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Why are azulenes much more reactive than benzene?
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Marco Pereira
Why are azulenes much more reactive than benzene?
The resonance energy for phenanthrene is 92 Kcal/mol, that for anthracene is 84 Kcal/mol and for naphthalene and benzene rings are 61 and 36 Kcal/mol respectively.
Stability can be compared only for isomeric or related compounds or at best for unsaturated hydrocarbons it is compared only when they give same hydrogenated products. However, for polycyclic aromatic hydrocarbons, stability can be said to be proportional to resonance energy per benzene rings.
Here resonance energy per benzene ring decreases from 36 Kcal/mol for benzene to 30.5 Kcal/mol for naphthalene, 30.3 Kcal/mol for phenanthene and 28 Kcal/mol for anthracene.
Hence, order of stability (or RE): Benzene > Phenanthrene ~ Naphthalene > Anthracene. In fact other fused polycyclic aromatic hydrocarbons react faster than benzene.
Note- Phenanthrene
Halogens like Cl2 or Br2 also add to phenanthrene. In phenanthrene, C9-C10 has 4/5 double bond character hence it is shorter than C1–C2.
The resonance energy for phenanthrene is 92 Kcal/mol, that for anthracene is 84 Kcal/mol and for naphthalene and benzene rings are 61 and 36 Kcal/mol respectively.
Stability can be compared only for isomeric or related compounds or at best for unsaturated hydrocarbons it is compared only when they give same hydrogenated products. However, for polycyclic aromatic hydrocarbons, stability can be said to be proportional to resonance energy per benzene rings.
Here resonance energy per benzene ring decreases from 36 Kcal/mol for benzene to 30.5 Kcal/mol for naphthalene, 30.3 Kcal/mol for phenanthene and 28 Kcal/mol for anthracene.
Hence, order of stability (or RE): Benzene > Phenanthrene ~ Naphthalene > Anthracene. In fact other fused polycyclic aromatic hydrocarbons react faster than benzene.
Note- Phenanthrene
Halogens like Cl2 or Br2 also add to phenanthrene. In phenanthrene, C9-C10 has 4/5 double bond character hence it is shorter than C1–C2.
The resonance energy for phenanthrene is 92 Kcal/mol, that for anthracene is 84 Kcal/mol and for naphthalene and benzene rings are 61 and 36 Kcal/mol respectively.
Stability can be compared only for isomeric or related compounds or at best for unsaturated hydrocarbons it is compared only when they give same hydrogenated products. However, for polycyclic aromatic hydrocarbons, stability can be said to be proportional to resonance energy per benzene rings.
Here resonance energy per benzene ring decreases from 36 Kcal/mol for benzene to 30.5 Kcal/mol for naphthalene, 30.3 Kcal/mol for phenanthene and 28 Kcal/mol for anthracene.
Hence, order of stability (or RE): Benzene > Phenanthrene ~ Naphthalene > Anthracene. In fact other fused polycyclic aromatic hydrocarbons react faster than benzene.
Note- Phenanthrene
Halogens like Cl2 or Br2 also add to phenanthrene. In phenanthrene, C9-C10 has 4/5 double bond character hence it is shorter than C1–C2.
The resonance energy for phenanthrene is 92 Kcal/mol, that for anthracene is 84 Kcal/mol and for naphthalene and benzene rings are 61 and 36 Kcal/mol respectively.
Stability can be compared only for isomeric or related compounds or at best for unsaturated hydrocarbons it is compared only when they give same hydrogenated products. However, for polycyclic aromatic hydrocarbons, stability can be said to be proportional to resonance energy per benzene rings.
Here resonance energy per benzene ring decreases from 36 Kcal/mol for benzene to 30.5 Kcal/mol for naphthalene, 30.3 Kcal/mol for phenanthene and 28 Kcal/mol for anthracene.
Hence, order of stability (or RE): Benzene > Phenanthrene ~ Naphthalene > Anthracene. In fact other fused polycyclic aromatic hydrocarbons react faster than benzene.
Note- Phenanthrene
Halogens like Cl2 or Br2 also add to phenanthrene. In phenanthrene, C9-C10 has 4/5 double bond character hence it is shorter than C1–C2.
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Azulene is this hydrocarbon:
Azulene is this hydrocarbon:
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