310_8 - Organic Lecture Series CH 310 N LECTURE 8 Textbook...

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Organic Lecture Series 1 CH 310 N LECTURE 8 Textbook Assignment: Chapter 16 Aldehydes & Ketones Homework (for credit): Problem set-none this week Today’s Topics: N nucleophiles; Oxidation & Reductions Notice & Announcements: EXAM 1: Grading in Progress Organic Lecture Series 2 Aldehydes Aldehydes And And Ketones Ketones
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Organic Lecture Series 3 Addition of Nitrogen Addition of Nitrogen Nucleophiles Nucleophiles • Ammonia, 1° aliphatic amines, and 1° aromatic amines react with the C=O group of aldehydes and ketones to give imines imines (Schiff bases) • Water is removed by Dean-Stark trap or chemical dehydration (e.g. molecular sieves) CH 3 H 2 N H + 3 CH=N H 2 O + + Acetaldehyde Aniline An imine (a Schiff base) O An imine (a Schiff base) Ammonia Cyclohexanone + +N H 3 H 2 O O NH H + Organic Lecture Series • Formation of an imine occurs in two steps Step 1: carbonyl addition followed by proton transfer Step 2: loss of H 2 O and proton transfer to solvent C O H 2 N-R H H C O: - N-R O H N-R H C + + OH H H H C O H N-R H C O H H O H H C N-R O H H H An imine + + + + + + H 2 O Addition of Nitrogen Addition of Nitrogen Nucleophiles Nucleophiles
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Organic Lecture Series – a value of imines is that the carbon-nitrogen double bond can be reduced to a carbon- nitrogen single bond + Dicyclohexylamine Cyclohexanone (An imine) Cyclohexylamine O NN H -H 2 O H 2 /Ni H + H 2 N Does not have to isolated Addition of Nitrogen Addition of Nitrogen Nucleophiles Nucleophiles Organic Lecture Series 6 Addition of Nitrogen Addition of Nitrogen Nucleophiles Nucleophiles • Secondary amines react with the C=O group of aldehydes and ketones to form enamines enamines (alk alk en en e and and amine amine ) – the mechanism of enamine formation involves formation of a tetrahedral carbonyl addition compound followed by its acid-catalyzed dehydration OH - N H + NH 2 O An enamine Piperidine (a secondary amine) + + Cyclohexanone
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Organic Lecture Series 7 N O HO N H H O H Protonated Ketone H N-Protonated Amino-alcohol N H Organic Lecture Series 8 N H N H O-Protonated N H 2 o Carbocation H N Enamine Product H H
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Organic Lecture Series 9 Addition of Nitrogen Addition of Nitrogen Nucleophiles Nucleophiles – the carbonyl group of aldehydes and ketones reacts with hydrazine and its derivatives in a manner similar to its reactions with 1° amines OH 2 NNH 2 NNH 2 H 2 O + Hydrazine + A hydrazone H 2 N -NHCNH 2 H 2 N -OH H 2 N -NH H 2 N NO 2 O 2 N Reagent, H 2 N-R Hydroxylamine Oxime Phenylhydrazine 2,4-Dinitrophenyl- hydrazine Semicarbazide 2,4-Dinitrophenylhydrazone Semicarbazone Name of Derivative Formed Name of Reagent Phenylhydrazone O Organic Lecture Series 10 Acidity of Acidity of α -Hydrogens Hydrogens Hydrogens alpha to a carbonyl group are
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310_8 - Organic Lecture Series CH 310 N LECTURE 8 Textbook...

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