SolutionsAcid-Base Properties
1. α-Hydrogens
Arrange in order of decreasing acidity the α-hydrogen of: acetone, acetaldehyde and ethyl acetate.
Acetaldehyde (pKa ≈ 17) > acetone (≈ 20) > ethyl acetate (≈ 25).
The alkoxy group donates electrons to the carbonyl by resonance and competes with the delocalization of the enolate charge, which is therefore less stabilized.
2. Which base?
To form the enolate of ethyl acetate quantitatively, can sodium ethoxide (pKa of ethanol ≈ 16) be used? And LDA (pKa of diisopropylamine ≈ 36)?
Ethoxide only forms a small amount of enolate at equilibrium, because the enolate is a stronger base than ethoxide. LDA forms it completely and irreversibly.