SolutionsAcid-Base Properties
1. Basicity
Acetic anhydride (pKa of the conjugate acid ≈ −8.5) is slightly more basic than acetyl chloride (≈ −9). Give two reasons.
- It has two carbonyls that can be protonated.
- The proton can sit between the two carbonyl oxygens through a hydrogen bond, which stabilizes the protonated form.
2. α-Hydrogens
Arrange in order of decreasing acidity the α-hydrogens of: N,N-dimethylacetamide, methyl acetate and acetic anhydride.
Acetic anhydride (pKa ≈ 16) > methyl acetate (≈ 25) > N,N-dimethylacetamide (≈ 30).