A study of some reaction rates in the homogeneous system glucose-sodium hydroxide-water
Date
1971
Authors
Harvie, Gordon Arnold
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Abstract
Rate constants for the isomerization, epimerization and degradation reactions occurring in the glucose-sodium hydroxide-water system were calculated in systems using each of the three expected carbohydrate products (glucose, fructose and mannose) in turn separately as starting material. A study of the dependence of the rate constants prevailing in the glucose reaction system on base concentration was accomplished by calculating these rate constants at four different sodium hydroxide concentrations, 0.49, 4.02, 6.07 and 8.08M. Only the magnitude of the fructose to degradation products reaction pathway was found to demonstrate a strong dependence on base concentration.
The materials of interest in the reaction systems were resolved by column chromatography using an anion resin in the borate form. Separation and elution of the carbohydrates required about six hours using a graded eluant. Elution began with 0.12M H₃BO₃ at pH 8.50 by adjustment with KOH and ended with 0.15M K₂B₄O₇. The column effluent was monitored continuously and analyzed colorimetrically using automated Technicon equipment. Absorbance was measured at 420 nm using orcinol/H₂SO₄ as the color forming reagent.
Graphical and numerical techniques were used to estimate the rate constants at each sodium hydroxide concentration. These estimates were then refined by a non-linear least squares analysis utilizing an IBM 360, Model 44 digital computer to give the best-fit to experimentally determined carbohydrate concentration vs reaction time curves.