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Hexafluorobenzene

April 12, 2024

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 In this derivative of benzene, all hydrogen atoms have been replaced by fluorine atoms.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.

Hexafluorobenzene
Names
Preferred IUPAC name
Hexafluorobenzene
Other names
Perfluorobenzene
Identifiers
  • 392-56-3 Y
3D model (JSmol)
  • Interactive image
Abbreviations HFB
1683438
ChEBI
  • CHEBI:38589 Y
ChemSpider
  • 13836549 Y
ECHA InfoCard 100.006.252
EC Number
  • 206-876-2
101976
  • 9805
UNII
  • CMC18T611K Y
  • DTXSID5043924
  • InChI=1S/C6F6/c7-1-2(8)4(10)6(12)5(11)3(1)9 Y
    Key: ZQBFAOFFOQMSGJ-UHFFFAOYSA-N Y
  • InChI=1/C6F6/c7-1-2(8)4(10)6(12)5(11)3(1)9
    Key: ZQBFAOFFOQMSGJ-UHFFFAOYAJ
  • Fc1c(F)c(F)c(F)c(F)c1F
Properties
C6F6
Molar mass 186.056 g·mol−1
Appearance Colorless liquid
Density 1.6120 g/cm3
Melting point 5.2 °C (41.4 °F; 278.3 K)
Boiling point 80.1 °C (176.2 °F; 353.2 K)
1.377
Viscosity cP (1.200 mPa•s) (20 °C)
0.00 D (gas)
Hazards[1]
GHS labelling:
Warning
H225
P210, P233, P240, P241, P242, P243
Flash point 10 °C (50 °F; 283 K)[2]
Related compounds
Related compounds
 Benzene
Hexachlorobenzene
Polytetrafluoroethylene
Perfluorotoluene
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Geometry of the aromatic ring edit

Hexafluorobenzene stands somewhat aside in the perhalogenbenzenes. When counting for bond angles and distances it is possible to calculate the distance between two ortho fluorine atoms. Also the non bonding radius of the halogens is known. The following table presents the results:[3]

Formula Name Calculated
inter-halogen
distance, aromatic ring assumed planar 		Twice nonbonding radius Consequent symmetry of the benzene
C6F6 hexafluorobenzene 279 270 D6h
C6Cl6 hexachlorobenzene 312 360 D3d
C6Br6 hexabromobenzene 327 390 D3d
C6I6 hexaiodobenzene 354 430 D3d

Hexafluorobenzene is the only perhalobenzene being planar, the other perhalobenzene species exhibiting buckling. As a consequence, in C6F6 the overlap between the p-orbitals is optimal versus the other perhalobenzenes, resulting in lower aromaticity of those compounds compared to C6F6.

Synthesis edit

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:[4]

C6Cl6 + 6 KF → C6F6 + 6 KCl

Reactions edit

Most reactions of hexafluorobenzene proceed with displacement of fluoride. One example is its reaction with sodium hydrosulfide to afford pentafluorothiophenol:[5]

C6F6 + NaSH → C6F5SH + NaF

The reaction of pentafluorophenyl derivatives has been long puzzling for its mechanism. Independent of the substituent, they all exhibit a para directing effect. The new introduced group too has no effect on the directing behaviour. In all cases, a 1,4-disubstituted-2,3,5,6-tetrafluorobenzene derivative shows up. Finally, the clue is found not in the nature of the non-fluorine substituent, but in the fluorines themselves. The π-electropositive effect introduces electrons into the aromatic ring. The non-fluorine substituent is not capable of doing so. As charge accumulates at the ortho and para positions relative to the donating group, the ortho and para-positions relative to the non-fluorine substituent receive less charge, so are less negative or more positive. Furthermore, the non-fluorine substituent in general is more bulky than fluorine, so its ortho-positions are sterically shielded, leaving the para-position as the sole reaction site for anionic entering groups.

UV light causes gaseous HFB to isomerize to hexafluoro derivative of Dewar benzene.[6]

Laboratory applications edit

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 19F NMR spin lattice relaxation (R1): specifically a linear dependence R1= a + bpO2 has been reported.[7] 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 19F 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 19F 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.[8] MRI measurements of HFB based on 19F relaxation have been shown to correlate with radiation response of tumors.[9] HFB has been used as a gold standard for investigating other potential prognostic biomarkers of tumor oxygenation such as BOLD (Blood Oxygen Level Dependent),[10] TOLD (Tissue Oxygen Level Dependent) [11] and MOXI (MR oximetry) [12] A 2013 review of applications has been published.[13]

HFB has been evaluated as standard in fluorine-19 NMR spectroscopy.[14]

Toxicity edit

Hexafluorobenzene may cause eye and skin irritation, respiratory and digestive tract irritation and can cause central nervous system depression per MSDS.[15] The National Institute for Occupational Safety and Health (NIOSH) lists it in its Registry of Toxic Effects of Chemical Substances as neurotoxicant.

