1,3-Indandione (sometimes simply indanedione) is an organic compound with the molecular formula C₆H₄(CO)₂CH₂. It is a β-diketone with indane as its structural nucleus. It is a colorless or white solid, but old samples can appear yellowish^[3] or even green. It is a popular chemical scaffold (building block of various useful chemical compounds).^[4][5]

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1,3-Indandione

Names
Preferred IUPAC name 1H-Indene-1,3(2H)-dione
Other names Indandione; 1,3-Diketohydrindene; 1,3-Dioxoindane; 1,3-Hydrindendione
Identifiers
CAS Number	606-23-5 Y
3D model (JSmol)	Interactive image Interactive image
ChEBI	CHEBI:78877
ChEMBL	ChEMBL283521 Y
ChemSpider	11322 Y
ECHA InfoCard	100.009.191
PubChem CID	11815
UNII	4DJN7YG35G Y
CompTox Dashboard (EPA)	DTXSID2060547
InChI InChI=1S/C9H6O2/c10-8-5-9(11)7-4-2-1-3-6(7)8/h1-4H,5H2 Y Key: UHKAJLSKXBADFT-UHFFFAOYSA-N Y InChI=1/C9H6O2/c10-8-5-9(11)7-4-2-1-3-6(7)8/h1-4H,5H2 Key: UHKAJLSKXBADFT-UHFFFAOYAR
SMILES C1C(=O)C2=CC=CC=C2C1=O O=C2c1ccccc1C(=O)C2
Properties
Chemical formula	C9H6O2
Molar mass	146.145 g·mol−1
Appearance	white solid
Density	1.37 g/cm3
Melting point	129 to 132 °C (264 to 270 °F; 402 to 405 K)[1][2]
Solubility in water	slight
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

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Solid 1,3-indandione is a diketone, As a solution in water, it is partially (~2%) enolized. The enolate anion exhibits significant delocalization, and the highest electron density is on the second carbon. This acid-base behavior explains many properties of the compound.^{[citation needed]}

1,3-Indandione can be prepared by decarboxylation of the sodium salt of 2-ethoxycarbonyl-1,3-indandione, which itself is obtained by Claisen condensation of ethyl acetate and dimethyl phthalate.^{[citation needed]}

The carbon at the C-2 position is alpha to both carbonyls, and thus can act as a nucleophile. It undergoes self-aldol condensation quite easily, resulting in bindone.

Bromination occurs at the 2-position:

One or both carbonyl groups can be reduced to alcohol groups or methylene groups, depending on the method used.

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