Trifluoroacetic acid

Last updated

Contents

Trifluoroacetic acid
Trifluoroacetic acid.svg
Trifluoroacetic-acid-3D-vdW.png
Trifluoroacetic-acid-elpot.png
Trifluoro acetic acid 1ml.jpg
Names
Preferred IUPAC name
Trifluoroacetic acid
Other names
2,2,2-Trifluoroacetic acid
2,2,2-Trifluoroethanoic acid
Perfluoroacetic acid
Trifluoroethanoic acid
TFA
Identifiers
3D model (JSmol)
742035
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.000.846 OOjs UI icon edit-ltr-progressive.svg
2729
PubChem CID
RTECS number
  • AJ9625000
UNII
  • InChI=1S/C2HF3O2/c3-2(4,5)1(6)7/h(H,6,7) Yes check.svgY
    Key: DTQVDTLACAAQTR-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/C2HF3O2/c3-2(4,5)1(6)7/h(H,6,7)
    Key: DTQVDTLACAAQTR-UHFFFAOYAP
  • FC(F)(F)C(=O)O
Properties
C2HF3O2
Molar mass 114.023 g·mol−1
Appearancecolorless liquid
Odor Pungent/Vinegar
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)
miscible
Vapor pressure 0.0117 bar (1.17 kPa) at 20 °C [1]
Acidity (pKa)0.52 [2]
Conjugate base trifluoroacetate
-43.3·10−6 cm3/mol
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
Highly corrosive
GHS labelling:
GHS-pictogram-acid.svg GHS-pictogram-exclam.svg
Danger
H314, H332, H412
P260, P261, P264, P271, P273, P280, P301+P330+P331, P303+P361+P353, P304+P312, P304+P340, P305+P351+P338, P310, P312, P321, P363, P405, P501
NFPA 704 (fire diamond)
NFPA 704.svgHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no code
3
1
1
Safety data sheet (SDS) External MSDS
Related compounds
Related perfluorinated acids
Heptafluorobutyric acid
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).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Trifluoroacetic acid (TFA) is an organofluorine compound with the chemical formula CF3CO2H. It is a haloacetic acid, with all three of the acetyl group's hydrogen atoms replaced by fluorine atoms. It is a colorless liquid with a vinegar-like odor. TFA is a stronger acid than acetic acid, having an acid ionisation constant, Ka, that is approximately 34,000 times higher, [3] as the highly electronegative fluorine atoms and consequent electron-withdrawing nature of the trifluoromethyl group weakens the oxygen-hydrogen bond (allowing for greater acidity) and stabilises the anionic conjugate base. TFA is widely used in organic chemistry for various purposes.

Synthesis

TFA is prepared industrially by the electrofluorination of acetyl chloride or acetic anhydride, followed by hydrolysis of the resulting trifluoroacetyl fluoride: [4]

CH
3
COCl
+ 4 HFCF
3
COF
+ 3 H
2
+ HCl
CF
3
COF
+ H
2
O
CF
3
COOH
+ HF

Where desired, this compound may be dried by addition of trifluoroacetic anhydride. [5]

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. [6]

Uses

Trifluoroacetic acid in a beaker Trifluoroacetic acid in a beaker.jpg
Trifluoroacetic acid in a beaker

TFA is the precursor to many other fluorinated compounds such as trifluoroacetic anhydride, trifluoroperacetic acid, and 2,2,2-trifluoroethanol. [4] 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. [7] 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 to remove protecting groups such as Boc used in organic chemistry and peptide synthesis. [8] [9]

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. [10]

TFA is used to produce trifluoroacetate salts. [11]

Safety

Trifluoroacetic acid is a corrosive strong acid [12] but it does not pose the hazards associated with hydrofluoric acid because the carbon-fluorine bond is not labile. TFA is harmful when inhaled, causes severe skin burns and is toxic for aquatic organisms even at low concentrations.