See also edit

References edit

  1. ^ "Hexafluorobenzene 99%". Sigma Aldrich.
  2. ^ Acros Organics:Catalog of fine Chemicals (1999)
  3. ^ 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.
  4. ^ 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.
  5. ^ 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.
  6. ^ Lemal, David M. (2001). "Hexafluorobenzene Photochemistry: Wellspring of Fluorocarbon Structures". Accounts of Chemical Research. 34 (8): 662–671. doi:10.1021/ar960057j. PMID 11513574.
  7. ^ 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.
  8. ^ 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.
  9. ^ 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.
  10. ^ Zhao, D.; Jiang, L.; Hahn, E. W.; Mason, R. P. (2009). "Comparison of 1H blood oxygen level–dependent (BOLD) and 19F MRI to investigate tumor oxygenation". Magnetic Resonance in Medicine. 62 (2): 357–364. doi:10.1002/mrm.22020. PMC 4426862. PMID 19526495.
  11. ^ 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.
  12. ^ 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.
  13. ^ Yu, J.-X.; Hallac, R. R.; Chiguru, S.; Mason, R. P. (2013). "New frontiers and developing applications in 19F NMR". Progress in Nuclear Magnetic Resonance Spectroscopy. 70: 25–49. doi:10.1016/j.pnmrs.2012.10.001. PMC 3613763. PMID 23540575.
  14. ^ 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.
  15. ^ "Material safety data sheet: Hexafluorobenzene, 99%". Fisher Scientific. Thermo Fisher Scientific. n.d. Retrieved 2020-02-08.

Further reading edit

  • 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. 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.

