Hexafluorobenzene
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| Names | |||
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IUPAC name
Hexafluorobenzene
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| Other names
Perfluorobenzene
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| Identifiers | |||
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3D model (Jmol)
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| ChEBI | |||
| ChemSpider | |||
| ECHA InfoCard | 100.006.252 | ||
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PubChem CID
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| Properties | |||
| C6F6 | |||
| Molar mass | 186.06 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) | ||
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Refractive index (nD)
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1.377 | ||
| Viscosity | cP (1.200 mPa•s) (20 °C) | ||
| 0.00 D (gas) | |||
| Hazards | |||
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EU classification (DSD)
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Highly Flammable (F) | ||
| R-phrases | R11 | ||
| S-phrases | S33 S29 S9 S16 | ||
| Flash point | 10 °C (50 °F; 283 K) | ||
| Related compounds | |||
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Related compounds
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Benzene Hexachlorobenzene Polytetrafluoroethylene |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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 (what is   ?) |
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| Infobox references | |||
Hexafluorobenzene, HFB, C
6F
6, or perfluorobenzene is an organic, aromatic 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 In this derivative of benzene all hydrogen atoms have been replaced by fluorine atoms.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 is recommended as a solvent in a number of reactions. In the laboratory hexafluorobenzene is used for several purposes:
Hexafluorobenzene in the perhalogenbenzenes stands somewhat aside. 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:
The conclusion of the table is HFB is the only perhalobenzene being planar, the others all are buckled more or less. As a consequence in C6F6 the overlap between the p-orbitals is optimal, while in the others it is less, also giving rise to a lower aromaticity in those compounds.
The direct synthesis of hexafluorobenzene from benzene and Fluorine is not possible. The synthetic route proceeds via the reaction of alkali-fluorides with halogenated benzene:
A substantial part of the chemistry of HFB is related to the position of fluorine in the periodic table. On its position at the end of the first row, fluorine is a halogen. It also is the smallest one, so taking up an electron releases one of the largest amounts of energy of all elements, it is the strongest oxidant, and it has the highest electronegativity. The carbon fluorine bond therefore is highly polarized: the carbon atom has (partially) positive charge, fluorine negative. This reasoning holds very much for the electrons in the σ-bonds. Electrons in p-orbitals encounter a totally different situation. The p-orbital at fluorine parallel to the one on the adjacent carbon will face an optimal interaction. Thereby fluorine, unlike the higher halogens, has no extra nodal plane in its orbitals, so size and geometry fit perfectly and no anti-bonding interactions occur. The dipole resulting from the σ-electronegativity will force a partial replacement of electric charge from fluorine towards carbon and the aromatic ring: fluorine behaves as a σ-electronegative, but as a π-electropositive element. This view is supported by the reactions C6F6 exhibits.
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Wikipedia