indene n : a colorless liquid hydrocarbon extracted from petroleum or coal tar and used in making synthetic resins

Noun

1. The bicyclic hydrocarbon consisting of a benzene ring fused to one of cyclopentadiene

Indene is a flammable polycyclic hydrocarbon with chemical formula C9H8. It is composed of a benzene ring fused with a cyclopentene ring and occurs as a colorless to pale yellow liquid. A principal industrial use of indene is in the production of indene/cumarone thermoplastic resins.

It is also known as benzocyclopentadiene, and occurs naturally in coal-tar fractions boiling around 175-185 °C. It can be obtained from this fraction by heating with sodium (indene is acidic), separating the solid sodio-indene, and recovering by steam distilling it.

Indene readily polymerises. Oxidation of indene with acid dichromate yields homophthalic 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.

See also

• Indane
• Indole
• Isoindene

References