Spectrophotometer Aided Kinetic, Mechanistic and Thermodynamic Study of Ruthenium(III) Catalysed Oxidation of Esmolol by Sulphate of Cerium(IV) in Aqueous Sulphuric Acid Medium

摘要

Aim: The kinetics and mechanism of Ruthenium catalysed oxidation of Esmolol by Cerium(IV) sulphate in aqueous H_2SO_4 at a constant ionic strength of 0.50 mol dm~(-3) was studied spectrophotometrically. Observation: The reaction showed first order kinetics in both Cerium(IV) and Ruthenium(III) whereas fractional order in Esmolol. Addition of products showed no effect on the rate of the reaction. The main product, methyl-3-(4-(2-hydroxy-3-oxopropoxy) phenyl) propanoate, was identified with the aid of IR and Mass Spectral data. Stoichiometry with respect to the drug substrate and reagent was established as 2:1. Added H_2SO_4, SO_4~(2-) and HSO_(4-) showed negligible influence on the rate of the reaction in the specified concentration limits. HCe(SO_4)_3-was found to be the predominant reactive species under the specified experimental conditions. Conclusion: The rate constants (k), catalytic constant (k_c) and equilibrium constant (K_6) for the proposed mechanism were determined. The kinetic and thermodynamic activation parameters were computed for both the slow rate determining step and complex forming equilibrium step. The catalyst exerted its influence by forming a complex with the drug substrate through metal-substrate bonding in the pre-rate determining step.