Complex Oxidation Process Research Articles

Reactivity of cobalt(II) complexes [CO(OEPh3)2X2](E = P or as; X = Cl, Br, I or NCS) with SO2 under aerobic and anaerobic conditions. Crystal structure of cocrystallised [Co(OPMe3)3(OH2)2]I2 and [Co(OPMe3)3(OH2)3]I2

Pseudo-tetrahedral complexes [Co(OEPh3)2X2](E = P or As; X = Cl, Br, I or NCS) and [Co(OPMe3)2I2] have been isolated by conventional synthesis from ethanolic solutions of the appropriate hydrated metal salt and Ph3EO. Their reactivity with sulfur dioxide has been examined in the solid state (anaerobic conditions) and for toluene slurries or solutions (aerobic and anaerobic conditions). The [Co(OEPh3)2X2](X = Cl or Br) complexes show no reactivity and are recovered unchanged from all forms of exposure to SO2. However, [Co(OEPh3)2X2](E = P or As, X = I or NCS) reacted slowly with SO2 in the solid state to form 1:1 adducts, as evidenced by elemental analyses and mass changes. The visible spectra of the precursor complexes and their adducts are similar, suggesting that SO2 is ligand-bound. On exposure to air, SO2-saturated toluene slurries and solutions of [Co(OPPh3)2I2] underwent a complex oxidation process resulting in the quantitative isolation of CoSO4·H2O, (Ph3PO)(Ph3POH)(HSO4) and I2. Visible spectroscopy indicates at least one iodine-containing intermediate, which may be analogous to the cocrystallised [Co(OPMe3)3(OH2)2]I2 and [Co(OPMe3)3(OH2)3]I2 recovered from the reaction of [Co(OPMe3)2I2] with SO2 and air. SO2-Saturated solutions of [Co(OAsPh3)2I2] afforded (Ph3AsOH)(HSO4), I2, Ph3AsI4 and CoSO4·H2O in the presence of air, although I2 and Ph3AsI4 appear to be produced even under anaerobic conditions. Aerobic reactivity was also observed for [Co(OEPh3)2(NCS)2](E = P or As); CoSO4·H2O and ligand derivatives of sulfuric acid were again isolated, however, the fate of the thiocyanate anion remains unclear. The inactivity of [Co(OPPh3)2(NCS)2] under anaerobic conditions contrasts with its subsequent aerobic reactivity and suggests that simple adduct formation and oxidation of SO2 to sulfuric acid are not closely linked processes.

Lipoprotein oxidation and measurement of hydroperoxide formation in a single microtitre plate.

The oxidative modification of lipoproteins is of clinical importance because of potential contribution to atherogenesis [1, 2, 3]. An early step in the complex process of oxidation is the peroxidation of polyunsaturated fatty acids. We describe here a method for the Cu(II)-catalyzed oxidation of human low density lipoproteins with the subsequent analysis of hydroperoxides formation in a single microtitre plate. The procedure includes a modification of an iodometric peroxide assay for test tubes using a commercially available reagent. The microtitre plate method correlated well with the test tube procedure (r = 0.99) and showed comparable sensitivity and reproducibility. It was sensitive down to 0.5 nmol hydroperoxides/well and linear up to at least 20 nmol well-1. The method can handle several hundreds of samples a day with considerably less labour than the test tube procedure. It was well suited to monitor the kinetics of lipoprotein oxidation. The method was also used to test the potency of antioxidants, however, some antioxidants may interfere with the iodometric reaction and should be tested in the assay before use.

The oxidation and oxide overlayer stability of AgMn alloys

AbstractThe oxidation of several compositions (5, 9 and 14% Mn) of polycrystalline Ag‐Mn alloys from room temperature to 650 °C in high vacuum and in 5 m Torr O2 has been investigated by x‐ray photoelectron spectroscopy (XPS). The behavior of the oxidation and the nature of the oxide films are controlled by tempearature, oxygen pressure, bulk alloy composition and the stability of the oxide overlayers. At low temperatures and pressures, the oxidation process is controlled by the relative free energies of oxide formation of the alloy components. At high temperatures the oxide of stabilities play a large role in determining the oxidation state of the oxide overlayer. The chemical state and the morphology of the oxide of manganese formed during the alloy oxidation has been examined. The chemical state and the morphology of the oxide overlayers have been studied by XPS, x‐ray diffraction (XRD) and scanning electron microscopy (SEM). The complex oxidation process has been delineated.

Properties of zinc oxide films prepared by the oxidation of diethyl zinc

Polycrystalline transparent semiconducting zinc oxide films have been deposited by the oxidation of diethyl zinc. The film growth rate is controlled by a complex multistep oxidation process which is dominated by radical reactions. The effect of substrate temperature and gas pressures have been studied. Samples deposited between 280 and 350 °C have a conductivity varying from 10−2 to 50 Ω−1 cm−1. The electrical properties of the films which are typical of polycrystalline material with small crystallites are shown to depend very closely on the film growth conditions. A study of oxygen chemisorption at grain boundaries confirms the importance of grain boundary effects in ZnO polycrystalline films.

The composition of the acids formed by the oxidation of n-decane in the liquid phase

1. The composition of the mixture of acids, and the kinetics of the behavior of the individual acids, have been studied for the oxidation of n-decane in the liquid phase. 2. It has been shown that oxidative combustion of the higher acids during the oxidation process does not occur. 3. The distribution of the acids obtained cannot be explained on the basis of the suppositions accepted at the present time, and needs a more thorough investigation of the mechanism of the separate stages taking place during the complex oxidation process leading to the development of the acids.