TFA's reaction with bases and metals, especially light metals, is strongly exothermic. The reaction with lithium aluminium hydride (LAH) results in an explosion. [13]

TFA is a metabolic breakdown product of the volatile anaesthetic agent halothane. It is thought to be responsible for halothane induced hepatitis. [14]

Environment

No known natural processes generate trifluoroacetic acid. [15] In the environment, trifluoroacetic acid may be formed by photooxidation of the commonly used refrigerant 1,1,1,2-tetrafluoroethane (R-134a).[ citation needed ] Moreover, it is formed as an atmospheric degradation product of almost all fourth-generation synthetic refrigerants, also called hydrofluoroolefins (HFO), such as 2,3,3,3-tetrafluoropropene.[ citation needed ]

Trifluoroacetic acid degrades very slowly in the environment, and has been found in increasing amounts as a contaminant in water, soil, food, and the human body. [16] Median concentrations of a few micrograms per liter have been found in beer and tea. [17] Sea water contains about 200 ng of TFA per liter. [18] [19] [20] No biodegradation mechanism for the compound is known in water, [21] although biotransformation apparently decarboxylates the acid to fluoroform. [22]

Trifluoroacetic acid is mildly phytotoxic. [23]

See also

Related Research Articles

In organic chemistry, an acyl chloride is an organic compound with the functional group −C(=O)Cl. Their formula is usually written R−COCl, where R is a side chain. They are reactive derivatives of carboxylic acids. A specific example of an acyl chloride is acetyl chloride, CH3COCl. Acyl chlorides are the most important subset of acyl halides.

<span class="mw-page-title-main">Acyl halide</span> Oxoacid compound with an –OH group replaced by a halogen

In organic chemistry, an acyl halide is a chemical compound derived from an oxoacid by replacing a hydroxyl group with a halide group.

<span class="mw-page-title-main">Peptide synthesis</span> Production of peptides

In organic chemistry, peptide synthesis is the production of peptides, compounds where multiple amino acids are linked via amide bonds, also known as peptide bonds. Peptides are chemically synthesized by the condensation reaction of the carboxyl group of one amino acid to the amino group of another. Protecting group strategies are usually necessary to prevent undesirable side reactions with the various amino acid side chains. Chemical peptide synthesis most commonly starts at the carboxyl end of the peptide (C-terminus), and proceeds toward the amino-terminus (N-terminus). Protein biosynthesis in living organisms occurs in the opposite direction.

<span class="mw-page-title-main">Organic acid anhydride</span> Any chemical compound having two acyl groups bonded to the same oxygen atom

An organic acid anhydride is an acid anhydride that is also an organic compound. An acid anhydride is a compound that has two acyl groups bonded to the same oxygen atom. A common type of organic acid anhydride is a carboxylic anhydride, where the parent acid is a carboxylic acid, the formula of the anhydride being (RC(O))2O. Symmetrical acid anhydrides of this type are named by replacing the word acid in the name of the parent carboxylic acid by the word anhydride. Thus, (CH3CO)2O is called acetic anhydride.Mixed (or unsymmetrical) acid anhydrides, such as acetic formic anhydride (see below), are known, whereby reaction occurs between two different carboxylic acids. Nomenclature of unsymmetrical acid anhydrides list the names of both of the reacted carboxylic acids before the word "anhydride" (for example, the dehydration reaction between benzoic acid and propanoic acid would yield "benzoic propanoic anhydride").

The Pummerer rearrangement is an organic reaction whereby an alkyl sulfoxide rearranges to an α-acyloxy–thioether (monothioacetal-ester) in the presence of acetic anhydride.

<span class="mw-page-title-main">Carbodiimide</span> Class of organic compounds with general structure RN=C=NR

In organic chemistry, a carbodiimide is a functional group with the formula RN=C=NR. On Earth they are exclusively synthetic, but in interstellar space the parent compound HN=C=NH has been detected by its maser emissions.

Fluoroform, or trifluoromethane, is the chemical compound with the formula CHF3. It is a hydrofluorocarbon as well as being a part of the haloforms, a class of compounds with the formula CHX3 with C3v symmetry. Fluoroform is used in diverse applications in organic synthesis. It is not an ozone depleter but is a greenhouse gas.

