Trifluoroacetic acid

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

1. ^ 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