Английская Википедия:Fluorene
Шаблон:Distinguish Шаблон:Chembox
Fluorene Шаблон:IPAc-en, or 9H-fluorene is an organic compound with the formula (C6H4)2CH2. It forms white crystals that exhibit a characteristic, aromatic odor similar to that of naphthalene. It has a violet fluorescence, hence its name. For commercial purposes it is obtained from coal tar.[1] It is insoluble in water and soluble in many organic solvents. Although sometimes classified as a polycyclic aromatic hydrocarbon, the five-membered ring has no aromatic properties.Шаблон:Citation needed Fluorene is mildly acidic.
Synthesis, structure, and reactivity
Although fluorene is obtained from coal tar, it can also be prepared by dehydrogenation of diphenylmethane.[1] Alternatively, it can be prepared by the reduction of fluorenone with zinc[2] or hypophosphorous acid–iodine.[3] The fluorene molecule is nearly planar,[4] although each of the two benzene rings is coplanar with the central carbon 9.[5]
Fluorene can be found after the incomplete combustion of plastics such as PS, PE and PVC.[6]
Acidity
The C9-H sites of the fluorene ring are weakly acidic (pKa = 22.6 in DMSO.[7]) Deprotonation gives the stable fluorenyl anion, nominally C13H9−, 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.[8]
Ligand properties
Fluorene and its derivatives can be deprotonated to give ligands akin to cyclopentadienide.
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.[1]
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.[10]
See also
References
External links
- Fluorene in the National Institute of Standards and Technology database.
- ↑ 1,0 1,1 1,2 Шаблон:Ullmann
- ↑ Fittig, Rud. (1873), "Ueber einen neuen Kohlenwasserstoff aus dem Diphenylenketon" Ber. Dtsch. Chem. Ges. volume 6, p. 187.Шаблон:Doi
- ↑ Шаблон:Cite journal
- ↑ D. M. Burns, John Iball (1954), Molecular Structure of Fluorene Nature volume 173, p. 635. Шаблон:Doi
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite journal.
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite journal