<span class="mw-page-title-main">Robinson–Gabriel synthesis</span> Organic reaction

The Robinson–Gabriel synthesis is an organic reaction in which a 2-acylamino-ketone reacts intramolecularly followed by a dehydration to give an oxazole. A cyclodehydrating agent is needed to catalyze the reaction It is named after Sir Robert Robinson and Siegmund Gabriel who described the reaction in 1909 and 1910, respectively.

Di-<i>tert</i>-butyl dicarbonate Chemical compound

Di-tert-butyl dicarbonate is a reagent widely used in organic synthesis. Since this compound can be regarded formally as the acid anhydride derived from a tert-butoxycarbonyl (Boc) group, it is commonly referred to as Boc anhydride. This pyrocarbonate reacts with amines to give N-tert-butoxycarbonyl or so-called Boc derivatives. These carbamate derivatives do not behave as amines, which allows certain subsequent transformations to occur that would be incompatible with the amine functional group. The Boc group can later be removed from the amine using moderately strong acids. Thus, Boc serves as a protective group, for instance in solid phase peptide synthesis. Boc-protected amines are unreactive to most bases and nucleophiles, allowing for the use of the fluorenylmethyloxycarbonyl group (Fmoc) as an orthogonal protecting group.

<span class="mw-page-title-main">Triflic acid</span> Chemical compound

Triflic acid, the short name for trifluoromethanesulfonic acid, TFMS, TFSA, HOTf or TfOH, is a sulfonic acid with the chemical formula CF3SO3H. It is one of the strongest known acids. Triflic acid is mainly used in research as a catalyst for esterification. It is a hygroscopic, colorless, slightly viscous liquid and is soluble in polar solvents.

<i>tert</i>-Butyloxycarbonyl protecting group Protecting group used in organic synthesis

The tert-butyloxycarbonyl protecting group or tert-butoxycarbonyl protecting group is a protecting group used in organic synthesis.

<span class="mw-page-title-main">Trifluoroacetic anhydride</span> Chemical compound

Trifluoroacetic anhydride (TFAA) is the acid anhydride of trifluoroacetic acid. It is the perfluorinated derivative of acetic anhydride.

<span class="mw-page-title-main">Acetic acid</span> Colorless and faint organic acid found in vinegar

Acetic acid, systematically named ethanoic acid, is an acidic, colourless liquid and organic compound with the chemical formula CH3COOH. Vinegar is at least 4% acetic acid by volume, making acetic acid the main component of vinegar apart from water. It has been used, as a component of vinegar, throughout history from at least the third century BC.

<span class="mw-page-title-main">1-Tetralone</span> Chemical compound

1-Tetralone is a bicyclic aromatic hydrocarbon and a ketone. In terms of its structure, it can also be regarded as benzo-fused cyclohexanone. It is a colorless oil with a faint odor. It is used as starting material for agricultural and pharmaceutical agents. The carbon skeleton of 1-tetralone is found in natural products such as Aristelegone A (4,7-dimethyl-6-methoxy-1-tetralone) from the family of Aristolochiaceae used in traditional Chinese medicine.

The Boekelheide reaction is a rearrangement of α-picoline-N-oxides to hydroxymethylpyridines. It is named after Virgil Boekelheide who first reported it in 1954. Originally the reaction was carried out using acetic anhydride, which typically required a period at reflux (~140 °C). The reaction can be performed using trifluoroacetic anhydride (TFAA), which often allows for a room temperature reaction.

<i>N</i>-Hydroxyphthalimide Chemical compound

N-Hydroxyphthalimide is the organic compound with the formula C6H4(CO)2NOH. A white or yellow solid, it is a derivative of phthalimide. The compound is as a catalyst in the synthesis of other organic compounds. It is soluble in water and organic solvents such as acetic acid, ethyl acetate and acetonitrile.

