Indene
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Names | |
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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)
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635873 | |
ChEBI | |
ChEMBL | |
ChemSpider | |
DrugBank | |
ECHA InfoCard | 100.002.176 |
27265 | |
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 | −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
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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] |
Related compounds | |
Related compounds
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Benzofuran, Benzothiophene, Indole |
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. Substituted indenes[3] and their closely related indane derivatives are important structural motifs found in many natural products 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.[4]
Reactivity
Indene readily polymerises. 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 aldehydes or ketones in the presence of alkali to form benzofulvenes. The latter are highly coloured. Treatment of indene with organolithium reagents give lithium indenyl compounds:
- C9H8 + RLi → LiC9H7 + RH
Indenyl is a ligand in organometallic chemistry, giving rise to many transition metal indenyl complexes.
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 Archived 2008-10-09 at the Wayback Machine
- ^ Das, Braja Gopal; Chirila, Andrei; Tromp, Moniek; Reek, Joost N. H.; Bruin, Bas de (2016-07-20). "CoIII–Carbene Radical Approach to Substituted 1H-Indenes". Journal of the American Chemical Society. 138 (28): 8968–8975. doi:10.1021/jacs.6b05434. ISSN 0002-7863.
- ^ 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.