Answer to Question #284586 in Organic Chemistry for Ridham

Question

Explain why is barbituric acid so strong. Write a scheme of its reaction with one mole of NaOH. Explain, why are barbiturates not so strong acids as barbituric acid. Write a reaction of sodium salt of 5,5-diethylbarbituric acid preparation.

Answer 1

Properties. The α-carbon has a reactive hydrogen atom and is quite acidic (pKa = 4.01) even for a diketone species (cf. dimedone with pKa 5.23 and acetylacetone with pKa 8.95) because of the additional aromatic stabilization of the carbanion.