Misplaced Pages

This is the current revision of this page, as edited by Beland (talk | contribs) at 22:35, 19 August 2024 (convert special characters found by Misplaced Pages:Typo Team/moss (via WP:JWB)). The present address (URL) is a permanent link to this version.

Hexafluorobenzene

Names
Preferred IUPAC name Hexafluorobenzene
Other names Perfluorobenzene
Identifiers
CAS Number	392-56-3
3D model (JSmol)	Interactive image
Abbreviations	HFB
Beilstein Reference	1683438
ChEBI	CHEBI:38589
ChemSpider	13836549
ECHA InfoCard	100.006.252
EC Number	206-876-2
Gmelin Reference	101976
PubChem CID	9805
UNII	CMC18T611K
CompTox Dashboard (EPA)	DTXSID5043924
InChI InChI=1S/C6F6/c7-1-2(8)4(10)6(12)5(11)3(1)9Key: ZQBFAOFFOQMSGJ-UHFFFAOYSA-N InChI=1/C6F6/c7-1-2(8)4(10)6(12)5(11)3(1)9Key: ZQBFAOFFOQMSGJ-UHFFFAOYAJ
SMILES Fc1c(F)c(F)c(F)c(F)c1F
Properties
Chemical formula	C6F6
Molar mass	186.056 g·mol
Appearance	Colorless liquid
Density	1.6120 g/cm
Melting point	5.2 °C (41.4 °F; 278.3 K)
Boiling point	80.3 °C (176.5 °F; 353.4 K)
Refractive index (nD)	1.377
Viscosity	cP (1.200 mPa•s) (20 °C)
Dipole moment	0.00 D (gas)
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H225
Precautionary statements	P210, P233, P240, P241, P242, P243
Flash point	10 °C (50 °F; 283 K)
Related compounds
Related compounds	Benzene Hexachlorobenzene Polytetrafluoroethylene Perfluorotoluene
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). Y verify (what is  ?) Infobox references

Hexafluorobenzene, HFB, C
₆F
₆, or perfluorobenzene is an organofluorine compound. In this derivative of benzene, all hydrogen atoms have been replaced by fluorine atoms. The technical uses of the compound are limited, although it has some specialized uses in the laboratory owing to distinctive spectroscopic properties.

Geometry of the aromatic ring

Hexafluorobenzene stands somewhat aside in the perhalogenbenzenes. If a perhalogenated benzene ring were to remain planar, then geometric constraints would force adjacent halogens closer than their associated nonbonding radius. Consequently the benzene ring buckles, reducing p-orbital overlap and aromaticity to avoid the steric clash. Perfluorobenzene is an exception: as shown in the following table, two fluorines are small enough to avoid collision, retaining planarity and full aromaticity.

Synthesis

The direct synthesis of hexafluorobenzene from benzene and fluorine has not been useful. Instead it is prepared by the reaction of alkali fluorides with halogenated benzene:

C₆Cl₆ + 6 KF → C₆F₆ + 6 KCl

Antimony fluoride instead adds to the ring, breaking aromaticity.

In principle, various halofluoromethanes pyrolyze to hexafluorobenzene, but commercialization was still in the initial stages in 2000.

Reactions

Hexafluorobenzene easily undergoes nucleophilic aromatic substitution. One example is its reaction with sodium hydrosulfide to afford pentafluorothiophenol:

C₆F₆ + NaSH → C₆F₅SH + NaF

The further reaction of pentafluorophenyl derivatives has long been puzzling, because the non-fluorine substituent has no effect. The second new substituent is always directed para, to form a 1,4-disubstituted-2,3,5,6-tetrafluorobenzene.

Hexafluorobenzene is thus a comonomer in certain heavily fluorinated heat-resistant polyethers' synthesis.

UV light causes gaseous HFB to isomerize to hexafluoro derivative of Dewar benzene.

