User:Benjah-bmm27/degree/2/AJM

Hückel, AJM

Understanding Structure and Reactivity, Part 2

• The course looks at carbon 2p orbitals and the π bonds they can form, especially in conjugated systems such as polyenes
• Secular equations — see Quantum Concepts lectures by FRM's predecessor Professor Balint-Kurti: GGBK lecture 6
• Hückel method
  • the circle method
  • Hückel's rule: aromaticity and antiaromaticity
• Pericyclic reactions: ChemTube3D - Jmol animations of pericyclic reactions
  • Woodward–Hoffmann rules: a set of rules for predicting the stereochemistry of pericyclic reactions based on orbital symmetry
  • Cycloadditions
    • Diels-Alder reaction
  • Electrocyclic reactions

Typical molecules studied in the course

• ethylene, C₂H₄
• 1,3-butadiene, C₄H₆
• benzene, C₆H₆
• cyclopropenyl radical, [C₃H₃]^•
• cyclopentadienyl anion, [C₅H₅]⁻
• trimethylenemethane,
  • this is a non-Kekulé molecule that came up in the 2009 exam
  • it's a diradical with a triplet ground state, but can 'rearrange' to methylenecyclopropane via an excited singlet state
• cyclopropenyl cation, [C₃H₃]⁺
• cyclobutadiene, C₄H₄

External links

• An Introduction to Molecular Orbital Theory
  by Dr Roger Nix of the School of Biological & Chemical Sciences at Queen Mary, University of London (www.qmul.ac.uk)
• Ring Synthesis and Pericyclic Reactions
  a former Level 2 course by Professor Roger Alder FRS (profile)