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Pentafluorobenzoic acid

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Pentafluorobenzoic acid
Names
Preferred IUPAC name Pentafluorobenzoic acid
Other names perfluorobenzoic acid
Identifiers
CAS Number
3D model (JSmol)
Beilstein Reference 2054395
ChemSpider
ECHA InfoCard 100.009.115 Edit this at Wikidata
Gmelin Reference 2054395
PubChem CID
UNII
CompTox Dashboard (EPA)
InChI
  • InChI=1S/C7HF5O2/c8-2-1(7(13)14)3(9)5(11)6(12)4(2)10/h(H,13,14)Key: YZERDTREOUSUHF-UHFFFAOYSA-N
  • InChI=1/C7HF5O2/c8-2-1(7(13)14)3(9)5(11)6(12)4(2)10/h(H,13,14)Key: YZERDTREOUSUHF-UHFFFAOYAQ
SMILES
  • Fc1c(c(F)c(F)c(F)c1F)C(=O)O
Properties
Chemical formula C7HF5O2
Molar mass 212.075 g·mol
Appearance White crystalline powder
Density 1.942 g/cm
Melting point 100–102 °C (212–216 °F; 373–375 K)
Boiling point 220 °C (428 °F; 493 K)
Solubility in water Very soluble
log P 2.06
Acidity (pKa) 1.60
Hazards
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2 0 0
Flash point 87 °C (189 °F; 360 K)
Related compounds
Related carboxylic acids benzoic acids,
Nitrobenzoic acids
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). Infobox references
Chemical compound

Pentafluorobenzoic acid (PFBA) is an organofluorine compound with the formula C6F5CO2H. It is a white crystalline powder that has a high solubility in water. Its pKa of 1.48 indicates that it is a strong acid.

Preparation

Pentafluorobenzoic acid is prepared by treating pentafluorophenyllithium (or pentafluorophenyl Grignard reagent) with carbon dioxide. These reagents are usually prepared in situ from pentafluorobenzene and bromopentafluorobenzene.

It arises via the reaction of perfluorotoluene with trifluoroacetic acid and antimony pentafluoride.

Substitution reactions

Substitution of fluoride occurs typically at the para position. This reaction has been used to anchor the −C6F4CO2H group to surfaces. Magnesium methoxide results in ortho methoxylation. Cleavage of this ether gives tetrafluorosalicylic acid. Via similar ortho-directed reactivity, nickel complexes catalyse the defluoridation of 2 and 5 positions. Without nickel, defluoridation occurs with para-selectivity.

References

  1. ^ Prakash, G. K. S.; Hu, J. "Pentafluorobenzoic Acid" in e-EROS Encyclopedia of Reagents for Organic Synthesis, 2005. doi:10.1002/047084289X.rn00682
  2. Harper, R. J. Jr.; Soloski, E. J.; Tamborski, C. (1964). "Reactions of Organometallics with Fluoroaromatic Compounds". J. Org. Chem. 29 (8): 2385. doi:10.1021/jo01031a067.
  3. Zonov, Yaroslav V.; Karpov, Victor M.; Platonov, Vyacheslav E. (2007). "Transformation of perfluorinated benzocycloalkenes and alkylbenzenes to their carbonyl derivatives under the action of CF3COOH/SbF5". Journal of Fluorine Chemistry. 128 (9): 1058–1064. doi:10.1016/j.jfluchem.2007.05.020.
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