Fluorene
| Fluorene[1] | |
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9H-Fluorene |
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| Identifiers | |
| CAS number | 86-73-7  |
| PubChem | 6853 |
| ChemSpider | 6592 |
| UNII | 3Q2UY0968A |
| EC number | 201-695-5 |
| KEGG | C07715 |
| ChEBI | CHEBI:28266 |
| ChEMBL | CHEMBL16236 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | C13H10 |
| Molar mass | 166.223 g/mol |
| Density | 1.202 g/mL |
| Melting point |
116-117 °C |
| Boiling point |
295 °C, 568 K, 563 °F |
| Acidity (pKa) | 22.6 |
| Hazards | |
| NFPA 704 |
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 (verify) (what is:  / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Fluorene, or 9H-fluorene, is a polycyclic aromatic hydrocarbon. It forms white crystals that exhibit a characteristic, aromatic odor similar to that of naphthalene. It is combustible. It has a violet fluorescence, hence its name. For commercial purposes it is obtained from coal tar. It is insoluble in water and soluble in benzene and ether.
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[edit] Synthesis, structure, and reactivity
Although fluorene is obtained from coal tar, it can also be prepared by dehydrogenation of diphenylmethane.[2]
The fluorene molecule is nearly planar,[3] although each of the two benzene rings is coplanar with the central carbon 9.[4]
[edit] Acidity
The C9-H sites of the fluorene ring are weakly acidic (pKa = 22.6 in DMSO.[5]) Deprotonation gives the stable fluorenyl "anion", nominally C13H9−, which is aromatic and has an intense orange colour. The anion is a nucleophile, and most electrophiles react with it by adding to the 9-position. The purification of fluorene exploits its acidity and the low solubility of its sodium derivative in hydrocarbon solvents.
Both protons can be removed from C9. For example, 9,9-fluorenyldipotassium can be obtained by treating fluorene with potassium metal in boiling dioxane.[6]
[edit] Uses
Fluorene is a precursor to other fluorene compounds; the parent species has few applications. Fluorene-9-carboxylic acid is a precursor to pharmaceuticals. 2-Aminofluorene, 3,6-bis-(dimethylamino)fluorene, and 2,7-diiodofluorene are precursors to dyes. Oxidation of fluorene gives fluorenone, which is nitrated to give commercially useful derivatives. 9-Fluorenylmethyl chloroformate (Fmoc chloride) is used to introduce the 9-fluorenylmethyl carbamate (Fmoc) protecting group on amines in peptide synthesis.[2]
Polyfluorene polymers (where carbon 7 of one unit is linked to carbon 2 of the next one, displacing two hydrogens) are electrically conductive and electroluminescent, and have been much investigated for use as a luminophore in organic light-emitting diodes.
[edit] References
- ^ Merck Index, 11th Edition, 4081
- ^ a b Karl Griesbaum, Arno Behr, Dieter Biedenkapp, Heinz-Werner Voges, Dorothea Garbe, Christian Paetz, Gerd Collin, Dieter Mayer, Hartmut Höke “Hydrocarbons” in Ullmann's Encyclopedia of Industrial Chemistry 2002 Wiley-VCH, Weinheim. doi:10.1002/14356007.a13_227
- ^ D. M. Burns, John Iball (1954), Molecular Structure of Fluorene Nature volume 173, p. 635. doi:10.1038/173635a0
- ^ R. E. Gerkin, A. P. Lundstedt and W. J. Reppart (1984) Structure of fluorene, C13H10, at 159 K Acta Crystallographica, volume C40, pp. 1892–1894 doi:10.1107/S0108270184009963
- ^ F. G. Bordwell (1988). "Equilibrium acidities in dimethyl sulfoxide solution". Acc. Chem. Res. 21 (12): 456–463. doi:10.1021/ar00156a004.
- ^ G. W. Scherf and R. K. Brown (1960), POTASSIUM DERIVATIVES OF FLUORENE AS INTERMEDIATES IN THE PREPARATION OF C9-SUBSTITUTED FLUORENES. I. THE PREPARATION OF 9-FLUORENYL POTASSIUM AND THE INFRARED SPECTRA OF FLUORENE AND SOME C9-SUBSTITUTED FLUORENES. Canadian Journal of Chemistry, Vol. 38, p. 697.
[edit] External links
- National Pollutant Inventory - Polycyclic Aromatic Hydrocarbon Fact Sheet
- Fluorene in the National Institute of Standards and Technology database.
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