Cyanosilylation of Aldehydes and Ketones Catalyzed by Nanocrystalline Magnesium Oxide

Abstract

Cyanosilylation of various aldehydes and ketones with TMSCN proceeded smoothly under mild conditions to give the corresponding cyanohydrin trimethylsilyl ethers in the presence of nanocrystalline magnesium oxide. The cyanohydrin trimethylsilyl ethers of aldehydes produced cyanohydrins in good to high yields on treatment with 2 N HCl. ²⁹Si NMR spectral evidence proved that the reaction proceeds through the hypervalent silicate species by coordination to O^2?/O^? (Lewis basic site) of nanocrystalline magnesium oxide.     

Rapid and Catalyst‐Free α‐Halogenation of Ketones using N‐Halosuccinamides in DMSO

α‐Halogenation of various carbonyl compounds such as β‐keto‐esters, cyclic ketones, and lactams with N‐halosuccinamides (NBS, NCS, NIS) in the presence of DMSO proceeded very smoothly to give the corresponding α‐monohalogenated products in good to excellent yields with high selectivity under catalyst‐free conditions.     

Interaction between asphaltenes and fatty-alkylamine inhibitor in bulk solution

In the present work, the mechanism of interaction between asphaltenes and a commercial fatty-alkylamine inhibitor was investigated by a combination of techniques. The “macro” properties, like the asphaltene precipitation onset and the amount of asphaltenes precipitated, were measured by near-infrared (NIR) and UV-vis spectroscopy, respectively, while the interaction enthalpy between asphaltenes and inhibitor was measured by isothermal titration calorimetry (ITC). Asphaltenes subfractions and derivatives were also used to identify the mechanism.

ITC indicated that only a small fraction (～6%) of asphaltenes interacts strongly with the inhibitor. The proportion of interacting species was found to be higher in irreversibly adsorbed asphaltenes subfraction. These 6% are mostly composed of acidic asphaltenes, as indicated by measurements involving ester asphaltenes. However, the measurement of precipitation onset and amounts precipitated for whole and ester asphaltenes indicated that the acid–base interaction was not the main interaction responsible for the inhibitory action. Other type(s) of interaction is/are responsible for the inhibition properties of the inhibitor, which are not detected by ITC. The nature of other interactions is not known for the moment, but it was shown that irreversibly adsorbed asphaltene fraction contains a higher concentration of the functionality (ies) responsible for the “other” type of interaction.     

Preparation and electrical properties of InSe

Abstract

Single crystals of Indium Selenide are prepared by vapour growth technique as it is difficult to prepare large single crystals by vertical Bridgman technique. The effect of stochiometric changes and doping have been studied. The electrical properties of n-type single crystals are discussed.     

Photoemission studies of the high TC superconductor,YBa2Cu3O7

Considerable changes are observed in the spectra of the valence band and O(ls) regions in YBa₂Cu₃O₇, when the temperature is lowered from 300K to 80K. The results are interpreted in terms of a progressive formation of O^2- ₂-like species with decreasing temperature. This is accompanied by the transformation of Cu to Cu. It is suggested that the holes generated at the top of the valence band forming the O^2- ₂-like species may play a crucial role in the superconductivity of the oxide.     

Photoelectrochemical water oxidation kinetics and antibacterial studies of one-dimensional SiC nanowires synthesized from industrial waste

Silicon wafers are significantly utilized in integrated circuits and memory devices for the fabrication of novel semiconductor devices. As a result, a substantial amount of silicon wastes are generated every year. But recycling process of pure silicon waste is expensive with an additional problem related to chemical waste generation. Thus, the possibility of inevitable silicon waste conversion into potential nanostructures is not only beneficial for the semiconductor industry but also resolves current e-waste pollution. Hence, we successfully achieved hexagonal silicon carbide (SiC) nanowires under a strategic combination of waste silicon wafers and graphite powder by robust high-energy ball milling and heat treatment approaches. Structural, morphological, chemical, and optical properties of SiC nanowires are systematically studied by XRD, SEM, TEM, XPS, and optical absorbance. This facile experimental technique recognized the value of SiC nanowire generation for exploring multifunctional photoelectrochemical (PEC) water splitting and antibacterial activity. Accordingly, SiC nanowires achieved a photocurrent density of about 0.21 mA cm⁻² vs. Ag/AgCl, which demonstrates enhanced light absorption capacity under reduced charge carrier recombination. Moreover, SiC nanowires prevailed decrement in the charge carrier resistance (27.53 Ω) under light state compared to the dark state (26.76 Ω). Specifically, potentiodynamic studies revealed superior exchange current density (− 3.17 mA cm⁻²), Tafel slope (80.1 mV dec⁻¹), and limiting diffusion current density (− 1.49 mA cm⁻²) under light state than the dark state. Also, these results are certainly applicable for superior antibacterial activity against E. coli and L. monocytogenes about 90% and 75% under visible light, respectively.

     

The duality of quantum Liouville field theory

It has been found empirically that the Virasoro center and three-point functions of quantum Liouville field theory with the potential exp(2bϕ(x)) and the external primary fields exp(αϕ(x)) are invariant with respect to the duality transformations ℏα→q−α, where q=b⁻¹+b. The steps leading to this result (via the Virasoro algebra and three-point functions) are reviewed in the path-integral formalism. The duality occurs because the quantum relationship between the α and the conformal weights Δ_α is two-to-one. As a result, the quantum Liouville potential can actually contain two exponentials (with related parameters). In the two-exponential theory, the duality appears naturally, and an important previously conjectured extrapolation can be proved. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 123, No. 2, pp. 299–307, May, 2000.