Synthesis, mechanism of formation, and molecular orbital calculations of arylamidoximes

Abstract  

A simple and easy synthesis of ten arylamidoximes from arylnitriles and hydroxylamine is described. The formation of the arylamides has been observed to a much lesser extent in the present work. A new mechanism for the formation of arylamidoximes, as well as arylamides, from arylnitriles and hydroxylamine is suggested. Quantum mechanical calculations have been carried out to support this mechanism. The enthalpy of formation in conjunction with atomic charges of the reactants and intermediates helped to understand more about the generation of the products.     

Synthesis,Structure and Characterization of Dinuclear Pentacoordinate Molybdenum(V) Complexes with Thiosemicarbazone Ligands

New dinuclear pentacoordinate molybdenum(V) complexes, [Mo₂^VO₃L₂] [L = thiosemicarbazonato ligand: C₆H₄(O)CH:NN:C(S)NHR′ and C₁₀H₆(O)CH:NN:C(S)NHR′; R′ = H, CH₃, C₆H₅) were obtained either by oxygen atom abstraction from Mo^VIO₂L with triphenylphosphine or by using [Mo₂O₃(acac)₄] in the reaction with the corresponding ligands H₂L. Crystal and molecular structure of [Mo₂O₃{C₆H₄(O)CH:NN:C(S)NHC₆H₅}₂] · CH₃CN has been determined by the single‐crystal X‐ray diffraction method.     

Stabilization of polyurethanes based on liquid OH-telechelic polybutadienes: Comparison of commercial and polymer-bound antioxidants

A soluble polyurethane was synthesized by a reaction of OH-telechelic, 1,2-rich, low-molecular-weight polybutadiene with toluene 2,4-diisocyanate. To the pendent vinyls of the polybutadiene blocks of the polyurethane, a sterically hindered phenolic antioxidant bearing a sulfanyl group (i.e., 6-sulfanylhexyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate) was added by a free-radical mechanism (in varying degrees of conversion). The self-stabilized polyurethane thus formed, bearing the antioxidant structures as side chains, was mixed in varying concentrations with the original (unstabilised) polyurethane and the thermo-oxidative stability of the mixtures was evaluated by DSC in air. The antioxidant effect of the polymeric stabilizer on the oxidative stability of polyurethane, expressed as the oxidation onset temperature, is approximately the same as that of a low-molecular-weight analogue, the commercial octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate (Irganox 1076), as related to the same molar concentration of the phenolic moiety, but the former is superior to the latter due to its ability to persist in the matrix. In both cases, the onset temperature of oxidation increases with increasing mole ratio of the phenolic structure and the total butadiene units in the mixture.     

The conversion of polyaniline nanotubes to nitrogen-containing carbon nanotubes and their comparison with multi-walled carbon nanotubes

Polyaniline (PANI) nanotubes were prepared by the oxidation of aniline in solutions of acetic or succinic acid, and subsequently carbonized in a nitrogen atmosphere during thermogravimetric analysis running up to 830 °C. The nanotubular morphology of PANI was preserved after carbonization. The molecular structure of the original PANI and of the carbonized products has been analyzed by FTIR and Raman spectroscopies. Carbonized PANI nanotubes contained about 8 wt.% of nitrogen. The molecular structure, thermal stability, and morphology of carbonized PANI nanotubes were compared with the properties of commercial multi-walled carbon nanotubes.     

Copper-catalyzed addition of water affording highly substituted furan and unusual formation of naphthofuran ring from 3-(1-alkenyl)-2-alkene-1-al

We have developed a novel one-pot reaction to generate highly substituted furan through the addition of water followed by oxidation and unusual cyclization to naphthofuran ring under the same reaction condition.     

Long-Term Impact of Wind Erosion on the Particle Size Distribution of Soils in the Eastern Part of the European Union

Wind erosion is the leading cause of soil degradation and air pollution in many regions of the world. As wind erosion is controlled by climatic factors, research on this phenomenon is urgently needed in soil and land management in order to better adapt to climate change. In this paper, the impact of wind erosion on the soil surface in relation to particle size distribution was investigated. Changes in percentage of sand, silt and clay fractions based on historical KPP data (1961–1970), LUCAS data base (2009), and field measurements (2016) were analysed in five cadastral areas impacted by wind erosion (Záhorie Lowlands, Slovakia). With the use of GIS tools, models of spatial distribution of sand, silt, clay and erodible fraction (EF) content were developed based on those measurements. Our findings proved that soil texture change driven by wind erosion could happen relatively quickly, and a significant proportion of soil fine particles may be carried away within a few years. The results indicate that the soil surface became much rougher over the period of more than 50 years, but also that the accumulation of fraction of the silt particles occurred in most of the areas affected by the erosive effect.     

