Indene
chemical compound
Indene is an aromatic, polycyclic hydrocarbon with chemical formula C9H8. It is composed of a benzene ring fused with a cyclopentene ring. This flammable liquid is colorless although samples often are pale yellow. The principal industrial use of indene is in the production of indene/coumarone thermoplastic resins. Substituted indenes and their closely related indane derivatives are important structural motifs found in many natural products and biologically active molecules, such as sulindac.
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 indene's weak acidity evidenced by its deprotonation by sodium to give the indenyl derivative. The sodio-indene is converted back to indene by steam distillation.
Reactivity
Indene readily polymerises. Oxidation of indene with acid dichromate yields homophthalic acid (o-carboxylphenylacetic acid).
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