What is the experimentally observed decreasing order of basic strength for simple methyl-substituted — Amines Chemistry Question

💡 Solution & Explanation

In aqueous solution, basicity is a delicate balance of the inductive effect, solvation (hydration) energy, and steric hindrance. For methyl groups, the secondary amine is the strongest base. The primary amine becomes stronger than the tertiary amine because the smaller methyl group makes hydrogen bonding (solvation) of the conjugate acid highly favorable, overwhelming the purely +I effect of the third methyl group, which severely introduces steric hindrance to hydration. Order: $2^\circ > 1^\circ > 3^\circ > NH_3$.