Preparation of copoly(vinyl alcohol–styrenesulfonic acid) resin and its catalytic activity on hydrolysis of carbohydrates. IV. Hydrolysis of dextrin in mixtures of organic solvents with water

Abstract

The reaction rates of dextrin hydrolysis in the presence of copoly(vinyl alcohol–styrenesulfonic acid) resin in mixtures of dimethyl sulfoxide and dioxane with water were measured and compared with those in the presence of Amberlite 120B. In the case of Amberlite 120B the second-order rate constant, κ2, of the reaction decreased continuously with increasing vol % of the organic solvents, whereas in the case of the copolymer resin it passed a minimum and increased again at the higher vol % range. The influence of blocking of the hydroxyl groups in the copolymer resin by formalization on the catalysis was investigated. The increase in κ2 in the higher vol % range of the organic solvent was suppressed with the blocking, and the interactions between hydroxyl groups in the substrate and the copolymer resin was confirmed to play an important role for the increase in the κ2 in the higher vol % range of the organic solvents. Temperature dependence of κ2 was also examined, and the increase in κ2 in the higher vol % range of the organic solvents was found to be due to pronounced decreases in enthalpy of activation, suggesting that the increase might be resulted from the enhancement of interactions between the substrate and the catalytic copolymer resin.