Formose Reactions. IV. The Formose Reaction in Homogeneous Systems and the Catalytic Functions of Calcium Ion Species

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Abstract
By using the previously developed analytical method of oxidation-reduction potential measurement, the formose reaction homogeneously-catalyzed by calcium formate-potassium hydroxide at pH 10.5–12.0 was found to proceed as effectively as that heterogeneously-catalyzed by calcium hydroxide. Other calcium salts, including chloride, bromide, acetate, and propionate, could be used in place of calcium formate. Kinetic studies with the calcium formate–KOH system showed a linear dependence of the concentration of the dissolved calcium ion species on the induction period (Tmin) and the formose-forming period (Tmax–Tmin) at a given pH. From the results, the relationships, Tmin=a[CaOH+]+c and Tmax–Tmin=a[CaOH+]+b[Ca(OH)2]+c, were obtained, suggesting that CaOH+ is the principal catalytic species in the induction step, while both CaOH+ and Ca(OH)2 (or OH−) are present in the formose-forming step. The effects of various factors on both steps and the sugar yield were also examined.