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Pericyclic Reactions (McM chapt 30)
Polar react. (nucleophiles and electrophiles) Radical react. Pericyclic react. (concerted, cyclic TS#) Electrocyclic react. Cycloadditions (i.e. Diels Alder) Sigmatropic rearrangement Rearrangement of polyene Termal (react. in ground state) or photochemical (react of exited state)
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Symmetry Allowed React.
Woodward Hoffmann rules Symmetry in reactants are preserved during pericyclic react. Results can generally be predicted just by looking at Front Orbitals (FMO; HOMO and LUMO) - Fukui
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Molecular orbitals 1,3-butadiene Stereospesific react. S: Symmetric
A: Antisym.
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Molecular orbitals hexatriene Symmetry allowed react
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Photochemical electrocyclic react.
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Cycloadditions (i.e. Diels Alder)
Stereospesific react.
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endo - exo selectivity Normal electron demand DA - Electron poor dienophile (Michael accept.) Ethene etc, very low react. Michael accept. Lower LUMO
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[2+2] Cycloadditions
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Carbene Cycloadditions
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Sigmatropic Rearrangements
[3,3] Rearrangements; Claisen rearrang. etc.
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[1,5] Rearrangement (H-shift)
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