Lecture 2A - Reversible Additions to Carbonyls 1. HCl...

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Reversible Additions to Carbonyls 1 . HCl addition (Bioremediation) 2a . Hydration 2b. Acetals (Protecting Groups, Glycobiology) Lecture 2A
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Recall: Chemistry of carbonyls vrs alkenes C C H H C C o dipole H + , E + H No dipole C O H H H . . . . δ + δ - C O δ δ + - Big dipole H + , E + - Nu - B
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A cid(Bronsted) B ase (Bronsted) E lectrophile Chemistry of Aldehydes and Ketones N ucleophile O xidant R eductant
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Introducing our Prototypical Carbonyl-containing Compounds C O H H H C O C H 3 H C H C H H Acetaldehyde Acetone
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Top 12 reactions 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) 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 - ) 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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A Note about Reaction Mechanisms Reaction mechanisms, unlike structures, cannot be “proven”. Mechanistic alternatives are considered and e most reasonable on is chosen based the most reasonable on on the experimental evidence: Consensus. Mechanisms are considered established on the basis of detailed labelling studies; evaluation of kinetic parameters and more recently, computational experiments.
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1) 1,1-halohydrin formation O O Cl H Cl H H H unstable 1,1-halohydrins are inherently unstable because halides are such good leaving groups (wk bases). Reaction goes in reverse readily.
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Cl : Mechanism H H Cl Cl H + slow + Recall: Now: O H + . . . . reversible
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This note was uploaded on 09/09/2010 for the course CHEM CHEM 2204 taught by Professor Peterbuist during the Summer '10 term at Carleton.

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Lecture 2A - Reversible Additions to Carbonyls 1. HCl...

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