Kinetics and Mechanism of Oxidation of Catechol by Oxygenated [Co2(O2)(NH3)10]5+ Complex

Nathaniel Oladunni; Suleiman Ola Idris; Ameh David Onu; Gideon Adamu Shallangwa

doi:doi:10.11648/j.sf.20210201.11

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Kinetics and Mechanism of Oxidation of Catechol by Oxygenated [Co₂(O₂)(NH₃)₁₀]⁵⁺ Complex

Nathaniel Oladunni, Suleiman Ola Idris, Ameh David Onu, Gideon Adamu Shallangwa

Published in Science Frontiers (Volume 2, Issue 1)

Received: 25 November 2020 Accepted: 28 December 2020 Published: 10 February 2021

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Abstract

The kinetics and mechanisms of the redox reaction of Catechol and μ-superoxo-bis[pentaamminecobalt(III)] pentachloridemonohydrate, [(NH₃)₅Co(O₂)Co(NH₃)₅]Cl₅.H₂O, hereafter represented as CoO₂Co⁵⁺was studied in aqueous perchloric acid under pseudo-first-order conditions at 27±1°C, I=0.35mol dm^-3 (NaClO₄) and λ_max=660nm. μ-superoxo-bis[pentaamminecobalt(III)] pentachloridemonohydrate was used as the oxidant and it was synthesized and characterized according to reported procedure. This study was aimed at generating kinetic data with respect to the oxidation of cathecol by µ-superoxo-bridged binuclear cobalt(III) complex of ammine and to propose plausible mechanism that underpin this reaction of interest. Effect of changes in acid concentration, ionic strength, dielectric constant and temperature on the reaction rate was investigated. The reaction was found to be first-order in both reactants, second-order overall, acid dependent and showed a negative Brønsted-Debye salt effect. Decreasing the dielectric constant from 80.1–74.01 (CH₃COCH₃/H₂O) increased the rate of reaction. A large negative value of ΔS^≠ (−224Jmol⁻¹K⁻¹) was obtained during the thermodynamic studies and that showed that the activated complex formed is more ordered. This confirmed that the reaction proceeded by associative mechanism. There was evidence for the presence of free radicals during the course of the reaction, but non to validate the formation of an intermediate complex. In overall, the results suggest an outer-sphere mechanism for the reaction. A probable mechanism is proposed.

Published in	Science Frontiers (Volume 2, Issue 1)
DOI	10.11648/j.sf.20210201.11
Page(s)	1-7
Creative Commons	This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.
Copyright	Copyright © The Author(s), 2024. Published by Science Publishing Group

Keywords

Kinetics, Mechanism, Oxidation, Dioxygen Complex, Observed Rate Constant (k_obs), Catechol (C₆H₄(OH)₂), Ionic Strength (I)

References

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APA Style

Nathaniel Oladunni, Suleiman Ola Idris, Ameh David Onu, Gideon Adamu Shallangwa. (2021). Kinetics and Mechanism of Oxidation of Catechol by Oxygenated [Co2(O2)(NH3)10]5+ Complex. Science Frontiers, 2(1), 1-7. https://doi.org/10.11648/j.sf.20210201.11

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ACS Style

Nathaniel Oladunni; Suleiman Ola Idris; Ameh David Onu; Gideon Adamu Shallangwa. Kinetics and Mechanism of Oxidation of Catechol by Oxygenated [Co2(O2)(NH3)10]5+ Complex. Sci. Front. 2021, 2(1), 1-7. doi: 10.11648/j.sf.20210201.11

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AMA Style

Nathaniel Oladunni, Suleiman Ola Idris, Ameh David Onu, Gideon Adamu Shallangwa. Kinetics and Mechanism of Oxidation of Catechol by Oxygenated [Co2(O2)(NH3)10]5+ Complex. Sci Front. 2021;2(1):1-7. doi: 10.11648/j.sf.20210201.11

