12 Aldol 2011 SPRING - Aldol Laboratory 10 Forma4on...

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Unformatted text preview: 4/27/11 Aldol Laboratory 10 Forma4on of enols and enolates 1 4/27/11 Tautomeriza4on vs. Resonance [acid or base catalysis] Keto form Enol form Keto and enol forms are tautomers Different chemical species Two arrows => Equilibrium Two representa2on of an enolate Resonance forms that represent the same chemical species Double headed arrow and Brackets => Resonance Enolate Aldol condensa4on 2 4/27/11 Base ­catalyzed aldol mechanism Synthesis of trans ­p ­anisalacetophenone Properly termed “aldol addi2on” reac4on Properly termed “aldol condensa2on” reac4on (has lost water) 3 4/27/11 Cannizzaro dispropor4ona4on (a frequent side reac4on of aldehydes) or Dispropor>ona>on 1HNMR of trans ­p ­anisalacetophenone 500 MHz 4 4/27/11 Representa4ve J ­values α,β ­unsaturated carbonyl chemical shiXs 7.438 – 7.407 = 0.031 0.031 ppm x 500 MHz = 15.6 Hz 500 MHz 5 4/27/11 α,β ­unsaturated carbonyl chemical shiXs 500 MHz Aroma4c proton chemical shiXs 6 4/27/11 Aroma4c proton chemical shiXs 500 MHz Other coupling constants Large ca. 9 Hz (ortho) Small ca. 3Hz (meta) 7 ...
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This note was uploaded on 04/27/2011 for the course CHEM 233 taught by Professor Staff during the Spring '08 term at University of Illinois, Urbana Champaign.

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