A kinetic-spectrophotometric study of MnII catalyzed oxidation of N,N-dimethylaniline by periodate ion

The present study deals with the kinetics and mechanism of Mn^II catalyzed periodate oxidation of N, Ndimethylaniline (DMA) in acetone-water medium at 30á´¼C. The reaction was initiated by mixing previously thermostated NaIO₄ solution of known concentration to the reaction mixture containing the DMA, MnII and buffer. The kinetics was followed under pseudo first order conditions,

[IO4 ⁻] >> [DMA], – d[IO4 –]/dt = k_obs . [DMA][Mn⁺⁺][IO4 ^–]

The stoichiometry of the reaction was observed to be 1:2 mole ratio of DMA to periodate ions. Free radical scavengers do not affect the reaction rate. The reaction products were identified and isolated using TLC separation techniques and characterized by IR, and GC-MS spectral studies. The reaction was found first order with respect to each reactant. The effect of pH, ionic strength and dielectric constants were also studied on the rate of reaction. A suitable mechanism is proposed based on the experimental results. The activation parameters were evaluated and found: Ea = 6.98 kcal mol⁻¹, A = 10.98× 10⁵ dm³ mol⁻¹ s⁻¹; ΔS# = -35.43 cal mol⁻¹, ΔF# = 17.34 kcal mol⁻¹ and ΔH# = 6.36 kcal mol⁻¹.

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