Arenes

Question 1

(Checked w sch notes)
Describe the hybridisation of benzene

Answer 1

sp2 hybridised
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Sigma bonds
- Three sp3 hybridised orbitals from each C atom are used to form 2 C—C bonds and 1 C—H bond in a trigonal planar shape
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- by overlapping head on to form sigma bonds.
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Delocalised pi electrons
- The unhybridised p orbitals lie perpendicular to the plane
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- The remaining six unhybridised p orbitals are close enough to overlap side on and form a ring of six delocalised pi electrons above and below the plane.
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- This gives rise to an aromatic ring with partial double bond character
- This strengthens the C—C bond and makes the structure more stable

Question 2

Why does benzene undergo substitution rxns instead of addition

Answer 2

• Additional would break the ring of delocalised pi electrons.
  .
• Substitution allows the ring to stay intact
• an allows benzene to maintain aromatic stability