1. Chemistry 125: Lecture 65 April 7, 2010 Addition to C=O Mechanism & Equilibrium Protecting Groups Oxidation/Reduction & Electron Transfer This For copyright notice see final page of this file

2. RCOOH Reactions (sec. 20.7, pp. 964-965) OH RC O H substitution at  -C substitution at C R substitution at O R addition A Nu

3. RC O OH Fischer Esterification (sec. 20.8, p. 965) H + H + + RO H + Tetrahedral Intermediate (A/D, not the pentavalent transition state of S N 2) substitution at C OR starts with addition to C=O H + + H OH Why protonate this oxygen instead of this one? and is stabilized still more after protonation on top because this pair was stabilized by  * (acid catalyzed) analogous to nucleophilic aromatic substitution RNH 2 F NO 2 +

4. Hydration (acid or base) (sec. 16.6-16.7) Acetal Formation (acid only) (sec. 16.9) OH Protecting Groups (& deprotection) (sec. 16.10) Imines and Enamines (sec. 16.11)

5. Oxidation/Reduction as e - Transfer CH 3 -Br ** Mg CH 3 -Br Mg + CH 3 Br CH 3 -Mg Br + Mg Grignard Reagent (like CH 3 - sec. 16.13 ) Nobel Prize (1912) ** (CH 3 ) 2 C=O Mg (CH 3 ) 2 C=O (CH 3 ) 2 C O “reduction” Mg +2 “reduction” (CH 3 ) 2 C O H 2 O ~50% (CH 3 ) 2 C OH “Pinacol” “Pinacolone” (CH 3 ) 3 C C CH 3 O H+H+

6. Oxidation/Reduction as Bookkeeping Arbitrarily assign shared electron pairs to the more electronegative element

7. 0:49-11:35 Carbon “Oxidation States” (Prof. Siegel, Lecture 47)

8. Oxidation/Reduction as Bookkeeping (for purposes of reagent selection) (CH 3 ) 3 C C CH 3 O “reduction” (CH 3 ) 3 C C CH 3 OH H +2 C C 0 -3 0 0 Need a “reducing agent” ?

9. End of Lecture 65 April 7, 2010 Copyright © J. M. McBride 2010. Some rights reserved. Except for cited third-party materials, and those used by visiting speakers, all content is licensed under a Creative Commons License (Attribution-NonCommercial-ShareAlike 3.0).Creative Commons License (Attribution-NonCommercial-ShareAlike 3.0) Use of this content constitutes your acceptance of the noted license and the terms and conditions of use. Materials from Wikimedia Commons are denoted by the symbol. Third party materials may be subject to additional intellectual property notices, information, or restrictions. The following attribution may be used when reusing material that is not identified as third-party content: J. M. McBride, Chem 125. License: Creative Commons BY-NC-SA 3.0