Purpurin (dye)

1,2,4-Trihydroxyanthraquinone

Names
IUPAC name 1,2,4-trihydroxyanthracene-9,10-dione
Other names Purpurin(e), Hydroxylizaric acid
Identifiers
CAS Number	81-54-9 N
3D model (JSmol)	Interactive image Interactive image
ChEBI	CHEBI:8645 Y
ChemSpider	6431 Y
ECHA InfoCard	100.001.237
KEGG	C10395 Y
PubChem CID	6683
InChI InChI=1S/C14H8O5/c15-8-5-9(16)14(19)11-10(8)12(17)6-3-1-2-4-7(6)13(11)18/h1-5,15-16,19H Y Key: BBNQQADTFFCFGB-UHFFFAOYSA-N Y InChI=1/C14H8O5/c15-8-5-9(16)14(19)11-10(8)12(17)6-3-1-2-4-7(6)13(11)18/h1-5,15-16,19H Key: BBNQQADTFFCFGB-UHFFFAOYAW
SMILES C1=CC=C2C(=C1)C(=O)C3=C(C2=O)C(=C(C=C3O)O)O O=C2c1ccccc1C(=O)c3c2c(O)cc(O)c3O
Properties
Chemical formula	C14H8O5
Molar mass	256.21 g/mol
Melting point	259 °C (498 °F; 532 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

1,2,4-Trihydroxyanthraquinone, commonly called purpurin, is an anthraquinone. It is a naturally occurring red/yellow dye. It is formally derived from 9,10-anthraquinone by replacement of three hydrogen atoms by hydroxyl (OH) groups.

Purpurin is also called verantin, smoke Brown G, hydroxylizaric acid, and C.I. 58205. It is a minor component of the classical lake pigment "madder lake" or Rose Madder.

Madder root has been used for dying cloth at least since 1500 BC. Purpurin and alizarin were isolated from the root by Pierre Robiquet and Colin, two French chemists, in 1826. They were identified as anthracene derivatives by Gräbe and Liebermann in 1868. They also synthesized alizarin from bromoanthraquinone, which, together with the conversion of alizarin into purpurin published previously by M. F. De Lalande, provided the first synthetic route to purpurin. The positions of the OH groups were determined by Bayer and Caro in 1874–1875.

Purpurin occurs in the roots of the madder plant (Rubia tinctorum), together with alizarin (1,2-dihydroxyanthraquinone). The root actually contains colorless glycosides of the dyes.

Purpurin is a crystalline solid, that forms orange needles melting at 259 °C (498 °F), but becomes red when dissolved in ethanol, and yellow when dissolved with alkalis in boiling water. It is insoluble in hexane but soluble in chloroform, and can be obtained from chloroform as reddish needles. Unlike alizarin, purpurin is dissolved by boiling in a solution of aluminum sulfate, from which it can be precipitated by acid. This procedure can be used to separate the two dyes.