4 HF → CF
3COF + 3 H
2 + HCl - CF
3COF + H
2O → CF
3COOH + HF
Where desired, this compound may be dried by addition of trifluoroacetic anhydride.[4]
An older route to TFA proceeds via the oxidation of 1,1,1-trifluoro-2,3,3-trichloropropene with potassium permanganate. The trifluorotrichloropropene can be prepared by Swarts fluorination of hexachloropropene.
TFA occurs naturally in sea water, but only in small concentrations (<200 ng/L).[5][6]
Uses
TFA is the precursor to many other fluorinated compounds such as trifluoroacetic anhydride and 2,2,2-trifluoroethanol.[3] It is a reagent used in organic synthesis because of a combination of convenient properties: volatility, solubility in organic solvents, and its strength as an acid.[7] TFA is also less oxidizing than sulfuric acid but more readily available in anhydrous form than many other acids. One complication to its use is that TFA forms an azeotrope with water (b. p. 105 °C).
TFA is popularly used as a strong acid in peptide synthesis and other organic synthesis to remove the t-butoxycarbonyl protecting group.[8][9]
At a low concentration, TFA is used as an ion pairing agent in liquid chromatography (HPLC) of organic compounds, particularly peptides and small proteins. TFA is a versatile solvent for NMR spectroscopy (for materials stable in acid). It is also used as a calibrant in mass spectrometry.[10]
TFA is used to produce trifluoroacetate salts.[11]
Safety
Trifluoroacetic acid is a corrosive acid but it does not pose the hazards associated with hydrofluoric acid because the carbon-fluorine bond is not labile. Toxic.
See also
- Fluoroacetic acid
- Trichloroacetic acid, the chlorinated analog.
References
- ↑ Ref 1 in Milne, J. B.; Parker, T. J. (1981). "Dissociation constant of aqueous trifluoroacetic acid by cryoscopy and conductivity". Journal of Solution Chemistry 10 (7): 479. doi:10.1007/BF00652082.
- ↑ Note: Calculated from Ka ratio of TFA and acetic acid
- 1 2 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
- ↑ Wilfred L.F. Armarego and Christina Li Lin Chai. "Chapter 4 -
Purification of Organic Chemicals". Purification of Laboratory Chemicals (6th ed.). doi:10.1016/B978-1-85617-567-8.50012-3. line feed character in
|chapter=at position 13 (help) - ↑ "Trifluoroacetate in ocean waters". Environ. Sci. Technol. 36 (1): 12–5. January 2002. Bibcode:2002EnST...36...12P. doi:10.1021/es0221659. PMID 11811478.
- ↑ "Trifluoroacetate profiles in the Arctic, Atlantic, and Pacific Oceans". Environ. Sci. Technol. 39 (17): 6555–60. September 2005. Bibcode:2005EnST...39.6555S. doi:10.1021/es047975u. PMID 16190212.
- ↑ Eidman, K. F.; Nichols, P. J. (2004). "Trifluoroacetic Acid". In L. Paquette. Encyclopedia of Reagents for Organic Synthesis. New York: J. Wiley & Sons. doi:10.1002/047084289.
- ↑ Lundt, Behrend F.; Johansen, Nils L.; Vølund, Aage; Markussen, Jan (1978). "Removal of t-Butyl and t-Butoxycarbonyl Protecting Groups with Trifluoroacetic acid". International Journal of Peptide and Protein Research 12 (5): 258–268. doi:10.1111/j.1399-3011.1978.tb02896.x. PMID 744685.
- ↑ Andrew B. Hughes. "1. Protection Reactions". In Vommina V. Sureshbabu, Narasimhamurthy Narendra. Amino Acids, Peptides and Proteins in Organic Chemistry: Protection Reactions, Medicinal Chemistry, Combinatorial Synthesis 4. doi:10.1002/9783527631827.ch1.
- ↑ Stout, Steven J.; Dacunha, Adrian R. (1989). "Tuning and calibration in thermospray liquid chromatography/mass spectrometry using trifluoroacetic acid cluster ions". Analytical Chemistry 61 (18): 2126. doi:10.1021/ac00193a027.
- ↑ O. Castano, A. Cavallaro, A. Palau, J. C. Gonzalez, M. Rossell, T. Puig, F. Sandiumenge, N. Mestres, S. Pinol, A. Pomar, and X. Obradors (2003). "High quality YBa2Cu3O7 thin films grown by trifluoroacetates metal-organic deposition". Superconductor Science and Technology 16 (1): 45–53. Bibcode:2003SuScT..16...45C. doi:10.1088/0953-2048/16/1/309.
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