Which of the following amines exhibits the highest basicity in an aqueous solution?

Solution

1. Basicity in aqueous solution depends on the inductive effect, steric hindrance, and solvation of the conjugate acid.
2. For ethylamines, the order of basicity is ${\text{(C}}_2{\text{H}}_5{)}_2\text{NH}>{\text{(C}}_2{\text{H}}_5{)}_3\text{N}>{\text{C}}_2{\text{H}}_5{\text{NH}}_2>{\text{NH}}_3$.
3. Diethylamine provides the optimal balance between electron donation and solvation stability.
4. Hence the answer is (A).