Title: Aurin
CAS Registry Number: 603-45-2
CAS Name: 4-[Bis(4-hydroxyphenyl)methylene]-2,5-cyclohexadien-1-one
Additional Names: 4-(p,p¢-dihydroxybenzhydrylidene)-2,5-cyclohexadien-1-one; p-rosolic acid; corallin; C.I. 43800
Molecular Formula: C19H14O3
Molecular Weight: 290.31
Percent Composition: C 78.61%, H 4.86%, O 16.53%
Literature References: Prepd by heating a mixture of phenol, oxalic and sulfuric acids: Zulkowsky, Ann. 194, 109, 122 (1878); 202, 179 (1880); Monatsh. Chem. 16, 358 (1895); Colour Index vol. 4 (3rd ed., 1971) pp 4407. By heating phenol with formic acid and stannous chloride: Nencki, Schmid, J. Prakt. Chem. [2] 23, 549 (1881). By heating phenol and carbon tetrachloride to 140-160° in presence of AlCl3 or ZnCl2 and treating the reaction product with water: Heumann, DE 68976 (Frdl. 3, 103).
Properties: Deep red (garnet-like) crystals with metallic luster. Orthorhombic bipyramidal. Technical product may occur as yellowish-brown pieces with dark green metallic fracture. Dec 308-310°. Not volatile in vacuo at 180°. Absorption max (KOH): 534.6, 479.5 nm. Practically insol in water (0.12%) and in benzene. Freely sol in alc, giving a golden yellow solution, in aq or alc NaOH and KOH giving a carmine-red solution, in concd or 70% H2SO4, in HCl, in HClO4 giving a yellow to orange soln. Moderately soluble in glacial acetic acid; slightly sol in ether, chloroform.
Absorption maximum: Absorption max (KOH): 534.6, 479.5 nm
Derivative Type: Sodium salt (yellow corallin)
Properties: Yellowish pieces with greenish, metallic luster; sol in water, giving a carmine-red soln.
Use: Dye intermediate.
Aurodox Aurothioglucose Aurothioglycanide Avasimibe Avermectins

Skeletal formula of aurin
Ball-and-stick model
CAS number 603-45-2
PubChem 5100
ChemSpider 4921 YesY
EC number 210-041-8
Beilstein Reference 2055205
Jmol-3D images Image 1
Molecular formula C19H14O3
Molar mass 290.313 g/mol
Density 1.283 g cm-3
Melting point 308 °C (decomp.)
Solubility in water insoluble
R-phrases R36 R37 R38
NFPA 704
NFPA 704.svg
Flash point 308 °C; 586 °F; 581 K
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references
For the French commune, see Aurin, Haute-Garonne.
For the Aragonese village, see Aurin, Sabiñánigo, Huesca, España.

Aurin (C.I. 43800), sometimes named rosolic acid or corallin is an organic compound, forming yellowish or deep-red crystals with greenish metallic luster. It is practically insoluble in water, freely soluble in alcohol. It is soluble in strong acids to form yellow solution, or in aqueous alkalis to form carmine red solutions. Due to this behaviour it can be used as pH indicator with pH transition range 5.0 - 6.8. It used as intermediate in manufacturing of dyes.