Inner sphere oxidation of 3,9-dimethyl-4,8-diaza-3,8-undecadiene-2,10- dione dioximecopper(II) complex by N-bromosuccinimide to copper(III) in aqueous acidic solutions

Title : Inner sphere oxidation of 3,9-dimethyl-4,8-diaza-3,8-undecadiene-2,10- dione dioximecopper(II) complex by N-bromosuccinimide to copper(III) in aqueous acidic solutions

Abstract:

The kinetics of the oxidation of the 3,9-dimethyl-4,8-diaza-3,8-undecadiene-2,10-dionedioximecopper(II) complex, [Cu^IIHL₂]⁺+, by N-bromosuccinimide (NBS) were studied in weakly acidic aqueous media (pH 3.36-5.25). The reaction exhibited autocatalysis, characterized by S-shaped absorbance-time curves. Under pseudo-first-order conditions in the presence of Hg(II), the reaction rate showed a first-order dependence on the total copper(II) complex concentration. The pseudo-first-order rate constant, k_obs ​, displayed Michaelis-Menten type saturation kinetics with respect to [NBS]. The dependence of k_obs ​ on acidity was complex, increasing only by a factor of ~2 across the pH range studied. An inner-sphere mechanism is proposed, consistent with the derived rate law and the known ability of the four-coordinate [CuIIHL]+ complex to form five-coordinate species. Considering [Cu^IIHL]⁺, [Cu^IIL], [NBS] and [HNBS]⁺ as the reactive species within four possible pathways, the following rate law was derived:
Rate =  {k1K2K3 + (k2K1K2K4+k4K6)[H+] + k3K2K5[H+]2}[NBS][CuIILH+]t  (i)
                     [H+] + K1 + {K1K3 + (K1K2K4 + K6)[H+] + K2K5[H+]2}[NBS]

Biography:

Amel Salah is a researcher in food technology currently working with the Sudan Industrial Research & Consultancy Centre (IRCC) since February 2020, focusing on areas like food inspection and grading. She holds Master's degrees in Food and Beverage Innovation and Management from Università Politecnica delle Marche (Italy) and in Chemistry from the University of Khartoum (Sudan). With previous experience as a Teacher Assistant and Laboratory Technician, Amel is seeking opportunities in roles such as Researcher, Chemist, or Quality Control Specialist.