Azulene

Azulene

Sublimated azulene on a cold finger
Names
Preferred IUPAC name Azulene
Systematic IUPAC name Bicyclo[5.3.0]deca-2,4,6,8,10-pentaene
Identifiers
CAS Number	275-51-4 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:31249 Y
ChemSpider	8876 Y
ECHA InfoCard	100.005.449
KEGG	C13392 Y
PubChem CID	9231
UNII	82R6M9MGLP Y
CompTox Dashboard (EPA)	DTXSID2059770
InChI InChI=1S/C10H8/c1-2-5-9-7-4-8-10(9)6-3-1/h1-8H Y Key: CUFNKYGDVFVPHO-UHFFFAOYSA-N Y InChI=1/C10H8/c1-2-5-9-7-4-8-10(9)6-3-1/h1-8H Key: CUFNKYGDVFVPHO-UHFFFAOYAT
SMILES c1cccc2cccc2c1
Properties
Chemical formula	C10H8
Molar mass	128.174 g·mol−1
Appearance	Dark blue crystalline solid
Melting point	99 to 100 °C (210 to 212 °F; 372 to 373 K)
Boiling point	242 °C (468 °F; 515 K)
Magnetic susceptibility (χ)	−98.5·10−6 cm3/mol
Thermochemistry
Std enthalpy of combustion (ΔcH⦵298)	−1266.5 kcal/mol
Related compounds
Related compounds	Naphthalene Bicyclo(6.2.0)decapentaene Pentalene Heptalene Sesquifulvalene
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Azulene is an aromatic organic compound and an isomer of naphthalene. Naphthalene is colourless, whereas azulene is dark blue. The compound is named after its colour, as "azul" is Spanish for blue. Two terpenoids, vetivazulene (4,8-dimethyl-2-isopropylazulene) and guaiazulene (1,4-dimethyl-7-isopropylazulene), that feature the azulene skeleton are found in nature as constituents of pigments in mushrooms, guaiac wood oil, and some marine invertebrates.

Azulene has a long history, dating back to the 15th century as the azure-blue chromophore obtained by steam distillation of German chamomile. The chromophore was discovered in yarrow and wormwood and named in 1863 by Septimus Piesse. Its structure was first reported by Lavoslav Ružička, followed by its organic synthesis in 1937 by Placidus Plattner.