In a Mannich reaction, 0.20 mol of formaldehyde, 0.20 mol of dimethylamine, and 0.15 mol of acetophenone are mixed under acidic conditions. After work‑up, 0.12 mol of the Mannich product (β‑amino carbonyl compound) is isolated. Calculate the percentage yield based on the limiting reagent.

Step-by-step solution

1. Write the overall stoichiometry: 1 mol formaldehyde + 1 mol secondary amine + 1 mol carbonyl compound $\to$ 1 mol Mannich product.
2. Compare the moles of the three reagents: formaldehyde = 0.20 mol, dimethylamine = 0.20 mol, acetophenone = 0.15 mol.
3. The smallest amount is acetophenone (0.15 mol); therefore it is the limiting reagent.
4. Theoretical amount of product = moles of limiting reagent = 0.15 mol.
5. Actual isolated product = 0.12 mol.
6. Percentage yield = (actual / theoretical) $\times$ 100 = (0.12 / 0.15) $\times$ 100 = 80 %.

Concept tested: Stoichiometry and yield in Mannich reaction

Published 10 September 2026 · How this solution was prepared and checked