THE EFFECT OF AQUEOUS COMPLEXATION ON THE DECARBOXYLATION RATE OF OXALATE

Understanding the role of carboxylic acid anions in sedimentary basin fluid-rock interactions requires an accurate knowledge of the decarbox ylation rates of the anions. In this study, the decarboxylation rate o f oxalate was measured in solutions with and without aqueous Al, a str ongly complexing cation, at 160, 170, and 180 degrees C. This is the f irst investigation of the effect of aqueous complexation on decarboxyl ation rates. Previous studies measured decarboxylation rates of carbox ylic acid anions only in solutions free of strongly complexing cations . This study indicates that aqueous aluminum can decrease the decarbox ylation rate of oxalate significantly. The magnitude of this effect in creases with decreasing temperature. Extrapolation of the experimental results suggests that when oxalate is present in solution as a part o f a highly stable aqueous complex, the half-life of oxalate at 80 degr ees C may be as much as three orders of magnitude longer than it would be when the oxalate is present as an acid anion only.