<p>The current study intends to investigate the impact of neutral, cationic, and anionic surfactants on the IO<sub>4</sub><sup>−</sup> oxidation of cobalt(II)-trans-cyclohexane-1,2-diamine-N,N,N’,N’-tetraacetate ([Co<sup>II</sup>CYDTA]<sup>2−</sup>). The kinetics of [Co<sup>II</sup>CYDTA]<sup>2−</sup> oxidation in both aqueous and CTAB micellar mediums is determined by quantifying a spike in absorbance at a wavelength of 538&#xa0;nm, serving as&#xa0;a measure of the concentration of [Co<sup>III</sup>CYDTA]<sup>−</sup>. In the acidic medium periodate ion predominantly exists as octahedral H<sub>4</sub>IO<sub>6</sub><sup>−</sup> ion. The electron transfer reaction involving [Co<sup>II</sup>CYDTA]<sup>2−</sup> and H<sub>4</sub>IO<sub>6</sub><sup>−</sup> proceeds preferentially through an outer-sphere mechanism via the formation of ion-pair. Throughout the range of concentration analyzed, the reaction exhibits first order dependence both on [Co<sup>II</sup>CYDTA<sup>2−</sup>] and [IO<sub>4</sub><sup>−</sup>]. The observed constancy in reaction rate within the examined pH range supports the dominant presence of the unprotonated form of [Co<sup>II</sup>CYDTA]<sup>2−</sup> and the single species of periodate ion. The linear increase in oxidation rate with the addition of electrolytes indicates a positive salt effect. The CTAB micellar media facilitates an approximate 2.5-fold enhancement in the rate of [Co<sup>II</sup>CYDTA]<sup>2−</sup> oxidation. TX-100 promotes the oxidation of [Co<sup>II</sup>CYDTA]<sup>2−</sup>, while SLS, an anionic surfactant, acts as an inhibitor. The calculated activation parameters further corroborate the suggested mechanistic framework.</p>

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Impact of micelles on the periodate oxidation of cobalt(II)-trans-cyclohexane-1,2-diamine-N,N,N’,N’-tetraacetate: a kinetic and mechanistic study

  • Abhishek Srivastava,
  • Ranjan Kumar Padhy,
  • Rajeev Kumar Dohare,
  • Neetu Srivastava

摘要

The current study intends to investigate the impact of neutral, cationic, and anionic surfactants on the IO4 oxidation of cobalt(II)-trans-cyclohexane-1,2-diamine-N,N,N’,N’-tetraacetate ([CoIICYDTA]2−). The kinetics of [CoIICYDTA]2− oxidation in both aqueous and CTAB micellar mediums is determined by quantifying a spike in absorbance at a wavelength of 538 nm, serving as a measure of the concentration of [CoIIICYDTA]. In the acidic medium periodate ion predominantly exists as octahedral H4IO6 ion. The electron transfer reaction involving [CoIICYDTA]2− and H4IO6 proceeds preferentially through an outer-sphere mechanism via the formation of ion-pair. Throughout the range of concentration analyzed, the reaction exhibits first order dependence both on [CoIICYDTA2−] and [IO4]. The observed constancy in reaction rate within the examined pH range supports the dominant presence of the unprotonated form of [CoIICYDTA]2− and the single species of periodate ion. The linear increase in oxidation rate with the addition of electrolytes indicates a positive salt effect. The CTAB micellar media facilitates an approximate 2.5-fold enhancement in the rate of [CoIICYDTA]2− oxidation. TX-100 promotes the oxidation of [CoIICYDTA]2−, while SLS, an anionic surfactant, acts as an inhibitor. The calculated activation parameters further corroborate the suggested mechanistic framework.