Application of Cope rearrangement in synthesis

Cope rearrangement is one of the pericyclic reactions in many organic rearrangements. It has high stereoselectivity and has been widely used in organic synthesis chemistry. Herein, the discovery, mechanism, and application of Cope rearrangement were analyzed and discussed.     

Heterogenous Oxidation of [2.2.1] Bridged Bicyclic Alkenes with KMnO4-CuSO4.5H2O: An Alternative Ozonolysis

Seven [2.2.1] bridged alkenes were cleaved to the corresponding dialdehyde products by neutral heterogenous oxidation with KMnO₄-CuSO₄.5H₂O. While endo, endo-dimethyl bicyclo[2.2.2]oct-5-ene-2,3-dicarboxylate, [2.2.2] bridged alkene, gave the corresponding α-hydroxy ketone, endo, endo-dimethyl bicyclo[3.2.2]non-8-ene-6,7-dicarboxylate afforded a diketone product.     

Trends in formation of the nanocrystalline structure and cationic ordering in the Dy2O3-HfO2 (1: 1) system

Evolution of the nanocrystalline structure of the complex oxide Dy₂HfO₅ in the course of thermal annealing at temperatures to 1600°C has been studied by a combination of X-ray and synchrotron methods, including traditional and anomalous X-ray diffraction, PDF, EXAFS, and SAXS. The changes in crystallite size upon annealing of the as-synthesized amorphous precursor have been analyzed in detail. The systematic distortions of a fluorite-type perfect crystal structure (space group $Fm\bar 3m$ ) related to the nonequivalence of the local environment of the Dy and Hf cations but not resulting in formation of a pyrochlore-type cationordered structure in this system have been examined.     

Zinc oxide nanoparticles immobilized on graphene flake

Interactions of ZnO nanoparticles with graphene oxide in isopropanol were studied; graphene oxide was shown to perform as an efficient substrate to immobilize zinc oxide nanoparticles on its surface. Interactions of nanocomposites consisting of graphene oxide-zinc oxide nanoparticles with supercritical isopropanol were studied. The conversion of graphene oxide into graphene does not appreciably changes the composition, morphology, or structure of ZnO nanoparticles.     

Synthesis and crystal structure of new sodium oxothiocyanofluoroantimonate(III) Na2Sb5F9O3(NCS)2

Na₂Sb₅F₉O₃(NCS)₂, a new complex, has been synthesized from NaSCN and SbF₃ aqueous solutions and studied by chemical, X-ray diffraction, and thermal analyses and IR, ^121,123Sb NQR, and ¹⁹F NMR spectroscopy. Its layered structure (triclinic symmetry system, a = 6.9998(1) Å, b = 9.4180(1) Å, c = 13.1094(2) Å, α = 74.815(1)°, β = 78.188(1)°, γ = 82.779(1)°, Z = 2, space group P $\bar 1$ ) is built of Na⁺ cations and [Sb₁₀F₁₈O₆(NCS)₄]^4? decanuclear complex anions that consist of two [Sb₅F₉O₃(NCS)₂]^2? pentanuclear complex anions linked by two weak Sb-F ionic bonds (2.529(2) Å). Decanuclear complex anions are linked into layers by secondary Sb…F bonds and Na-F bonds. Van der Waals interactions link these layers into a framework. The complex is stable up to 200°C.     

Preparation of aqueous sols of Ce1 − x Gd x O2-δ, Y0.9Eu0.1VO4 and nanocomposites Ce1 − x Gd x O2-δ/Y0.9Eu0.1VO4 stabilized by polyacrylic acid

A method for the synthesis of stable aqueous sols of nanocrystalline solid solutions Ce_1?x Gd _x O_2-δ (x = 0.10, 0.15, 0.20) and Y_0.9Eu_0.1VO₄ and nanocomposites Ce_{1 ? x} Gd _x O_2-δ/Y_0.9Eu_0.1VO₄ stabilized by biocompatible low-molecular-weight polyacrylic acid was proposed. Polyacrylic acid was shown to be a promising matrix for the preparation of polyfunctional composite materials.     

Chemical transformations of methane in trifluoroacetic acid

The reaction of methane conversion in anhydrous trifluoroacetic acid (TFA) is shown to take place at room temperature and atmospheric pressure and to result in the formation of a resinous product. Signals of ions with molecular weights of 684 and 700 are observed in MALDI-TOF spectra of the dry residue of methane conversion products.     

Study of tautomeric transformations of 1,4,5,8-tetraaminoanthraquinone by electronic spectroscopy

Based on the example of 1,4,5,8-tetraamino-9,10-anthraquinone, a method is described for establishing the tautomeric compositions and sequences of tautomeric transformations that occur in known samples of quinones. An analysis of electronic absorption spectra shows that this substance is a dynamic equilibrium mixture of 4,5,8,9-tetraamino-1,10-anthraquinone and the imines tautomeric to it. The tautomeric compositions of different samples of matter differ and can contain 1,4,8-triamino-5-hydroxy-9,10-anthraquinone-10-imine, 4,8,9-triamino-10-hydroxy-1,5-anthraquinone-5-imine, 5,8-diamino-4,9-dihy-droxy-1,10-antraquinonediimine, and 8,10-diamino-5,9-dihydroxy-1,4-antraquinonediimine. Tautomeric equilibrium shifts can accompany not only chemical reactions but physical processes as well, so any investigation of the properties of substances without establishing their tautomeric compositions would be incorrect.     

Synthesis,Structures, Luminescent and Magnetic Properties of Heterometallic 5p‐4f Compounds with Ethylenediaminetetra­acetate

A series of heterometallic Ln^III–Sb^III edta‐containing compounds with the formulas [Sb₂(edta)₂Ln]NO₃ · nH₂O [edta = ethylenediaminetetraacetate; Ln = Eu, n = 7 ( 1 ); Gd, n = 7.5 ( 2 ) and Tb, n = 8 ( 3 )] were synthesized and characterized by elemental analyses (EA), powder X‐ray diffraction (PXDP), Fourier transform infrared spectroscopy (FT‐IR), and thermogravimetric analyses (TGA). Their fluorescence and magnetic properties were also studied. The thermal analysis demonstrates the compounds formation of the antimony, lanthanide ions, and edta^4– ligands. FT‐IR spectra reveal that the antimony and lanthanide ions are connected through the carboxylate bridges. The studies of luminescence properties show that compounds 1 and 3 exhibit typical luminescence in the visible region. Furthermore, magnetic properties reveal compounds 2 and 3 have weak ferromagnetic behavior.     

Phosphate Removal from Aqueous Solution by an Effective Clay Composite Material

Adsorption is an effective treatment process for removing phosphorus and thus controlling eutrophication. In this study, a clay composite material called Al–dolomite–montmorillonite (Al–DM) was prepared and characterized. Al–DM performed well with respect to phosphate removal, with its performance depending on the Al–DM loading, contact time, initial phosphorus concentration and initial solution pH. Adsorption mechanisms were investigated by conducting batch tests on phosphate adsorption using the Al–DM. The adsorption process fitted both the pseudo-second-order kinetics model and the intra-particle diffusion model. The Langmuir, Freundlich and BET models all adequately described the adsorption isotherm data. Thermodynamic studies showed that the adsorption process was endothermic and spontaneous in nature. Al–DM is an effective adsorbent for phosphate removal mainly due to its hierarchical porous structures as shown by characterization with SEM and EDS. Chemical changes occurring before and after adsorption in a water environment indicated that Al–DM had little negative effect on water quality.