Lecture 3A - Chem 2204/2206/2208 Tuesday July. 13 Lecture...

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Chem 2204/2206/2208 Tuesday July. 13 Lecture 3A on Irreversible Carbonyl Additions; Lecture 3B on Aldol; Review 1 Thursday July 15 Test 1 on Lectures 1-3, Test will be held in class. Sample test 1 and Answers posted on WEB CT Lecture 3A
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Irreversible Carbonyl Reactions rignard addition (Nobel Prize ) 2 5 . Grignard addition (Nobel Prize ) 6 . Wittig Reaction (Nobel Prize) 7. Reduction (Alcohol synthesis) 8 . Oxidation Lecture 5 2009
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Top 12 reactions of Aldehydes and Ketones 1. 1,1- halo hydrin formation 2. a) Hydration b) Acetal formation 3. a) Imine formation 8. a) O xidation with Jones Reagent (Aldehydes) b) Bayer-Villiger o xidation (Ketones) 3 b) En amine formation 4. Cya n ohydrin formation 5. Grignard Addition 6. Wittig Reaction 7. Reduction 9. Deuterium exchange 10. α - Halogen ation 11. α -alkylation 12. Ald ol formation
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Rxns 1- 7 are Nucleophilic Additions to Carbonyl R -C= O H : nu Halides ( Cl - ) 4 Oxygen (H 2 O , R O H) Nitrogen (1 ° , 2 ° , 3 ° amines ) Carbon (-C N, Grignard, Wittig) Hydrogen (hydride) (NaBH 4 , LiAlH 4 )
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Irreversible Carbonyl Additions 5) Grignard Reaction . 5 H O RMgBr Cl H H O H R Cl Mg 2+ Br 1. 2. + R = Alkyl or phenyl
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Preparation of the Grignard Reagent From last semester…. . Br H 1.Mg 2. H 2 O 6 Br Mg : MgBr CH 2 Mg 2+ Br H OH H OH Mg 2+ Br + Grignard reagent We can also use the Grignard carbanion to attack carbonyls.
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Mechanism of Grignard Addition C O CH 3 Mg 2+ Br - Cl H Use HCl to protonate O- in a separate operation 7 C O CH 3 Mg 2+ Br Cl H The Grignard addition is irreversible. C O CH 3 X NO!!! CH 3 - is very unstable: bad leaving group
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Leaving Group Ability CH 3 - 8 CH 3 - (like all simple R - )right off the charts in terms of low leaving group ability: CH 3 - is not resonance stabilized carbon has low electronegativity Carbon-carbon (C-CH 3 ) bond relatively strong
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Lecture 3A - Chem 2204/2206/2208 Tuesday July. 13 Lecture...

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