Meldrum's acid or 2,2-dimethyl-1,3-dioxane-4,6-dione is an organic compound. The main ring structure is a dioxane. The compound was discovered in 1908 by A.N. Meldrum ¹ and it is prepared by a condensation reaction of malonic acid with acetone in acetic anhydride with sulfuric acid. Meldrum misidentified ² the structure as a beta-lactone with a fully fledged carboxylic acid group. Yet Meldrum's acid has a high acidity with a pKa of 4.97, because like ascorbic acid, deprotonation at the methylene next tothe carbonyls produces a stable enolate. Because of this property Meldrum's acid like malonic acid is a reactant in Knoevenagel condensations.