OXIDATION OFD-GALACTURONIC ACID WITH SOME DELIGNIFYING AND BLEACHING AGENTS

Abstract

D-Galacturonic acid was oxidized with decreasing ease, and in the approximate order shown, by excess of the following agents: sodium chlorite near pH 2.8 and 75°; sodium hypochlorite at pH 10–11 and 25°; chlorine dioxide, pH 1.3 or 5 at 75°; chlorine near 0° and pH 5 (slight); and hydrogen peroxide at pH 10–11 and 25° (negligible). Some uronic acid was always recovered unchanged, even from conditions that would have oxidized glucose quantitatively to gluconic acid. The only other products were mucic acid, together with DL-tartaric acid and tartronic acid presumably derived therefrom. Chlorine dioxide, however, never produced tartronic acid. Methyl-α-D-galacturonoside methyl ester yielded some galacturonic acid when exposed to alkaline hypochlorite or peroxide, and this cleavage of the glycosidic group was tentatively attributed to the oxidants rather than to the alkalinity of the systems.Anhydrous bromine degraded the silver salt of methyl-α-D-galacturonoside in poor yield to a syrup which was probably L-arabotrihydroxyglutaric dialdehyde.