This flammable liquid is colorless although samples often are pale yellow.

Substituted indenes and their closely related indane derivatives are important structural motifs found in many natural products and biologically active molecules, such as sulindac.

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.

It condenses with diethyl 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, which are highly coloured.