Preconcentration of Polycyclic Aromatic Hydrocarbons on Polyurethane Foams and Their Determination in Waters with the Use of Luminescence and High-Performance Liquid Chromatography

A technique was developed for the sorption preconcentration of polycyclic aromatic hydrocarbons on polyurethane foams in the batch and dynamic modes providing their simultaneous quantitative extraction. A procedure was proposed for screening waters for polycyclic aromatic hydrocarbons based on the preconcentration of these compounds with polyurethane foam, determination of their total amount by the luminescence method, desorption of adsorbed compounds with acetonitrile, and determination of individual compounds in the eluate by high-performance liquid chromatography with fluorescence detection. The procedure was tested with model and real samples of water.     

Sorption of Ion Associates on Polyurethane Foams and Its Application to Sorption–Spectroscopic and Test Methods of Analysis

The results of studying the sorption of various ion associates on polyurethane foams were generalized. The main sorption-affecting factors were found to be the nature, hydrophobicity, and charge of the associate ion; the nature and concentration of the counter ion; the composition of the polymer unit of the polyurethane foam; and the pH and salt composition of the aqueous phase. Correlation equations were proposed to relate the partition coefficients with the hydration energy of counter ions in the ion associates of cationic dyes and metal complexes of 1,10-phenanthroline and with the number of carbon atoms in the alkyl fragment of cationic alkyltrimethylammonium surfactants. A sorption scheme was proposed and substantiated. Examples were given of the practical use of sorption for determining anionic and cationic surfactants, phenols, 1-naphthol, Fe(III), and Ru(IV).     

Use of a Scanner and Digital Image-Processing Software for the Quantification of Adsorbed Substances

The possibility of using a desktop scanner and digital image-processing software for the numerical evaluation of the color intensity of substances adsorbed on polyurethane foam is studied. The method is based on scanning colored samples of polyurethane foam using a desktop scanner, processing the color images using Adobe Photoshop as a graphics editor, and building calibration plots of the luminosity of the selected channel (R, G, or B) as a function of the concentration of the test compound using the Origin software. It has been found that the calibration plots are described by a first-order exponential decay function. The advantages of the method are its high performance, rapidity, and the possibility of mathematical processing of the results. It has been found that substances adsorbed on polyurethane foam can be determined with the use of a scanner and the corresponding image-processing software with the same sensitivity as with the use of diffuse-reflectance spectroscopy.     

Selective Cross-Coupling of Unsaturated Substrates on AlI

The Al^I compound NacNacAl ( 1 , NacNac = [ArNC(Me)CHC(Me)NAr]⁻, Ar = 2,6-iPr₂C₆H₃) serves as a template for the chemoselective coupling between carbonyls (benzophenone, fenchone, isophorone, p-tolyl benzoate, N,N-dimethylbenzamide, (1-phenylethylidene)aniline) and pyridine. With the CH-acidic ketone (1R)-(+) camphor, the reaction affords a hydrido alkoxide compound of Al, formed as the result of enolization, whereas an enolizable imine, (1-phenylethylidene)aniline, and the bulky ketone isophorone, still chemoselectively couple with pyridine. In contrast, reaction with the ester p-tolyl benzoate results in cleavage of the ester bond together with replacement of the alkoxy group by a hydrogen atom of the pyridine moiety. This study demonstrates that for carbonyl substrates featuring phenyl substituents, the reaction proceeds via intermediate formation of η²(C,X)-coordinated (X = O, N) carbonyl adducts, whereas the reaction of 1 with (R)-(−)-fenchone in the absence of pyridine leads to CH activation in the pendant isopropyl group of the Ar substituent of the NacNac ligand.     

Design and Synthesis of Nitrogen-Rich Azo-Bridged Furoxanylazoles as High-Performance Energetic Materials

A series of novel energetic materials comprising of azo-bridged furoxanylazoles enriched with energetic functionalities was designed and synthesized. These high-energy materials were thoroughly characterized by IR and multinuclear NMR (¹H, ¹³C, ¹⁴N) spectroscopy, high-resolution mass spectrometry, elemental analysis, and differential scanning calorimetry (DSC). The molecular structures of representative amino and azo oxadiazole assemblies were additionally confirmed by single-crystal X-ray diffraction and X-ray powder diffraction. A comparison of contributions of explosophoric moieties into the density of energetic materials revealed that furoxan and 1,2,4-oxadiazole rings are the densest motifs while the substitution of the azide and amino fragments on the nitro and azo ones leads to an increase of the density. Azo bridged energetic materials have high nitrogen-oxygen contents (68.8–76.9 %) and high thermal stability. The synthesized compounds exhibit good experimental densities (1.62–1.88 g cm⁻³), very high enthalpies of formation (846–1720 kJ mol⁻¹), and, as a result, excellent detonation performance (detonation velocities 7.66–9.09 km s⁻¹ and detonation pressures 25.0–37.7 GPa). From the application perspective, the detonation parameters of azo oxadiazole assemblies exceed those of the benchmark explosive RDX, while a combination of high detonation performance and acceptable friction sensitivity of azo(1,2,4-triazolylfuroxan) make it a promising potential alternative to PETN.     

X-ray spectroscopy of thermally distorted electronic states in crystals

A new type of x-ray spectroscopy is proposed which can detect the thermal-motion-induced distortions of atomic electronic states in crystals. It is shown that those distortions can cause extra Bragg reflections (so-called forbidden reflections) and that their intensity should grow with increasing temperature. The reason is that the thermal displacements, which change the symmetry of atomic environment, can modify the tensor amplitude of x-ray resonant scattering. In the first approximation, the structure factor of extra reflections is proportional to the reflection vector H and to the mean-square thermal displacement for optical phonons. It is demonstrated that the forbidden resonant reflections, observed recently in Ge, could be caused by the thermal motion. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 12, 885–889 (25 June 1999) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Untersuchungen zur Katalyse der Ammoniaksynthese und des Stickstoffisotopenaustausches durch Schichtverbindungen von Graphit mit Eisen,Ruthenium und Osmium

Investigations on the Catalysis of Ammonia Synthesis and Nitrogen Isotope Exchange by Lamellar Compounds of Graphite with Iron, Ruthenium, and Osmium The catalytic activity of transition metal potassium-graphite lamellar compounds for the synthesis of ammonia from the elements and the catalysis of the equilibration by isotope exchange of the isotopic nitrogen molecules are shown to correlate. Connections between the state of metal in the catalyst exist with iron as metal which is shown by Mössbauer spectroscopy and the catalytic activity in relation to the potassium content.     

Vladimir Evgen’evich Dmitrienko (On the occasion of his 60th birthday)

Crystallography Reports -