Vanadox--a new reagent for the photometric determination of vanadium

A new reagent, 2,2-dicarboxydiphenylamine, vanadox, is proposed for the photometric determination of vanadium in steels, high temperature alloys and ferrotitanium ores. In strongly acidic medium the reagent is selective for vanadium(V) and only eerium(IV) interferes.     

Real-Time Imaging of the Coil-Globule Transition of Single Adsorbed Poly(2-vinylpyridine) Molecules

Summary: We applied scanning force microscopy to study, in real time, the mobility and reorganisation of single poly(2-vinylpyridine) molecules that were adsorbed on mica and exposed to vapours of ethanol or water. The macromolecules adopted a compact globular conformation in ethanol-saturated vapour and extended to a surface-bound two-dimensional coil in water-saturated vapour. Hence, reversible coil-to-globule conformational transitions of flexible polymer chains were directly visualized with unique molecular resolution.

Left: individual P2VP molecules on mica compacted by exposure to ethanol vapour, right: the same macromolecules extended in water vapour.     

New ferrites of the composition TbM3 IIFe5O12 (MII = Ca, Sr, or Ba) and their XRD properties

For the first time double ferrites from terbium oxide, iron carbonates, and alkaline earth metals were synthesized using a solid phase procedure. Symmetry and unit cell parameters of the synthesized compounds were determined by X-ray diffraction method.     

A DFT,X- and W-band EPR and ENDOR Study of Nitrogen-Centered Species in (Nano)Hydroxyapatite

Incorporation of the nitrogen-containing impurities in hydroxyapatite (HAp) powders with the sizes of the crystallites of (20–50) nm was studied using first-principles modeling combined with the multi-frequency (9 and 94 GHz) electron paramagnetic resonance (EPR) methods. It is shown that the observed EPR spectra are undoubtedly due to the presence of the bulk radiation-induced NO₃ ^2? radicals. This conclusion is based on spin-polarized density functional theory calculations of spectroscopic parameters within gauge-including projector augmented wave framework followed by the exact comparison of the simulated EPR and electron–nuclear double resonance spectra with the experimental findings. In addition, a comprehensive analysis of the simulated properties allows us to suggest that the paramagnetic centers preferably occupy PO₄ ^3? sites in the HAp structure.     

Effect of the β-substituent with respect to the azido group on the reactivity of methyl (2E)-3-[5-(azidomethyl)-2,2-diethyl-1,3-dioxolan-4-yl]-2-methylprop-2-enoate

Unlike methyl (2E)-3-[5-(azidomethyl)-2,2-diethyl-1,3-dioxolan-4-yl]-2—methylprop-2-enoate which is stable on storage, its acyclic derivative, methyl (2E,4S,5S)-6-azido-5-hydroxy-2-methyl-4-(pent-3-yloxy) hex-2-enoate at 20°C undergoes unusual decomposition with formation of exo-methylidenepyrrolidine. Analogous transformation was also observed in the epoxide ring opening in methyl (2E)-2-methyl-4-[(S)-oxiran-2-yl]-4-(pent-3-yloxy)but-2-enoate and in the substitution reaction of ethyl 5,6-bis(methanesulfonyloxy)-2-methyl-4-(pent-3-yloxy)hex-2-enoate with azide ion. Opening of the oxirane ring in the former by the action of azide ion was accompanied by formation of oxazetidine derivative as a minor product. The major intramolecular cyclization products, 4-hydroxy- and 4-mehtanesulfonyloxypyrrolidines were converted into stable pyrrole derivatives via elimination of the leaving groups. The hydrogenation of methyl and ethyl (2E)-3-[5-(azidomethyl)-2,2-diethyl-1,3-dioxolan-4-yl]-2-methylprop-2-enoates over palladium catalyst afforded the expected reduction products.