The water-catalyzed mechanism of the ring-opening reaction of glucose

The transition path sampling simulations of the water-assisted ring-opening reaction of α- and β-glucose anomers allow us to elucidate the molecular details of the process.

Brönsted Acidic Ionic Liquid 1-(1-Propylsulfonic)-3-methylimidazolium-Chloride Catalyzed Hydrolysisof D-Cellobiose in Aqueous Medium

Brönsted acidic ionic liquid 1-(1-propylsulfonic)-3-methylimidazolium chloride (PSMIMCl) shows a higher catalytic activity than sulfuric acid in the hydrolysis of D-cellobiose to D-glucose in water at 90–120°C. This catalytic activity enhancement is more significant at higher temperatures, and at 120°C, PSMIMCl produced 64.5% glucose yield, whereas H2SO4 produced only 42.2% after 40 min. reaction, and this is a 52.8% enhancement of catalytic activity due to the alkylimidazolium group attached to the sulfonic acid group. 1H NMR monitoring of the D-cellobiose hydrolysis in PSMIMCl and sulfuric acid mediums failed to reveal intermediates in the hydrolysis reaction, and this is probably due to rapid conversion of the intermediate(s) to a mixture of D-glucose anomers with α:β≈1:1.6.

Factors Affecting Accuracy and Time Requirements of a Glucose Oxidase–Peroxidase Assay for Determination of Glucose

Accurate and rapid assays for glucose are desirable for analysis of glucose and starch in food and feedstuffs. An established colorimetric glucose oxidaseperoxidase method for glucose was modified to reduce analysis time and evaluated for factors that affected accuracy. Time required to perform the assay was reduced by approximately 40 by decreasing incubation time and removing steps that do not affect absorbance. Although linear regressions of absorbance and glucose concentrations of standard solutions exceeded R2 of 0.9997, evaluation of sum of squared residuals, root mean squared error, and significance of the quadratic term indicated that the curves were approximately quadratic in form. Inadequate equilibration of glucose anomers did not appear to be the issue. Historic data suggest that the standard curve is inherently nonlinear. Quadratic curves predicted standard solution glucose concentrations more accurately than did linear forms; overestimations at the midpoint of the curve averaged 0.04, 0.48, and 0.92 for quadratic and linear equations calculated from 5 standard solutions and a linear equation calculated from the 0 and most concentrated standard solution, respectively. A hydrophilic antioxidant at levels no greater than 10 mol ascorbic acid/0.10 g air-dried sample did not affect absorbance values.