Question 1

Why is benzene aromatic?

Accepted Answer

Benzene is a planar, cyclic, fully conjugated molecule containing a continuous delocalised π system with 6 π electrons. These structural features allow p-orbital overlap around the entire ring and characterise benzene as aromatic.

Question 2

What is the hybridisation of carbon in benzene?

Accepted Answer

Every carbon atom in benzene is sp2 hybridised. It forms three sigma bonds in the ring plane—two to neighbouring carbon atoms and one to hydrogen—and retains one unhybridised p orbital perpendicular to the plane.

Question 3

How is benzene’s π-electron cloud formed?

Accepted Answer

The six unhybridised p orbitals overlap sidewise around the cyclic structure. Together they form a continuous delocalised π-electron cloud above and below the molecular plane, containing a total of 6 π electrons.

Question 4

Do the two Kekulé structures alternate?

Accepted Answer

No. The two equivalent Kekulé structures are contributing representations connected by a double-headed resonance arrow. The actual benzene molecule is a resonance hybrid, not a molecule alternating between two separate structures.

Question 5

Why are all carbon-carbon bond lengths in benzene equal?

Accepted Answer

Continuous π-electron delocalisation makes the six carbon-carbon connections equivalent. Each C-C bond length is 139 pm, intermediate between a conventional single and double carbon-carbon bond.

Aromaticity Lab: Ring, Electrons and Planarity

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