Chapter 18--Complete - Addition of N Nucleophiles Ammonia,...

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Addition of N Nucleophiles Ammonia, 1° aliphatic amines, and 1° aromatic amines react with the C=O group of aldehydes and ketones to give imines (Schiff bases). CH 3 CH H 2 N H + CH 3 CH=N H 2 O + + Acetaldehyde Aniline     An imine (a Schiff base) O An imine (a Schiff base) Ammonia Cyclohexanone + + NH 3 H 2 O O H +
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Addition of N Nucleophiles 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 N-R H C O: - H H C O H + A tetrahedral carbonyl  addition compound + : O H H H H C O H H C O H H O H H C H 2 O   An imine + + + + :
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Addition of N Nucleophiles Secondary amines react with the C=O group of aldehydes and ketones to form enamines. The mechanism of enamine formation involves formation of a tetrahedral carbonyl addition compound followed by its acid-catalyzed dehydration We will discuss the chemistry of enamines in more detail in Chapter 19. O H-N H + N H 2 O An enamine Piperidine (a secondary amine) + + Cyclohexanone
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A Very Important Reaction of Some Carboxylic Acids: Decarboxylation (17.9) R OH O CO 2 HEAT! RH + OH O O O CO 2 + WARM β -Decarboxylation NOT SYNTHETICALLY USEFUL
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Mechanism of β- Decarboxylation C H 2 O RC C=O O H CH 2 OH O=C=O RC + O RCCH 3 Enol form of a ketone
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Which One of the Following Will Most Readily Decarboxylate (Lose CO 2 )? C C 0% 0% 0% 0% COOH COOH HOOC-COOH COOH COOH CH 3 CCH 2 CH 2 COOH O 1. 2. 3. 4. C C C C 0 of 30 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 25
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Why Doesn’t This Compound Undergo β-Decarboxylation? O HOOC OH X trans-cyclohexene does not exist trans-cyclooctene: smallest isolable trans-cycloalkene
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Retrosynthetic Analysis (7.9) How might you synthesize the following? Cl CH 2 OH R COOH Oxidation Grignard + CO 2 Ozonolysis
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CHAPTER 18 CHAPTER 18 Functional Derivatives of Carboxylic Acids
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Acid Chlorides Acid Chlorides Acid Anhydrides Acid Anhydrides Esters Esters THESE ARE CONCEPTIONAL REPRESENTATIONS, NOT NECESSARILY SYNTHETIC METHODS!
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This note was uploaded on 04/08/2008 for the course CHEM 203 taught by Professor Shulman during the Spring '08 term at University of Cincinnati.

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Chapter 18--Complete - Addition of N Nucleophiles Ammonia,...

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