Indene

Indene
Ball-and-stick model of the indene molecule
Names
IUPAC name
1H-indene
Systematic IUPAC name
Bicyclo[4.3.0]nona-1,3,5,7-tetraene
Other names
benzocyclopentadiene
Indonaphthene
Identifiers
95-13-6 Yes
ChEBI CHEBI:41921 Yes
ChEMBL ChEMBL192812 Yes
ChemSpider 6949 Yes
DrugBank DB02815 Yes
Jmol-3D images Image
KEGG C11565 Yes
PubChem 7219
Properties
C9H8
Molar mass 116.16
Appearance Colorless liquid[1]
Density 0.997 g/mL
Melting point −25 °C (−13 °F; 248 K)
Boiling point 181.6 °C (358.9 °F; 454.8 K)
Insoluble
Acidity (pKa) 20.1 (in DMSO)[2]
Hazards
Main hazards Flammable
Flash point 78.3 °C (172.9 °F; 351.4 K)
US health exposure limits (NIOSH):
none[1]
TWA 10 ppm (45 mg/m3)[1]
N.D.[1]
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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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/coumarone 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 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.[3]

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

References

  1. ↑ 1.0 1.1 1.2 1.3 "NIOSH Pocket Guide to Chemical Hazards #0340". National Institute for Occupational Safety and Health (NIOSH).
  2. ↑ Bordwell FG (1988). "Equilibrium acidities in dimethyl sulfoxide solution". Accounts of Chemical Research 21 (12): 456–463. doi:10.1021/ar00156a004. Bordwell pKa Table in DMSO
  3. ↑ 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