Kinetic Studies and Mechanistic Pathway of the Oxidation of L-Lysine by Alkaline Periodate

International Journal of Chemistry | Vol. 10, No. 3, March 2019 | pp. 17–24

DOI: 10.46882/2019/IJC/000125

Article Type: Original Research Paper

Title: Kinetic Studies and Mechanistic Pathway of the Oxidation of L-Lysine by Alkaline Periodate

Names of Authors: T. M. Usman¹, A. M. Al-Rasheed²*

Authors’ Affiliations:
¹Department of Chemistry, Bayero University, Kano, Nigeria.
²Department of Chemistry, King Saud University, Riyadh, Saudi Arabia.

Abstract: The kinetics of transition metal and non-metal electron transfer reactions involving amino acids yield foundational data required to map metabolic oxidation-reduction transformations in biological models. The oxidation of L-lysine by periodate ions (IO₄⁻) was investigated spectrophotometrically in an aqueous alkaline environment at a constant ionic strength of 0.20 M (NaClO₄). The reaction was monitored under pseudo-first-order conditions by tracking the absorbance decay of periodate at its wavelength maximum of 222 nm. The empirical rate law showed a first-order dependence on [IO₄⁻] and a fractional-first-order dependence on [L-lysine]. The reaction rate increased with rising hydroxyl ion concentration, revealing a base-catalyzed pathway governed by the active deprotonated amine species. Variations in the dielectric constant of the solvent medium produced significant kinetic shifts, indicating a rate-determining step involving two ionic species. Stoichiometric determinations confirmed that 1 mole of L-lysine consumed 2 moles of periodate, producing 5-aminopentanal and iodate ions as the primary end products. Thermodynamic activation parameters were computed from temperature dependence studies using the Eyring equation; the enthalpy of activation (delta H*) was 42.6 kJ/mol, and the entropy of activation (delta S*) was calculated to be -118.4 J/mol K. A plausible free-radical mechanism proceeding via an inner-sphere intermediate complex is proposed.

Keywords: Reaction kinetics; Spectrophotometry; Periodate oxidation; L-lysine; Activation parameters; Reaction mechanisms

Manuscript Timeline: Received: May 02, 2018; Revised: June 15, 2018; Accepted: July 12, 2018; Published: March 04, 2019.

Citation: Usman, T. M., & Al-Rasheed, A. M. (2019). Kinetic Studies and Mechanistic Pathway of the Oxidation of L-Lysine by Alkaline Periodate. International Journal of Chemistry, 10(3), 17–24.

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