<span class="mw-page-title-main">Trifluoroperacetic acid</span> Chemical compound

Trifluoroperacetic acid is an organofluorine compound, the peroxy acid analog of trifluoroacetic acid, with the condensed structural formula CF
3
COOOH
. It is a strong oxidizing agent for organic oxidation reactions, such as in Baeyer–Villiger oxidations of ketones. It is the most reactive of the organic peroxy acids, allowing it to successfully oxidise relatively unreactive alkenes to epoxides where other peroxy acids are ineffective. It can also oxidise the chalcogens in some functional groups, such as by transforming selenoethers to selones. It is a potentially explosive material and is not commercially available, but it can be quickly prepared as needed. Its use as a laboratory reagent was pioneered and developed by William D. Emmons.

<span class="mw-page-title-main">(Diacetoxyiodo)benzene</span> Chemical compound

(Diacetoxyiodo)benzene, also known as phenyliodine(III) diacetate (PIDA) is a hypervalent iodine chemical with the formula C
6
H
5
I(OCOCH
3
)
2
. It is used as an oxidizing agent in organic chemistry.

<span class="mw-page-title-main">Sodium trifluoroacetate</span> Chemical compound

Sodium trifluoroacetate is a chemical compound with a formula of CF3CO2Na. It is the sodium salt of trifluoroacetic acid. It is used as a source of trifluoromethylations.

<span class="mw-page-title-main">Ethyl trifluoroacetate</span> Chemical compound

Ethyl trifluoroacetate is a chemical compound from the trifluoroacetate group.

