Simple synthesis of 3-acyl-5-alkyl(aryl)isoxazoles from terminal alkynes and nitrates of alkaline metals or ammonium

A simple and general synthesis of 3-acyl-5-alkyl(aryl)isoxazoles by reaction of terminal alkynes with nitrates in acetic acid in the presence of SO₃ or alkaline salts is described.     

Growth feature of PTFE coatings on rubber substrate by low‐energy electron beam dispersion

Polytetrafluoroethylene (PTFE) coatings were prepared on Si and acrylonitrile‐butadiene rubber substrates by low‐energy electron beam dispersion. The effects of substrate nature, distance of target to substrate (d_ts) and coatings thickness on the surface morphology, structure, and tribological properties of the coatings were investigated. The results showed that substrate nature affects the shape and size distribution of surface conglomerations of PTFE coatings due to the interaction process of active dispersion particles with underlying polymer layer. Surface energy of PTFE coatings decreases first with the coatings thickness increases to 1.25 µm and then slowly increases with the thickness. Structure defects (pore, interstice, and so on) in the coatings increase with the thickness increases but reduce significantly with the d_ts increases. PTFE coating prepared at the d_ts of 20 cm had a higher intensity of the amorphous absorption bands. Friction experiment indicated that the destroyed area of the coatings in the friction region decreases with increases the coatings thickness but increases with the d_ts. The rubber modified by PTFE coatings with spherical structure possesses a higher stability in the friction process and a lower coefficient of friction. Copyright © 2015 John Wiley & Sons, Ltd.     

The composition of saturated and superheated vapors and molecular structure of Lu(C5O2HF6)3

The molecular structure of lutetium tris-hexafluoroacetylacetonate Lu(hfa)₃ was studied in a synchronous electron diffraction and mass spectrometric experiment and quantum-chemically by the HF and DFT/B3LYP methods. Saturated vapor over Lu(hfa)₃ was found to be oligomerized to a substantial extent. The mass spectrum of saturated Lu(hfa)₃ vapor was studied over the temperature range 76–100°C; it contained peaks of ions with one to three metal atoms. The peak of the highest intensity corresponded to the M₂L ₅ ⁺ stoichiometry. It was found in experiments with vapor superheating in a double two-temperature effusion cell that oligomeric forms disappeared above 150°C, whereas the decomposition of the monomeric form became noticeable above 250°C. The results obtained in theoretical and experimental studies allowed us to determine the structure of the Lu(hfa)₃ molecule.     

Tantalum Complex with 2-(2-Pyridine)Benzimidazolate

The reaction of Ta(NMe₂)₅ with 2-(2-pyridine)benzimidazole (HBzImPy) gave the molecular complex [Ta(NMe₂)₄(BzImPy)], which was characterized by X-ray diffraction (CIF file CCDC no. 1531835). Data of ¹H and ¹³C NMR spectroscopy in solution confirmed the structure detected in the crystalline phase.     

Functionalized Corannulene Carbocations: A Structural Overview

A detailed structural overview of a family of bowl‐shaped polycyclic aromatic carbocations of the type [C₂₀H₁₀R]⁺ with different R functionalities tethered to the interior surface of corannulene (C₂₀H₁₀) is provided. Changing the identity of the surface‐bound groups through alkyl chains spanning from one to four carbon atoms and incorporating a different degree of halogenation has led to the fine tuning of the bowl structures and properties. The deformation of the corannulene core upon functionalization has been revealed based on X‐ray crystallographic analysis and compared for the series of cations with R=CH₃, CH₂Cl, CHCl₂, CCl₃, CH₂CH₃, CH₂CH₂Cl, and CH₂CH₂Br. The resulting carbocations have been isolated with several metal‐based counterions, varying in size and coordinating abilities ([AlCl₄]^?, [AlBr₄]^?, [(SnCl)(GaCl₄)₂]^?, and [Al(OC(CF₃)₃)₄]^?). A variety of aggregation patterns in the solid state has been revealed based on different intermolecular interactions ranging from cation–anion to π–π stacking and to halogen???π interactions. For the [C₂₀H₁₀CH₂Cl]⁺ ion crystallized with several different counterions, the conformation of the R group attached to the central five‐membered ring of corannulene moiety was found to depend on the solid‐state environment defined by the identity of anions. Solution NMR and UV/Vis investigations have been used to complement the X‐ray diffraction studies for this series of corannulene‐based cations and to demonstrate their different association patterns with the solvent molecules.