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  • 1 Department of Chemistry, Gurukul Kangri University, Haridwar, 249404 Uttarakhand India
  • | 2 Department of Chemistry, D.A.V. (P.G.) College, Muzaffarnagar, Uttar Pradesh India
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Abstract

The kinetics of the periodate oxidation of p-toluidine (TOL) in acetone–water medium has been followed by monitoring the increase in the absorbance of the reaction intermediate, C4, and the main reaction product is 4-methyl-1,2-benzoquinone. Results under pseudo first order conditions, [IO4] > [TOL], are in agreement with the rate law d[C]/dt = kK3K4Kw[MnII] [S] [IO4]0 [H+]/{K2Kw + (Kw + KbK2)[H+] + Kb [H+]2} where kK3K4 is the empirical composite rate constant, Kw is ionic product of water, K2 is acid dissociation constant of H4IO6, Kb is base dissociation constant of TOL i.e. substrate [S] and [IO4]0 represents the concentration of periodate that has been taken in excess in most of the kinetic runs. In agreement with the rate law, the 1/kcat versus pH profile passes through a minimum. Free radical scavengers do not affect the reaction rate. The rate is found to decrease with an increase in ionic strength and decrease in dielectric constant of the medium. Activation parameters evaluated are: ∆E = 12.2 ± 1.1 kJ mol−1, A = (1.57 ± 0.005) × 107 dm3 mol−1 s−1; ∆S# = −115.9 ± 0.2 J mol−1 K−1, ∆G# = 46.2 ± 0.9 kJ mol−1 and ∆H# = 9.60 ± 0.06 kJ mol−1.

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