Question

How many uncharged resonance structure are there for azulene?

Answer 1

Azulene (1) is a nonalternant 10π-electron nonbenzenoid aromatic hydrocarbon, which has a fused structure of five- and seven-membered rings. Although the structural isomer naphthalene is a colorless compound, azulene (1) shows a deep blue color. Therefore, its compound name originates from “azur” and “azul,” which mean “blue” in Arabic and Spanish, respectively. Since the ionic cyclopentadienide and tropylium structures contribute to the azulene skeleton, electrophilic substitution reactions take place at the 1- and 3-positions, and nucleophilic addition occurs at the 4-, 6-, and 8-positions. The reason for the large dipole moment of 1.08 D and a blue color of azulene, despite the hydrocarbon structure, is explained by the intramolecular charge transfer (ICT) derived from the polarized resonance structure as shown in Scheme 1.

Answer 2

Answer:

2 uncharged resonance structures are there for azulene.

Explanation:

Azulene is a nonbenzoid combined ring system. in which 7 membered ring of carbon and 5 membered ring of carbon are fused together.

• The presence of$sp^2$ hybridized carbon atoms facilitates the  delocalization of electrons.
• This Delocalisation of elctrons give rise to various resonance structure of azulene.

There are total 5 C=C bonds in an azulene molecule.

2 uncharged resonance structures are there for azulene are in the attached image.