The initiation properties of 2-cyano-2-propyl hydroperoxide in oxidation processes

The initiating ability of 2-cyano-2-propyl hydroperoxide in the oxidation reaction of cumene by molecular oxygen has been investigated and compared with the initiating ability of cumene hydroperoxide.

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Die Initiierungseigenschaften von 2-Cyano-2-propyl-hydroperoxid bei Oxydations-prozessen

Zusammenfassung Es wurde die Initiierungsfähigkeit des 2-Cyan-2-hydroperoxypropans in der Oxidation von Cumol mit molekularem Sauerstoff untersucht und mit der Initiierungsfähigkeit des Cumolhydroperoxids verglichen.

     

Influence of calcination and lithium promotion on the surface properties of oxide supports

Thermal treatment and the addition of lithium influence the surface area of the oxides SiO₂, Al₂O₃ and MgO. A calcination temperature 1073 K causes a significant decrease of the surface area of SiO₂ and Al₂O₃; the same is not observed in case of MgO. Systems Li/MgO and Li/SiO₂ are characterized by a much smaller specific surface area than pure oxides thermally treated at the same temperature.     

Coordination of Schiff bases derived from pyrrole-2-carboxaldehyde and triamines to copper(II) and nickel(II) ions. Crystal structures of [Cu(C15H20N5)]NO3 and [Ni(C15H20N5)]ClO4

The Schiffbases 1,9-bis(2-pyrrolyl)-2,5,8-triazanona-1,8-diene (H₂L¹), 1,10-bis(2-pyrrolyl)-2,5,9-triazaundeca-l,9-diene (H₂L²), and 1,11-bis(2-pyrrolyl)-6-methyl-2,6,10-triazaundeca-l,10-diene (H₂L⁴) react with copper(II) nitrate or nickel(II) perchlorate in the presence of triethylamine to give new complexes [Cu(HL^1,2,4)]NO₃ and [Ni(HL^1,2,4)]ClO₄. The crystal structures of [Cu(HL²)]NO₃ and [Ni(HL²)]CIO₄ have been determined from single crystal diffractometer data and refined to finalR factors of 5.09 and 5.3%, respectively. Crystallographic data: [Cu(HL²)]NO₃: monoclinic,P2₁/c,a=10.036(2),b=14.500(2),c=13.317(2) Å,=108.14(1)°,Z=4, andd _c =11.427 Mg m^–3; [Ni(HL²)]ClO₄: monoclinic,P2₁/n,a=10.578(3),b=13.953(3),c=12.394(4) Å,=93.78(2)°,Z=4, andd _c =1.549 Mg m^–3. In both the structures the potentially pentadentate ligand (HL²)^– acts as a tetradentate one leaving one pyrrole group uncoordinated. Interesting is the metal dependent sequence of the three chelate rings. While the Ni (II) ion coordinates the (HL²)^– ligand to form a 5-5-6-membered ring system, the ring arrangement in the copper complex is of the 5-6-5 type.     

Microtiter plate assay for phosphate using a europium-tetracycline complex as a sensitive luminescent probe

A new luminescent europium probe is presented for the determination of phosphate (P) in microtiter plate format. The assay is based on the quenching of the luminescence of the europium-tetracycline (EuTc) 1:1 complex by phosphate using a reagent concentration of 20.8 μmol/L. The probe is excited at 400 nm and displays a large Stokes’ shift of 210 nm. The emission maximum is located at 616 nm. The system works best at neutral pH 7 and is therefore suitable for phosphate determination in biological and biochemical systems. The linear range of the calibration plot is from 5 × 10⁻⁶ mol/L to 7.5 × 10⁻⁴ mol/L of phosphate, and the limit of detection is 3 μmol/L.     

Adsorptive stripping voltammetric determination of cobalt in the presence of dimethylglyoxime and cetyltrimethylammonium bromide

A sensitive procedure for determination of micro-traces of Co(II) by adsorptive stripping voltammetry is proposed. The procedure exploits the enhancement of the cobalt peak obtained by use of the system Co(II)–dimethylglyoxime–piperazine-1,4-bis(2-ethanesulfonic acid)–cetyltrimethylammonium bromide. Using the optimized conditions, a detection limit (based on the 3 criterion) for Co(II) of 1.2×10^–11 mol L^–1 (0.7 ng L^–1) was achieved. The calibration plot for an accumulation time of 30 s was linear from 5×10^–11 to 4×10^–9 mol L^–1. The procedure was validated by analysis of certified reference materials and natural water samples.     

Influence of sodium dodecyl sulfate and static magnetic field on the properties of freshly precipitated calcium carbonate

Properties of calcium carbonate precipitated from aqueous solutions of CaCl(2) and Na(2)CO(3) in the presence of sodium dodecyl sulfate (SDS) and S-S 0.1 T magnetic field (MF) were studied. The nucleation and precipitation processes of CaCO(3) were investigated by pH and zeta potential measurements at 20 +/- 1 degrees C up to 2 h after mixing the solutions. Also the amounts of calcium carbonate deposited on the glass surfaces and its structure were examined. It was found that SDS influences the kinetics of precipitation, crystallographic forms, and crystal size of CaCO(3). The SDS effects are more pronounced in MF presence. A small amount of SDS accelerates transformation of vaterite into calcite, whereas increasing surfactant concentration moderates such a transformation. On the other hand, in all the systems, MF in the presence of SDS causes a slower transformation of vaterite into calcite. These effects are reflected in pH and zeta potential changes, although there is no clear dependence between the SDS amount present during the precipitation and changes of the parameters investigated. It seems that MF effect is most significant at a defined optimal SDS concentration. The results, however, do not allow suggestion of any detailed mechanism of the field interaction.     

Validation of an in-house measurement procedure for determination of selected priority hazardous substances in water and estimation of measurement uncertainty

Accreditation and Quality Assurance - This study investigates measurement procedure validation for the determination of hexachlorobenzene, pentachlorobenzene and trifluralin as priority hazardous...     

Anion driven ionic liquid crystals: The effect of the connecting group in [closo-1-CB9H10]- derivatives on mesogenic properties

Replacement of the connecting CH₂ group in ionic liquid crystal 1a[Pyr] with an oxygen atom in 1b[Pyr] resulted in significant destabilisation of the nematic and, to a greater extent, smectic A (SmA) phases, as established from binary mixture studies in 2a[Pyr]. Density functional theory (DFT) modelling of both anions suggests that the destabilisation results from the difference in charge distribution rather than conformational changes. Binary mixture studies demonstrated that all three ionic liquid crystals are compatible with a non-ionic benzoate nematic host 3a.