lecture 23 - Chapter 23. Carbonyl Condensation Reactions...

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Chapter 23. Carbonyl Condensation Reactions Based on McMurry’s Organic Chemistry , 7 th edition
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2 Condensation Reactions Carbonyl compounds are both the electrophile and nucleophile in carbonyl condensation reactions
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3 Why this Chapter? Carbonyl condensation reactions also occur often in metabolic pathways. Also one the general methods used to form C-C bonds.
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4 23.1 Carbonyl Condensation: The Aldol Reaction Acetaldehyde reacts in basic solution (NaOEt, NaOH) with another molecule of acetaldhyde The β -hydroxy aldehyde product is aldol ( ald ehyde + alcoh ol ) This is a general reaction of aldehydes and ketones
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5 The Equilibrium of the Aldol The aldol reaction is reversible, favoring the condensation product only for aldehydes with no α substituent Steric factors are increased in the aldol product
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6 Aldehydes and Ketones and the Aldol Equilibrium
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7 Mechanism of Aldol Reactions Aldol reactions, like all carbonyl condensations, occur by nucleophilic addition of the enolate ion of the donor molecule to the carbonyl group of the acceptor molecule The addition intermediate is protonated to give an alcohol product
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8 23.2 Carbonyl Condensation versus Alpha- Substitution Carbonyl condensations and α substitutions both involve formation of enolate ion intermediates Alpha-substitution reactions are accomplished by converting all of the carbonyl compound to enolate form so it is not an electrophile Immediate addition of an alkyl halide to completes the alkylation reaction
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9 Conditions for Condensations A small amount of base is used to generate a small amount of enolate in the presence of unreacted carbonyl compound After the condensation, the basic catalyst is regenerated
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10 23.3 Dehydration of Aldol Products: Synthesis of Enones The
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lecture 23 - Chapter 23. Carbonyl Condensation Reactions...

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