Self-decomposition of 14C carbohydrates

Abstract

PART I. A commercial sample of glucose, from the Radiochemical Centre, Amersham, was found to have decomposed under the influence of its own B-radiation. The products of the decomposition have been examined by chromatography, ionophoresis and carrier dilution analysis, and found to be mainly oxidation products. The fact that the actual rate of self-decomposition was ca. ten times that of the theoretical rate suggested the participation of a secondary effect in the decomposition. A similarity between the products of self-decomposition and the products of hydroxyl radical attack on D-glueose was noted. It was inferred that water in the glucose sample enhanced self-decomposition by absorbing some of the B-radiation and yielding hydroxyl radicals in situ. PART II. The products of the oxidation of D-glucitol with a deficiency of periodate were identified and measured. The results were explained on a stereochemical basis assuming the formation of a 5-membered cyclic intermediate in the periodate reaction. Periodate oxidation of the glucitol-borate complex in solution at pH 10 was attempted and compared with a similar oxidation of glucitol in phosphate buffer. The increased yield of L-xylose in the borate buffered oxidation was explained by the complexing of borate with glucitol. Certain anomalous results in both borate and phosphate were noted and are discussed. The complexing of molybdate with carbohydrates has been examined with a view to elucidating the structure of complexes and utilising the complexes.The results of (mainly) ionophoresis experiments have shown that the pyranose ring will complex with molybdate only if it possesses three hydroxyl groups in a cis-cis-1:2:3-triol arrangement. Ionophoresis in molybdate solution has been found to be a valuable analytical method for carbohydrates, complementary with the borate method.