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Trifluoroacetic acid

Trifluoroacetic acid

General
Systematic name	Trifluoroacetic acid
Other names	Perfluoroacetic acid Trifluoroethanoic acid TFA
Molecular formula	C₂HF₃O₂
SMILES	FC(F)(F)C(O)=O
Molar mass	114.03 g/mol
Appearance	colorless liquid
CAS number	[76-05-1]
Properties
Density and phase	1.5351 g/cm³, 20 °C
Solubility in water	miscible
Melting point	-15.4 °C; 257.75 K
Boiling point	72.4 °C; 345.55 K
Acidity (pK_a)	0.3
Viscosity	? cP at ? °C
Hazards
MSDS	External MSDS
Main hazards	Highly corrosive
NFPA 704	1 3 1
Flash point	-3 °C
R/S statement	R: R20 R35 R52/53 S: S9 S26 S27 S28 S45 S61
RTECS number	AJ9625000
Related compounds
Related compounds	Acetic acid Trichloroacetic acid
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Trifluoroacetic acid (TFA) is the chemical compound with the formula CF₃CO₂H. It is a strong carboxylic acid due to the influence of the three very electronegative fluorine atoms. Relative to acetic acid, TFA is almost 100,000-fold more acidic. TFA is widely used in organic chemistry.

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Uses

TFA is a reagent used frequently in organic synthesis because of a combination of convenient properties: volatility, solubility in organic solvents, and its strength.^[1] It is also less oxidizing than sulfuric acid but more readily available in anhydrous form than hydrochloric acid. One complication to its use is that TFA forms an azeotrope with water with a boiling point of 105 °C.

It is also frequently used as a buffer in liquid chromatography for separation of organic compounds, particularly peptides and small proteins. It is a versatile solvent for NMR spectroscopy.

The derived acid anhydride, [CF₃C(O)]₂O, is a common reagent for introducing the trifluoracetyl group.

Synthesis

Electrofluorination of acetic acid with the Simons method is the best way to obtain trifluoroacetic acid. The anodic reaction of the electrolysis of a mixture of hydrogen fluoride and acetic acid below the voltage at which elemental fluorine (F₂) develops is a mild reaction which leaves the carboxylic group intact.

References

^ 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

Categories: Carboxylic acids | Organofluorides