2025, Vol. 6, Issue 1, Part B
Mechanistic insights into the oxidation of 2,6-diphenylpiperidine-4-one and its 3-methyl derivative using transition metal oxidants
Author(s): Vinod Kumar
Abstract: The redox behavior of transition metal ions plays a pivotal role in modern inorganic and organic chemistry, particularly in oxidation processes involving complex organic molecules. In this study, a detailed kinetic and mechanistic investigation was conducted on the oxidation of 2,6-diphenylpiperidine-4-one and its 3-methyl-substituted analog using three manganese-based oxidants: Mn(III), Mn(IV), and Mn(VII), in acidic aqueous media. The primary aim was to explore the effect of both metal oxidation state and substrate structure on the oxidation kinetics, mechanistic pathway, and thermodynamic feasibility of the reactions. UV-Visible spectrophotometry was employed to monitor the oxidation reactions under pseudo-first-order conditions, where the substrate was present in large excess over the oxidant. All three manganese oxidants exhibited first-order dependence on substrate concentration, but the magnitude of the rate constants varied significantly, with Mn(IV) showing the highest reactivity followed by Mn(III) and Mn(VII). The substitution of a methyl group at the 3-position of the piperidone ring significantly reduced the oxidation rate, indicating the influence of steric hindrance and electronic effects on transition state formation. Temperature-dependent studies were used to calculate activation parameters (ΔH*, ΔS*, and ΔG*) using the Eyring equation, revealing distinct enthalpic and entropic characteristics for each oxidant. Mn(IV)-mediated reactions were marked by high enthalpic and positive entropic contributions, supporting an inner-sphere mechanism, whereas Mn(VII) exhibited lower enthalpy and negative entropy, favoring an outer-sphere electron transfer pathway. The variations in reaction conditions such as acidity, ionic strength, and solvent polarity had a substantial impact on the rate constants, underlining the importance of the reaction medium in influencing oxidation dynamics. Product analysis via GC-MS confirmed the formation of key oxidation products such as pyrrolidine-3-carboxylic acid and amino dicarboxylic acid derivatives, consistent with oxidative ring-opening mechanisms. The results provide valuable mechanistic insights and demonstrate how minor structural changes in both oxidant and substrate can significantly alter the oxidation behavior of nitrogen-containing heterocycles.
DOI: 10.22271/reschem.2025.v6.i1b.182
Pages: 134-139 | Views: 60 | Downloads: 30
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How to cite this article:
Vinod Kumar. Mechanistic insights into the oxidation of 2,6-diphenylpiperidine-4-one and its 3-methyl derivative using transition metal oxidants. J Res Chem 2025;6(1):134-139. DOI: 10.22271/reschem.2025.v6.i1b.182