References

  1. Kreglewski, A. (1962). "Trifluoroacetic acid". Welcome to the NIST WebBook. 10 (11–12): 629–633. Retrieved 1 March 2020.
  2. W. M. Haynes.; David R. Lide; Thomas J. Bruno, eds. (2016–2017). CRC Handbook of Chemistry and Physics . CRC Press. pp. 954–963. ISBN   978-1-4987-5429-3.
  3. Note: Calculated from the ratio of the Ka values for TFA (pKa = 0.23) and acetic acid (pKa = 4.76)
  4. 1 2 G. Siegemund; W. Schwertfeger; A. Feiring; B. Smart; F. Behr; H. Vogel; B. McKusick. "Fluorine Compounds, Organic". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a11_349. ISBN   978-3527306732.
  5. Wilfred L.F. Armarego & Christina Li Lin Chai (2009). "Chapter 4 - Purification of Organic Chemicals". Purification of Laboratory Chemicals (6th ed.). pp. 88–444. doi:10.1016/B978-1-85617-567-8.50012-3. ISBN   978-1-85617-567-8.
  6. Gergel, Max G. (March 1977). Excuse me sir, would you like to buy a kilo of isopropyl bromide? (PDF). Pierce Chemical. pp. 88–90.
  7. Eidman, K. F.; Nichols, P. J. (2004). "Trifluoroacetic Acid". In L. Paquette (ed.). Encyclopedia of Reagents for Organic Synthesis. New York: J. Wiley & Sons. doi:10.1002/047084289X.rt236.pub2. hdl: 10261/236866 . ISBN   978-0-471-93623-7.
  8. Lundt, Behrend F.; Johansen, Nils L.; Vølund, Aage; Markussen, Jan (1978). "Removal of t-Butyl and t-Butoxycarbonyl Protecting Groups with Trifluoroacetic acid". International Journal of Peptide and Protein Research. 12 (5): 258–268. doi:10.1111/j.1399-3011.1978.tb02896.x. PMID   744685.
  9. Andrew B. Hughes (2011). "1. Protection Reactions". In Vommina V. Sureshbabu; Narasimhamurthy Narendra (eds.). Amino Acids, Peptides and Proteins in Organic Chemistry: Protection Reactions, Medicinal Chemistry, Combinatorial Synthesis. Vol. 4. pp. 1–97. doi:10.1002/9783527631827.ch1. ISBN   978-3-527-63182-7.
  10. Stout, Steven J.; Dacunha, Adrian R. (1989). "Tuning and calibration in thermospray liquid chromatography/mass spectrometry using trifluoroacetic acid cluster ions". Analytical Chemistry. 61 (18): 2126. doi:10.1021/ac00193a027.
  11. O. Castano; A. Cavallaro; A. Palau; J. C. Gonzalez; M. Rossell; T. Puig; F. Sandiumenge; N. Mestres; S. Pinol; A. Pomar & X. Obradors (2003). "High quality YBa2Cu3O7 thin films grown by trifluoroacetates metal-organic deposition". Superconductor Science and Technology. 16 (1): 45–53. Bibcode:2003SuScT..16...45C. doi:10.1088/0953-2048/16/1/309. S2CID   250765145.
  12. Henne, Albert L; Fox, Charles J (1951). "Ionization constants of fluorinated acids". Journal of the American Chemical Society . 73 (5): 2323–2325. doi:10.1021/ja01149a122.
  13. Safety data sheet for Trifluoroacetic acid (PDF) from EMD Millipore, revision date 10/27/2014.
  14. "Halothane", LiverTox: Clinical and Research Information on Drug-Induced Liver Injury, Bethesda (MD): National Institute of Diabetes and Digestive and Kidney Diseases, 2012, PMID   31643481 , retrieved 15 July 2021
  15. Joudan, Shira; De Silva, Amila O.; Young, Cora J. (2021). "Insufficient evidence for the existence of natural trifluoroacetic acid". Environmental Science: Processes & Impacts. 23 (11): 1641–1649. doi:10.1039/D1EM00306B. hdl: 10315/40884 . ISSN   2050-7887. PMID   34693963. S2CID   239768006.
  16. https://www.theguardian.com/environment/2024/may/01/rapidly-rising-levels-of-tfa-forever-chemical-alarm-experts
  17. Marco Scheurer, Karsten Nödler (2021). "Ultrashort-chain perfluoroalkyl substance trifluoroacetate (TFA) in beer and tea – An unintended aqueous extraction". Food Chemistry. 351: 129304. doi:10.1016/j.foodchem.2021.129304. ISSN   0308-8146. PMID   33657499. S2CID   232115008.
  18. Frank, H.; Christoph, E. H.; Holm-Hansen, O.; Bullister, J. L. (January 2002). "Trifluoroacetate in ocean waters". Environ. Sci. Technol. 36 (1): 12–5. Bibcode:2002EnST...36...12P. doi:10.1021/es0221659. PMID   11811478.
  19. Scott, B. F.; MacDonald, R. W.; Kannan, K.; Fisk, A.; Witter, A.; Yamashita, N.; Durham, L.; Spencer, C.; Muir, D. C. G. (September 2005). "Trifluoroacetate profiles in the Arctic, Atlantic, and Pacific Oceans". Environ. Sci. Technol. 39 (17): 6555–60. Bibcode:2005EnST...39.6555S. doi:10.1021/es047975u. PMID   16190212.
  20. Frank, Hartmut; Christoph, Eugen H.; Holm-Hansen, Osmund; Bullister, John L. (2002). "Trifluoroacetate in Ocean Waters". Environmental Science & Technology. 36 (1): 12–15. Bibcode:2002EnST...36...12F. doi:10.1021/es0101532. ISSN   0013-936X. PMID   11811478.
  21. "Refreshingly cool, potentially toxic". Ludwig-Maximilians-Universität (LMU) Munich. 2014. Retrieved 26 July 2018.
  22. Kirschner, E., Chemical and Engineering News 1994, 8.
  23. Boutonnet, Jean Charles; Bingham, Pauline; Calamari, Davide; Rooij, Christ de; Franklin, James; Kawano, Toshihiko; Libre, Jean-Marie; McCul-Loch, Archie; Malinverno, Giuseppe; Odom, J Martin; Rusch, George M; Smythe, Katie; Sobolev, Igor; Thompson, Roy; Tiedje, James M (1999). "Environmental risk assessment of trifluoroacetic acid". International Journal of Human and Ecological Risk Assessment. 5 (1): 59–124. Bibcode:1999HERA....5...59B. doi:10.1080/10807039991289644.