Lecture 2B - Reversible Additions to Carbonyls 3a...

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Reversible Additions to Carbonyls 3a . Imines (Biological Reactions) 3b . Enamines 4 . Cyanohydrins (Biodefence weapon ) Lecture 2B
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Top 12 reactions 1. 1,1- halo hydrin formation 2. a) Hydration b) Acetal formation 3. a) Imine formation b) En amine formation 8. a) O xidation with Jones Reagent (Aldehydes) b) Bayer-Villiger o xidation (Ketones) 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 O , R O H) 2 Nitrogen (1 ° , 2 ° , 3 ° amines ) Carbon (-C N, Grignard, Wittig) Hydrogen (hydride) (NaBH 4 , LiAlH 4 )
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3a,b Nucleophilic attack by nitrogen nucleophiles H C H O N H + O .. H C H N + + H 3 H 2 H . . Simplest case Note: Most simple imines decompose in water to give the parent carbonyl group. Carbonyl group is the thermodynamic resting place Aldimine Imino group Aldehyde Carbonyl group
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3a) Imine Formation with Primary Amines (R = alkyl) and ammonia (R = H). H O H N R N H + O + H 2 R H 2 3b) Enamine Formation with Secondary Amines (R = alkyl) H O H N R R N H + O + HR 2 H 2
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C O C O NH 2 -H .. NH 2 R .. + + multi step multi step ammonia 1 ° amine Reaction outcomes depends on type of amine used and ability to generate H 2 O. ( Imine ) ( Imine ) C O NHR 2 .. C N R R H H .. + -H + multi step 2 ° amine ( Enamine ) C O NR 3 .. + 3 ° amine Product very unstable
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An Aside: Comparison of Nomenclature for Alcohols vrs Amines Alcohols H 2 O RCH 2 O H (Primary alcohol) ----- R 2 CH O H (Secondary alcohol)--- R C O H (Tertiary alcohol)--------- Amines N H 3 --------------- --------------- (Primary Amines) -------------- 3 R O R (ether) R O + R (oxonium salt) R - ------------- (Secondary Amine) - ------------- (Tertiary Amine) ---------------------- (Quaternary Ammonium salt) Note: For Alcohols - # of carbons attached to the carbon-bearing hydroxyl determines whether it is primary, secondary or tertiary.
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