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Trifluoroacetic acid
Trifluoroacetic-acid-skeletal.png
Trifluoroacetic-acid-3D-vdW.png
Trifluoroacetic-acid-elpot.png
IUPAC name
Other names Perfluoroacetic acid
Trifluoroethanoic acid
TFA
Identifiers
CAS number 76-05-1 Yes check.svgY
RTECS number AJ9625000
SMILES
ChemSpider ID 10239201
Properties
Molecular formula C2HF3O2
Molar mass 114.02 g/mol
Appearance colorless liquid
Density 1.5351 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) 0.3
Hazards
MSDS External MSDS
R-phrases R20 R35 R52/53
S-phrases S9 S26 S27 S28 S45 S61
NFPA 704
NFPA 704.svg
1
3
1
 
Flash point -3 °C
Related compounds
Related compounds Acetic acid
Trichloroacetic acid
Perfluorononanoic acid
 Yes check.svgY (what is this?)  (verify)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Trifluoroacetic acid (TFA) is the simplest stable[1] 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.

Contents

Synthesis

Trifluoroacetic acid is prepared industrially by the electrofluorination of acetyl chloride and acetic anhydride, followed by hydrolysis of the resulting trifluoroacetyl fluoride:[2]

CH3COCl + 4 HF → CF3COF + 3 H2 + HCl
CF3COF + H2O → CF3CO2H + HF

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.[3]

Uses

TFA is the precursor to trifluoroacetic anhydride and 2,2,2-trifluoroethanol. 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.[4]

Another use of TFA is in peptide synthesis, and related reactions where TFA is used as a strong acid to remove the t-butoxycarbonyl protecting group from boc-protected amines.

TFA is used to produce trifluoroacetate salts that serve as precursors to ceramic materials such as YBa2Cu3O{7-x}.[5]

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As a solvent

It 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). It is used in ion pairing agent in liquid chromatography 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.[6]

TFA mass spectrum

References

  1. ^ The even simpler fluoroformic acid would be a very unstable compound, on formation it desintegrates immediatly into hydrogen fluoride and carbon dioxide
  2. ^ G. Siegemund, W. Schwertfeger, A. Feiring, B. Smart, F. Behr, H. Vogel, B. McKusick “Fluorine Compounds, Organic” in “Ullmann’s Encyclopedia of Industrial Chemistry” 2005, Wiley-VCH, Weinheim. doi:10.1002/14356007.a11 349
  3. ^ Max Gergel "Excuse me, would you like to buy a kilo of isopropyl bromide" 1979, Pierce Chemical Company. A vivid account is found in chapter 10.
  4. ^ Eidman, K. F.; Nichols, P. J. "Trifluoroacetic Acid" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. doi:10.1002/047084289
  5. ^ 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. doi:10.1088/0953-2048/16/1/309.  
  6. ^ Stout, Steven J.; Dacunha, Adrian R. (1989). "Tuning and calibration in thermospray liquid chromatography/mass spectrometry using trifluoroacetic acid cluster ions". Analytical Chemistry 61: 2126. doi:10.1021/ac00193a027.  

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