SolutionsAcid-Base Properties
1. Basicity
Why is the nitrogen of a nitrile (pKa of the conjugate acid ≈ −10) far less basic than that of an amine (≈ 10.6)?
Its lone pair is in an sp orbital, with 50 % s character, close to the nucleus and poorly available; in the amine it is in an sp3 orbital.
2. α-Hydrogens
Acetonitrile (pKa ≈ 31) is less acidic than acetone (≈ 20). Why?
The anion formed delocalizes the charge onto nitrogen, less electronegative than oxygen, and is less stabilized than an enolate.