QUALITATIVE MOLECULAR ORBITAL THEORY AND PERICYCLIC REACTIONS

QUALITATIVE MOLECULAR ORBITAL THEORY AND PERICYCLIC REACTIONS 

Orbitals are mathematical descriptions of standing waves. Standing waves are a series of harmonics (increasing number of half-wavelengths) and are similar to the MOs for linear pi systems. Shorter wavelength harmonics are higher energy. 

Two p Orbitals a Simple Pi Bond Three p Orbitals the Allyl Unit Four p Orbitals the Diene Unit HOMO and LUMO General Trends of MO Nodes and Phase 

3 MOLECULAR ORBITAL THEORY FOR CYCLIC CONJUGATED PI SYSTEMS 

Filled Shell, Antiaromaticity Half-Filled Shell, Antiaromaticity 4n+2 rule for Aromaticity. Circle Trick For Cyclic Conjugated MO Energies. 

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This chapter is an introduction to qualitative molecular orbital theory and pericyclic reactions. Pericyclic reactions have cyclic transition states and electron flow paths that appear to go around in a loop. The regiochemistry and stereochemistry of these reactions are usually predictable by HOMO-LUMO interactions, so to understand them we need to understand molecular orbital theory, at least on a qualitative basis. 

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