Trifluoroacetic acid

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Trifluoroacetic acid
Names
IUPAC name
Trifluoroacetic acid
Preferred IUPAC name
Trifluoroacetic acid
Other names
2,2,2-Trifluoroacetic acid
2,2,2-Trifluoroethanoic acid
Perfluoroacetic acid
Trifluoroethanoic acid
TFA
Properties
C2HF3O2
CF3COOH
Molar mass 114.02 g/mol
Appearance Colorless liquid
Odor Strong pungent odor
Density 1.531 g/cm3 (20 °C)
1.489 g/cm3 (25 °C)
Melting point −15.4 °C (4.3 °F; 257.8 K)
Boiling point 72.4 °C (162.3 °F; 345.5 K)
Miscible
Solubility Reacts with alkali, amines
Miscible with acetone, benzene, carbon tetrachloride, diethyl ether, ethanol, hexane
Vapor pressure 82.5 mmHg (20 °C)
Acidity (pKa) 0.23
Hazards
Safety data sheet Sigma-Aldrich
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
200 mg/kg (rat, oral)
Related compounds
Related compounds
Acetic acid
Fluoroacetic acid
Difluoroacetic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Trifluoroacetic acid (TFA) is an organofluorine compound, an organic acid with the formula CF3COOH. 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.

Properties

Chemical

Trifluoroacetic acid reacts with bases to form trifluoroacetate salts.

CF3COOH + MOH → CF3COOM + H2O

Decarboxylation of trifluoroacetic acid yields fluoroform.[1]

Physical

Trifluoroacetic acid is a colorless volatile liquid, with a strong pungent acetic smell. It reacts with bases and amines, while miscible with water and organic solvents.

Availability

TFA is sold by various chemical suppliers.

Preparation

TFA can be synthesized by the electrofluorination of acetyl chloride and acetic anhydride, followed by hydrolysis of the resulting trifluoroacetyl fluoride:

CH3COCl + 4 HF → CF3COF + 3 H2 + HCl
CF3COF + H2O → CF3COOH + HF

An older route to TFA involves the oxidation of 1,1,1-trifluoro-2,3,3-trichloropropene with potassium permanganate, the latter being prepared by Swarts fluorination of hexachloropropene.

Oxidation of 1,1,1-trifluoroethane aka R-143a, a freon commonly used as refrigerent and propellant in canned air products will also yield TFA. The oxidation is done by mixing R-143a with air and passing the mixture through an electric discharge of 15,000 V. Water vapor is used as carrying medium, which also helps preventing the degradation of TFA and unreacted R-143a.[2]

Projects

Handling

Safety

TFA is corrosive and should be handled with proper protection, in well ventilated areas.

Storage

Trifluoroacetic acid should be kept in closed bottles, away from heat and light, in a corrosive acid cabinet. Don't store it near ammonia or other volatile chemicals.

Disposal

Trifluoroacetic acid can be neutralized with a base. Trifluoroacetates have low toxicity and generally do not require special disposal.

References

  1. Kirschner, E., Chemical and Engineering News 1994, p. 8
  2. http://pubs.acs.org/doi/abs/10.1021/jo01062a068

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