Indene
Names | |
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IUPAC name
1H-indene
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Systematic IUPAC name
Bicyclo[4.3.0]nona-1,3,5,7-tetraene | |
Other names
benzocyclopentadiene
Indonaphthene | |
Identifiers | |
3D model (JSmol)
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ChEBI | |
ChEMBL | |
ChemSpider | |
DrugBank | |
ECHA InfoCard | 100.002.176 |
KEGG | |
PubChem CID
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CompTox Dashboard (EPA)
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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 | |
Occupational safety and health (OHS/OSH): | |
Main hazards
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Flammable |
Flash point | 78.3 °C (172.9 °F; 351.4 K) |
NIOSH (US health exposure limits): | |
PEL (Permissible)
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none[1] |
REL (Recommended)
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TWA 10 ppm (45 mg/m3)[1] |
IDLH (Immediate danger)
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N.D.[1] |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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
- ^ a b c d NIOSH Pocket Guide to Chemical Hazards. "#0340". National Institute for Occupational Safety and Health (NIOSH).
- ^ 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
- ^ 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
- 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.