Synthesis,S-alkylation,and fungicidal activity of 4-(benzylideneamino)thioglycolurils

A series of 1,3-disubstituted 4-benzylideneamino-5-thioxohexahydroimidazo[4,5-d]imidazol-2(1H)-ones (thioglycolurils) was synthesized via the reaction of 5,7-disubstituted 3-thioxoperhydroimidazo[4,5-e]-1,2,4-triazin-6-ones with hydroxy-, alkoxy-, and fluorocontaining benzaldehyde derivatives. An alkylation of the obtained thioglycolurils with methyl iodide or 4-bromobenzyl bromide provided the corresponding 6-benzylideneamino-5-alkylsulfanyl-3,3a,6,6a-tetrahydroimidazo[4,5-d]imidazol-2(1H)-ones. The fungicidal activity of some synthesized compounds against pathogens causing diseases of agricultural crops was studied.     

Valence States of Lead and Bismuth Atoms in the High-Temperature Superconductor BaPb1-xBixO3

X-ray photoelectron spectra of valence bands and core levels of BaPb_0.8Bi_0.2O₃, PbO, PbO₂, BaPbO₃, BaBiO₃, NaBiO₃, and Bi₂O₃ were studied. Comparison of the electron binding energies of the Pb 4f7/2 or Bi 4f7/2 core levels for all the oxides studied showed that the high-temperature oxide superconductor BaPb_0.8Bi_0.2O₃ contains simultaneously two different valence forms of lead atoms (Pb^IV and Pb^II) and two different valence forms of bismuth atoms (Bi^V and BiIII). Parameters of the X-ray photoelectron spectra of the valence bands do not contradict the conclusion on heterovalent states of lead and bismuth atoms in BaPb_0.8Bi_0.2O₃.     

Role of core and valence atomic orbitals in the formation of chemical bonds

The general principles of the electronic structure of molecules and complexes are discussed. An analysis of photoelectron and x-ray photoelectron spectra reveals that in most cases, the interaction of the valence AO's results in the formation of delocalized MO's, which are populated by electrons, but are not bonding according to their energies (molecules with small atomic cores are exceptions). These MO's do not make a positive contribution to the exothermic effect of chemical bonding. The delocalization of the valence electrons in such MO's reduces their charge density in the region of the atomic cores and lowers the energy of the inner atoms-in-molecules levels as a result of the reduction of the internal shielding; the ESCA shifts of the inner electronic levels confirm this stabilization. In accordance with the virial theorem, the lowering of the energy of the core levels of the central atoms (with simultaneous, generally small changes in the energy of the core levels of the ligands and despite the significant destabilization of the delocalized MO's in comparison to the valence orbitals of the corresponding free atoms) makes up the main contribution to the energy of chemical bonds.This article is being published for purposes of discussion.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 5, pp. 572–578, September–October, 1986.     

Influence of macroscopic factors on the composition of the products of cohydrolysis of triorganochlorosilanes

The composition of the products of heterogeneous cohydrolysis of trimethyl- and dimethylphenylchlorosilanes by excess aqueous ammonia (4–5% solution) is determined by the regime of heterofunctional condensation of the initial chlorosilanes with the products of their hydrolysis, triorganosilanols. In a diffusion regime, hexaorganodisiloxanes are formed because of the limited possibility of removing silanols from the reaction zone, while silanols are predominantly formed in a kinetic regime. The influence of the nature of the solvent and surfactant and the intensity of stirring of the reaction mixture on the composition of the final products of hydrolytic cocondensation of triorganochlorosilanes is considered.     

Synthesis and evaluation of cytotoxicity of S-substituted 5-sulfanylmethyl(ethyl)-1,3,4-thiadiazol-2-amines

Russian Chemical Bulletin - A general and efficient method for the synthesis of S-substituted 5-sulfanylmethyl(ethyl)-1,3,4-thiadiazol-2-amines via cyclocondensation of aryl(benzyl)sulfanylacetic...     

Scandium Extraction with Benzo-15-crown-5 from Neutral Nitrate–Trichloroacetate Solutions

A systematic study for scandium extraction with benzo-15-crown-5 in chloroform from trichloroacetate solutions has been performed. The presence of free trichloroacetic acid in extraction system has been found to prevent scandium transfer into organic phase. Scandium is extracted from neutral trichloroacetate solutions as partially hydrolyzed trichloroacetate complexes, the extracted compound includes two crown ether molecules. The presence of nitrate anions has no effect on scandium distribution ratios and nitrate anion is not involved in extracted compound composition. Optimal process conditions for selective scandium recovery from concentrated solutions of rare-earth nitrates in the presence of lithium trichloroacetate with high separation factors (>100) on the use of B15C5 as extractant have been determined.     

Complexation in Benzo-15-Crown-5–Chloroform–Substituted Acetic Acid Extraction Systems

To study the complexing processes occurring in the extraction systems, the extraction of acetic, propionic (methylacetic), monochloroacetic, dichloroacetic and trichloroacetic acids using benzo-15- crown-5 as an extractant is considered. The extraction isotherms of acids with the pure solvent and 1 M benzo-15-crown-5 in chloroform are determined. The dependences of the distribution ratios of the considered acids on the extractant concentration in the organic phase are presented. Based on the experimental data and the “blank” extraction isotherm equations, the acid: benzo-15-crown-5 ratio in the complexes formed in the extract have been calculated (minus the contribution of extraction with the pure solvent). No complexation of methylacetic acid with benzo-15-crown-5 occurs, and the stability of the complexes of chloro-substituted acetic acids rises in the order acetic acid < monochloroacetic acid < dichloroacetic acid < trichloroacetic acid.     

Velocity and Attenuation of Acoustic Waves in Polymers and Polymer Composites

The acoustic properties of polymers and polymer composites have been studied. The dependence of the propagation characteristics of ultrasonic waves on polymer kind and composite content has been shown. We have established that there is no frequency dependence of the ultrasonic velocity in either polymers and composite materials based on them, whereas the ultrasonic attenuation is strongly frequencydependent.