Substitution reactions of carbonyl compounds

Which of the following statements best describes an α-hydrogen in carbonyl compounds?

• It is bonded to the carbonyl carbon.

• It is bonded to a carbon adjacent to the carbonyl carbon.

• It is the least acidic hydrogen in the molecule.

• • It cannot be removed by a strong base.

Why is an α-hydrogen more acidic than other sp³ hydrogens in carbonyl compounds?

• Due to the increased electronegativity of the carbonyl carbon.

• Because the electrons left behind when the proton is removed are delocalized.

• Because the α-hydrogen is always involved in hydrogen bonding.

• Because the α-hydrogen is less shielded by other atoms.

What is the relative acidity of α-hydrogens in aldehydes, ketones, and esters?

• Aldehydes > Ketones > Esters

• Ketones > Aldehydes > Esters

• Esters > Aldehydes > Ketones

• • Aldehydes > Esters > Ketones

Which reaction involves the substitution of an α-hydrogen with a halogen in the presence of an acid or a base?

• Aldol Condensation

• Cannizzaro Reaction

• Halogenation of α-hydrogen

• Perkin Reaction

In base-catalyzed halogenation of aldehydes or ketones, what intermediate is formed after the removal of an α-hydrogen?

• Enol

• Carbanion

• Enolate ion

• Carbocation

What is the role of LDA (lithium diisopropylamide) in the formation of enolate ions?

• It acts as a weak base and nucleophile.

• It converts only a small amount of the carbonyl compound to the enolate ion.

• It is a strong base but a poor nucleophile.

• It forms enolate ions by adding to the carbonyl carbon.

What is the major product when an unsymmetrical ketone undergoes alkylation at low temperature (-78°C)?

• The thermodynamic enolate product

• The kinetic enolate product

• The more substituted alkene

• The less substituted alkene

Which intermediate is formed when an aldehyde or ketone reacts with a secondary amine?

• Enolate

• Imine

• Enamine

• Hydrazone