The polycondensation of aldohexoses and related derivatives

Abstract

The condensation reactions of the anomers of d-glucose, d-mannose, and d-galactose, as well as of certain of their derivatives, have been investigated in the molten state in the absence of catalysts. The reaction was followed thermogravimetrically, the products being analyzed by means of chromatography, polarimetry, and end-group determinations. The loss in weight associated with the condensation reactions was found to be different for each of the monosaccharides heated under a variety of conditions, provided that analyses were performed well before completion of the reaction. At temperatures below 220°, intermolecular condensation predominated; above 220°, intramolecular condensation became more apparent. Study of the behavior of derivatives indicated that the hydroxyl group on C-1 is essential to condensation. As already known, for d-glucose, the intermolecular condensation reaction occurred primarily between C-1 and C-6. The extent of polymerization under standardized conditions was greatest for the d-galactoses, followed by the d-mannoses; the d-glucoses yielded the smallest polymers. It was also observed that a higher degree of polymerization is obtained for the α- d anomers of d-mannose and d-galactose than for the β- d anomers. A possible explanation of this behavior is given on the basis of the conformations of the aldohexoses employed.