Indene

Indene
Names
	Preferred IUPAC name 1H-Indene
	Systematic IUPAC name Bicyclo[4.3.0]nona-1,3,5,7-tetraene
	Other names Benzocyclopentadiene; Indonaphthene
Identifiers
CAS Number	95-13-6 ;
3D model (JSmol)	Interactive image;
Beilstein Reference	635873
ChEBI	CHEBI:41921 ;
ChEMBL	ChEMBL192812 ;
ChemSpider	6949 ;
DrugBank	DB02815 ;
ECHA InfoCard	100.002.176
Gmelin Reference	27265
KEGG	C11565 ;
PubChem CID	7219;
CompTox Dashboard (EPA)	DTXSID8042052 ;
	InChI InChI=1S/C9H8/c1-2-5-9-7-3-6-8(9)4-1/h1-6H,7H2 Key: YBYIRNPNPLQARY-UHFFFAOYSA-N ; InChI=1/C9H8/c1-2-5-9-7-3-6-8(9)4-1/h1-6H,7H2 Key: YBYIRNPNPLQARY-UHFFFAOYAJ;
	SMILES c1ccc2c(c1)CC=C2;
Properties
Chemical formula	C9H8
Molar mass	116.16
Appearance	Colorless liquid
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)
Solubility in water	Insoluble
Acidity (pKa)	20.1 (in DMSO)
Magnetic susceptibility (χ)	-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
REL (Recommended)	TWA 10 ppm (45 mg/m3)
IDLH (Immediate danger)	N.D.
Related compounds
Related compounds	Benzofuran, Benzothiophene, Indole
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) 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. 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.

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.

[PGCH-1] 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] 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.

[4] 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.

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Isolation

Reactivity

See also

References

External links