{{distinguish|Hydrogen fluoride{{!}}Fluorane|Fluorine|Fluorone|Fluorenone}} {{chembox | Watchedfields = changed | verifiedrevid = 443822810 | Reference = <ref>''Merck Index'', 11th Edition, '''4081'''</ref> | Name = Fluorene | ImageFile_Ref = {{chemboximage|correct|??}} | ImageFile = Fluorene.svg | ImageClass = skin-invert-image | ImageSize = | ImageName = | ImageFile1 = Fluorene-from-xtal-3D-balls.png | ImageFile2 = Fluorene-3D-vdW.png | ImageClass2 = bg-transparent | PIN = 9''H''-Fluorene<ref>{{cite book |author=International Union of Pure and Applied Chemistry |date=2014 |title=Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013 |publisher=The Royal Society of Chemistry |pages=207 |doi=10.1039/9781849733069 |isbn=978-0-85404-182-4}}</ref> | SystematicName = Tricyclo[7.4.0.0<sup>2,7</sup>]trideca-2,4,6,9,11,13-hexaene |Section1={{Chembox Identifiers | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | ChemSpiderID = 6592 | PubChem = 6853 | RTECS = LL5670000 | KEGG_Ref = {{keggcite|correct|kegg}} | KEGG = C07715 | InChI = 1/C13H10/c1-3-7-12-10(5-1)9-11-6-2-4-8-13(11)12/h1-8H,9H2 | InChIKey = NIHNNTQXNPWCJQ-UHFFFAOYAW | ChEMBL_Ref = {{ebicite|correct|EBI}} | ChEMBL = 16236 | StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChI = 1S/C13H10/c1-3-7-12-10(5-1)9-11-6-2-4-8-13(11)12/h1-8H,9H2 | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey = NIHNNTQXNPWCJQ-UHFFFAOYSA-N | CASNo_Ref = {{cascite|correct|CAS}} | CASNo = 86-73-7 | EINECS = 201-695-5 | UNII_Ref = {{fdacite|correct|FDA}} | UNII = 3Q2UY0968A | ChEBI_Ref = {{ebicite|correct|EBI}} | ChEBI = 28266 | SMILES = c1ccc2c3ccccc3Cc2c1 }} |Section2={{Chembox Properties | C=13|H=10 | MeltingPtC = 116 to 117 | MeltingPt_notes = | BoilingPtC = 295 | Density = 1.202 g/mL | Solubility = 1.992 mg/L | SolubleOther = organic solvents | pKa = 22.6 | LogP = 4.18 | MagSus = −110.5·10<sup>−6</sup> cm<sup>3</sup>/mol }} |Section7={{Chembox Hazards | ExternalSDS = [http://www.sigmaaldrich.com/MSDS/MSDS/DisplayMSDSPage.do?country=PL&language=EN-generic&productNumber=46880&brand=ALDRICH&PageToGoToURL=http%3A%2F%2Fwww.sigmaaldrich.com%2Fcatalog%2Fproduct%2Faldrich%2F46880%3Flang%3Dpl Sigma-Aldrich] | NFPA-H = 1 | NFPA-F = 1 | NFPA-R = 0 | NFPA-S = | FlashPtC = 152 | LD50 = 16000 mg/kg (oral, rat) }} }}
'''Fluorene''' {{IPAc-en|ˈ|f|l|ʊər|iː|n}}, or '''9''H''-fluorene''' is an organic compound with the formula (C<sub>6</sub>H<sub>4</sub>)<sub>2</sub>CH<sub>2</sub>. It forms white crystals that exhibit a characteristic, aromatic odor similar to that of naphthalene. Despite its name, it does not contain the element fluorine, but rather it comes from the violet fluorescence it exhibits. For commercial purposes it is obtained from coal tar,<ref name=Ullmanns/> where it was discovered and named by Marcellin Berthelot in 1867.<ref>{{Cite book |url=https://books.google.com/books?id=lLZJAQAAMAAJ&pg=PA222 |title=Annales de chimie et de physique |date=1867 |publisher=Masson. |language=fr}}</ref>
As a polycyclic aromatic hydrocarbon, it is insoluble in water and soluble in many organic solvents. However, thanks to its central ring, fluorene is relatively acidic - powerful bases may remove one of the protons of CH<sub>2</sub> group.
