The Acid-Base Catalysis of the Mutarotation of Glucose in Protium Oxide-Deuterium Oxide Mixtures

The kinetics of the mutarotation of glucose has been studied in protium-deuterium oxide mixtures (H2O–D2O) to ascertain the effect of substituting deuterium for hydrogen upon catalysis by the aqueous solvent, by the acid ion, by an anion base and the conjugate molecular acid. The velocity of the water catalyzed reaction varies linearly with the fraction of heavy glucose and depends only indirectly upon the composition of the water. The velocity of the acid ion catalysis varies linearly with the H2O–D2O content. For acetate ion catalysis the rate varies linearly with the fraction of D2O or of DOAc. Measurements of the temperature coefficient show that the observed decrease in the rate of the water catalyzed reaction arises primarily from a decrease in the entropy of activation (B) and not from an increase in the energy of activation (Eact). A method has been devised for determining whether or not any property depends linearly upon the deutero fraction of a substance which may assume two isotopic forms, HX and DX. For the available data on the inversion of sucrose, DX has been identified with D+. For the present work on the water catalyzed mutarotation of glucose, DX has been identified with heavy glucose.