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@article{10.11648/j.sf.20210201.11,
  author = {Nathaniel Oladunni and Suleiman Ola Idris and Ameh David Onu and Gideon Adamu Shallangwa},
  title = {Kinetics and Mechanism of Oxidation of Catechol by Oxygenated [Co2(O2)(NH3)10]5+ Complex},
  journal = {Science Frontiers},
  volume = {2},
  number = {1},
  pages = {1-7},
  doi = {10.11648/j.sf.20210201.11},
  url = {https://doi.org/10.11648/j.sf.20210201.11},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.sf.20210201.11},
  abstract = {The kinetics and mechanisms of the redox reaction of Catechol and μ-superoxo-bis[pentaamminecobalt(III)] pentachloridemonohydrate, [(NH3)5Co(O2)Co(NH3)5]Cl5.H2O, hereafter represented as CoO2Co5+ was studied in aqueous perchloric acid under pseudo-first-order conditions at 27±1°C, I=0.35mol dm-3 (NaClO4) and λmax=660nm. μ-superoxo-bis[pentaamminecobalt(III)] pentachloridemonohydrate was used as the oxidant and it was synthesized and characterized according to reported procedure. This study was aimed at generating kinetic data with respect to the oxidation of cathecol by µ-superoxo-bridged binuclear cobalt(III) complex of ammine and to propose plausible mechanism that underpin this reaction of interest. Effect of changes in acid concentration, ionic strength, dielectric constant and temperature on the reaction rate was investigated. The reaction was found to be first-order in both reactants, second-order overall, acid dependent and showed a negative Brønsted-Debye salt effect. Decreasing the dielectric constant from 80.1–74.01 (CH3COCH3/H2O) increased the rate of reaction. A large negative value of ΔS≠ (−224Jmol−1K−1) was obtained during the thermodynamic studies and that showed that the activated complex formed is more ordered. This confirmed that the reaction proceeded by associative mechanism. There was evidence for the presence of free radicals during the course of the reaction, but non to validate the formation of an intermediate complex. In overall, the results suggest an outer-sphere mechanism for the reaction. A probable mechanism is proposed.},
 year = {2021}
}

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TY  - JOUR
T1  - Kinetics and Mechanism of Oxidation of Catechol by Oxygenated [Co2(O2)(NH3)10]5+ Complex
AU  - Nathaniel Oladunni
AU  - Suleiman Ola Idris
AU  - Ameh David Onu
AU  - Gideon Adamu Shallangwa
Y1  - 2021/02/10
PY  - 2021
N1  - https://doi.org/10.11648/j.sf.20210201.11
DO  - 10.11648/j.sf.20210201.11
T2  - Science Frontiers
JF  - Science Frontiers
JO  - Science Frontiers
SP  - 1
EP  - 7
PB  - Science Publishing Group
SN  - 2994-7030
UR  - https://doi.org/10.11648/j.sf.20210201.11
AB  - The kinetics and mechanisms of the redox reaction of Catechol and μ-superoxo-bis[pentaamminecobalt(III)] pentachloridemonohydrate, [(NH3)5Co(O2)Co(NH3)5]Cl5.H2O, hereafter represented as CoO2Co5+ was studied in aqueous perchloric acid under pseudo-first-order conditions at 27±1°C, I=0.35mol dm-3 (NaClO4) and λmax=660nm. μ-superoxo-bis[pentaamminecobalt(III)] pentachloridemonohydrate was used as the oxidant and it was synthesized and characterized according to reported procedure. This study was aimed at generating kinetic data with respect to the oxidation of cathecol by µ-superoxo-bridged binuclear cobalt(III) complex of ammine and to propose plausible mechanism that underpin this reaction of interest. Effect of changes in acid concentration, ionic strength, dielectric constant and temperature on the reaction rate was investigated. The reaction was found to be first-order in both reactants, second-order overall, acid dependent and showed a negative Brønsted-Debye salt effect. Decreasing the dielectric constant from 80.1–74.01 (CH3COCH3/H2O) increased the rate of reaction. A large negative value of ΔS≠ (−224Jmol−1K−1) was obtained during the thermodynamic studies and that showed that the activated complex formed is more ordered. This confirmed that the reaction proceeded by associative mechanism. There was evidence for the presence of free radicals during the course of the reaction, but non to validate the formation of an intermediate complex. In overall, the results suggest an outer-sphere mechanism for the reaction. A probable mechanism is proposed.
VL  - 2
IS  - 1
ER  -

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Author Information

Nathaniel Oladunni

Department of Chemistry, Ahmadu Bello University, Zaria, Nigeria
Suleiman Ola Idris

Department of Chemistry, Ahmadu Bello University, Zaria, Nigeria
Ameh David Onu

Department of Chemistry, Ahmadu Bello University, Zaria, Nigeria
Gideon Adamu Shallangwa

Department of Chemistry, Ahmadu Bello University, Zaria, Nigeria

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APA Style

Nathaniel Oladunni, Suleiman Ola Idris, Ameh David Onu, Gideon Adamu Shallangwa. (2021). Kinetics and Mechanism of Oxidation of Catechol by Oxygenated [Co2(O2)(NH3)10]5+ Complex. Science Frontiers, 2(1), 1-7. https://doi.org/10.11648/j.sf.20210201.11

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ACS Style

Nathaniel Oladunni; Suleiman Ola Idris; Ameh David Onu; Gideon Adamu Shallangwa. Kinetics and Mechanism of Oxidation of Catechol by Oxygenated [Co2(O2)(NH3)10]5+ Complex. Sci. Front. 2021, 2(1), 1-7. doi: 10.11648/j.sf.20210201.11

