video tutorial Barbituric acid synthesis

Summary:

• The video notes the Feast of St. Barbara and that Adolf von Bayer 151 years ago discovered how to synthesize barbituric acid, the precursor to barbiturate sedatives.
• Barbituric acid is synthesized from purified diethylmalonate via a dry, carefully controlled distillation and reaction sequence.
• Pure diethylmalonate is distilled and collected in small portions to minimize decomposition; reagents and apparatus must be completely dry.
• Reaction setup uses dry glassware, anhydrous ethanol, and sodium metal to form sodium ethoxide; urea is dissolved in ethanol separately.
• Diethylmalonate is combined with the dry urea solution and heated to reflux for several hours with stirring to prevent violent bumping.
• Workup involves quenching with water, acidifying with hydrochloric acid to precipitate barbituric acid, and chilling to crystallize.
• Filtration and drying yield about 2.3 g of barbituric acid from 4 g starting material (roughly 72% crude yield); purification by recrystallization is needed for a pure sample.
• The product is only sparsely soluble in water; it can form the sodium salt with NaOH for demonstration.