MCQ
Which compound posses highest dipole moment ?
- Anaphthalene
- Bphenanthrene
- Canthracene
- ✓azulene
✓
Answer
Correct option: D.
azulene
d
$(d)$ Polycyclic systems : Huckel's $(4n + 2)$ rule applies to monocyclic systems. The rule, however, is not necessarily successful for p'olycyclic conjugated systems the. $( 4n + 2)$ rule should be applied to the peripheral (conjugated) $\pi$ - electrons. The five-membered ring has five and the seven-membered ring has seven $\pi$ -electrons (two $1^{st}-$electrons are common to both rings). If one $\pi$ - electron is transferred from the seven - to the five - ring, each ring will now have a closed shell of six $\pi$ - electrons ($cf$. naphthalene). In this condition, the molecule will have a dipolar structure, and this has been shown to be the case from dipole - moment measurements. Azulene also behaves chemically as an aromatic compound.
$(d)$ Polycyclic systems : Huckel's $(4n + 2)$ rule applies to monocyclic systems. The rule, however, is not necessarily successful for p'olycyclic conjugated systems the. $( 4n + 2)$ rule should be applied to the peripheral (conjugated) $\pi$ - electrons. The five-membered ring has five and the seven-membered ring has seven $\pi$ -electrons (two $1^{st}-$electrons are common to both rings). If one $\pi$ - electron is transferred from the seven - to the five - ring, each ring will now have a closed shell of six $\pi$ - electrons ($cf$. naphthalene). In this condition, the molecule will have a dipolar structure, and this has been shown to be the case from dipole - moment measurements. Azulene also behaves chemically as an aromatic compound.
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