Laboratory applications

Hexafluorobenzene has been used as a reporter molecule to investigate tissue oxygenation in vivo. It is exceedingly hydrophobic, but exhibits high gas solubility with ideal liquid gas interactions. Since molecular oxygen is paramagnetic it causes F NMR spin lattice relaxation (R1): specifically a linear dependence R1= a + bpO₂ has been reported. HFB essentially acts as molecular amplifier, since the solubility of oxygen is greater than in water, but thermodynamics require that the pO2 in the HFB rapidly equilibrates with the surrounding medium. HFB has a single narrow F NMR signal and the spin lattice relaxation rate is highly sensitive to changes in pO₂, yet minimally responsive to temperature. HFB is typically injected directly into a tissue and F NMR may be used to measure local oxygenation. It has been extensively applied to examine changes in tumor oxygenation in response to interventions such as breathing hyperoxic gases or as a consequence of vascular disruption. MRI measurements of HFB based on 19F relaxation have been shown to correlate with radiation response of tumors. HFB has been used as a gold standard for investigating other potential prognostic biomarkers of tumor oxygenation such as BOLD (Blood Oxygen Level Dependent), TOLD (Tissue Oxygen Level Dependent) and MOXI (MR oximetry) A 2013 review of applications has been published.

HFB has been evaluated as standard in fluorine-19 NMR spectroscopy.

Toxicity

Hexafluorobenzene may cause eye and skin irritation, respiratory and digestive tract irritation and can cause central nervous system depression per MSDS. The National Institute for Occupational Safety and Health (NIOSH) lists it in its Registry of Toxic Effects of Chemical Substances as neurotoxicant.

See also

• Pentafluorobenzene
• Hexabromobenzene

References

1. Siegemund, Günter; Schwertfeger, Werner; Feiring, Andrew; Smart, Bruce; Behr, Fred; Vogel, Herward; McKusick, Blaine; Kirsch, Peer (2016). "Fluorine compounds, organic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. p. 44. doi:10.1002/14356007.a11_349.pub2. ISBN 978-3-527-30673-2.{{cite encyclopedia}}: CS1 maint: multiple names: authors list (link)
2. "Hexafluorobenzene 99%". Sigma Aldrich.
3. Acros Organics:Catalog of fine Chemicals (1999)
4. Delorme, P.; Denisselle, F.; Lorenzelli, V. (1967). "Spectre infrarouge et vibrations fondamentales des dérivés hexasubstitués halogénés du benzène" [Infrared spectrum and fundamental vibrations of the hexasubstituted halogen derivatives of benzene]. Journal de Chimie Physique (in French). 64: 591–600. Bibcode:1967JCP....64..591D. doi:10.1051/jcp/1967640591.
5. Vorozhtsov, N. N. Jr.; Platonov, V. E.; Yakobson, G. G. (1963). "Preparation of hexafluorobenzene from hexachlorobenzene". Bulletin of the Academy of Sciences of the USSR, Division of Chemical Science. 12 (8): 1389. doi:10.1007/BF00847820.
6. ^ Bajzer, William X., "Fluorine compounds, organic", Kirk-Othmer Encyclopedia of Chemical Technology, vol. 11, New York: John Wiley, doi:10.1002/0471238961.0914201802011026.a01.pub2, ISBN 9780471238966
7. ^ Boudakian, Max M., "Fluorinated aromatic compounds", Kirk-Othmer Encyclopedia of Chemical Technology, New York: John Wiley, doi:10.1002/0471238961.0612211502152104.a01, ISBN 9780471238966
8. Robson, P.; Stacey, M.; Stephens, R.; Tatlow, J. C. (1960). "Aromatic polyfluoro-compounds. Part VI. Penta- and 2,3,5,6-tetra-fluorothiophenol". Journal of the Chemical Society (4): 4754–4760. doi:10.1039/JR9600004754.
9. Cassidy, Patrick E.; Aminabhavi, Tejraj M.; Reddy, V. Sreenivasulu, "Heat-resistant polymers", Kirk-Othmer Encyclopedia of Chemical Technology, New York: John Wiley, p. 18, doi:10.1002/0471238961.0805012003011919.a01, ISBN 9780471238966
10. Lemal, David M. (2001). "Hexafluorobenzene Photochemistry: Wellspring of Fluorocarbon Structures". Accounts of Chemical Research. 34 (8): 662–671. doi:10.1021/ar960057j. PMID 11513574.
11. Zhao, D.; Jiang, L.; Mason, R. P. (2004). "Measuring changes in tumor oxygenation". In Conn, P. M. (ed.). Imaging in Biological Research, Part B. Methods in Enzymology. Vol. 386. Elsevier. pp. 378–418. doi:10.1016/S0076-6879(04)86018-X. ISBN 978-0-12-182791-5. PMID 15120262.
12. Zhao, D.; Jiang, L.; Hahn, E. W.; Mason, R. P. (2005). "Tumor physiologic response to combretastatin A4 phosphate assessed by MRI". International Journal of Radiation Oncology, Biology, Physics. 62 (3): 872–880. doi:10.1016/j.ijrobp.2005.03.009. PMID 15936572.
13. Zhao, D.; Constantinescu, A.; Chang, C.-H.; Hahn, E. W.; Mason, R. P. (2003). "Correlation of tumor oxygen dynamics with radiation response of the Dunning prostate R3327-HI tumor". Radiation Research. 159 (5): 621–631. doi:10.1667/0033-7587(2003)159[0621:COTODW]2.0.CO;2. PMID 12710873.
14. Zhao, D.; Jiang, L.; Hahn, E. W.; Mason, R. P. (2009). "Comparison of H blood oxygen level–dependent (BOLD) and F MRI to investigate tumor oxygenation". Magnetic Resonance in Medicine. 62 (2): 357–364. doi:10.1002/mrm.22020. PMC 4426862. PMID 19526495.
15. Hallac, R. R.; Zhou, H.; Pidikiti, R.; Song, K.; Stojadinovic, S.; Zhao, D.; Solberg, T.; Peschke, P.; Mason, R. P. (2014). "Correlations of noninvasive BOLD and TOLD MRI with pO₂ and relevance to tumor radiation response". Magnetic Resonance in Medicine. 71 (5): 1863–1873. doi:10.1002/mrm.24846. PMC 3883977. PMID 23813468.
16. Zhang, Z.; Hallac, R. R.; Peschke, P.; Mason, R. P. (2014). "A noninvasive tumor oxygenation imaging strategy using magnetic resonance imaging of endogenous blood and tissue water". Magnetic Resonance in Medicine. 71 (2): 561–569. doi:10.1002/mrm.24691. PMC 3718873. PMID 23447121.
17. Yu, J.-X.; Hallac, R. R.; Chiguru, S.; Mason, R. P. (2013). "New frontiers and developing applications in F NMR". Progress in Nuclear Magnetic Resonance Spectroscopy. 70: 25–49. doi:10.1016/j.pnmrs.2012.10.001. PMC 3613763. PMID 23540575.
18. Rosenau, Carl Philipp; Jelier, Benson J.; Gossert, Alvar D.; Togni, Antonio (2018). "Exposing the Origins of Irreproducibility in Fluorine NMR Spectroscopy". Angewandte Chemie International Edition. 57 (30): 9528–9533. doi:10.1002/anie.201802620. PMID 29663671.
19. "Material safety data sheet: Hexafluorobenzene, 99%". Fisher Scientific. Thermo Fisher Scientific. n.d. Retrieved 2020-02-08.

