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Edexcel IAL Chemistry 18.2 delocalised model of benzene

State the bonding model clearly: carbon sigma bonds form in the ring, while p orbitals overlap sideways above and below the plane to make delocalised π electrons.

Syllabus
First assessment 2019
Course
Chemistry YCH11
Level
A2

Exam points

  • Describe sideways p-orbital overlap above and below the benzene ring plane.
  • Count sigma and π bonds or delocalised electrons in benzene and related arenes.
  • Use dichlorobenzene isomer evidence to support the delocalised benzene model.

18.2—The delocalised model for the structure of benzene involves overlap of p-orbitals to form π-bonds question 1

[Maximum number: 3]

In 1865, Friedrich August Kekulé suggested a structure for benzene which consisted of alternating single and double carbon-carbon bonds.

Figure for Question 18.2—The delocalised model for the structure of benzene involves overlap of p-orbitals to form π-bonds question 1 — Edexcel A-Level Chemistry A2

Kekulé structure
However, modern analytical techniques indicate a structure in which the electrons are delocalised.

Figure for Question 18.2—The delocalised model for the structure of benzene involves overlap of p-orbitals to form π-bonds question 1 — Edexcel A-Level Chemistry A2

delocalised structure

Describe the structure of benzene in terms of the atomic orbitals involved, the bonds formed and the delocalised electrons.

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