Kinetic and Salt Effect Studies of the Mechanistic Oxidation of D-Glucose by Cerium(IV) in Acidic Medium

International Journal of Chemistry | Vol. 5, No. 2, February 2014 | pp. 9–16

DOI: 10.46882/2014/IJC/000065

Article Type: Original Research Paper

Title: Kinetic and Salt Effect Studies of the Mechanistic Oxidation of D-Glucose by Cerium(IV) in Acidic Medium

Names of Authors: T. M. Usman¹, A. M. Al-Ghoul²*

Authors’ Affiliations:
¹Department of Chemistry, Bayero University, Kano, Nigeria.
²Department of Chemistry, American University of Beirut, Beirut, Lebanon.

Abstract: Transition metal oxidants like Cerium(IV) provide vital kinetic benchmarks required to map carbohydrate oxidation mechanisms and electron transfer pathways in aqueous systems. The kinetics of the oxidation of D-glucose by Cerium(IV) was investigated spectrophotometrically in an aqueous perchloric acid medium at a constant ionic strength of 0.50 M (NaClO₄). The reaction progress was monitored under pseudo-first-order conditions by following the absorbance decay of Cerium(IV) at its absorption maximum of 320 nm. The reaction exhibited a first-order dependence on [Cerium(IV)] and a fractional-first-order dependence on [D-glucose]. The reaction rate increased with rising hydronium ion concentration, revealing an acid-catalyzed pathway governed by the reactive protonated oxidant species, [Ce(OH)³⁺]. The introduction of sodium sulfate produced a significant retarding salt effect on the reaction velocity due to the formation of less reactive sulfato-complexes of Cerium(IV). Stoichiometric determinations confirmed that 1 mole of D-glucose consumed 2 moles of Cerium(IV), producing gluconic acid as the primary end product. Thermodynamic activation constants were calculated from temperature-dependence datasets using the Eyring equation, yielding an activation enthalpy (delta H*) of 52.4 kJ/mol and an activation entropy (delta S*) of -85.6 J/mol K, supporting an inner-sphere mechanism.

Keywords: Reaction kinetics; Spectrophotometry; Cerium oxidation; D-glucose; Activation parameters; Retarding salt effect

Manuscript Timeline: Received: March 20, 2013; Revised: May 15, 2013; Accepted: June 28, 2013; Published: February 07, 2014.

Citation: Usman, T. M., & Al-Ghoul., A. M. (2014). Kinetic and Salt Effect Studies of the Mechanistic Oxidation of D-Glucose by Cerium(IV) in Acidic Medium. International Journal of Chemistry, 5(2), 9–16.

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