Oil in water emulsions stabilized by maillard conjugates of sodium caseinate-locust bean gum

Conjugates composed by sodium caseinate and locust bean gum (LBG) were produced through Maillard reaction in order to enhance their emulsifying properties. The reactions were performed (80?°C/76% relative humidity) at three protein/polysaccharide ratios (0.3, 0.6, 1.2), and the conjugates were added in emulsions at two pH values (3.5 and 7). The formation of protein-polysaccharide conjugates was confirmed by SDS-polyacrylamide gel electrophoresis and by FTIR spectra. At both pH values, the conjugates subjected to longer reaction times presented less emulsifying capability, probably due to insoluble compounds formation. Furthermore, the conjugates provided high stability in O/W emulsions at pH 7 due to the electrostatic repulsion of protein charged groups. However, even though the conjugates were not charged at pH 3.5, the stabilization process occurred at this condition probably due to the formation of a thicker interfacial layer, which provided an increase in steric repulsion between the droplets. Thus, the conjugates formed by sodium caseinate and locust bean gum can be characterized as a good emulsifying agent to be applied in different pH conditions.     

Comparison of Insulin Determination on NiNPs/chitosan‐ MWCNTs and NiONPs/chitosan‐MWCNTs Modified Pencil Graphite Electrode

The rising amount of patients suffering for diabetes mellitus increases the requirements for effective insulin sensors. Carbon materials are a suitable choice for the development of insulin sensors due to their electrochemical characteristics. Pencil graphite electrodes (PGE) represent the trade‐off between price and excellent conductive properties. The modification of PGE by NiO and Ni nanoparticles fixed by chitosan results in surface area enlargement and improved electrocatalytic properties. This paper is focused on the comparison of different properties of Ni and NiO nanoparticles and their effect on redox reaction mechanism of insulin and detection characteristics. The electrode modified by Ni nanoparticles displays linear range of 1 μM–5 μM (R² 0.80), limit of detection (LOD) of 4.34 μM and sensitivity of 0.12 μA/μM. On the other hand, the electrode modified by NiO nanoparticles displays enhanced electrochemical characteristics such as linear range of 0.05 μM–5 μM (R² 0.99), limit of detection of 260 nM and sensitivity of 0.64 μA/μM. These properties make the NiO nanoparticles modified PGE the appropriate candidate for insulin determination.     

Nanostructured Gold Microelectrodes for Non‐enzymatic Glucose Sensor

A novel, highly stable, selective, and sensitive non‐enzymatic glucose sensor was developed by simple and effective modification procedure. The modification of gold microelectrodes by electrochemically deposited gold nanoparticles resulted in increase of surface area up to 37 %. The nanostructured surfaces of the gold microelectrodes obtained by different modifications were studied by confocal microscopy, atomic force microscopy, and scanning electron microscopy. The gold nanoclusters exhibit great electrocatalytic properties toward glucose with a wide linear range from 0.5 to 50 mM, with a limit of detection 218 μM, and sensitivity of 185.2 mA mM^?1cm^?2. Moreover, the modified microelectrodes display good reproducibility, stability, and selectivity in the presence of poisoning compounds. Due to the small dimensions of gold microelectrodes and a very small volume of the sample, the microelectrodes make a contribution to miniaturisation of the system.     

Pyrimidine Derivatives with Terminal Pyridyl Heterocycles: Facile Synthesis and Their Antiproliferative Activities

Incorporation of heterocyclic pyrimidine or pyridine motifs is common in the drug design for various therapeutic applications. Herein, we describe the facile synthesis of two molecules containing both pyrimidine and pyridine scaffolds. A variety of analytical techniques (multinuclear NMR, Fourier transform infrared, and mass spectrometry analyses) confirmed the purity of these molecules. In pristine form, their potential as antitumor drugs was screened by investigating their cytotoxicity against various cell lines (cancerous and normal cells). Experimental results confirmed that the two molecules exhibited cell growth inhibition at very low concentrations. This was evident from their IC₅₀ values that are in the range of 0.45–2.20 μM.