Chapter 21: Alpha Carbon Chemistry - Lecture Review

These flashcards cover key concepts from Chapter 21 on alpha carbon chemistry, focusing on enols, enolates, alpha halogenation, aldol reactions, and mechanisms.

What is the significance of the alpha position in carbonyl chemistry?

The alpha position is one carbon away from the electrophilic carbon in the carbonyl and is where many chemical reactions occur.

What are tautomers?

Tautomers are rapidly interconverting constitutional isomers that differ in the placement of a hydrogen or a proton and the position of the double bond.

What happens when a ketone is treated with a strong base?

The alpha position of the ketone is deprotonated to form a resonance-stabilized intermediate called the enolate.

How are enols different from enolates?

Enols are less reactive than enolates; enolates possess a full negative charge and can be isolated and stored.

What is alpha halogenation?

Alpha halogenation is the process of adding a halogen at the alpha position of a carbonyl compound, which can occur under both acidic and basic conditions.

What is the first step in the acid-catalyzed mechanism for enol formation?

Protonation of the carbonyl group.

What happens during aldol reactions?

The enolate of an aldehyde or ketone reacts at the alpha carbon with the carbonyl of another molecule to form a beta-hydroxy aldehyde or ketone.

What is an aldol condensation?

An aldol condensation involves heating the aldol addition product to eliminate water and form a double bond between the alpha and beta positions.

What is the role of LDA in enolate formation?

LDA (lithium diisopropyl amide) is a strong base used to achieve irreversible enolate formation from ketones.

What is a common outcome when performing alpha halogenation in basic conditions?

With multiple hydrogens at the alpha position, multiple halogenations may occur, resulting in a heavily halogenated product.