 The mechanism concludes with the removal of an alcohol, a series of proton transfers, and a keto/enol tautomerization to form a 4-hydroxyquinoline, the final product of the Conrad–Limpach synthesis.Perhaps the most important step (and the rate-determining step) in the reaction mechanism is the annulation of the molecule via an electrocyclic ring closing.For this step, the Schiff base must be heated to ~250 °C for the ring closure to occur.