Fluorene

Fluorene, or 9H-fluorene, is a polycyclic aromatic hydrocarbon. It has the form of odorless white crystals. It is combustible. It has a violet fluorescence, which gave it its name. It is manufactured artificially, although it occurs in the higher boiling fractions of coal tar. It is insoluble in water and soluble in benzene and ether.

Fluorene is used to make dyes, plastics, and pesticides. It can be found in corn silk and engine exhaust gas. It is used for production of fluorenone and fluorene-9-methanol.

Poly(fluorene) is commonly used as a luminophore in organic light-emitting diodes. Fluorene copolymers are being investigated as materials for solar cells.

The protons in the 9-position of the fluorene ring are acidic (pKa = 22.6 in DMSO ) and removal of one of them with a strong base, such as n-butyllithium, leads to the stable fluorenyl anion, 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 carbamate ester of 9-hydroxymethylfluorene, 9-fluorenylmethyl carbamate (FMOC), is used a N-terminal protective group in peptide synthesis.

Fluorene should not be confused with fluorone, nor with the element fluorine.