A Kinetic Photometric Assay for the Quantification of the Open‐Chain Content of Aldoses

Abstract

Aldoses exist predominantly in the cyclic hemiacetal form, which is in equilibrium with the open‐chain aldehyde form. The small aldehyde content hampers reactivity when chemistry addresses the carbonyl moiety. This low concentration of the available aldehyde is generally difficult to ascertain. Herein, we demonstrate a new kinetic determination of the (minute) open‐chain content (OCC) of aldoses. This kinetic approach exploits the aldehyde‐selectivity of 2‐aminobenzamidoxime (ABAO), which furnishes a strongly UV‐active adduct. Simple formation curves can be measured in a photometer or plate reader for high‐throughput screening. Under pseudo‐first order kinetics, these curves correlate with a prediction model yielding the relative OCC. The OCCs of all parent aldoses (pentoses and hexoses) were determined referencing against the two tetroses with exceptionally high OCCs and were in very good agreement with literature data. Additionally, the assay was extended towards higher‐carbon sugars with unknown OCC and also applied to rationalise a lack of reactivity observed in a recent synthetic investigation.

Low‐energy Hemiacetal Dehydrogenation Pathway: Co‐production of Gluconic Acid and Green Hydrogen via Glucose Dehydrogenation

“…In solution at equilibrium, 99% of glucose (a six‐carbon aldose) exists as pyranose rings, which feature hemiacetal groups [2] . The hemiacetal groups of cyclic glucose are chemically active and this reactivity of the hemiacetal group can potentially be leveraged in fields such as catalytic biomass conversion [3,4] . Thus, the hemiacetal groups of cyclic glucose may enable the efficient and cost‐effective catalytic conversion of biomass to high‐value‐added chemicals and fuels under relatively mild conditions.…”

“…[2] The hemiacetal groups of cyclic glucose are chemically active and this reactivity of the hemiacetal group can potentially be leveraged in fields such as catalytic biomass conversion. [3,4] Thus, the hemiacetal groups of cyclic glucose may enable the efficient and cost-effective catalytic conversion of biomass to high-value-added chemicals and fuels under relatively mild conditions. The conversion of biomass into highvalue-added chemicals and fuels reduces our dependence on rapidly depleting, non-renewable resources such as fossil fuels.…”