==Synthesis, structure, and reactivity== Although fluorene is obtained from coal tar, it can also be prepared by dehydrogenation of diphenylmethane.<ref name=Ullmanns>{{Ullmann|doi=10.1002/14356007.a13_227|title=Hydrocarbons|year=2000|last1=Griesbaum|first1=Karl|last2=Behr|first2=Arno|last3=Biedenkapp|first3=Dieter|last4=Voges|first4=Heinz-Werner|last5=Garbe|first5=Dorothea|last6=Paetz|first6=Christian|last7=Collin|first7=Gerd|last8=Mayer|first8=Dieter|last9=Höke |first9=Hartmut|isbn=3527306730}}</ref> Alternatively, it can be prepared by the reduction of fluorenone with zinc<ref>Fittig, Rud. (1873), "Ueber einen neuen Kohlenwasserstoff aus dem Diphenylenketon" Ber. Dtsch. Chem. Ges. volume 6, p. 187.{{doi|10.1002/cber.18730060169}}</ref> or hypophosphorous acid–iodine.<ref>{{cite journal | last1=Hicks | first1=Latorya D. | last2=Han | first2=Ja Kyung | last3=Fry | first3=Albert J. | title=Hypophosphorous acid–iodine: a novel reducing system. | journal=Tetrahedron Letters | publisher=Elsevier BV | volume=41 | issue=41 | year=2000 | issn=0040-4039 | doi=10.1016/s0040-4039(00)01359-9 | pages=7817–7820}}</ref> The fluorene molecule is nearly planar,<ref name=burns>D. M. Burns, John Iball (1954), ''Molecular Structure of Fluorene'' Nature volume 173, p. 635. {{doi|10.1038/173635a0}}</ref> although each of the two benzene rings is coplanar with the central carbon 9.<ref>{{cite journal |doi=10.1107/S0108270184009963|title=Structure of fluorene, C13H10, at 159 K|year=1984|last1=Gerkin|first1=R. E.|last2=Lundstedt|first2=A. P.|last3=Reppart|first3=W. J.|journal=Acta Crystallographica Section C Crystal Structure Communications|volume=40|issue=11|pages=1892–1894|bibcode=1984AcCrC..40.1892G }}</ref>
Fluorene can be found after the incomplete combustion of plastics such as PS, PE and PVC.<ref>{{Cite journal|last1=Wang|first1=Zhenlei|last2=Richter|first2=Henning|last3=Howard|first3=Jack B.|last4=Jordan|first4=Jude|last5=Carlson|first5=Joel|last6=Levendis|first6=Yiannis A.|date=2004-06-01|title=Laboratory Investigation of the Products of the Incomplete Combustion of Waste Plastics and Techniques for Their Minimization|url=https://doi.org/10.1021/ie030477u|journal=Industrial & Engineering Chemistry Research|volume=43|issue=12|pages=2873–2886|doi=10.1021/ie030477u|issn=0888-5885|url-access=subscription}}</ref>
===Acidity=== The C9-H sites of the fluorene ring are weakly acidic (pK<sub>a</sub> = 22.6 in DMSO.<ref>{{cite journal | title = Equilibrium acidities in dimethyl sulfoxide solution | author = F. G. Bordwell | journal = Acc. Chem. Res. | volume = 21 | year = 1988 | pages = 456–463 | doi = 10.1021/ar00156a004 | issue = 12}}</ref>) Deprotonation gives the stable '''fluorenyl''' anion, nominally C<sub>13</sub>H<sub>9</sub><sup>−</sup>, which is aromatic and has an intense orange colour. The anion is a nucleophile. 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.<ref name=scherf>{{cite journal|author1=G. W. Scherf|author2=R. K. Brown|year=1960|title=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|journal=Canadian Journal of Chemistry|volume=38|page=697|doi=10.1139/v60-100}}.</ref>
===Ligand properties=== Fluorene and its derivatives can be deprotonated to give ligands akin to cyclopentadienide. [[File:Syndiotactic-zirconocene-front-3D-balls.png|thumb|left|A fluorenyl-derived Kaminsky precatalyst for producing syndiotactic polypropylene.<ref>{{cite journal|author1=Ewen, J. A.|author2=Jones, R. L.|author3=Razavi, A.|author4=Ferrara, J. D.|title=Syndiospecific Propylene Polymerizations with Group IVB Metallocenes|journal=Journal of the American Chemical Society|year=1988|volume=110|issue=18|pages=6255–6256|doi=10.1021/ja00226a056|pmid=22148816|bibcode=1988JAChS.110.6255E }}</ref>]]
==Uses== Fluorene is a precursor to other fluorene compounds; the parent species has few applications. Fluorene-9-carboxylic acid is a precursor to pharmaceuticals. 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.<ref name=Ullmanns/>
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 as a luminophore in organic light-emitting diodes.
===Fluorene dyes=== Fluorene dyes are well developed. Most are prepared by condensation of the active methylene group with carbonyls. 2-Aminofluorene, 3,6-bis-(dimethylamino)fluorene, and 2,7-diiodofluorene are precursors to dyes.<ref>{{cite journal|title=Organic dyes based on fluorene and its derivatives|author1=Kurdyukova, I. V. |author2=Ishchenko, A. A. |journal=Russian Chemical Reviews|year=2012|volume=81|issue=3|pages=258–290|doi=10.1070/RC2012v081n03ABEH004211|bibcode=2012RuCRv..81..258K|s2cid=95312830 }}</ref>
==See also== *CataCXium F sulf *Fluorenol *Fluorenylidene *Indecainide *PD-137889 *Carbazole *Dibenzothiophene
==References== {{reflist}}
==External links== * [http://webbook.nist.gov/cgi/cbook.cgi?ID=86-73-7&Units=SI Fluorene] in the National Institute of Standards and Technology database.
{{PAHs}}
Category:Molecular electronics Category:Fluorenes Category:Polycyclic aromatic hydrocarbons