Indene is an aromatic, polycyclic hydrocarbon with chemical formula . 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 product 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
polymerization. Oxidation of indene with acid
dichromate yields homophthalic acid (
o-carboxylphenylacetic acid). It condenses with diethyl
oxalate in the presence of
sodium ethoxide to form indene–oxalic ester, and with
or
in the presence of
alkali to form
, which are highly coloured. Treatment of indene with
organolithium reagents gives lithium
indenyl compounds:
Indenyl is a
ligand in organometallic chemistry, giving rise to many transition metal indenyl complexes.
See also
External links
