Sustained and damped oscillations in the permanganate-hydroxylamine reaction in a continuous-flow stirred tank reactor

Influence of Pyrophosphate on the Generation of Soluble Mn(III) from Reactions Involving Mn Oxides and Mn(VII)

“…Hydroxylamine was reported to reduce Mn­(VII) through two steps: Mn­(VII) was first reduced to soluble Mn­(IV) followed by the successive reduction of Mn­(IV) by hydroxylamine . Besides, the oxidation products of hydroxylamine was reported to be a mixture of N 2 and N 2 O under neutral conditions .…”

“…Remarkably, an initial lag phase of absorbance at 258 nm was observed in the case of hydroxylamine, which should result from the competition between the induced production of Mn­(III)-PP from the reduction of Mn­(VII) and the consumption of Mn­(III)-PP by hydroxylamine since the absorption peaks of Mn­(VI), Mn­(V), and Mn­(IV) were not observed during the loss of Mn­(VII) (Figure S14). The lag phase was shortened with increasing concentrations of PP due to the depressed reactivity between Mn­(III)-PP and reductant when the molar ratio of PP:Mn­(III) was larger. , …”

“…Hydroxylamine was reported to reduce Mn(VII) through two steps: Mn(VII) was first reduced to soluble Mn(IV) followed by the successive reduction of Mn(IV) by hydroxylamine. 49 Besides, the oxidation products of hydroxylamine was reported to be a mixture of N 2 and N 2 O under neutral conditions. 50 The amount of Mn(III)-PP generated from the Mn(VII)/hydroxylamine/PP system increased as the initial concentration of the reductant increased from 100 to 150 μM because of the more complete reduction of Mn(VII) at higher hydroxylamine dosage (Figure 4A).…”

“…The lag phase was shortened with increasing concentrations of PP due to the depressed reactivity between Mn(III)-PP and reductant when the molar ratio of PP:Mn(III) was larger. 48,49 Thermodynamic Calculation. To better understand the influence of PP on the generation of Mn(III)-PP in these redox reactions, the Gibbs free energies (ΔG) of the reduction of Mn(VII) by thiosulfate or hydroxylamine as well as that for the disproportionation of free Mn(III) ion or Mn(III)-PP were calculated as a function of pH and the results are summarized in Figure 5.…”

Oxidative chemiluminescence of some nitrogen nucleophiles in the presence of formic acid as an ancillary reductant

“…It seems inconceivable that in these cases two isolated nitrogen atoms will come together to form an excited dinitrogen molecule. However, the oxidation of hydroxylamine by permanganate acidified by phosphoric acid is said to proceed via an unstable NOH intermediate which undergoes bimolecular decomposition to dinitrogen oxide, 34 which has molecular orbitals in the same energy range as dinitrogen. 35 Under conditions of excess of permanganate, NOH could further oxidise to nitrogen oxide, which has orbital energies closely similar to those of nitrogen and, because it has an electron in the 2pp * orbital in the ground state, it probably requires less energy to form excited species capable of emission.…”