Trifluoroacetic acid
| Trifluoroacetic acid | |
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2,2,2-Trifluoroacetic acid |
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Other names
Perfluoroacetic acid |
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| Identifiers | |
| CAS number | 76-05-1  |
| ChemSpider | 10239201 |
| UNII | E5R8Z4G708 |
| ChEBI | CHEBI:45892  |
| ChEMBL | CHEMBL506259 |
| RTECS number | AJ9625000 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | C2HF3O2 |
| Molar mass | 114.02 g/mol |
| Appearance | colorless liquid |
| Density | 1.489 g/cm3, 20 °C |
| Melting point |
-15.4 °C, 258 K, 4 °F |
| Boiling point |
72.4 °C, 346 K, 162 °F |
| Solubility in water | miscible |
| Acidity (pKa) | 0.23 [1] |
| Hazards | |
| MSDS | External MSDS |
| R-phrases | R20 R35 R52/53 |
| S-phrases | S9 S26 S27 S28 S45 S61 |
| Main hazards | Highly corrosive |
| NFPA 704 |
 1
3
1
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| Flash point | −3 °C |
| Related compounds | |
| Related perfluorinated acids | Perfluorooctanoic acid Perfluorononanoic acid |
| Related compounds | Acetic acid Trichloroacetic acid |
 (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 | |
Trifluoroacetic acid (TFA) is the simplest stable[2] perfluorinated carboxylic acid chemical compound, with the formula CF3CO2H. It is a strong carboxylic acid due to the influence of the electronegative trifluoromethyl group. TFA is almost 100,000-fold more acidic than acetic acid. TFA is widely used in organic chemistry.
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[edit] Synthesis
TFA occurs naturally in sea water, but only in small concentrations (<200 ng/L).[3][4] Therefore, TFA is prepared industrially by the electrofluorination of acetyl chloride and acetic anhydride, followed by hydrolysis of the resulting trifluoroacetyl fluoride:[5]
- CH3COCl + 4 HF → CF3COF + 3 H2 + HCl
- CF3COF + H2O → CF3COOH + HF
Where desired, this compound may be dried by addition of trifluoroacetic anhydride.[6]
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.[7]
[edit] Uses
TFA is the precursor to many other fluorinated compounds such as trifluoroacetic anhydride and 2,2,2-trifluoroethanol.[5] 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.[8] 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.[9][10]
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.[11]
TFA is used to produce trifluoroacetate salts that serve as precursors to ceramic materials such as YBa2Cu3O{7-x}.[12]
[edit] See also
- Fluoroacetic acid
- Trichloroacetic acid, the chlorinated analog.
[edit] References
- ^ Dippy, J.F.J., Hughes, S.R.C., Rozanski, A. (1959). "498. The dissociation constants of some symmetrically disubstituted succinic acids". J. Chem. Soc.: 2492. doi:10.1039/jr9590002492.
- ^ The even simpler fluoroformic acid is not isolable in substance; in protic media it disintegrates rapidly through a proton-catalyzed pathway into hydrogen fluoride and carbon dioxide. See Z. Havlas, T. Kovář, R. Zahradník (1985). "Does fluoroformic acid exist?". J. Am. Chem. Soc. 107: 7243–7246. doi:10.1021/ja00311a002.
- ^ . PMID 11811478.
- ^ . PMID 16190212.
- ^ a b 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. ed.). doi:10.1016/B978-1-85617-567-8.50012-3.
- ^ Max Gergel "Excuse Me Sir, Would You Like to Buy a Kilo of Isopropyl Bromide?" 1979, Pierce Chemical Company. A vivid account is found in chapter 10.
- ^ Eidman, K. F.; Nichols, P. J. (2004). L. Paquette. ed. 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 YBa2Cu3O{7-x} thin films grown by trifluoroacetates metal-organic deposition". Supercond. Sci. Technol. 16: 45–53. Bibcode 2003SuScT..16...45C. doi:10.1088/0953-2048/16/1/309.
