Trifluoroacetic acid

Trifluoroacetic acid

Names
IUPAC name 2,2,2-Trifluoroethanoic acid
Other names Perfluoroacetic acid Trifluoroethanoic acid TFA
Identifiers
CAS Number	76-05-1 Y
ChEBI	CHEBI:45892 N
ChEMBL	ChEMBL506259 Y
ChemSpider	10239201 Y
Jmol 3D model	Interactive image
PubChem	6422
RTECS number	AJ9625000
UNII	E5R8Z4G708 Y
InChI InChI=1S/C2HF3O2/c3-2(4,5)1(6)7/h(H,6,7) Y Key: DTQVDTLACAAQTR-UHFFFAOYSA-N Y InChI=1/C2HF3O2/c3-2(4,5)1(6)7/h(H,6,7) Key: DTQVDTLACAAQTR-UHFFFAOYAP
SMILES FC(F)(F)C(=O)O
Properties
Chemical formula	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)
Solubility in water	miscible
Acidity (pKa)	0.23
Vapor pressure	{{{value}}}
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).
N verify (what is YN ?)
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 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:

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.

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).

Uses

TFA is the precursor to many other fluorinated compounds such as 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. 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.

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.

TFA is used to produce trifluoroacetate salts.

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.