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AMA Style

Nathaniel Oladunni, Suleiman Ola Idris, Ameh David Onu, Gideon Adamu Shallangwa. Kinetics and Mechanism of Oxidation of Catechol by Oxygenated [Co2(O2)(NH3)10]5+ Complex. Sci Front. 2021;2(1):1-7. doi: 10.11648/j.sf.20210201.11

Copy | Download

@article{10.11648/j.sf.20210201.11,
  author = {Nathaniel Oladunni and Suleiman Ola Idris and Ameh David Onu and Gideon Adamu Shallangwa},
  title = {Kinetics and Mechanism of Oxidation of Catechol by Oxygenated [Co2(O2)(NH3)10]5+ Complex},
  journal = {Science Frontiers},
  volume = {2},
  number = {1},
  pages = {1-7},
  doi = {10.11648/j.sf.20210201.11},
  url = {https://doi.org/10.11648/j.sf.20210201.11},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.sf.20210201.11},
  abstract = {The kinetics and mechanisms of the redox reaction of Catechol and μ-superoxo-bis[pentaamminecobalt(III)] pentachloridemonohydrate, [(NH3)5Co(O2)Co(NH3)5]Cl5.H2O, hereafter represented as CoO2Co5+ was studied in aqueous perchloric acid under pseudo-first-order conditions at 27±1°C, I=0.35mol dm-3 (NaClO4) and λmax=660nm. μ-superoxo-bis[pentaamminecobalt(III)] pentachloridemonohydrate was used as the oxidant and it was synthesized and characterized according to reported procedure. This study was aimed at generating kinetic data with respect to the oxidation of cathecol by µ-superoxo-bridged binuclear cobalt(III) complex of ammine and to propose plausible mechanism that underpin this reaction of interest. Effect of changes in acid concentration, ionic strength, dielectric constant and temperature on the reaction rate was investigated. The reaction was found to be first-order in both reactants, second-order overall, acid dependent and showed a negative Brønsted-Debye salt effect. Decreasing the dielectric constant from 80.1–74.01 (CH3COCH3/H2O) increased the rate of reaction. A large negative value of ΔS≠ (−224Jmol−1K−1) was obtained during the thermodynamic studies and that showed that the activated complex formed is more ordered. This confirmed that the reaction proceeded by associative mechanism. There was evidence for the presence of free radicals during the course of the reaction, but non to validate the formation of an intermediate complex. In overall, the results suggest an outer-sphere mechanism for the reaction. A probable mechanism is proposed.},
 year = {2021}
}

Copy | Download

TY  - JOUR
T1  - Kinetics and Mechanism of Oxidation of Catechol by Oxygenated [Co2(O2)(NH3)10]5+ Complex
AU  - Nathaniel Oladunni
AU  - Suleiman Ola Idris
AU  - Ameh David Onu
AU  - Gideon Adamu Shallangwa
Y1  - 2021/02/10
PY  - 2021
N1  - https://doi.org/10.11648/j.sf.20210201.11
DO  - 10.11648/j.sf.20210201.11
T2  - Science Frontiers
JF  - Science Frontiers
JO  - Science Frontiers
SP  - 1
EP  - 7
PB  - Science Publishing Group
SN  - 2994-7030
UR  - https://doi.org/10.11648/j.sf.20210201.11
AB  - The kinetics and mechanisms of the redox reaction of Catechol and μ-superoxo-bis[pentaamminecobalt(III)] pentachloridemonohydrate, [(NH3)5Co(O2)Co(NH3)5]Cl5.H2O, hereafter represented as CoO2Co5+ was studied in aqueous perchloric acid under pseudo-first-order conditions at 27±1°C, I=0.35mol dm-3 (NaClO4) and λmax=660nm. μ-superoxo-bis[pentaamminecobalt(III)] pentachloridemonohydrate was used as the oxidant and it was synthesized and characterized according to reported procedure. This study was aimed at generating kinetic data with respect to the oxidation of cathecol by µ-superoxo-bridged binuclear cobalt(III) complex of ammine and to propose plausible mechanism that underpin this reaction of interest. Effect of changes in acid concentration, ionic strength, dielectric constant and temperature on the reaction rate was investigated. The reaction was found to be first-order in both reactants, second-order overall, acid dependent and showed a negative Brønsted-Debye salt effect. Decreasing the dielectric constant from 80.1–74.01 (CH3COCH3/H2O) increased the rate of reaction. A large negative value of ΔS≠ (−224Jmol−1K−1) was obtained during the thermodynamic studies and that showed that the activated complex formed is more ordered. This confirmed that the reaction proceeded by associative mechanism. There was evidence for the presence of free radicals during the course of the reaction, but non to validate the formation of an intermediate complex. In overall, the results suggest an outer-sphere mechanism for the reaction. A probable mechanism is proposed.
VL  - 2
IS  - 1
ER  -

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