KINETICS AND MECHANISMS OF THE OXIDATION OF AMINOCARBOXYLATOCOBALTATE(II) COMPLEXES BY HYPOCHLORITE AND SILVER-CATALYSED PERSULPHATE IONS IN AQUEOUS ACIDIC MEDIUM

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KINETICS AND MECHANISMS OF THE OXIDATION OF AMINOCARBOXYLATOCOBALTATE(II) COMPLEXES BY HYPOCHLORITE AND SILVER-CATALYSED PERSULPHATE IONS IN AQUEOUS ACIDIC MEDIUM

 

CHAPTER ONE

1.0 INTRODUCTION

Electron transfer (ET) reaction is simply the transfer of electrons between two species like ions, molecules, biological systems etc. The reaction usually involves rearrangement and transfer of outermost shell electrons of reacting species in order to gain stability. Thus, oxidation is the loss of electrons while reduction is the gain of electrons (Wong et al., 2002). Many reactions in inorganic and biological systems involve transfer of electron, thus, electron transfer reaction plays a key role to various physical and biological systems (Onu et al., 2008, 2009, 2015 and 2016; François and Jamal, 2016; Idris et al., 2015; Ilbert and Bonnefoy, 2013; Xie et al., 2012; Xiang-Rong and Xiang-Zhong 2010; Naik et al., 2007 and 2010).

Both Adenosine triphosphate (ATP) and dioxygen radical/hydrogen peroxide (O2-./H2O2) are generated in living cell by electron transfer. ATP is the product of oxidative phosphorylation whereas O2-. is generated by singlet electron reduction of dioxygen, O2 which is reduced by superoxide dismutase, SOD to H2O2 (Mailloux, 2015). Importantly, the controlled production of O2-./H2O2 is required for intrinsic mitochondria signaling (e.g. Modulation of mitochondria processes) and communication with the rest of the cell. This can be checked by understanding the effect of various parametres on the reaction. Moreover, the damaging effect of oxygen towards anaerobic organism is associated with its free radical properties (Ilbert and Bonnefoy, 2013). One of the promising areas that explains the effect of various parametres on this electron transfer reaction is chemical kinetics.

Chemical kinetics also known as reaction kinetics is the area of Chemistry concerned with reaction rates, factors affecting the rates and sequence of steps (mechanistic pathways) by which reactions occur (McMurry and Fay, 2008). The two well established general mechanisms of electron transfer reactions are the outer-sphere and the inner-sphere mechanisms (Cox, 2004). In the outer-sphere mechanism, no substitution of the ligands into the inner coordination spheres of either reactant is needed for electron transfer to take place (Housecroft and Sharpe, 2008). On the other hand, the inner-sphere mechanism involves distortion of the inner-coordination sphere of reactants with the formation of a bridged activated intermediate prior to electron transfer (Jagannadham, 2012).

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KINETICS AND MECHANISMS OF THE OXIDATION OF AMINOCARBOXYLATOCOBALTATE(II) COMPLEXES BY HYPOCHLORITE AND SILVER-CATALYSED PERSULPHATE IONS IN AQUEOUS ACIDIC MEDIUM