Chapter 21-22 November 14

Chapter 21-22 November 14 - The Difference Between...

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1 Let's Draw Kevlar: Starting Materials 1,4­diaminobenzene 1,4­benzenedicarboxylic acid
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2 Spectroscopy of Carboxylic Acid Derivatives Infrared Absorptions:
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3 Spectroscopy of Carboxylic Acid Derivatives Proton NMR: The presense of a carbonyl group deshields the H's on adjacent carbons. It is difficult to determine the exact carbonyl structure using IR alone. NMR uses the resulting chemical shifts to help make a final structure determination.
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4 Chapter 22 ­ Carbonyl Alpha­Substitution Reactions General Overview: General Reaction Scheme: The carbon adjacent to a carbonyl is designated as the alpha ( α )­carbon Electrophilic substitution occurs at the alpha ( α ) position via one of two possible intermediates:
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5 Keto­Enol Tautomerism The Difference Between Tautomers and Resonance Forms:
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Unformatted text preview: The Difference Between Tautomers and Conventional Structural Isomers: A carbonyl compound with a hydrogen on its α-carbon rapidly equilibrates with its enol tautomer Tautomers are structural isomers Resonance forms are representations of contributors to a single structure Tautomers interconvert rapidly while ordinary isomers do not 6 Enols: The enol tautomer is usually present in only an extremely small percentage and cannot be isolated It can (and does) serve as a reactive intermediate because it forms so rapidly 7 Acid Catalysis of Enolization Mechanism: Bronsted­Lowrey acids catalyze keto­enol tautomerization by protonating the carbonyl and activating the α ­protons...
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Chapter 21-22 November 14 - The Difference Between...

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