SolutionsAcid-Base Properties
1. The least basic
Why is the carbonyl of an acid chloride the least basic among the derivatives (pKa of the conjugate acid ≈ −9)?
Chlorine, very electronegative and a poor resonance donor, cannot stabilize the positive charge of the protonated form.
2. α-Hydrogens
Why are the α-hydrogens of acetyl chloride (pKa ≈ 16) more acidic than those of methyl acetate (≈ 25)?
Chlorine withdraws electrons and does not compete with the delocalization of the enolate charge; the methoxy group donates electrons by resonance and destabilizes it.