Mendeleev Communications最新文献

The effect of the second metal (Pt, Pd, Ni and Fe) on the activity of copper phyllosilicate-based catalysts was investigated in the selective hydrogenation of dimethyl oxalate to ethylene glycol at 160–200 °C. The prepared catalysts were characterized by XRD, DRIFTS-CO and TEM methods. The conversion achieved over 10Fe/10Cu-PhySi catalyst was 68 % at 200 °C; at the same time, the full conversion with selectivity 98% was obtained at the temperature of 180 °C over a bimetallic 1Pt/Cu-PhySi catalyst.

The microwave-assisted cycloaddition of 2,6-disubstituted benzonitrile oxides to 1-iodobuta-1,3-diynes occurs at the iodo-substituted triple bond giving predominantly 5-alkynyl-4-iodo-1,2,3-isoxazoles. The Suzuki–Miyaura and Sonogashira cross-coupling reactions were used for the modification of the thus obtained 4-iodoisoxazoles.

Ni–P coatings, with their high microhardness (HV) and wear resistance, have been proposed as a viable alternative to hard chromium. However, wear testing experiments on electroless Ni–P coatings were conducted under a variety of conditions, including test equipment, load, substrate materials and counterface materials, resulting in unreliable comparative evaluations of experimental results. Therefore, this article presents an analysis of experimental research on Ni–P and Cr coatings, as well as a statistical analysis of the results obtained under similar conditions. The results of simultaneous wear tests on Ni–P and Cr coatings published from 1958 to 2022 were used for evaluation and comparative analysis. The relative wear of Ni–P versus hard Cr was calculated from experimental data and analyzed using statistical methods such as Tukey’s statistical methods, nonparametric and parametric statistics. This review found that the wear performance of electroless nickel coatings generally does not match that of hard chromium coatings. The results of this analysis indicate that: (i) Ni–P coating can be used as a protective and hardening coating; (ii) the wear resistance of the electroless Ni–P coating, being 1.9 ± 0.4 times less, does not reach the same level of wear resistance as that of hard Cr; (iii) there is a tendency for the wear resistance of Ni–P to gradually approach the wear resistance of Cr; (iv) the dependence of the wear rate on the phosphorus content of the Ni–P alloy indicates that the minimum possible wear rate is achieved at a P content of about 4–7 wt%. The search for effective alternatives to hard chromium plating is ongoing, and this review has identified several areas where effective engineering solutions could be found.

The effectiveness of the combined action of ultrasound and γ-radiation on Lactobacillus casei is studied. A superadditive death effect is shown, whose magnitude depends on dose levels, sequence of effects, and the presence of theraphthal (sodium salt of cobalt 4,5-octacarboxyphthalocyanine) as a sonosensitizer.

Addition of allylzinc to cyrene affords diastereomeric 4-allyl-6,8-dioxabicyclo[3.2.1]octan-4-ols. Opening of their 1,6-anhydro bridge with Ac₂O followed by selective deacetylation of the resulting tertiary and acetal acetates yields diastereomeric 2-acetoxymethyl-5-allyl-tetrahydro- pyran-5,6-diols whose oxidation by the action of DMSO–Ac₂O system is accompanied by etherification of tertiary hydroxy groups leading to methylthiomethoxy pyrone derivatives. The opening of 1,6-anhydro bridge in 4-allyl-6,8-dioxabicyclo[3.2.1]octan-4-ols with MeOH–HCl followed by oxidation with PCC gives individual (4S,6S)- 1-allyl-6-methoxy-2,5-dioxabicyclo[2.2.2]octan-3-one.

Poly(vinyl alcohol) (PVA) was incorporated into the mesoporous structure of high-density polyethylene (HDPE) directly upon the tensile drawing of films via crazing in water–ethanol PVA solutions. The structure and thermophysical properties of the HDPE–PVA nanocomposites were explored by differential scanning calorimetry and X-ray analysis. PVA was found to exist in an amorphized state within the mesoporous structure of the HDPE host matrix since its crystallization is prevented by the spatial confinements.