Indene

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Indene
Skeletal formula
Ball-and-stick model of the indene molecule
Names
Preferred IUPAC name
1H-Indene
Systematic IUPAC name
Bicyclo[4.3.0]nona-1,3,5,7-tetraene
Other names
Benzocyclopentadiene
Indonaphthene
Identifiers
3D model (JSmol)
635873
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.002.176 Edit this at Wikidata
27265
KEGG
  • InChI=1S/C9H8/c1-2-5-9-7-3-6-8(9)4-1/h1-6H,7H2 checkY
    Key: YBYIRNPNPLQARY-UHFFFAOYSA-N checkY
  • InChI=1/C9H8/c1-2-5-9-7-3-6-8(9)4-1/h1-6H,7H2
    Key: YBYIRNPNPLQARY-UHFFFAOYAJ
  • c1ccc2c(c1)CC=C2
Properties
C9H8
Molar mass 116.16
Appearance Colorless liquid[1]
Density 0.997 g/mL
Melting point −1.8 °C (28.8 °F; 271.3 K)
Boiling point 181.6 °C (358.9 °F; 454.8 K)
Insoluble
Acidity (pKa) 20.1 (in DMSO)[2]
-80.89·10−6 cm3/mol
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Flammable
Flash point 78.3 °C (172.9 °F; 351.4 K)
NIOSH (US health exposure limits):
PEL (Permissible)
 none[1]
REL (Recommended)
 TWA 10 ppm (45 mg/m3)[1]
IDLH (Immediate danger)
 N.D.[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

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. ^ a b c d 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 Archived 2008-10-09 at the Wayback Machine
  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.

External links

  • W. v. Miller, Rohde (1890). "Zur Synthese von Indenderivaten". Berichte der deutschen chemischen Gesellschaft. 23 (2): 1881–1886. doi:10.1002/cber.18900230227.
  • W. v. Miller, Rohde (1890). "Zur Synthese von Indenderivaten". Berichte der deutschen chemischen Gesellschaft. 23 (2): 1887–1902. doi:10.1002/cber.18900230228.
  • Finar, I. L. (1985). Organic Chemistry. Longman Scientific & Technical. ISBN 0-582-44257-5.
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