Further reading

• Pummer, W. J.; Wall, L. A. (1958). "Reactions of hexafluorobenzene". Science. 127 (3299): 643–644. Bibcode:1958Sci...127..643P. doi:10.1126/science.127.3299.643. PMID 17808882.
• US patent 3277192, Fielding, H. C., "Preparation of hexafluorobenzene and fluorochlorobenzenes", issued 1966-10-04, assigned to Imperial Chemical Industries 
• Bertolucci, M. D.; Marsh, R. E. (1974). "Lattice parameters of hexafluorobenzene and 1,3,5-trifluorobenzene at −17 °C". Journal of Applied Crystallography. 7 (1): 87–88. Bibcode:1974JApCr...7...87B. doi:10.1107/S0021889874008764.
• Samojłowicz, C.; Bieniek, M.; Pazio, A.; Makal, A.; Woźniak, K.; Poater, A.; Cavallo, L.; Wójcik, J.; Zdanowski, K.; Grela, K. (2011). "The doping effect of fluorinated aromatic solvents on the rate of ruthenium-catalysed olefin metathesis". Chemistry: A European Journal. 17 (46): 12981–12993. doi:10.1002/chem.201100160. PMID 21956694.

• Fluorobenzenes
• Aromatic solvents
• Neurotoxins
• Fluorocarbons
• Solvents