Metal-ion-catalysed Decarboxylation of Oxalacetic Acid in Water-Ethanol Mixtures

OXALACETIC acid (OAA) decarboxylates spontaneously in water 1,2 and in various organic solvents with a rate that is dependent on the polarity of the solvent 3 . Additions of a number of polyvalent metal ions to aqueous solutions of oxalacetic acid promote decarboxylation 4–9 . The degree of this rate promotion depends on the nature of the metal, on its concentration and on the p H. Addition of ethanol to the aqueous system of the metal ion-promoted decarboxylation of oxalacetic acid decreases the polarity, diminishing both dissociation of the acid and the extent of hydration of the metal ion. These polarity effects are demonstrated by changes in chelation and decarboxylation of oxalacetic acid using magnesium and manganese ion.