April 12, 2024
hexafluorobenzene, perfluorobenzene, organofluorine, compound, this, derivative, benzene, hydrogen, atoms, have, been, replaced, fluorine, atoms, technical, uses, compound, limited, although, some, specialized, uses, laboratory, owing, distinctive, spectroscop. Hexafluorobenzene HFB C6 F6 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 Hexafluorobenzene NamesPreferred IUPAC name HexafluorobenzeneOther names PerfluorobenzeneIdentifiersCAS Number 392 56 3 Y3D model JSmol Interactive imageAbbreviations HFBBeilstein Reference 1683438ChEBI CHEBI 38589 YChemSpider 13836549 YECHA InfoCard 100 006 252EC Number 206 876 2Gmelin Reference 101976PubChem CID 9805UNII CMC18T611K YCompTox Dashboard EPA DTXSID5043924InChI InChI 1S C6F6 c7 1 2 8 4 10 6 12 5 11 3 1 9 YKey ZQBFAOFFOQMSGJ UHFFFAOYSA N YInChI 1 C6F6 c7 1 2 8 4 10 6 12 5 11 3 1 9Key ZQBFAOFFOQMSGJ UHFFFAOYAJSMILES Fc1c F c F c F c F c1FPropertiesChemical formula C 6F 6Molar mass 186 056 g mol 1Appearance Colorless liquidDensity 1 6120 g cm3Melting point 5 2 C 41 4 F 278 3 K Boiling point 80 1 C 176 2 F 353 2 K Refractive index nD 1 377Viscosity cP 1 200 mPa s 20 C Dipole moment 0 00 D gas Hazards 1 GHS labelling PictogramsSignal word WarningHazard statements H225Precautionary statements P210 P233 P240 P241 P242 P243Flash point 10 C 50 F 283 K 2 Related compoundsRelated compounds BenzeneHexachlorobenzenePolytetrafluoroethylenePerfluorotolueneExcept where otherwise noted data are given for materials in their standard state at 25 C 77 F 100 kPa Y verify what is Y N Infobox references Contents 1 Geometry of the aromatic ring 2 Synthesis 3 Reactions 4 Laboratory applications 5 Toxicity 6 See also 7 References 8 Further readingGeometry of the aromatic ring editHexafluorobenzene stands somewhat aside in the perhalogenbenzenes When counting for bond angles and distances it is possible to calculate the distance between two ortho fluorine atoms Also the non bonding radius of the halogens is known The following table presents the results 3 Formula Name Calculatedinter halogendistance aromatic ring assumed planar Twice nonbonding radius Consequent symmetry of the benzeneC6F6 hexafluorobenzene 279 270 D6hC6Cl6 hexachlorobenzene 312 360 D3dC6Br6 hexabromobenzene 327 390 D3dC6I6 hexaiodobenzene 354 430 D3dHexafluorobenzene is the only perhalobenzene being planar the other perhalobenzene species exhibiting buckling As a consequence in C6F6 the overlap between the p orbitals is optimal versus the other perhalobenzenes resulting in lower aromaticity of those compounds compared to C6F6 Synthesis editThe 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 4 C6Cl6 6 KF C6F6 6 KClReactions editMost reactions of hexafluorobenzene proceed with displacement of fluoride One example is its reaction with sodium hydrosulfide to afford pentafluorothiophenol 5 C6F6 NaSH C6F5SH NaFThe reaction of pentafluorophenyl derivatives has been long puzzling for its mechanism Independent of the substituent they all exhibit a para directing effect The new introduced group too has no effect on the directing behaviour In all cases a 1 4 disubstituted 2 3 5 6 tetrafluorobenzene derivative shows up Finally the clue is found not in the nature of the non fluorine substituent but in the fluorines themselves The p electropositive effect introduces electrons into the aromatic ring The non fluorine substituent is not capable of doing so As charge accumulates at the ortho and para positions relative to the donating group the ortho and para positions relative to the non fluorine substituent receive less charge so are less negative or more positive Furthermore the non fluorine substituent in general is more bulky than fluorine so its ortho positions are sterically shielded leaving the para position as the sole reaction site for anionic entering groups UV light causes gaseous HFB to isomerize to hexafluoro derivative of Dewar benzene 6 Laboratory applications editHexafluorobenzene 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 19F NMR spin lattice relaxation R1 specifically a linear dependence R1 a bpO2 has been reported 7 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 19F 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 19F 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 8 MRI measurements of HFB based on 19F relaxation have been shown to correlate with radiation response of tumors 9 HFB has been used as a gold standard for investigating other potential prognostic biomarkers of tumor oxygenation such as BOLD Blood Oxygen Level Dependent 10 TOLD Tissue Oxygen Level Dependent 11 and MOXI MR oximetry 12 A 2013 review of applications has been published 13 HFB has been evaluated as standard in fluorine 19 NMR spectroscopy 14 Toxicity editHexafluorobenzene may cause eye and skin irritation respiratory and digestive tract irritation and can cause central nervous system depression per MSDS 15 The National Institute for Occupational Safety and Health NIOSH lists it in its Registry of Toxic Effects of Chemical Substances as neurotoxicant See also editPentafluorobenzene HexabromobenzeneReferences edit Hexafluorobenzene 99 Sigma Aldrich Acros Organics Catalog of fine Chemicals 1999 Delorme P Denisselle F Lorenzelli V 1967 Spectre infrarouge et vibrations fondamentales des derives hexasubstitues halogenes du benzene 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 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 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 Lemal David M 2001 Hexafluorobenzene Photochemistry Wellspring of Fluorocarbon Structures Accounts of Chemical Research 34 8 662 671 doi 10 1021 ar960057j PMID 11513574 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 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 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 Zhao D Jiang L Hahn E W Mason R P 2009 Comparison of 1H blood oxygen level dependent BOLD and 19F MRI to investigate tumor oxygenation Magnetic Resonance in Medicine 62 2 357 364 doi 10 1002 mrm 22020 PMC 4426862 PMID 19526495 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 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 Yu J X Hallac R R Chiguru S Mason R P 2013 New frontiers and developing applications in 19F NMR Progress in Nuclear Magnetic Resonance Spectroscopy 70 25 49 doi 10 1016 j pnmrs 2012 10 001 PMC 3613763 PMID 23540575 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 Material safety data sheet Hexafluorobenzene 99 Fisher Scientific Thermo Fisher Scientific n d Retrieved 2020 02 08 Further reading editPummer 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 doi 10 1107 S0021889874008764 Samojlowicz C Bieniek M Pazio A Makal A Wozniak K Poater A Cavallo L Wojcik 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 Retrieved from https en wikipedia org w index php title Hexafluorobenzene amp oldid 1194482258, wikipedia, wiki, book, books, library,

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