indene

Indene
IUPAC name	1H-indene
Other names	benzocyclopentadiene
Identifiers
CAS number	[95-13-6]
PubChem	7219
SMILES	C1C=CC2=CC=CC=C21
Properties
Molecular formula	C9H8
Molar mass	116.16
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references

Indene is a flammable polycyclic hydrocarbon with chemical formula C₉H₈. It is composed of a benzene ring fused with a cyclopentene ring. This aromatic liquid is colorless although samples often are pale yellow. The principal industrial use of indene is in the production of indene/cumarone thermoplastic resins.

Isolation

Indene occurs naturally in coal-tar fractions boiling around 175-185 °C. It can be obtained by heating this fraction with sodium to precipitate solid "sodio-indene." This step exploits indenes weak acidity evidenced by its deprotonation by sodium to give the indenyl derivative. The sodio-indene is converted back to indene by steam distillation.^[1]

Reactivity

Indene readily polymerises. Oxidation of indene with acid dichromate yields homophthalic acid (o-carboxylphenylacetic acid). It condenses with ethyl oxalate in the presence of sodium ethoxide to form indene-oxalic ester, and with aldehydes or ketones in the presence of alkali to form benzofulvenes. The latter are highly coloured. An indene is also a precursor to the indenyl anion, a ligand in organometallic chemistry with some notability due to the indenyl effect.

See also

• Indane
• Indole
• Isoindene
• Indenyl effect

References

1. ^ Gerd Collin, Rolf Mildenberg, Mechthild Zander, Hartmut Höke, William McKillip, Werner Freitag, Wolfgang Imöhl “Resins, Synthetic” Ullmann's Encyclopedia of Industrial Chemistry Wiley-VCH, Weinheim, 2000.

See also

• W. v. Miller, Rohde (1890). "Zur Synthese von Indenderivaten". Berichte der deutschen chemischen Gesellschaft 23 (2): 1881–1886. doi:10.1002/cber.18900230227. 
• W. v. Miller, Rohde (1890). "Zur Synthese von Indenderivaten". Berichte der deutschen chemischen Gesellschaft 23 (2): 1887–1902. doi:10.1002/cber.18900230228. 
• Finar, I. L. (1985). Organic Chemistry. Longman Scientific & Technical. ISBN 0582442575. 

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