13_lec_13_14_06 - is formed during the course of the...

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13 14 Massachusetts Institute of Technology Organic Chemistry 5.13 October 11 and 13, 2006 Prof. Timothy F. Jamison Notes for Lectures 13 and 14 Electrocyclic Reactions Molecule of the Day vitamin D (biosynthesis) HO H H H HO H H h ! 7-dehydrocholesterol previtamin D 3 Definition: A pericyclic reaction in which 1 conjugated, overlapping array of orbitals combines . Electrocyclic reactions proceed by way of a cyclic transition state , and 1 sigma bond
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Unformatted text preview: is formed during the course of the reaction. Conrotatory: Orbitals rotate in the same direction (both clockwise or both counter-clockwise) Disrotatory: Orbitals rotate in opposite directions (one clockwise, one counter-clockwise) Woodward-Hoffmann Rules for Electrocyclic Reactions Stereochemical Course # Electrons Thermal Mode Photochemical Mode 4n + 2 disrotatory conrotatory 4n conrotatory disrotatory...
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