Azulene

Names

Preferred IUPAC name

Azulene

Systematic IUPAC name

Bicyclo[5.3.0]decapentaene

Identifiers

CAS Number

275-51-4^Y

3D model (Jmol)

CHEBI:31249^Y

8876^Y

C13392^Y

82R6M9MGLP^Y

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

128.17 g·mol⁻¹

Melting point

99 to 100 °C (210 to 212 °F; 372 to 373 K)

Boiling point

242 °C (468 °F; 515 K)

Solubility in water

0.02

Magnetic susceptibility (χ)

-98.5·10⁻⁶ cm³/mol

g/l

Thermochemistry

Std enthalpy of
combustion (Δ_cH^o₂₉₈)

−1266.5 kcal/mol

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

(what is ^YN ?)

Infobox references

g/l

Azulene is an organic compound and an isomer of naphthalene. Whereas naphthalene is colourless, azulene is dark blue. Its name is derived from the Spanish word azul, meaning "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.

Azulene is usually viewed as resulting from fusion of cyclopentadiene and cycloheptatriene rings. Like naphthalene and cyclodecapentaene, it is a 10 pi electron system. It exhibits aromatic properties: (i) the bonds have similar lengths and (ii) it undergoes Friedel-Crafts-like substitutions. The stability gain from aromaticity is estimated to be half that of naphthalene.

Its dipole moment is 1.08 D, in contrast with naphthalene, which has a dipole moment of zero. This polarity can be explained by regarding azulene as the fusion of a 6 π-electron cyclopentadienyl anion and a 6 π-electron tropylium cation: one electron from the seven-membered ring is transferred to the five-membered ring to give each ring aromatic stability by Hückel's rule. Reactivity studies confirm that seven-membered ring is electrophilic and the five-membered ring is nucleophilic.

...
Wikipedia