chapter 7: aldehydes and ketones II

What is the outcome of an aldol condensation?

Formation of a carbon-carbon bond and a new molecule called an aldol.

What functional groups are present in an aldol?

Aldehyde and alcohol functional groups.

What acts as the nucleophile in aldol condensation?

The enolate formed by deprotonation of the α-carbon.

What is the electrophile in aldol condensation?

The aldehyde or ketone in its keto tautomer form.

What happens during the condensation reaction in aldol condensation?

Two molecules come together to form the aldol.

What is the result after the formation of an aldol?

A dehydration reaction occurs, leading to an α,β-unsaturated carbonyl.

What are retro-aldol reactions?

They are the reverse of aldol condensations.

What catalyzes retro-aldol reactions?

They are catalyzed by heat and base.

What bond is cleaved in retro-aldol reactions?

The bond between the α-carbon and the 3-carbon.

What is the significance of enolates in aldol reactions?

They enable the formation of new carbon-carbon bonds.

What are the primary components in Aldol Condensation?

Aldol formation, Dehydration reaction, Retro-aldol reaction

What is the term for the carbon adjacent to the carbonyl carbon?

The a-carbon.

What are the hydrogens attached to the a-carbon called?

a-hydrogens.

How can a-hydrogens be removed?

By a strong base due to their relative acidity.

What effect does the electron-withdrawing oxygen of the carbonyl have?

It weakens the C-H bonds on a-carbons.

What stabilizes the enolate formed from deprotonation?

Resonance with the carbonyl.

Why are ketones less reactive toward nucleophiles?

Due to steric hindrance and a-carbanion destabilization.

What happens when an additional alkyl group is present on a ketone?

It increases the energy of the transition state and crowds it.

What is the keto form of aldehydes and ketones?

C=O.

What describes tautomers?

Isomers that can interconvert by moving a hydrogen and a double bond.

How can the enol form be converted into an enolate?

By deprotonation.

What is formed when an enolate attacks an a,ß-unsaturated carbonyl?

A bond in the Michael addition.

When is the kinetic enolate favored?

By fast, irreversible reactions at lower temperatures with strong bases.

What conditions favor the thermodynamic enolate?

Slower, reversible reactions at higher temperatures with weaker bases.

What are enamines?

Tautomers of imines and less common than imines.

What do the keto and enol forms represent?

They are tautomers of each other.

What type of reactions form new carbon-carbon bonds via enolates?

Aldol condensation.

Identify the main roles of enolates in chemistry.

Form new bonds and Act as good nucleophiles

What is the significance of the retro-aldol reaction?

It involves breaking apart aldol products to regenerate reactants.