Computational and Kinetic Study for the Degradation of Sulfadiazine Sulfa Drug by Potassium Permanganate in Acetate Buffer

Objective: This study thoroughly examined the kinetic, reaction process, and thermodynamic parameters for the degradation of sulfadiazine (SDZ) utilizing permanganate as an oxidizing agent in acetate buffer, encompassing degradation kinetics and mechanisms. Methodology: The degradation of sulfadiazine was examined under controlled conditions using permanganate as the oxidant in acetate buffer across a wide pH range. Kinetic experiments were performed using titrimetric and iodometric methods to ascertain reaction order, rate constant, and temperature dependence. Activation parameters were assessed by employing Arrhenius and Eyring equations. Reaction pathways and DFT calculations were utilized to examine electronic properties, activation barriers, and orbital interactions to substantiate the experimentally determined mechanism. Findings: Sulfadiazine (SDZ) degradation followed an overall second-order rate law under experimental conditions. A higher sulfadiazine (SDZ) removal rate is attainable at lower pH levels, with the removal rate diminishing as pH increases from 3.76 to 8.80. The activation energy was determined to be 26.853 kJ mol−1 and the pre-exponential factor is 7.5486 by using the Arrhenius equation. According to the observed results, a mechanism of the reaction has been proposed. Activation parameters such as enthalpy, entropy, and Gibbs free energy at 40°C were determined and found to be 24.3 kJ mol⁻¹, -191 J mol⁻¹K⁻¹, and 84.1 kJ mol⁻¹, respectively. Calculations utilizing density functional theory additionally validate the proposed reaction mechanism derived from kinetic measurements. Novelty: This study reports for the first time a comprehensive kinetic–mechanistic and DFT-supported investigation of sulfadiazine oxidation by potassium permanganate in acetate buffer, establishing a non-radical, charge-controlled electron transfer pathway. Unlike conventional Advanced Oxidation Processes(AOP)-based studies focused on degradation efficiency, this work elucidates medium effects, activation parameters, and selective S–N/C–S bond cleavage through integrated experimental–computational analysis, providing a new structure–reactivity perspective on sulfonamide oxidation. Keywords: Oxidation, Sulfadiazine, Potassium Permanganate, Acetate Buffer, Computational, Kinetic