THE CATALYTIC EFFECT OF BROMIDE IN THE HYPOCHLORITE OXIDATION OF LINEAR DEXTRINS AND INULIN

The effect of bromide in the hypochlorite oxidation of amylodextrins (short chain amylose) and inulin on the reaction rate was investigated. It was found both in the linear dextrins and inulin oxidation that the rate increases linearly with the sodium bromide concentration, which proves the catalytic effect of this substance. The origin of the catalysis is the rapid Br-/OCl- conversion. The second-order rate constant of the reaction Carbohydrate + HOBr/OBr- --> polycarboxylates + HBr/Br- was determined at pH 9.0 and 294-298 K. The activation energy for the oxidation of amylodextrins amounts to 67 kJ.mole-1. The highest rate was found at pH 8.25. The reaction rate is almost independent of pH in the region 8.5-9.5. Because of the simultaneous occurrence of bromine, Br3-, hypobromous acid and hypobromite in the pH region investigated, it is difficult to elucidate the oxidation mechanism.