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MCAT Org. Chem Ch. 7
Term | Definition |
---|---|
α-Carbon | Carbon adjacent to the carbonyl carbon |
α-Hydrogens | Hydrogens attached to the α-carbon |
α-Hydrogens Are Relatively: | Acidic and can be removed by a strong base |
The Electron-Withdrawing Oxygen Of The Carbonyl: | Weakens the C-H bonds on α-carbons |
The Enolate Resulting From Deprotonation Can Be: | Stabilized by resonance with the carbonyl |
Ketones Are Less Reactive Toward Nucleophiles Because Of: | Steric hindrance and α-carbanion destabilization |
Reasons For Ketones' Less Reactivity Towards Nucleophilicity | The presence of an additional alkyl group crowds the transition step and increases its energy. The alkyl group also donates electron density to the carbanion, making it less stable. |
Aldehydes And Ketones Exist In The Traditional: | Keto form, C=O, and less in teh enol form (enol = ene + ol = double bond + alcohol) |
Tautomers | Isomers that can be interconverted by moving a hydrogen and a double bond. The keto and enol forms are tautomers of each other. |
The Enol Form Can Be Deprotonated As An: | Enolate. |
Enolates Are Good: | Nucleophiles |
In The Michael Addition, An Enolate Attacks: | An α, β-unsaturated carbonyl, creating a bond |
Kinetic Enolate Is Favored By: | Fast, irreversible reactions at lower temperatures with strong, sterically hindered bases |
Thermodynamic Enolate Is Favored By: | Slower, reversible reactions at higher temps with weaker, smaller bases |
Enamines | Tautomers of imines. Enamines are the less common tautomer. |
In The Aldol Condensation, The Aldehyde Or Ketone Acts: | As both nucleophile and electrophile, resulting in the formation of carbon-carbon bond in a new molecule called an aldol |
Aldol Contains: | Both aldehyde and alcohol functional groups |
Nucleophile Of Aldol Condensation Is: | The enolate formed from the deprotonation of the α-carbon |
Electrophile Of Aldol Condensation Is: | The aldehyde or ketone in the form of keto tautomer |
Steps Of Aldol Condensation: | First, a condensation reaction occurs in which two molecules come together. After the aldol is formed, a dehydration reaction (loss of a water molecule) occurs which results in an α, β-unsaturated carbonyl. |
Retro-aldol Reactions | Are the reverse of aldol condensations. They result in the bond between an α- and β-carbon being cleaved. |
Retro-aldol reactions Are Catalyzed By: | Heat and base |