Abstract
At neutral and alkaline pH cobalt(II)histidine complex binds with molecular oxygen reversibly to form μ-dioxytetrakis(histidinato)dicobalt(II), an oxygen adduct complex. The reaction proceeds in such a way that the addition of N-acetyl cysteine to μ-dioxytetrakis(histidinato)dicobalt(II) results in the fading away of brown color of μ-dioxytetrakis(histidinato)dicobalt(II) due to the oxidation of N-acetyl cysteine. Thus, kinetic measurement of this oxidation was exploited and studied spectrophotometrically at different concentration of N-acetyl cysteine, μ-dioxytetrakis(histidinato)dicobalt(II) and hydroxide ion. Effect of μ-dioxytetrakis(histidinato)dicobalt(II) was studied in the concentration range from 1.0×10−3moldm−3 to 5.0×10−3moldm−3 and it was found that rate constant was independent on [Co(II)histidine] with the average value of rate constant 1.11×10−3s−1. It was observed that the values of rate constant were found to be independent of [N-acetyl cysteine] at higher concentrations, but, varied linearly with [N-acetyl cysteine] at lower concentrations (1–6×10−3moldm−3). The values of rate constant increased from 1.17×10−3s−1 (at [NaOH]=5.0×10−4moldm−3) to 2.55×10−3s−1 when the concentration of NaOH is increased to 1.0×10−2moldm−3.
Repetitive scans of absorption spectra of solution containing [CoL2]=4.0×10−3moldm−3, [N-acetyl cysteine]=2.0×10−3moldm−3 and [NaOH]=5.0×10−4moldm−3 at 15.0±0.1°C. The scans were recorded at the intervals of 120s. [Display omitted]
•Oxidation of N-acetyl cysteine is studied mechanistically.•N-acetyl cysteine is oxidized at both neutral and alkaline pH.•Rate constant were found to be independent of [N-acetyl cysteine].•Rate constant varied linearly with [N-acetyl cysteine] at lower concentrations.